Isbw14 Abstract booklet 
 

 

 

Session 1A: Chesapeake Bay Partnership and Collaboration 

Session Convener(s): Brooke Landry, Maryland Department of Natural Resources 
 
The conservation, restoration, and management of Chesapeake Bay and its resources has been a 
40+ year exercise in multi-jurisdictional partnership and collaboration. During this session, 
participants will hear from the agencies and organizations that have led the way and made 
progress possible. Leaders from the Chesapeake Bay Program, the Chesapeake Bay Trust, the 
Alliance for the Chesapeake Bay, the Chesapeake Research Consortium, and Waterkeepers 
Chesapeake will discuss their unique roles in the partnership - specifically how those roles have 
contributed to the recovery of SAV in Chesapeake Bay. 
 

The following invited presentations are included in this session: 
The CBP's SAV Workgroup: The benefits of multi-institutional collaboration in SAV restoration 
and management, Brooke Landry 
Chesapeake Bay Program: Approaches for Setting, Overseeing, and Attaining Restoration Goals, 
Carin Bisland 
Chesapeake Research Consortium: Translating Science to Management, Denice Wardrop 
Chesapeake Bay Trust: Identifying and Funding Key Barriers to Meeting Goals, Jana Davis 
Alliance for the Chesapeake Bay: Engaging a Watershed, Kate Fritz 
Waterkeepers Chesapeake: The role of Riverkeepers in SAV Monitoring, Restoration, Outreach, 
and Advocacy, Betsy Nicholas 
 
 
Session 1B: Successful tropical/subtropical seagrass restoration: Longevity, species for 
various impacts, services reassembled 

Session Convener(s): Anitra Thorhaug, Greater Caribbean Energy and Environment Foundation 
and Yale University 
 

This session will highlight the results of over 80 sets of trials, over 300 ha of seagrass in the 
Indo-Pacific and Atlantic tropical/subtropical basins. Speakers will demonstrate the methods, 
species, and planting designs creating the successful plantings in both the Indo-Pacific and 
Atlantic tropics/subtropics from multiple sets of restorations in key areas. These have been 
highlighted in our three recent seagrass reviews. The impacts overcome by means of restorative 
plantings will also be detailed as to species and techniques. This will emphasize data due to 
various types of impacts, and their successful solutions. The end result of successful longevity 
and sustainability will be emphasized with restoration sustaining as old as 47 years. The services 
measured from these restorations will be delineated such as animal recolonization studies, 



biodiversity, blue carbon results in restorations, sediment/seagrass interactive resilience. The 
various restoration projects have had layers of preliminary tests creating better final larger-scale 
restorations, which will be discussed. Large scale restoration techniques from 12 ha to 50 ha will 
also be emphasized as to differing techniques to rapidly install large areas manually. Studies of 
differences and similarities of restoration species especially in co-generators (Thalassia, 
Halodule, Syringodium, Halophila, Ruppia) and mixed plantings across the major large tropical 
oceanic basins of Atlantic and Indo-Pacific will be emphasized. 
 
 
Talks: 
 
Tropical and subtropical Southeast Asian Seagrass restoration review and analysis 
 

Anitra Thorhaug, GCEEF; Jennifer Verduin, Murdoch Univ. Perth, Australia; Wawan Kiswara, 
Indonesian Academy Science; Barry Gallagher, Univ. Malaysia, Sabah; Michael Yap, Univ. 
Malaysia, Sabah; Xiaoping Huang, Institute Oceanology, Chinese Academy of Sciences; 
Anchana Prathep, Seaweed and Seagrass Institute, Prince of Songla Univ., Phuket, Thailand; 
Arthur Schwarz, SWAU, Keene, TX 
 

Southeast Asia contains the highest seagrass regional extent globally (5.5million ha), suffering 
the highest seagrass degradation. Seagrass areas are found in tropical/subtropical estuaries and 
shallow shelves. Solutions to seagrass destruction include restoration and preservation. 
Objectives: An analysis of “state of the restoration practice” of Southeast Asia seagrass. 
Approach: reviewing national and global seagrass data are analyzed in categories critical to 
restoration sustainability. Results: Twelve of the 26 Southeast Asian species are under 
cultivation including the dominant food-web producing &sediment stabilization, and high 
carbon-sequestering genera: Enhalus, Thalassia, Halodule, Halophila, Syringodium, 
Cymadocea, Amphibolis, & Posidonia. Analysis demonstrates 1.5 Million seagrass restoration 
planting units in 42 efforts 9 Southeast Asian nations provided technically sufficient information 
for large-scale initiation. Successful species, planting methods, anchoring,fertilizer, planting 
season, and physico-chemical constraints are analyzed. Large-scale efforts occurred in five 
nations; smaller efforts occurred in 4 others. The Western Australia example provides an 
excellent of large-scale successful restoration (Posidonia australis) (Verduin et al 2011, Paling et 
al 2001). The Philippines’ inquisitiveness led seagrass restoration& preservation for four decades 
(Thorhaug& Cruz 1986, Campulong 1994, Fortes et al 2019). Multiple efforts were recorded in 
tropical China (dominant species, and preserving centers of population genetics) and in Vietnam. 
Conclusions: This analysis refines the regional restoration success following global seagrass 
restoration analysis of 1786 investigations (Van Katwijk, Thorhaug et al 2016) in which the 
Atlantic demonstrated the highest trial number of seagrass restoration. Seagrass restoration is 
poised for large scale, but political will for funding appears the obstacle for restoration. 
 
 
Metrics of seagrass restoration – case of Oceana serrulata in the Western Indian Ocean 
 

Maria Cuambe, Department of Biological Sciences, Eduardo Mondlane University; Manuela 
Amone-Mabuto, Department of Biological Sciences, Eduardo Mondlane University and  
Department of Botany Nelson Mandela University; Maria Américo, Department of Biological 
Sciences, Eduardo Mondlane University; Salomão Bandeira, Department of Biological Sciences, 
Eduardo Mondlane University 
 



The seagrass Oceana serrulata (former Cymodocea serrulata) is a pioneer species in sand 
accretion areas of the western Indian Ocean region. In Maputo Bay (Mozambique), an area 
subjected to impact of currents is prone to both constant transportation and erosion leading to a 
constant denudation of the intertidal and immediate subtidal areas. This manuscript describes the 
ongoing seagrass restoration in the Western Indian Ocean that started in 2019. Several 
techniques were tested: sediment-free method (rod and finger/spring methods) and seagrass with 
sediment method (sod method). The rod method recorded the highest survival rate of over 60%. 
Around 2 hectares of restored seagrass, comprising nearly 150 000 modules of 3-6 shoots 
of Oceana serrulata were accomplished in February 2022. Restoration site in now visible over 
the Google Earth. Monitoring of the restoration have target mainly the metrics based on 
calculating seagrass percentage cover, shoot density, canopy height and biomass of both the 
restored and donor sites. Monitoring maps were also produced using drone.  
 

The seagrass restoration success, out of Inhaca Island was assessed after 2,5 years through the 
calculation of a threshold value and quality ratio. While this is still an ongoing activity we 
determined that the restoration is being successful; having the quality ratio greater than the 
threshold value (0,52> 0,51). Inhaca island seagrassrestoration story continues to evolve with 
engagement of local communities who developed an association devoted 
to seagrass conservation. 
 
 
Adaptive seagrass restoration - a habitat restoration experiment comparing stoic Zostera 
marina & opportunistic Ruppia maritima bed structure and function 
 

Enie Hensel, Virginia Institute of Marine Science; Stephanie J. Wilson, Virginia Institute of 
Marine Science; Christopher J. Patrick, Virginia Institute of Marine Science; Bongkeun Song, 
Virginia Institute of Marine Science; Robert J. Orth, Virginia Institute of Marine Science 
 

Habitat restoration is a powerful tool to help mitigate seagrass loss. Yet, many efforts focus 
on revegetating declining or lost species opposed to planting alternative species more conducive 
to current and future conditions. In the Chesapeake Bay, seagrass meadows are declining and 
there has been a dominant species shift from Zostera marina to Ruppia maritima– a more 
tolerant species to the observed increase in heatwave spikes and frequencies. Here, we conducted 
a field experiment to test the effectiveness of seed-broadcasting for R. maritima and 
how seagrass identity, Z. marina and R. maritima, alters bed structure and function. Our study 
showed broadcast seeding is successful for planting R. maritima – the first field test to our 
knowledge. Comparing the first growing season of these species, Z. marina plots produced on 
average, five times more biomass than R. maritima with grass shoots being four times higher and 
denser than R. maritima. For epifaunal responses, R. maritima plots had higher guild richness 
and animal abundance on average. Lastly, preliminary findings suggest seagrass species identity 
influences sediment nitrogen removal verse recycling rates. In conclusion, we show 
R. maritima is a promising species for seagrass restoration efforts in warming nearshore systems 
like the Chesapeake Bay. Importantly though, we found species identity can alter seagrass bed 
structure and function, and therefore if local conditions are conducive for either lost or 
opportunistic species like Z. marina and R. maritima, respectively, choice of species could 
potentially depend on targeted restoration goals (carbon sequestration vs. faunal habitat quality). 
 
 
A collated evidence review to identify the gaps in the restoration ecology of the seagrass 
Posidonia oceanica 
 



A. Pansini, Dipartimento di Architettura, Design, Urbanistica, Università di Sassari; Mar Bosch-
Belmar, Dipartimento di Scienze della Terra e del Mare (DISTEM), Università di Palermo; 
Manuel Berlino, Dipartimento di Scienze della Terra e del Mare (DISTEM), Università di 
Palermo; Gianluca Sarà, Dipartimento di Scienze della Terra e del Mare (DISTEM), Università 
di Palermo; Giulia Ceccherelli, Dipartimento di Chimica e Farmacia, Università di Sassari 
 

Active restoration actions are now considered reliable strategies to return seagrass ecosystems to 
their original state in a reasonable time frame. Decision making for correct seagrass restoration 
management requires valuable information on the effectiveness of past restoration actions. At 
this aim, evidence regarding restoration actions of the slow-growing seagrass 
Posidonia oceanica, endemic to the Mediterranean Sea, have been here collated. Combined 
information from a literature systematic review and specific questionnaire 
consulting seagrass ecology experts were synthesized, providing evidence on any human 
mediated active restoration, transplanting or rehabilitation outcomes on P. oceanica. Results 
identified the geographical distribution of P. oceanica interventions across countries, as well as 
the key relationship between environmental variables (such as depth and type of substrate), 
different techniques and plant portions used on transplanting trials and the final outcome of the 
restoration action (success vs failure). The current study identified an overall poor consistency of 
the available information on P. oceanica restoration, probably due to the wide portfolio of 
practices and methodologies used in different conditions. It may support the urgent need of 
testing different anchoring techniques, type of substrates and transplanted plant materials in field 
crossed experiments and in various environmental contexts to fill the identified gaps. Overall, the 
current situation clamours for an international effort from scientists and stakeholders to jointly 
design the strategy forward in identifying the best practices that lead to efficient restorations 
of P. oceanica habitat and functioning. 
 
