Seagrass Sediment Metabolism
Identifying what drives carbon sequestration in seagrass beds
Seagrass beds are critical coastal ecosystems that have a disproportionate effect in mitigating climate change compared to unvegetated areas. They do this by “locking away” large amounts of organic material in their underlying sediments, preventing that material from being metabolized (broken down) by microbes and returned to the environment as climate-warming carbon. The balance of organic matter sequestration versus metabolism in seagrass sediments is therefore crucially important to accurately estimate their capacity to mitigate climate change. However, seagrass sediment metabolism rates can be highly variable for reasons we don’t fully understand; but an answer may lie in the complex structure of the plant’s roots and rhizomes. The seagrass “rhizosphere” as it is called, creates complex subsurface structures that exchange nutrients and oxygen with the surrounding sediment in ways that likely affect sediment metabolism, and burrowing macroinvertebrates such as clams, worms, and shrimp can increase sediment metabolism with their sediment-mixing and irrigating behaviors. This introduces additional variability in sediment metabolism rates that may be crucial to understanding how and why carbon is (or isn’t) sequestered. This project integrates the complex physical structure and geochemical activity around it into a model of the seagrass below-ground environment to assess which features of that environment most affect sediment metabolism. Dense, complex root mats may oxygenate sediments more and drive higher sediment metabolism rates, and the 3D structure of the roots may control what fauna can live there and by extension, the metabolism-enhancing activities the fauna perform. It is important to determine what drives seagrass sediment metabolism to fully account for their contribution to storing carbon and mitigating climate change.
Lab personnel: Kara Gadeken
Eelgrass Early Life History
Decoupling the early influences on eelgrass seed germination in the context of climate change
These studies address the “establishment bottleneck” associated with meadow restoration and how novel techniques can bolster success. Flowers are collected during the seasonal reproductive period of Zostera marina and are used for manipulative experiments to determine how the maternal environment influences seed production, quality, survivorship, and rate of germination. Experiments are then used to uncouple how factors like maternal investment, carbon enrichment, and temperature influence seedling physiology. These experiments address how elevated temperature influences seedling physiology and if excess carbon relieved associated temperature stress. Field deployments determine the presence or absence and speciation of novel marine oomycete Phytophthora in East End, Long Island meadows. Manipulative field experiments were conducted to determine how carbon enrichment and copper treatment influenced seed germination and seedling success.
Lab personnel: Alyson Lowell
Bay Scallop Die-Off
Understanding the effects of climate change and predation on local bay scallop populations
Bay scallops in the Peconic Estuary have experienced devastating die-offs in the late summers of 2019-2021, with population monitoring surveys revealing almost complete mortality over the course of the summer. Prior to 2019, scallop stocks had been successfully restored from ecologically non-existent in the 1990s to a stable, $6 million fishery since 2012. Our lab has partnered with researchers at the Cornell Cooperative Extension to investigate the drivers of recent mortality events. Field monitoring efforts beginning in 2020 are providing high-frequency and high-resolution data documenting environmental metrics as well as scallop spawning/survival rates to provide a fuller picture of the timing and conditions of scallop death. In-situ respirometry data is being collected on scallops at several sites throughout the bay to investigate if and how environmental stressors manifest as physiological stress responses. We are also investigating the potential role of cownose ray predation in the die-off through predator exclusion experiments.
Lab personnel: Jessica MacGregor
Carbon Utilization of Zostera marina
Feasibility for eelgrass to biogeochemically manipulate the local environment and the impacts on the community at large
Eelgrass’s role as a photosynthesizer provides a mechanism for the potential amelioration of coastal acidification, especially for marine calcifiers. We determined the critical biomass necessary to successfully modulate and offset coastal acidification. These experiments also included manipulations of light to determine both critical light attenuation and biomass to successfully mitigate coastal acidification. At larger scales, the biogeochemistry of eelgrass is coupled with the metabolism of the larger community. We assessed the community metabolism of biogeochemically and morphologically distinct seagrass meadows in the East End of Long Island and in Bocas del Toro, Panama. Continuous monitoring of pHNBS, pHT, Dissolved Oxygen (mg L-1 & Percent (%)), Conductivity (µS cm-1), Temperature (oC), Total Algae (RFUs), PAR (Photosynthetically Active Radiation; µmol m-2 s-1), current velocity (νx m s-1) and benthic flux (νz m s-1) to calculate Net Ecosystem Metabolism. Covariates include biomass, productivity, sulfide production, organic matter content, and Total Carbon burial.