 
Assessing the role of seagrasses as a socio-ecological system: A case study from Cape Verde 
(Gamboa Bay) 
 

S. Soumah, University Technical of Atlantic, Institute of Engineering and Marine Sciences 
 

The marine ecosystems are extremely productive and valuable, with importance for the health of 
marine and terrestrial environments. However, climate change and intensive exploitation of 
natural resources have significant impacts on ocean ecosystems, including seagrasses. Globally, 
important areas of seagrass have been lost, with no certainty for recovery. In West Africa, their 
knowledge is still rudimentary, and their presence is confirmed in only seven countries. In Cape 
Verde, seagrass was reported in 2016 at Gamboa bay, the only documented site of 
a seagrass meadow. However, the site is exposed to human activities, with no study exploring the 
impacts on seagrass health and status. This study aims to assess and compare the present to the 
previous state of seagrass meadows in Gamboa and evaluate fishers’ perception of seagrass. 
Field assessments and questionnaires were used. The results show that parameters such as total 
cover, biomass, rhizome, and canopy height of Halodule wrightii species identified have 
increased, while the shoot density has decreased. The actual shoot density is 5-fold less than that 
reported in 2016, and the total biomass is 1-fold more than that reported in 2016. The 10 patches 
of 20 m2 recorded then have extended to 6243 m2. Fishers understand the importance of the sea 
and are conscious about its cleanliness, but not fully aware of seagrasses, their ecosystem 
services, and not sure about protection. To further enhance conservation and management 
of seagrasses, socio-economic adjustment is required to provide guidance and information that 
can positively impact conservation and management activities. 



 
 
Sexual Reproductive Ecology of Thalassia testudinum in Tampa Bay, Florida 
 

Sheila Scolaro, Tampa Bay Estuary Program 
 

Successful sexual reproduction and recolonization are critical in maintaining genetic diversity 
within seagrass meadows. Thalassia testudium flower, fruit, and seedling production were 
monitored visually at 10 sites in Tampa Bay, Florida approximately every 4 weeks from May to 
July 2017 to determine if there is spatial and temporal variation in sexual reproductive effort and 
success. Results from this study revealed strong temporal variability throughout the reproductive 
season. Additionally, results suggest that site location, water quality, seagrass density and 
localized reproductive variability affect sexual reproductive effort and success. Only 7 seedlings 
were observed throughout the monitoring period suggesting that asexual reproduction is the 
dominant form of meadow growth and expansion in Tampa Bay, Florida. 
 
 
Posters: 
 
Study of Sea grass beds in Sangomar AMP and Saloum Delta National Park: ecology, 
diversity and role for marine turtles 
 

G.D. Diouf, University Institute of Fisheries and Aquaculture IUPA 
 

Underwater plants or angiosperms are of terrestrial origin adapted to marine environments. They 
are distributed in all seas except Antarctica and the western African fringe remains the least 
known part. Their growth and distribution depend on physical, chemical, and biological 
environmental factors (light, nutrients, substrate, temperature, and nutrients). 
The main objective of this work is to study seagrass ecology 
in Sangomar MPA and Diombos estuary through surveys, data collection and sampling. Results 
show the presence of Cymodocea nodosa and Halodule wrightii constituting a 
mixed subtidal seagrass bed in Sangomar MPA with sparse to medium coverage. 
In Diombos estuary, these two are associated with Zostera noltii on a dense intertidal bed. Their 
associated fauna is diverse and composed of crustaceans (shrimps), mollusks, gastropods 
(cuttlefish) and fish (Mugilidae, Clupeidae). These sea grasses also prevent erosion by fixing 
sediments as observed in a part of Sangomar MPA. Their leaves provide habitat 
for epibionts (micro-organisms, algae and epiphytic sponges). 
 

Local natural and anthropogenic factors limiting their distribution are more apparent 
in Sangomar MPA such as: sandbank siltation, micro-cyclone and seasonal swell, turbid water 
with strong hydrodynamics and presence of algae, motorized pirogues anchoring, pollution, 
dredging by trawling gear. These threats lead to a progressive decline of seagrass meadows, 
disappearance of both associated biodiversity and its goods and services provided. However, the 
lack of knowledge of this habitat by the young active inhabitants constitutes the first source of 
threat. 
 
 
An examination of cold tolerance in Halodule wrightii: Is there a latitudinal gradient from 
Florida to North Carolina, USA? 

 



Lindsey Stevenson, University of North Carolina Wilmington; Bradley Furman, Florida Fish and 
Wildlife Conservation Commission; Kelly Darnell, University of Southern Mississippi; Jessie 
Jarvis, University of North Carolina Wilmington 
 

North Carolina is located in a unique biogeographic transition zone where climate change is 
altering the relative abundance of temperate (Zostera marina) and tropical 
(Halodule wrightii) seagrass species. North Carolina seagrass meadows change seasonally, 
where Z. marina dominates during the colder winter to early summer and H. wrightii dominates 
during the warmer late summer to early fall. Currently, warmer water temperatures are driving 
the loss in Z. marina biomass, which may competitively advantage the heat-
tolerant H. wrightii for longer periods throughout the year. However, H. wrightii becomes 
thermally stressed during colder periods where Z. marina dominates, and little is known 
about H. wrightii cold tolerance. Previous studies suggest that H. wrightii cold tolerance may 
vary across regions. Based on these findings, this study aimed to investigate H. wrightii cold 
tolerance across a latitudinal gradient from Florida to North Carolina. The effects of cold stress 
on H. wrightii were quantified during a 3-week laboratory experiment. Shoots were collected and 
planted from North Carolina, Florida Bay, and the Northern Gulf of Mexico. H. wrightii shoots 
from each location were exposed to optimal (20-23oC), stressful (10oC), and extreme (5oC) 
temperatures. The resilience of H. wrightii to cold temperatures was quantified structurally 
(shoot height, number of leaves, mortality) and physiologically (pulse-amplitude modulation-
fluorometry, C:N ratios). This study helps to fill the knowledge gaps on H. wrightii cold 
tolerance and provide a better understanding of how H. wrightii may persist at the leading edge 
of its geographic distribution. 
 
 
Marine coastal restoration: an animal eye’s view 
 

Michael Sievers; Elisa Bayraktarov; Christopher Brown; Christina Buelow; Ellen Ditria; 
Kimberly Finlayson; Rob Hale; Michaela Kitchingman; Andria Ostrowski; Ryan Pearson; 
Megan Saunders; Brian Silliman; Stephen Swearer; Mischa Turschwell; Rod Connolly 
 

Ecosystem restoration is a key challenge of the 21st century. Coastal restoration efforts are 
accelerating, and billions of dollars are already being invested globally in restoration each year. 
Yet, despite some notable exceptions and promising novel techniques, restoration outcomes are 
highly variable in terms of ‘success’. Seagrass restoration initiatives could be suffering in part to 
animals being overlooked in restoration planning, efforts, and evaluations of success. Significant 
effort and investment in restoration are currently being directed towards seagrass plants, but 
greater integration of animals in restoration approaches will likely enhance success. To 
encourage scientists, managers, practitioners, and funding bodies to better incorporate animals 
into coastal restoration planning, action and monitoring, we outline key animal interactions and 
functions that are important for influencing restoration outcomes, and highlight ideas and 
strategies to better account for animals. 
 
 
Changes in sediment carbon stock following seagrass restoration in Shark Bay, Western 
Australia 
 

Yusmiana P. Rahayu, School of Biological Sciences, the University of Western Australia, 
Marine Research Centre, Ministry of Marine Affairs and Fisheries Republic of Indonesia; 



Gary A. Kendrick, School of Biological Sciences, the University of Western Australia; Mathew 
A. Vanderklift, CSIRO Oceans and Atmosphere; Matthew W. Fraser, the University of Western 
Australia 
 

Seagrass restoration can contribute substantially to climate change mitigation efforts by 
enhancing carbon sequestration capacity. However, there have been few empirical investigations 
into changes in sediment organic carbon stock following seagrass restoration. This study aims to 
compare patterns of sediment organic carbon stock in early ages 
of seagrassPosidonia australis restoration (6 month, 2 year, 2.5 year and 5 year) to 
adjacent unvegetated sand and continuously vegetated seagrass in Shark Bay, Western Australia. 
Our study shows that seagrass restoration in Shark Bay experiences a lag period in accumulating 
carbon in the sediment. Furthermore, carbon stock in restored seagrass sediment in the study 
sites indicate that carbon storage in early ages of restoration (up to 5 years) is still not showing 
differences from that of unvegetated areas. We highlighted the importance of designing location 
for seagrass restoration, adequate restoration project duration and long-term monitoring to 
justify seagrass restoration better success/failure. This study contributes to the growing body of 
literature on seagrass restoration and blue carbon by adding information on sedimentary carbon 
stocks in the early ages of restoration. 
 
 
Session 2A: Trajectories of recovery after degradation in seagrass ecosystem structure, 
function and services 

Session Convener(s): Jessie Jarvis, University of North Carolina Wilmington 
 
Seagrass ecosystems are inherently dynamic and respond to disturbance across a range of scales. 
Globally many seagrass ecosystems have been lost or declined but in the last decade the rate of 
decline has reduced and, in some places, there has been successful recovery of seagrass 
ecosystems, at times facilitated by restoration. Recovery is a concept with varied definitions and 
trajectories of recovery can differ depending on the nature of the pressure and the system. This 
session invites participants to share research and monitoring on the recovery of seagrass 
ecosystems, particularly on the trajectories of recovery and how the structure, function and 
ecosystem services of seagrass ecosystems change following degradation and during recovery. 
As restoration can also be used to initiate recovery or supplement natural recovery processes this 
is also of interest. We welcome presentations on recovery at the level of seagrass structure (e.g. 
area, biomass, cover), function (e.g. productivity, nutrient uptake) or ecosystem service (e.g. 
carbon storage, provision of fisheries). This could include submissions on definitions of 
recovery, metrics to measure recovery, timescales of recovery and factors that influence 
recovery. We want to uncover the latest news from practitioners, managers and researchers on 
seagrass recovery. 
 
 
Talks: 
 
Widgeongrass: The seagrass of the future in a warming Chesapeake Bay 
 

Christopher J. Patrick, Virginia Institute of Marine Science; Marc Hensel, Virginia Institute of 
Marine Science; David Wilcox, Virginia Institute of Marine Science 
 



Climate change and local stressors are not only causing loss of foundation habitats worldwide, 
these drivers are also causing changes to the identity of species forming foundation habitats. 
Changes to species identity can fundamentally change ecosystem dynamics, posing a unique 
managerial challenge. In the Chesapeake Bay, summer temperature extremes have caused 
widespread loss of the dominant foundation species eelgrass (Zostera marina). Using 36 years of 
data on SAV coverage and environmental drivers, we reveal that much of the previously 
eelgrass-dominated Bay is now occupied by a temperature-tolerant foundation species, 
widgeongrass (Ruppia maritima). The shift from a species with a resistant (eelgrass) to a more 
resilient life history (widgeongrass) has changed temporal dynamics of Chesapeake Bay SAV 
(submersed aquatic vegetation), driving both the much-lauded recent recovery and subsequent 
crash, the largest in the last 40 years, in total SAV across the Bay. While widgeongrass is heat 
tolerant, it is more sensitive than eelgrass to declines in water quality during the spring when 
new shoots are too short to exhibit ecosystem engineering capabilities. For the Chesapeake Bay, 
this indicates that nutrient management efforts to reduce inter-annual variation in water quality 
have greater importance than ever before. Worldwide, this case study suggests that climate 
change may select, at least initially, for opportunistic foundation species present in the system 
that grow and reproduce quickly (e.g. resilient), but lack resistance to punctuated disturbances 
that are typical of system dynamics. Given the many functions provided by foundation habitats, 
shifts toward instability may have far reaching consequences. 
 
 
Return of multiple ecosystem services after eelgrass (Zostera marina) transplantations in 
Danish estuaries 
 

Rune C. Steinfurth, Department of Biology University of Southern Denmark; Troels Lange, 
Department of Biology University of Southern Denmark; Timi L. Banke, Department of Biology 
University of Southern Denmark; Paula Canal-Verges, Department of Biology University of 
Southern Denmark; Mikkel Keller Lees, Department of Biology University of Southern 
Denmark; Niels Svane, Department of Biology University of Southern Denmark; Mogens R. 
Flindt, Department of Biology University of Southern Denmark 
 

Eelgrass (Zostera marina) habitats have declined massively during the last century in Denmark 
because of anthropogenic disturbances, primarily eutrophication. Several important ecosystem 
services (ES) have disappeared along with it, contributing to a further deterioration of ecosystem 
functions. The United Nations has called for ecosystem restoration to be the primary strategy to 
counteract loss of important ecosystems. In Denmark, seagrass restoration has been implemented 
in the national water action plans, as a marine measure to negate the effects of land-based run-
off. Researchers at the University of Southern Denmark have had the responsibility to develop 
this marine measure and to monitor the associated improvement of ES. Three large-scale (>5.000 
shoots) eelgrass transplantations have been successful in Danish estuaries. The restored beds 
have developed shoot densities equivalent to natural eelgrass meadows. This presentation 
highlights the return of multiple associated ES such as blue carbon, nutrient sequestration and 
improvements in biodiversity. 
 
 
Predicted warming intensifies the negative effects of eutrophication on tropical 
 

Pedro Beca-Carretero, Department of Oceanography, Institute of Marine Research (IIM-CSIC), 
Vigo, Spain; The Dead Sea-Arava Science Center, Tamar Regional Council, Neve Zohar 86910, 
Israel; Department of Theoretical Ecology and Modelling, Leibniz Centre for Tropical Marine 



Research, Bremen, Germany; Tomás Azcárate-García, The Dead Sea-Arava Science Center, 
Tamar Regional Council, Neve Zohar 86910, Israel; Institute of Marine Sciences (ICM-CSIC), 
Passeig Marítim de la Barceloneta 37-49, Barcelona 08003, Catalonia, Spain; Mirta Teichberg, 
Leibniz Centre for Tropical Marine Research (ZMT) GmbH, Bremen, Germany; The 
Ecosystems Center, Marine Biological Laboratory, Starr 7 MBL Street   Woods Hole, MA 
02543, United States of America; Priyanka Patra, The Dead Sea-Arava Science Center, Tamar 
Regional Council, Neve Zohar 86910, Israel; Farhan Feroze, The Dead Sea-Arava Science 
Center, Tamar Regional Council, Neve Zohar 86910, Israel; Maria J. González, Department of 
Oceanography, Institute of Marine Research (IIM-CSIC), Vigo, Spain; Isabel Medina, 
Department of Oceanography, Institute of Marine Research (IIM-CSIC), Vigo, Spain; Gidon 
Winters, The Dead Sea-Arava Science Center, Tamar Regional Council, Neve Zohar 86910, 
Israel 
 

Famous for its coral reefs, the Gulf of Aqaba (the northern Red Sea) also supports extensive 
seagrass meadows, dominated by Halophila stipulacea. Nutrient loading and warming are 
considered the biggest threats to seagrass meadows, and their combination can potentially 
amplify their negative effects. We exposed two seagrass populations with different 
eutrophication "history" to control (27oC) and simulated warming (31oC), with and without 
nutrients (20 µg DIN). Results showed that exposure to only thermal stress actually favored 
growth, while exposure to only eutrophication reduced Fv/Fm and elongation but favored algal 
proliferation. Combined effects negatively enhanced seagrass performance with the highest 
mortality rates observed after four weeks of combined exposure. Negative effects of combined 
stressors were stronger in the population with low eutrophication "history". Lipidomic analyses 
showed stress significantly decreased ratios of the fatty acids 16:3n-3/16:2n-6 and 18:3n-
3/18:2n-6 with bigger declines in these ratios following exposure to the interaction of both 
stressors. These results have important ecological and management implications to the seagrass 
meadows in the GoA and elsewhere. Recent studies showed that the GoA’s water is actually 
warming faster than the average of the world’s coastal warming trends. While it might be 
difficult to directly control the effects of ocean warming, sources of eutrophication are usually on 
local scales, due to anthropogenic activity such as coastal development and terrestrial runoffs 
from local agricultural fields. For seagrasses to survive climate change, managers must put 
efforts into limiting other stressors such as eutrophication that would reduce the resilience of 
meadows to future changes. 
 
 
Spatial and Temporal Distribution of Intertidal Seagrass Meadows at Banc d’Arguin 
 

Mohamed Ahmed Sidi Cheikh, Caisse dépots et developpement; ME. Hacen, University of 
Groningen; OY. Lemhaba, Parc National of Banc d'Arguin; S. Bandeira, University of Moputo; 
M. Poutouroglou, WRI 
 

Since the beginning of the 20s, seagrass beds have undergone considerable human anthropogenic 
pressure, which is at the origin of their strong regression in several sites around the world. This 
degradation has caused a major disturbance in biodiversity due to the loss of ecosystem services 
provided by these habitats. However, in the West Africa region, scarce knowledge is available on 
the spatial and temporal variation as well as on the conservation status of seagrass meadows. 
This study aims to investigate the current trend of the dynamics of seagrass beds in the Banc 
d'Arguin National Park. This world heritage site shelters the largest area of seagrass beds in West 
Africa, and constitutes the most important East Atlantic Flyway for seabird migration. The 
combined analysis of remote sensing imagery coupled with field surveys allowed the mapping of 



the abundance and spatiotemporal distribution of the Zostera noltei species. The results showed 
an increase of the seagrass coverage since the 1990s. To explain the variability observed, several 
abiotic factors were tested on three topographic levels of the mudflat complex. The most marked 
variations in the seagrass beds seem to be explained by specific conditions related to climate 
drivers such as dust loading. Beyond the causes of inter annual variation, the intertidal seagrass 
of the Gulf of Arguin showed a rapid natural regeneration. This work demonstrates also a strong 
sensitivity of the ecosystem to climate change impacts and supports the hypothesis that the 
protection status of this park promotes resilience to stressors of natural origin. 
 
 
Envisioning the future for seagrass ecosystems under climate change: critical role of 
nutrient management for a vegetated Chesapeake Bay 
 

Marc J. S. Hensel, Virginia Institute of Marine Science; Christopher J. Patrick, Virginia Institute 
of Marine Science; Jonathan S. Lefcheck, Tennenbaum Marine Observatories Network; David J. 
Wilcox, Virginia Institute of Marine Science 
 

Climate change puts undue pressure on coastal seagrasses because novel environmental 
conditions threaten foundation species that support fisheries and coastal protection. Habitat 
management usually operates off of past knowledge but evidence suggests that future ecosystem 
change is uncharted by historical observations. Thus, predicting a future that is outside of the 
realm of the past is a critical challenge in creating a sustainable relationship between humans and 
nature. Here, we explore future scenarios with a novel predictive modelling technique to project 
how climate change (i.e., temperature and rainfall) and human activities (i.e., nutrient 
management) will affect the four major seagrass communities of the Chesapeake Bay over the 
next 40 years. While we find that temperature extremes will exacerbate shifts in dominant 
foundation species identity, we identify a crucial role for expanded nutrient reductions to 
mitigate the risks of future human activities to bay grasses. Increased nutrient management 
generates the only future with any temporal stability for all seagrass communities, and supports 
large-scale expansion of climate-tolerant plants in the mid- and upper-bay to fuel total 
Chesapeake vegetated area. Ecological predictions allow us to identify options for better 
managing our relationship with ecosystems, and seagrasses should be at the forefront of 
predictive ecology and foresight-driven management of a changing coastal seascape. Because 
adaptations, acclimation, and recovery potential across temperate and tropical seas elevate 
seagrass foundation species as a potential winner in the Anthropocene, predicting the future for 
seagrass ecosystems is the path forward to create a sustainable relationship between humanity 
and nature. 
 
 
Monitoring reveals similar recovery progress among sediment-tube-based propeller scar 
restoration approaches 
 

Savanna Barry, University of Florida; Nature Coast Biological Station, Cedar Key, FL; Shelby 
Thomas, University of Florida, School of Forest, Fisheries, and Geomatics Sciences, Apollo 
Beach, FL; Conor MacDonnell, University of Florida, Florida Sea Grant, Gainesville, FL; 
Brittany Scharf, University of Florida, School of Forest, Fisheries, and Geomatics Sciences, 
Ruskin, FL; Josh Patterson, University of Florida, School of Forest, Fisheries, and Geomatics 
Sciences, Apollo Beach, FL 
 

Propeller scaring is a growing problem in Florida’s coastal waters, especially high traffic, 
shallow areas. In 2018, propeller scars within a seagrass bank near Crystal River, FL were 



restored using the sediment tube approach. Different restoration treatments (tubes alone, tubes + 
planting, tubes + planting + cage, and unrestored control) were applied to a subset of scars. 
These scars (n = 4 for treatments, n = 2 for control) underwent quarterly monitoring for two 
years where percent total seagrass cover, percent cover by species, and blade lengths were 
measured in five randomized 0.25 m2 quadrats per scar and two quadrats from undisturbed 
seagrass adjacent to each scar. After 2 years, total seagrass cover in treatment scars ranged from 
a mean ± SEM of 38.6 ± 4.6% (tubes alone) to 44.7 ± 6.8% (tubes + planting + cage) while 
untreated control scars had only 0.3 ± 0.1% cover. Adjacent, undisturbed seagrass cover ranged 
from 73.8 ± 10.8% (tubes alone) to 83.8 ± 8.2% (tubes + planting + cage) for treatments and 97.5 
± 2.5% for unrestored control. At two years post-restoration, scars that received tubes, regardless 
of planting or caging, reached total seagrass % cover that was slightly more than 50% of adjacent 
seagrass cover values while unrestored scars showed no signs of recovery. This suggests 
investment in plantings or cages provide no additional benefit in this system and tubes alone are 
sufficient to achieve restoration goals. Ongoing investigation into species composition and 
temporal dynamics may yield a more nuanced understanding. 
 
 
Hurricanes and Humans: Conflicts in seagrass restoration and mitigation efforts 
 

Paul A. X. Bologna, Montclair State University; Robert Fiorile, Matrix New World Engineering 
 

Natural and anthropogenic disturbances reset the clock in seagrass recovery and restoration. 
Over the last 20 years we have been conducting both restoration and mitigation for seagrass 
losses to enhance ecosystem services. In several locations we have demonstrated long-term 
success (>10 years), including survival post Super Storm Sandy in 2012, only to find these sites 
devastated by human activities like aquaculture and shoreline stabilization. While both of these 
activities provide economic and ecological benefits, it presents a dilemma in sighting new areas 
for restoration. While modeling efforts demonstrate the potential to identify high priority regions 
for restoration activities, multiple competing groups may also be designating these regions for 
their activities. In New Jersey, the eelgrass (Zostera marina) distribution is relegated to shallow 
water due to reduced water clarity and restricted to one remaining coastal lagoon. These shallow 
regions are also favored by aquaculture for access during low tide, as well as near shore in 
regions dealing with erosion and sea level rise looking for options to stabilize shorelines. We 
present the success and challenges for restoration efforts in the context of these user conflicts and 
potential management solutions. 
 
 
Degradation and recovery of seagrass carbon stocks under thermal stress: a large seagrass 
disturbance field experiment  
 

Carolyn J. Ewers Lewis, University of Virginia; S. Tassone, Department of Environmental 
Sciences, University of Virginia and Virginia; Coast Reserve Long-Term Ecological Research 
Program; M. Pace, Department of Environmental Sciences, University of Virginia and Virginia 
Coast; Reserve Long-Term Ecological Research Program; Karen McGlathery, Department of 
Environmental Sciences, University of Virginia and Virginia Coast Reserve Long-Term 
Ecological Research Program 
 

Seagrass ecosystems have suffered substantial global losses over the last century, but success 
stories of large-scale restorations and natural recovery offer signs of hope. Still, the impact of 
the accelerating stressors of climate change on the resilience and recovery of seagrasses and 
the ecosystem services they provide are poorly understood. In the Virginia Coast Reserve 



Long-Term Ecological Research site, a large-scale restored seagrass site was hit by a marine 
heatwave in 2015 that resulted in a massive die-off and loss of sediment carbon stocks. 
However, the meadow was not impacted uniformly, and it is believed that differences in 
water temperatures and residence times played a key role in the degree of impact of the 
heatwave and recovery thereafter. We set up the largest in situ seagrass disturbance 
experiment to date in two areas of the meadow that experience differing degrees of thermal 
stress to 1) measure the impact of seagrass loss, as would be experienced during a heatwave, 
on sediment carbon stocks, and 2) characterize the recovery trajectory of carbon stocks and 
sequestration rates in disturbed sites. Using a novel in situ sediment plate method, we tracked 
changes in surface elevation to quantify changes in sediment accumulation, carbon stocks, 
and sequestration rates, as well as organic matter and grain size. This study will help elucidate 
the role of thermal stress in seagrass carbon stock preservation during disturbance and 
recovery trajectories concurrent with seagrass recolonization. 
 
A process-based modelling approach to assessing soil carbon assimilation and 
sequestration in eelgrass meadows 
 

Siti Maryam Yaakub, DHI Water & Environment; Danielle Su, Kadri Kuusemae; Dayna Hui, 
Rikke Margrethe Closter; Erik Kock Rasmussen; Anders Chr. Erichsen; Jessica Hinojosa 
 

Seagrass meadows are effective carbon sinks, but the rate of carbon assimilation and 
sequestration varies greatly. Manual assessments of carbon accumulation are both laborious and 
time-consuming. Here we explore the use of process-based dynamic models evaluating carbon 
accumulation over time in eelgrass meadows. We conducted a pilot study modelling rates of 
carbon sequestration in two eelgrass (Zostera marina) meadows – one in the Chesapeake Bay and 
a second meadow in the costal inlets of South Bay using a previously established eelgrass model 
for Danish estuaries created using the MIKE ECO Lab module in MIKE Software. We modelled 
two scenarios at each site; with eelgrass present and without eelgrass present to compare 
accumulation rates in soil organic carbon. Results of the model runs in Chesapeake Bay showed 
good calibration with monitoring data of key water quality parameters collected from stations 
within Chesapeake Bay. Accumulated carbon content (g C/m2) in eelgrass meadows was 
approximately two times that of areas without eelgrass in Chesapeake Bay, whereas it was more 
than twice in the coastal inlets of South Bay. This pilot study demonstrates the portability and 
scalability of process-based models and paves the way for using biogeochemical models as a 
faster and cost-effective approach to understanding carbon accumulation rates in eelgrass 
meadows. This is an important component that contributes towards understanding and managing 
eelgrass meadows and their capacity to act as effective carbon pools. 
 
 
Halodule uninervis above- and belowground lipids in varying environmental conditions in 
Tambac Bay, Philippines 
 

Caroline Marie B Jaraula, University of the Philippines, Marine Science Institute; William P 
Dimalanta, University of the Philippines, Marine Science Institute; Maria Anna Michaela R. De 
La Cruz, University of the Philippines, Marine Science Institute; Rene N Rollon, University of 
the Philippines, Institute of Environmental Science and Meteorology 
 

Lipids of the cell membrane is the first line of defense of a cell and have expressed chemical 
qualities for adaptation to environmental factors. Above- and belowground lipid profile of 
Halodule uninervis, a common and widely distributed seagrass in the Indo-Pacific, is studied. 
The tropical Indo-Pacific consist of the largest and most diverse bioregion in seagrass species. 



Samples were collected from contrasting areas of sedimentation, dissolved oxygen content and 
open water conditions along a discharge pathway from Tambac Bay to Lingayen Gulf in 
Bolinao, Philippines. Halodule uninervis was present in all sites, even monospecific in the most 
turbid, anoxic, hottest (34.4°C) and saline (34.5 PSU) site. As with seagrass lipids in the 
temperate areas, C16 and C18 fatty acids predominate, comprising 92% to 99% of the total fatty 
acids. We verified this in the above- or belowground components. The tri-unsaturated moiety, 
C18:3, linked to photosynthetic activity, is consistently higher in aboveground components than 
in their belowground counterparts. Moreover, C18:3 systematically varies with seagrass density. 
Aboveground component of H. uninervis has a carbon range C21 to C25, whereas below 
component has longer chain components, C21 to C29. Odd-numbered carbon predominance in the 
anoxic area reflects better preservation of seagrass lipids, whereas branched hydrocarbons in 
more open conditions indicate prevalence of oxidative biodegradation. 
 
 
Posters: 
 
How local environment and neighboring habitat influence seagrass stability – a 13 year 
case study 
 

Alyson Hall, Virginia Institute of Marine Science; Enie Hensel, Virginia Institute of Marine 
Science; Michael Hannam, National Park Service; Donald Weller, Smithsonian Environmental 
Research Center; Dave Wilcox, Virginia Institute of Marine Science; Christopher J. Patrick, 
Virginia Institute of Marine Science 
 

Seagrasses create biogenic habitats that are threatened worldwide due to climate change and 
human activities. Seagrass meadows are stabilized through positive feedback loops that include 
interactions between the meadow and the abiotic environment, other organisms, and itself. 
Importantly, these feedback loops can improve local water quality, buffering local stressors, and 
thus prevent future die-off through patch persistence and recolonization within the meadow. 
However, few studies have quantified this to date. Here, we leveraged interannual, spatially 
explicit seagrass and water monitoring data from the St. Mary’s River in the Chesapeake Bay 
and quantified how neighboring seagrass density (e.g., percent cover and patch proximity) and 
environmental conditions interact to affect local-scale stability of Ruppia maritima. Examining 
10 m2 patches, local seagrass stability (i.e., presence) was defined as either not present, newly 
colonized, or persistent. Using a Bayesian hierarchal occupancy model, we found that the 
probability of seagrass colonization and persistence was positively related to neighboring density 
but responded to different environmental conditions. Specifically, colonization was positively 
related to salinity and negatively related to water depth and =total suspended solids, while patch 
persistence was only negatively related to depth. Our work quantifies how intraspecific 
facilitation can influence stability ranging from dense to sparse seagrass patches, and how high 
density can buffer whole meadow loss under declining environmental conditions. Our findings 
provide a framework for considering patch configuration for effective conservation and 
restoration plans and how thoughtful density goals may improve resilience to degradation. 
 
 
Where does the plastic go? Microplastic loading in seagrass 
 

Angela Capper, CQUniversity; K.L. Jones, Heriot-Watt University; M.G.H. Hartl, Heriot-Watt 
University; M.C. Bell, Heriot-Watt University; A. Irving, CQUniversity; A. Anastasi, 
CQUniversity 
 



Plastic pollution from anthropogenic activities on land and sea is a ubiquitous global issue. Much 
less conspicuous is the extent of microplastics (<5 mm) contamination. Microplastic fibres, 
fragments and particles, which sorb multiple contaminants, are now found in every aquatic 
ecosystem, including seagrass habitats. These highly dynamic habitats reduce water velocity, 
increasing the settling of small particles. In a recent study in Orkney, Scotland, we found 
microplastics adhered to biofilms on Zostera marina blades, with likely trophic transfer to 
important seagrass grazers. Microplastic loading was also significantly higher in Z. marina 
sediments than bare adjacent sediments and sediment grain size may be linked to trapping 
capability. Seagrass may actually play a beneficial role in trapping microplastics and reducing 
flux to offshore habitats. An ideal location to investigate this potential buffering role is 
Gladstone, central Queensland, Australia, where seagrass (predominantly Z. muelleri) are often 
referred to as the 'kidneys of the Great Barrier Reef'. The results of this research will be 
discussed: (1) microplastic loading of seagrass beds in relation to urban and industrial proximity; 
(2) microplastic trapping capabilities as a function of sediment grain size; and (3) the potential 
impacts of trapping and adherence on seagrass productivity in leaves and root systems. This 
research will provide vital information on the impacts of microplastic contamination in seagrass 
ecosystems. 
 
 
Restoring eelgrass meadows following invasion of the European green crab in Placentia 
Bay, Newfoundland, Canada 
 

Elanor Dillabough, Marine Institute of Memorial University of Newfoundland; A. Le Bris, 
Marine Institute of Memorial University of Newfoundland; T Prystay, Marine Institute of 
Memorial University of Newfoundland; C Brennan, Marine Institute of Memorial University of 
Newfoundland; G Adams, Marine Institute of Memorial University of Newfoundland; M Clarke, 
Marine Institute of Memorial University of Newfoundland 
 

Following the invasion of the European green crab in 2007 in Placentia Bay, Newfoundland, the 
percent cover of eelgrass decreased by 50% to 100% at several sites. This decrease was 
accompanied by a 10-fold decline in fish abundance and biomass. In 2017, as part of Canada’s 
Ocean Protection Plan, restoration for eelgrass was initiated in Placentia Bay. The first objective 
was to reduce local density of green crab through a mitigation fishery, as the main stressor for 
eelgrass. Between 2017 and 2021, around 375 metric tons of green crab were removed from 
Placentia Bay. Preliminary analyses suggest that, while catch rates are still high, average size of 
green crab has significantly decreased. The second objective was to facilitate the recovery of 
seagrass extent at five sites using a combination of restoration techniques, including sod 
transplants and seed bag deployments. Recovery of seagrass meadows extent was apparent at 
two sites 2 to 3 years after the start of restoration activities. Restoration was less successful at 
two other sites and ineffective at one site. Green crab catches rates did not explain restoration 
success rates. Proximity of remaining eelgrass and sediment types seemed to better explain 
restoration success rates. Future monitoring will help better understand the factors influencing 
recovery and help evaluate if eelgrass restoration benefited local fish diversity, density and 
biomass. 
 
 
Intertidal seagrass restoration in the UK -Pilot study assessing the potential for re-
establishment of ecosystem services 
 

Emma A. Ward; Bronwen Paxton; Hannah Stead; Tim Ferrero; Ian Hendy; Joanne Preston 



 
Seagrass habitat provides a wealth of ecosystem services including increased biodiversity, 
carbon sequestration and nutrient filtration, yet is suffering major declines globally. In the UK 
historic loss of seagrass (44-92%) highlights the scope for restoration to restore associated 
ecosystem services. This pilot study focused on restoration of intertidal Zostera noltei off the 
South Coast of England. Restoration happened in three stages, spathe collection, seed 
preparation and seed deployment. Z. noltei spathes were collected on foot from seagrass beds 
adjacent to the restoration sites. Over 21,000 seeds were extracted after a 3-month rotting process 
and seed separation. Seeds with mixed sediment were placed in hessian pouches at densities of 
15 seeds bag-1 and 30 seeds bag-1 . Seed pouches were deployed on foot at 60cm intervals across 
two restoration sites of low (43 seeds m-2 , 15 seeds bag-1 ) and high density (82.5 seeds m-2 , 30 
seeds bag-1 ) in December 2021. Effectiveness of restoration trials to increase ES provision will 
be assessed with a Before-after-control-impact (BACI) design. Seasonal monitoring of the 
restoration sites and three reference seagrass meadows will be conducted for: seagrass metrics 
(abundance, shoot density, blades shoot-1 , blade length and width), habitat biodiversity (infauna 
and epifauna) and carbon storage (sedimentary standing stock, plant productivity and algal mat 
biomass). This will assess the potential for seagrass restoration activities and the synergistic 
reestablishment of ecosystem services, in temperate intertidal seagrass habitat. Quantification of 
a broad range of ecosystem services will support the upscale of seagrass restoration and 
commercialisation through stacked ecosystem finance accreditation. 
 
 
 
A trajectory of Zostera marina ecosystem recovery, pre- and post-Hurricane Sandy 
degradation in Barnegat Bay, New Jersey 
 

James J. Campanella, Montclair State University, Dept. of Biology; Paul A.X. Bologna, 
Montclair State University, Dept. of Biology; Abdullah Alhaddad, Montclair State University, 
Dept. of Biology; Adi Ackerman, Montclair State University, Dept. of Biology; Julia Kopell, 
Montclair State University, Dept. of Biology; Edgar Medina, Montclair State University, Dept. 
of Biology; Nicole Rodriguez Ortiz, Montclair State University, Dept. of Biology; Mya 
Theodore , Montclair State University, Dept. of Biology 

In 2010/2012, studies were published examining the population genetic structure of both natural 
and restored Zostera marina in Barnegat Bay, NJ. In late 2012, Hurricane Sandy struck Barnegat 
Bay, scouring the sea bed, ripping up extensive beds of Z. marina, and causing  major benthic 
ecosystem disruptions. The results of those previous studies suggested low heterozygosity, low 
connectivity, and high levels of inbreeding among both natural and  restored populations. After 
such devastation, we became concerned with the fate of these plant populations that were already 
threatened by such serious genetic issues. This present study tracks the trajectory of the Barnegat 
Bay Z. marina ecosystem over a period of 12-13  years before and after the major disturbance of 
the hurricane. In 2021, we collected populations of eelgrass (N=30/population) from grass beds 
throughout the bay (Oyster  Creek, Ham Island, Connective Sedge, Rt.72 South, and Barnegat 
Inlet). Additionally, we obtained frozen stock populations from 2013 and 2017 (Oyster Creek 
2013 & 2017,  Connective Sedge 2017, Ham Island 2017, Barnegat Inlet 2013& 2017) 
(N=30/population).  In combination with the published data from 2010 and 2012, we are 
ascertaining what genetic changes have occurred in these populations in the decade since they 
were decimated.  We will make historical comparisons of heterozygosity, fixation, diversity, 
inbreeding, and differentiation, and investigate evidence for genetic drift and bottlenecking. 



Additionally, we will compare the genetic structure of theses populations using Markov chain 
Monte Carlo  techniques. These studies are performed in the hopes of obtaining more directed 
and successful restoration for these populations.  

 
A post-hurricane Sandy examination of the population genetic “health” and diversity of 
Zostera marina (eelgrass) in Barnegat Bay, New Jersey 
 

James J. Campanella, Montclair State University, Dept. of Biology; Paul A.X. Bologna, 
Montclair State University, Dept. of Biology; Abdullah Alhaddad, Montclair State University, 
Dept. of Biology; Adi Ackerman, Montclair State University, Dept. of Biology; Julia Kopell, 
Montclair State University, Dept. of Biology; Edgar Medina, Montclair State University, Dept. 
of Biology; Nicole Rodriguez Ortiz, Montclair State University, Dept. of Biology; Mya 
Theodore , Montclair State University, Dept. of Biology 
 

Hurricane Sandy struck the New York metropolitan region on October 29, 2012. The storm 
severely impacted the physical state of Barnegat Bay, New Jersey, with its heavy storm surge 
which scoured the sea bottom, affecting many forms of benthic life and ripping up extensive 
beds of Zostera marina. Previous studies of the genetic status of Z. marina in Barnegat Bay 
suggested low levels of heterozygosity and high levels of inbreeding. We are presently 
examining the long-term effects of Hurricane Sandy on the eelgrass beds of New Jersey. 
Preliminary data among all population sites studied (Oyster Creek, Ham Island, Connective 
Sedge, Rt.72 South, and Barnegat Inlet) suggest that present observed levels of heterozygosity 
are low compared to expected levels (mean Ho = 0.499+0.089 and He=0.560+0.060), indicating 
worsening diversity. Overall mean inbreeding levels (Fis = 0.202+0.102) indicate little 
outbreeding within grass beds and the fixation index (mean Fst = 0.175+0.106) suggests low 
connectivity between populations with a “medium” level of differentiation. Phylogenetic 
cladograms generated using Chord and Delta Mu distances coincide with Fixation values and 
indicate differentiation among these populations. This initial analysis suggests that the genetic 
health of grass beds in Barnegat Bay have declined in the last decade. We continue to study these 
Z. marina populations with additional polymorphic alleles. 
 
 
Monitoring reveals similar recovery progress among sediment-tube-based propeller scar 
restoration approaches 
 

Savanna Barry, University of Florida, Nature Coast Biological Station, Cedar Key, FL; Shelby 
Thomas, University of Florida, School of Forest, Fisheries, and Geomatics Sciences, Apollo 
Beach, FL; Conor MacDonnell, University of Florida, Florida Sea Grant, Gainesville, FL 
Brittany Scharf, University of Florida, School of Forest, Fisheries, and Geomatics Sciences, 
Ruskin, FL; Josh Patterson, University of Florida, School of Forest, Fisheries, and Geomatics 
Sciences, Apollo Beach, FL 
 

Propeller scaring is a growing problem in Florida’s coastal waters, especially high traffic, 
shallow areas. In 2018, propeller scars within a seagrass bank near Crystal River, FL were 
restored using the sediment tube approach. Different restoration treatments (tubes alone, tubes + 
planting, tubes + planting + cage, and unrestored control) were applied to a subset of scars. 
These scars (n = 4 for treatments, n = 2 for control) underwent quarterly monitoring for two 
years where percent total seagrass cover, percent cover by species, and blade lengths were 
measured in five randomized 0.25 m2 quadrats per scar and two quadrats from undisturbed 
seagrass adjacent to each scar. After 2 years, total seagrass cover in treatment scars ranged from 



a mean ± SEM of 38.6 ± 4.6% (tubes alone) to 44.7 ± 6.8% (tubes + planting + cage) while 
untreated control scars had only 0.3 ± 0.1% cover. Adjacent, undisturbed seagrass cover ranged 
from 73.8 ± 10.8% (tubes alone) to 83.8 ± 8.2% (tubes + planting + cage) for treatments and 97.5 
± 2.5% for unrestored control. At two years post restoration, scars that received tubes, regardless 
of planting or caging, reached total seagrass % cover that was slightly more than 50% of adjacent 
seagrass cover values while unrestored scars showed no signs of recovery. This suggests 
investment in plantings or cages provide no additional benefit in this system and tubes alone are 
sufficient to achieve restoration goals. Ongoing investigation into species composition and 
temporal dynamics may yield a more nuanced understanding.  
 
 
Piney Point Seagrass and Macroalgae Response Monitoring 
 

Sheila Scolaro, Tampa Bay Estuary Program; Marcus W. Beck, Tampa Bay Estuary Program; 
Maya C. Burke, Tampa Bay Estuary Program; Edward T. Sherwood, Tampa Bay Estuary 
Program; Gary E. Raulerson, Tampa Bay Estuary Program 
 

From March 30 to April 9, 2021, 215 million gallons of nutrient-rich phosphate mining 
wastewater and salt water-mix was discharged into Lower Tampa Bay. An estimated 205 
tons of nitrogen, the estuary’s primary limiting nutrient, was released into Lower Tampa Bay. 
Because excess nitrogen can create unfavorable seagrass growing conditions, both seagrass 
and macroalgae communities were monitored as part of a larger monitoring effort in 
response to the release from Piney Point. Seagrass and macroalgae density and diversity were 
monitored approximately biweekly along 38, 50-meter transects in Lower Tampa Bay from 
April to September 2021, with data visualizations available in an open science format. 
Macroalgae diversity and density varied throughout the monitoring period. Red macroalgae 
(Rhodophyta) was the dominant phyla observed at all transects, except in June when 
filamentous cyanobacteria (Dapis spp.) abundance increased. Large floating and benthic mats 
of cyanobacteria were observed in Anna Maria Sound near the mouth of Tampa Bay and at 
Port Manatee near the release site. Green macroalgae (Chlorophyta) was observed along 
transects beginning in July, but at generally low abundances. Overall diversity and density of 
seagrass remained stable and did not change throughout the monitoring period. Long-term 
impacts of the Piney Point discharge on seagrass and macroalgae communities in Tampa Bay 
is uncertain. Continued monitoring and additional data on the long-term seasonal trends of 
macroalgae and seagrasses is needed to better understand the results of the 2021 response-based 
monitoring. 
 
Large-scale transplantation success of Zostera marina in Danish estuaries through site-
selection and identification of stressor thresholds 
 

Timi L. Banke, Department of Biology University of Southern Denmark; Troels Lange, 
Department of Biology University of Southern Denmark; Rune C. Steinfurth, Department of 
Biology University of Southern Denmark; Paula Canal-Verges, Department of Biology 
University of Southern Denmark; Mikkel Keller Lees, Department of Biology University of 
Southern Denmark; Niels Svane, Department of Biology University of Southern Denmark; 
Mogens R. Flindt, Department of Biology University of Southern Denmark 
 

In Denmark, seagrass habitats have undergone a massive decline and less than 10 - 20 % remains 
today, which is similar to the global decline tendencies of seagrass. This has resulted in a 
growing interest in restoring seagrass habitats and is in Denmark planned to be implemented as a 
marine measure to reach a good ecological status in according to the EU Water Frame Directive 



(WFD). Researchers from the University of Southern Denmark have since 2014 been developing 
and testing technics to successfully restore eelgrass (Zostera marina). Through identification of 
stressor thresholds (e.g. nitrogen loading parameters and destructive bioturbation) and careful 
site-selection three large-scale transplantations (> 5.000 shoots) of Zostera marina have been 
successfully established. These large-scale transplantation efforts have reached shoot densities 
similar to those of natural meadows within app. two years. The transplantations were made in the 
shallow Danish estuaries (one in Horsens Fjord and two in Vejle Fjord) and are one of the few 
examples of a successful large-scale restoration of seagrass in Europe. This presentation 
highlights the site-selection process, the identification of stressor thresholds and the temporal 
development of the successful transplantations. 
 
 
Session 2B: Seagrass wasting disease: understanding host-pathogen interactions to ensure 
success in seagrass conservation & management 

Session Convener(s): Randall Hughes, Northeastern University; Forest Schenck, Northeastern 
University; Torrance Hanley, Northeastern University 
 
The largest reported seagrass die-off was caused by an outbreak of seagrass wasting disease, 
caused by parasitic protists in the genus Labyrinthula, along both sides of the Atlantic in the 
1930’s. In a sign of success, eelgrass has largely recovered across this region, and disease 
outbreaks of similar magnitude have not re-occurred. In addition, we have made great progress in 
our understanding of wasting disease since it was first hypothesized to be behind the declines of 
eelgrass in the 1930s. Key highlights include the identification of Labyrinthula spp. as the 
causative agents of wasting disease, the development of visual and molecular parasite detection 
protocols, and the identification of environmental factors that moderate the seagrass-wasting 
disease interaction. 
 

However, wasting disease is endemic throughout the range of eelgrass, and infections have now 
been observed in all four major seagrass families - Cymodoceaceae, Hydrocharitaceae, 
Posidoniaceae, and Zosteraceae - suggesting that seagrasses remain at risk of future large-scale 
outbreaks. This session will bring together seagrass scientists and managers to share our 
emerging understanding of seagrass-wasting disease interactions, identify remaining areas of 
uncertainty, and discuss strategies for seagrass management and conservation. 
 
 
Talks: 
 
Temperature and host characteristics predict large-scale patterns in wasting disease 
prevalence 
 

Forest Schenck, MA Division of Marine Fisheries; A. Randall Hughes, Northeastern University 
Biogeographic patterns in the prevalence of plant and animal diseases arise from interactions 
between large-scale forcing factors and regional- and local-scale abiotic and biotic processes. 
Recently, global climate change has coincided with shifts in the distribution of many diseases, 
suggesting temperature is a key mediator of disease. Past outbreaks of seagrass "wasting disease" 
have decimated populations of eelgrass, Zostera marina, and small-scale studies have identified 
temperature as well as salinity, nutrients, eelgrass density, and eelgrass leaf length to be 
mediators of wasting disease. However, the relative importance of these risk factors in 
determining large-scale patterns of wasting disease distribution has yet to be explored, and this 



knowledge gap has limited our understanding of wasting disease and its potential response to 
global change. We sampled 20 eelgrass beds among oceans and across >20o of latitude in the 
Northern Hemisphere to document geographic variation in wasting disease prevalence and to 
examine how a suite of abiotic, biotic, and spatial variables contribute to biogeographic gradients 
in disease prevalence. Large-scale seawater temperature and local-scale eelgrass density were the 
strongest predictors of prevalence. The shape of these relationships generally matched 
predictions from small-scale studies. However, contrary to expectations, seawater salinity and 
nutrient content were not as strongly related to biogeographic gradients in wasting disease. These 
results suggest warming seawater temperatures may shift the distribution of wasting disease 
poleward, but they also highlight the important role of local-scale biotic factors in mediating 
disease prevalence in this system. 
 
 
Disease surveillance using artificial intelligence links seagrass wasting disease to ocean 
warming across latitudes 
 

Lillian R Aoki, University of Oregon; Brendan Rappazzo, Cornell University; Deanna Beatty, 
University of California – Davis; Lia K Domke, University of Alaska – Fairbanks; Ginny L 
Eckert, University of Alasksa – Fairbanks; Olivia J Graham, Cornell University; Leah Harper, 
Smithsonian Institution; Timothy L Hawthorne, University of Central Florida; Margot Hessing-
Lewis, Hakai Institute; Kevin Hovel, San Diego State University; Zachary L Monteith, Hakai 
Institute; Ryan Mueller, Oregon State University; Angeleen M Olson, Hakai Institute; Carolyn 
Prentice, Hakai Institute; Carmen Ritter, Smithsonian Institution; John J Stachowicz, University 
of California – Davis; Fiona Tomas, Oregon State University; Bo Yang, San Jose State 
University; J Emmett Duffy, Smithsonian Institution; Carla Gomes, Cornell University; C Drew 
Harvell, Cornell University 
 

Ocean warming endangers coastal ecosystem through increased risk of infectious disease, yet 
detection, surveillance, and forecasting of marine diseases remain limited. Eelgrass (Zostera 
marina) meadows provide essential coastal habitat and are vulnerable to seagrass wasting 
disease, caused by the protist Labyrinthula zosterae. We assessed seagrass wasting disease 
sensitivity to warming temperatures across a 2,500 km study range over three years by 
combining long-term satellite remote sensing of ocean temperatures with field surveys from 32 
meadows along the Pacific coast of North America. From 2019-2021, wasting disease infected 
up to 90% of plants and damaged up to 30% of plant tissue across the study range. In 2019, 
disease prevalence was 3x higher in locations with warm temperature anomalies in early 
summer, suggesting that the risk of seagrass wasting disease will increase with climate warming. 
Over the three-year study period, wasting disease severity increased with temperature anomalies 
in spring, highlighting the importance of local warming in determining meadow disease status. 
Aerial imagery from annual drone surveys captured significant losses of upper intertidal 
meadows at some locations. Resilience of local populations to disease is likely important to 
infection dynamics over time and may interact with temperature effects. Continental-scale 
surveys were made possible by the Eelgrass Lesion Image Segmentation Application, an 
artificial intelligence system that quantifies wasting disease 5000x faster and with comparable 
accuracy to a human expert. This work highlights the value of artificial intelligence in marine 
biological observing, specifically for the detection of widespread climate-driven disease 
outbreaks. 
 
 
Under every stone? Phytomyxid parasites in seagrass meadows 



 

Viktorie Kolátková, University of Victoria; Martin Vohník; Joel Elliott; Ryan Gawryluk 
 

Phytomyxids are a group of obligate intracellular biotrophic protists that have been recognized as 
parasites of seagrasses for over a century. Since our understanding of their prevalence and 
diversity in seagrass meadows has historically been based on incidental findings of galls in 
seagrass shoots, they are generally considered rare in coastal ecosystems and remain overlooked 
and greatly understudied. However, our recent surveys applying systematic screening and 
modern molecular methods show that seagrass-associated phytomyxids are most likely 
ubiquitous and highly diversified microorganisms. In 2017, we began searching for phytomyxid-
induced galls in the petioles of the invasive seagrass Halophila stipulacea and found evidence of 
widespread and well-established infection throughout both native and alien H. stipulacea 
populations, with the prevalence reaching up to 50% of infected shoots in some microsites. 
Subsequent molecular analyses of the 18S rRNA gene of phytomyxids collected from three 
different species of Halophila revealed three host-specific congeneric parasites, indicating that 
phytomyxids have been long-present and co-evolving with their seagrass hosts. Recently, we 
also observed this phenomenon in the eelgrasses Zostera marina and Zostera japonica from the 
Salish Sea (Northeast Pacific), in which primary phytomyxid life stages - root hair galls - were 
reported for the first time in the marine environment. Shockingly, unlike much scarcer shoot 
galls (i.e., the secondary infection), root hair galls were present in >99% of examined eelgrass 
specimens. As the effect of phytomyxids on seagrass health remains poorly understood, we urge 
that further research is necessary to assess their ecological role in these vital ecosystems. 
 

Marine herbivores facilitate transmission of a seagrass pathogen 

Olivia J. Graham, Cornell University; Natalie Nivlin; C. Drew Harvell 

Invertebrate herbivores play key ecological roles in food webs and ecosystem 
dynamics.  Herbivores can positively and negatively influence hosts—by stimulating growth, 
reducing photosynthesis, or vectoring disease. While herbivores commonly vector terrestrial 
plant pathogens, their role in transmitting marine plant pathogens remains unknown. Here, 
we tested three hypotheses to determine if eelgrass (Zostera marina) herbivores 
facilitate transmission of the pathogen Labyrinthula zosterae (Lz), the causative agent of 
seagrass  wasting disease: i) Herbivores can directly vector Lz through mouthparts and feces 
or  indirectly via grazing scars. ii) Some herbivores preferentially feed on diseased over 
healthy eelgrass. iii) Herbivores that consume diseased eelgrass contain Lz. We used three 
eelgrass herbivores, including amphipods (Ampithoe lacertosa), snails (Lacuna spp.), and 
isopods (Pentidotea wosnesenskii) in vector experiments, herbivory choice assays, molecular 
diagnostics  (qPCR), and fecal assays. Herbivores did not directly transmit Lz from diseased to 
healthy eelgrass, but indirectly facilitated disease transmission by increasing disease in eelgrass 
via grazing scars. In choice assays, amphipods selected diseased over healthy eelgrass, 
while snails and isopods selected healthy eelgrass. qPCR analyses confirmed that herbivores 
that consumed diseased eelgrass contained Lz. Finally, Lz was isolated from herbivore feces, 
demonstrating herbivores that eat diseased eelgrass can pass the live pathogen. This is the first 
report of herbivores indirectly facilitating the spread of a marine plant pathogen.  Herbivore-
facilitated pathogen transmission could be more common in marine systems than previously 
believed and has important implications for plant-herbivore-pathogen  interactions. More 



broadly, these interactions can have important consequences for disease transmission in the 
ocean. 

 
Pacific oysters are a sink and potential source of the eelgrass pathogen, Labyrinthula 
zosterae 
 

M. Victoria Agnew, Institute of Marine and Environmental Technology, University of Maryland 
Baltimore County; Maya L. Groner, Prince William Sound Science Center; Morgan E. Eisenlor, 
Department of Ecology & Evolutionary Biology, Cornell University; Carolyn S. Friedman, 
School of Aquatic & Fishery Sciences, University of Washington; Colleen A. Burge, Institute of 
Marine and Environmental Technology, University of Maryland Baltimore County 
Seagrasses and oysters are ecosystem engineers that often co-occur and are vital to the ecological 
and economic value of coastal ecosystems. Global declines in seagrasses, including Zostera 
marina, have recently been observed in association with multiple factors, including diseases such 
as seagrass wasting disease (SWD) caused by the protist Labyrinthula zosterae (Lz). 
Consequential protection of seagrasses has led to restrictions on oyster aquaculture due to 
concerns regarding the negative impacts from bivalve aquaculture on seagrass population growth 
and density. An important aquaculture species, the Pacific oyster (Crassostrea gigas), can filter 
Lz from the water, potentially reducing pathogen transmission. However, oysters may be a 
source of infection if they accumulate and release live Lz into the water. We investigated if 
oyster presence decreases lesion severity and infection intensity in eelgrass, or act as a vector of 
Lz, via laboratory experiments in the San Juan Islands, WA, USA. Oysters and eelgrass were 
exposed to Lz for 24hrs and kept at 11ºC or 18ºC for 13d. The presence of oysters significantly 
decreased lesion severity and infection intensity, but oysters previously exposed to Lz did 
transmit the pathogen to naïve eelgrass. Temperature did not affect the oysters’ ability to 
mitigate SWD; however, increased temperature caused significantly increased lesion severity 
and infection intensity in eelgrass shoots. Further research is needed regarding oysters as vectors 
of Lz and to demonstrate these results in the field, but these results have important implications 
for co-habitation of oysters and eelgrass. 
 
 
Effects of eelgrass (Zostera marina) source identity and diversity on wasting disease 
prevalence and restoration success 
 

Randall Hughes, Northeastern University; Tay Evans, Massachusetts Division of Marine 
Fisheries; Jill Carr, Massachusetts Division of Marine Fisheries; Forest Schenck, Massachusetts 
Division of Marine Fisheries 
 

Eelgrass (Zostera marina) serves as a model system both for our understanding of disease in the 
ocean and for tests of the ecological effects of genetic diversity. Although theory predicts that 
genetic diversity will decrease disease prevalence, the clear positive effect of eelgrass genetic 
diversity on plant production and density could instead result in disease amplification through 
increased transmission. We conducted multiple eelgrass restoration experiments in Salem Sound, 
MA, to test the effects of eelgrass source identity and diversity on wasting disease prevalence, 
eelgrass density and percent cover, and ultimately, restoration success. We manipulated the 
number of source sites as our metric of diversity, with 1-source, 3-source, and 5-source plots. At 
annual intervals from the time of planting in 2017-8 through summer 2021, we measured 
eelgrass presence/absence, canopy height, percent cover, and flowering and vegetative shoot 
density in multiple quadrats within each plot. One year following planting, we also measured 



wasting disease prevalence and intensity. We found variation in wasting disease and plant 
production based on source identity, with the relative performance of source sites generally 
consistent across experiments. In contrast, there were few clear effects of source diversity on 
plant metrics, and wasting disease prevalence and intensity were higher in multi-source plots 
than in single-source plots. These results suggest that using multiple source sites in restoration 
efforts does not result in increases in plant production as observed in small-scale manipulations 
of genetic diversity, and this practice may even increase the prevalence and intensity of wasting 
disease. 
 
 
Session 3A: Ecosystem ecology: Advances in understanding seagrass and submersed 
aquatic vegetation ecosystem functioning 

Session Convener(s): Cassie Gurbisz, St. Mary’s College of Maryland; Lillian Aoki, Cornell 
University 
 
Ecosystem ecology is the integrated study of living and non-living components of ecosystems 
and their interactions within an ecosystem framework. The field emphasizes energy and matter 
flows through an ecosystem and the ecological functions that drive these flows. Ecosystem 
ecologists aim to understand how changing ecosystem structures, human stressors, climate 
change, and ecological interactions affect these functions and how, in turn, ecosystem services 
are affected. The aim of this session is to highlight new work that advances our understanding of 
these concepts as they apply to seagrass and submersed aquatic vegetation ecosystems. 
Presentations will touch on primary production and energy flows, biogeochemical cycling, 
carbon and nutrient dynamics, ecological interactions, feedback processes, and other topics that 
frame research questions from an ecosystem perspective. In keeping with the conference theme, 
the session will emphasize but is not limited to research that draws linkages between ecosystem 
functioning and seagrass recovery. 
 
 
Talks: 
 
Linkages between seagrass tissue O2 dynamics and ecosystem oxidation and feedbacks 
revealed using microsensors in situ 
 

Marguerite Koch, Florida Atlantic University; Chris Johnson; Kasey MacLeod; Chris Madden; 
Ole Pedersen 
 

Water column hypoxia, low tissue pO2 and H2S intrusion, a known phytotoxin, are linked to 
global seagrass decline. While many lab experiments have examined these relationships, only 
field studies capture the complexity of gas dynamics in situ. We examined internal pO2 and H2S 
dynamics in a dominant tropical seagrass Thalassia testudinum using microsensors. Based on 12 
field deployments (48–72-h) across seasons, we show that T. testudinum has a high capacity for 
daytime leaf oxidation (42–53 kPa) that sustains oxic conditions in its tissues and supersaturates 
the water column with O2 (>21 kPa). While internal daytime O2 is consumed near sunset, 
positive feedback between seagrass O2 production and the supersaturated water column going 
into the night contributes to buffering of internal plant hypoxia at the beginning of the night. 
Leaf meristems went anoxic/hypoxic (0.6 kPa) at night even with high daytime irradiance, 
indicating a high ecosystem O2 consumption, and reliance on water column pO2 (19 kPa) 
through leaf pO2 (9 kPa) to prevent H2S from entering the meristem at night. Newly recruiting 



shoots into bare sediment also had the ability to minimize H2S intrusion. At ambient irradiance, 
we only detected H2S in the meristem when water column pO2 was hypoxic (<2 kPa) coincident 
with maximum water column temperatures (33 oC), an occurrence likely to increase with global 
warming. These data reinforce the importance of water quality management to sustain seagrass-
dominated systems, particularly in nutrient-enriched estuaries and coastal lagoons. 
 
 
Assessing the role of light and epibiota in seagrass sulfide incorporation 
 

Katherine Haviland, Cornell University; Robert W. Howarth, Cornell University; Roxanne 
Marino, Cornell University; Melanie Hayn, Cornell University 
 

Under future climate scenarios, many coastal ecosystems are expected to receive less light as a 
result of enhanced eutrophication. Eutropic conditions can produce highly sulfidic sediments in 
seagrass meadows. We carried out a mesocosm experiment assessing levels of sulfide intrusion 
in seagrass (Zostera marina) under various levels of shading, and with and without epiphytes. 
Light and temperature were continuously monitored during the 8-week experiment, with PAR 
and porewater sulfide measured weekly. At the end of the experiment we sampled all plants for 
epiphyte biomass, and leaf and rhizome/root tissue sulfur isotopic composition (d34S) and 
percent sulfur (%S). We saw different relationships between dissolved sulfide and light 
depending on epiphyte presence. Where epiphytes were present, sulfide decreased as light 
increased, but the opposite occurred in treatments without epiphytes, suggesting the role of 
epiphytes in seagrass oxygen transport dynamics. Additionally, we saw responses of d34S and 
%S to both epiphyte and light treatments, with 34S enriched in the tissues of plants grown in high 
light and depleted in light-limited plants, while %S followed the opposite pattern. Plants with 
epiphyte cover had greater %S than those without epiphytes across all treatments, and a higher 
d34S than plants without epiphytes. Our results indicate that epiphytes impact the relationship 
between seagrass and sulfide beyond light limitation alone, by impacting sulfide uptake through 
alterations in gas transport throughout the plant. 
 
 
Herbivory as a driving force of seagrass species composition and resilience in Caribbean 
seagrass ecosystems 
 

Fee Smulders, AEW, Wageningen University & Research; J.E. Campbell, Institute of 
Environment, Florida international University; E.S. Bakker, Netherlands Institute of Ecology 
(NIOO-KNAW); J.A. Vonk, IBED, University of Amsterdam; M.J.A. Christianen, AEW, 
Wageningen University & Research 
 

Global warming and anthropogenic impacts as the introduction of exotic species can alter the 
local ecological equilibrium of coastal ecosystems, by shifting plant-herbivore and other 
ecological interactions. We studied how seagrasses respond to shifts in temperature, nutrients, 
herbivory and seagrass invasion by performing manipulative field experiments in the Caribbean 
Sea. We found that herbivores can shape plant communities in invaded seagrass ecosystems: on 
the one hand sea turtles facilitate invasion, while on the other hand diverse fish communities are 
able to provide biotic resistance, resulting in spatial patterns of seagrass species dominance 
depending on herbivore presence. Additionally, in a region-wide experiment, seagrass above- 
and belowground recovery rates and therefore resilience was found to vary with latitude and was 
mainly driven by a combination of temperature and herbivore grazing pressure, with implications 
for plant-herbivore equilibria in a warming sea. Overall, our findings increase our understanding 



of seagrass ecosystems in times of change, leading to management recommendations to improve 
the conservation and restoration of these valuable coastal ecosystems. 
 
 
The macrobenthic invertebrate assemblage of a newly established intertidal seagrass 
meadow in SW England 
 

Oliver Thomas, Marine Research Plymouth; Professor Melanie Austen, The University of 
Plymouth; Professor Martin Attrill, The University of Plymouth; Dr. Dan Smale, The Marine 
Biological Association; Dr. Lauren Biermann, Plymouth Marine Laboratory 
 

Macrobenthic invertebrate assemblages of intertidal seagrass meadows are poorly studied within 
the United Kingdom. Elsewhere, existing studies have focused on the macrobenthic assemblages 
of established meadows, or those recovered from degradation. This study investigated whether 
the assemblage of a newly established seagrass meadow (<5 years old) differed from 
surrounding bare sediment. Samples were collected from a 7.3 ha monospecific intertidal Zostera 
noltei meadow situated within the Tamar estuary, SW England. Twenty-five sediment cores were 
collected along two transects covering both seagrass and bare sediment biotopes. Sediment cores 
were sieved to 0.5mm and macrobenthos were identified to the lowest possible taxonomic level. 
Findings demonstrated significant differences between macrobenthic assemblages sampled from 
bare sediment (<10% seagrass cover/0.5m2) and seagrass (>10% seagrass cover/0.5m2). 
Macrobenthic assemblages did not significantly differ among samples >10% seagrass cover. 
Mean biodiversity was lower in bare sediment samples (Simpsons Index: 0.52, Delta+: 82.5) 
than samples collected from seagrass (Simpsons Index: 0.67, Delta+: 85). Bare sediment samples 
also had a high abundance of opportunistic species, and were classed as ‘Heavily disturbed’ on 
the AMBI Marine Biotic Index. Sediment samples from >10% seagrass cover contained fewer 
opportunistic species and were classed as ‘Slightly disturbed’. In total 55 species were recorded 
across all biotopes: 45 of which were found in samples with >10% seagrass cover. These 
findings suggest that, even within a relatively short period of time from initial establishment, 
intertidal seagrass meadows can significantly alter the benthic communities associated with the 
underlying sediment. 
 
 
An agent-based model approach to assessing the role of vegetative fragments in seagrass 
connectivity 
 

Samantha Lai, National Parks Board, Singapore; Theophilus Zhi En Teo, DHI Water & 
Environment; Arief Rullyanto, DHI Water & Environment; Jeffery Low, National Biodiversity 
Centre; Karenne Tun, National Biodiversity Centre; Peter A. Todd, Experimental Marine 
Ecology Laboratory; Siti Maryam Yaakub, DHI Water & Environment 
 

Understanding how populations in the marine environment exchange genetic material is vital for 
the implementation of suitable conservation measures. However, dispersal can be challenging to 
empirically assess as they occur over such vast distances. Increasingly, agent-based models 
(ABMs) are being used to predict the potential dispersal pathways of populations, including 
seagrass. Most seagrass ABMs have been based on sexual propagules (i.e. fruits, seeds, spathes), 
overlooking the potential role of asexual vegetative fragments in long-distance dispersal. In this 
study, we have developed two contrasting ABMs, one for vegetative fragments and another for 
fruits and seeds, to evaluate (i) the dispersal potential of these two dispersal strategies and (ii) the 
local and regional seagrass connectivity around Singapore. Our models demonstrated that 
vegetative fragments could potentially be an effective mode of dispersal, having similar 



establishment patterns to fruits/seeds and establishing at greater distances on average. Most 
meadows were well connected locally and regionally, regardless of the mode of dispersal, 
although exchange of propagules was uneven between selected sink and source sites. The ABMs 
identified potential source and sink meadows that should be conserved to provide a repository of 
genetic material, as well as a supply of propagules for recruitment. We highlight the need to 
include vegetative fragments alongside sexual propagules when evaluating seagrass connectivity 
in future modelling efforts. 
 
 
Local pressures alter seagrass survival to climate change 
 

Jessica Pazzaglia, Stazione Zoologica Anton Dohrn/University of Trieste; E. Dattolo, Stazione 
Zoologica Anton Dohrn; M. Ruocco, Stazione Zoologica Anton Dohrn; A. Santillán-Sarmiento, 
Stazione Zoologica Anton Dohrn; A. Terlizzi, Stazione Zoologica Anton Dohrn; L. Marín-
Guirao, Centro Oceanográfico de Murcia; G. Procaccini, Stazione Zoologica Anton Dohrn 
 

Posidonia oceanica (L.) is one of the most abundant seagrass species in the Mediterranean Sea, 
ranking amongst the slowest-growing and longest-lived plants on earth. However, sea warming 
and the occurrence of different anthropogenic pressures result in cumulative impacts that are 
forcing native populations to respond quickly. In this context, studying populations living under 
different stress regimes is fundamental for exploring their resilience capacity against further 
pressures and the molecular background that have favored their survival to past environmental 
changes. Here, we explored the response capacity of P. oceanica plants growing in environments 
with different nutrient conditions (oligotrophic, Ol; eutrophic, Eu) to altered temperature and 
nutrients levels and their combination, through a multi-level approach. Performing a mesocosm 
experiment, we first assessed plants' performances measuring morphological and physiological 
traits after tress exposures. then we analyzed transcriptomic reprogramming in leaves and shoot 
apical meristems (SAMs), concluding with the analysis of DNA-methylation. The complex 
plant's responses underlined that local conditions modulate plant ability to cope with single and 
multiple stressors, being temperature the most impacting one. The organ-specific vulnerability 
observed by a different transcriptomic reprogramming indicated that leaves were more 
vulnerable to nutrient enrichment, while SAMs were particularly affected by heat stress, whose 
intensity depends on the plant's origin. The dynamics of DNA-methylation observed between 
plants strengthens the importance of local disturbances in stress responses. These findings could 
have important implications for conservation and restoration management of seagrass 
ecosystems underling the relevance of local pressures in driving different responses to climate 
changes. 
 
 
Posters: 
 
Trajectories of nutrient flows and ecosystem trophic status in a low-salinity freshwater 
submerged aquatic vegetation bed 
 

Cassie Gurbisz, St. Mary's College of Maryland; Cindy Palinkas, University of Maryland Center 
for Environmental Science Horn Point Laboratory; Jeremy Testa, University of Maryland Center 
for Environmental Science Chesapeake Biological Laboratory; Lora Harris, University of 
Maryland Center for Environmental Science Chesapeake Biological Laboratory 
 

Chesapeake Bay submerged aquatic vegetation (SAV) has been increasing in abundance, most 
notably in low-salinity reaches of the estuary. As SAV recovers, the diverse ecosystem services 



it provides are also presumably returning to the system. However, most research on submerged 
macrophyte ecosystem functioning, particularly in relation to carbon and nutrient cycling, has 
focused on seagrasses in marine waters. Here, we investigate trajectories of restored ecological 
functioning in tidal fresh upper Chesapeake Bay SAV beds by synthesizing several datasets, 
including publicly available monitoring data, simulation model output, and a suite of physical 
and biogeochemical field measurements. Our analyses demonstrate how a large, recovering SAV 
bed affects regional sediment and particulate nutrient transport and seasonal and long-term 
carbon and nutrient retention. We also make inferences about how shifts in autotrophic 
dominance from pelagic production by phytoplankton to benthic vascular plants might impact 
the overall trophic status of the ecosystem. 
 
 
The Impact of Artificial Shading on the Seagrasses at Sandals South Coast, Westmorland, 
Jamaica 
 

Hugh Small, University of the West Indies, Mona; Mona Webber 
 

Jamaica, the third largest Caribbean island, has a coastline of 675 km, lined by mangrove forests, 
rocky shores and sandy beaches. Beyond the tidal zone lie expansive seagrass meadows which 
function as fish nurseries, primary producers for the food web, (carbon sequestration) and 
sediment stabilizers. Seagrasses in Jamaica are poorly described with few studies conducted on 
their ecology and value in providing ecosystem services. 
The paucity of attention to seagrasses in Jamaica, evidence of their losses through direct and 
indirect factors and the non-existent understanding of the impact of light loss on the seagrasses 
are the reasons for this study. The opportunity to conduct this investigation was created by the 
construction of over-water structures (bungalows) which cause differential shading of a 
Thalassia testudinum dominated seagrass bed on Jamaica’s south coast. 
Fourteen (14) stations were established for monthly data collection of physicochemical 
parameters (e.g., pH, DO, turbidity/light attenuation) and T. testudinum biological parameters 
including shoot density, spatial coverage and blade length. Permanent plots were established to 
conduct long-term monitoring of light attenuation throughout the duration of the study. 
Physicochemical parameters (pH, dissolved oxygen and turbidity) were found to be significantly 
different between stations. Light attenuation was also found to be significantly different with the 
stations clearly differentiated into shaded and non-shaded. Significant correlations between 
seagrass cover/density and decreasing light intensity were established. However, contrary to 
expectations, blade length weakly correlated with light levels. All biological parameters 
associated with the seagrasses were shown to be deleteriously affected by shading of the 
bungalows.  
 
 
Will overgrowth of cyanobacteria hinder submerged aquatic vegetation resurgence in 
Chesapeake Bay? 
 

Judith M. O’Neil, University of Maryland Center for Environmental Science; Cassie Gurbisz, 
Saint Mary's College of Maryland; J. Brooke Landry, Maryland Department of Natural 
Resources; Catherine Wazniak, Maryland Department of Natural Resources; Jeffrey Cornwell, 
University of Maryland Center for Environmental Science 
 

One of the ‘signs of success’ in terms of ecosystem recovery in the Chesapeake Bay is the 
increase in submerged aquatic vegetation (SAV) in response to Chesapeake Bay-wide 
improvements in water quality over the last several decades. Nowhere is this more profoundly 



evident than in the northern portion of the bay at the Susquehanna Flats where the largest (~50 
km2) and most diverse continuous SAV bed has re-emerged after disappearing 50 years ago due 
to degrading water quality and Tropical Storm Agnes. This SAV bed acts as a significant 
seasonal nutrient sink, which is important given the large particulate nutrient load delivered to 
the Chesapeake Bay from its largest tributary, the Susquehanna River. Co-occurring benthic 
cyanobacteria, dominated by Lyngbya (Microseira) wollei, have been observed proliferating 
attached to and over-topping the SAV (predominantly Vallisneria americana). This may be 
problematic, as overgrowth of cyanobacteria on SAV leads to reduced light availability and 
inhibits gas exchange, which ultimately decreases photosynthetic rates of the aquatic grasses and 
increases sediment anoxia and nutrient fluxes. Consequently, the severity of cyanobacteria 
coverage can be strongly related to changes in sediment biogeochemistry, SAV losses and 
sediment stability. It is unclear what is causing increases in Lyngbya growth and whether it could 
threaten long-term SAV recovery and resilience. Therefore, we are investigating how these 
cyanobacteria are functioning in this system, and what controls the dynamic interplay between 
the cyanobacteria and SAV in terms of biogeochemical processes, including nitrogen fixation. 
 
 
Changing foundation species in Chesapeake Bay: implications for faunal communities of 
two dominant seagrass species 
 

Lauren Alvaro, VIMS; Christopher J. Patrick; Marc Hensel 
 

Foundation species, such as seagrasses, provide many ecosystem functions in coastal habitats 
and support diverse food webs. Environmental changes and anthropogenic activities are strongly 
impacting coastal ecosystems globally. When these changes cause shifts in foundation species, 
whole food webs can be transformed. Thus, there is a need to understand how these changes are 
affecting coastal ecosystems. Seagrass meadows in the Chesapeake Bay are an ideal study 
system for studying these impacts, because a shift in the dominant foundation species of two 
structurally different seagrasses is occurring in the lower bay. Due to rising water temperatures 
over the last few decades, the once-dominant species, Zostera marina, has been declining, while 
Ruppia maritima has been expanding on large spatial scales. To understand how the structure 
and function of faunal communities differ between Z. marina and R. maritima meadows, we 
performed quantitative surveys on epifaunal, nektonic, and infaunal communities associated with 
these species. Preliminary results indicate that Z. marina meadows had higher diversity and 
richness of epifauna while R. maritima meadows had a higher total abundance of individuals. 
Nekton also had a higher total abundance in Z. marina meadows compared to R. maritima 
meadows. Overall, this study advances our understanding of how the shift occurring in the lower 
Chesapeake Bay impacts the food web and serves as a case study for predicting how changes in 
the identity of foundation species may affect community structure in other estuaries. 
 
 
Effects of epiphytes on the thermal tolerances of edge-of-range seagrasses in NC, USA 
 

Mike Wheeler, University of North Carolina Wilmington; Dr. Jessie Jarvis, University of North 
Carolina Wilmington; Dr. Martin Posey, University of North Carolina Wilmington; Troy Alphin, 
University of North Carolina Wilmington 
 

North Carolina, USA seagrass meadows consist of two species located at their edge of 
distributional range: Zostera marina, a seasonally heat-stressed temperate species, and Halodule 
wrightii, a seasonally cold-stressed tropical species. Epiphytes, micro- and macroalgae that grow 
on the leaf surface of seagrasses, have been shown to create a thermal boundary layer with the 



potential to alter the temperature of the leaf microenvironment. Warmer nutrient-rich waters 
associated with climate change and coastal development have the potential to increase epiphyte 
biomass which may influence and potentially aggravate heat stress in Z. marina. However, these 
same conditions may alleviate cold stress in H. wrightii providing a mechanism to withstand 
winter temperatures. The ability of epiphytes to alter the microenvironment of edge-of-range 
seagrasses was quantified in two separate laboratory experiments. Seagrasses were collected 
from Topsail Sound, NC, and placed in treatments with and without epiphytes and under optimal 
(23°C Zm; 25°C Hw) and stressful (30°C Zm; 10°C Hw) temperatures (N=6). Experiments were 
run for 6 weeks to mimic in situ stressful conditions, and seagrass structural and physiological 
responses were quantified bi-weekly. Results of this study will provide understanding of how the 
interactions between abiotic and biotic stressors may influence the survival and persistence of 
edge-of-range seagrasses. 
 
 
Trait and taxonomic diversity of macrophytes shapes benthic community structure in 
mixed surfgrass, kelp, and wakame meadows 
 

Mizuho Namba, Hokkaido University; Kensuke Ichihara, H