Lab personnel: Alyson Lowell
Blue carbon sequestration in Long Island estuaries
Quantifying the spatial carbon storage of eelgrass
Ocean Acidification is a global problem that is already revealing adverse impacts on marine fisheries, especially shellfish. Recognizing the potential consequences for NY coastal waters, the Ocean Acidification Task Force was established to ensure that the best available science is used to assess and respond to this emerging threat. Carbon sequestration by eelgrass was promoted as one potential mitigation strategy for New York. While seagrass meadows occupy less than 0.2% of the area of the world’s oceans, they are estimated to bury roughly 10% of the yearly estimated carbon burial in the oceans. As such, seagrass meadows are recognized among the most significant blue carbon sinks capturing CO2 and sequestering carbon out of the water column. Although the contribution of seagrass to carbon storage has been acknowledged, most estimates come from just a few sites and seagrass species. Furthermore, interactions between seagrass and bed characteristics with local environmental drivers may confound extrapolation of the magnitude of seagrass carbon stocks in the absence of localized sampling. The rapidly growing Blue Carbon literature suggests large variability in seagrass soil carbon stocks is due to a combination of biotic and abiotic factors acting at different spatial scales. Variation exists among and within estuaries, in terms of turbidity and water flow, which may determine seagrass spatial extent and landscape configuration. The proposed work is aimed at understanding the spatial variability of carbon storage in eelgrass sediments by assessing the spatial distribution of sedimentary carbon stocks, sources and accretion rates across the Long Island South Shore Estuaries and Peconic Estuary. This project funded by New York Seagrant will allow the mitigation costs for carbon storage in eelgrass sediments to be quantified. The carbon accumulation rates will be useful as NY state assesses various OA mitigation strategies and compares them to the potential of eelgrass ecosystems to sequester Blue Carbon.
Lab personnel: Bradley Peterson
Peconic Estuary Program Groundwater Refugia Project
Locating cool zones for eelgrass meadows within our warming estuaries
Climate change is altering the distribution of marine species around the globe. This change in distribution is tied to significant sea surface temperature (SST) increases worldwide, which has increased at an average rate of 0.2 o C per decade since the beginning of the 20th century and is expected to rise by 0.4-4.4 o C by 2025. However, SST is not rising uniformly across the globe. The water temperatures along the northwest Atlantic have risen at a rate nearly twice the global average. This accelerated temperature increase has had a significant impact on eelgrass. Temperature stress has altered eelgrass growth rates, caused distribution shifts in coverage, and changes in patterns of sexual reproduction. The ability of the plant populations to adjust to these temperature changes is likely outpaced by the rapid rate of SST increase. The impacts of extreme temperature events, such as large-scale losses of seagrass have been documented in association with marine heatwaves. With this has come an awareness that changes in mean temperature do not always cause the most dramatic biological responses as compared to temperature variability, leading to alternative ways in which temperature effects are characterized (e.g., warm water events, temperature variation, consecutive days above a temperature threshold). In addition, the temperature has a strong influence on the timing of life-history events of eelgrass populations. The severity of increasing temperature on reproductive timing, seedling emergence, and survival will depend on the ability of the plant to adapt, which may be on timescales greater than the current temperature increase along the northeast coast of the US. The Peconic Estuary, like much of the northeast, has seen eelgrass retreat over the past two decades towards the inlets or areas of increased ocean exchange. Outliers of extant eelgrass in areas removed from this cooling oceanic influence are anecdotally in areas where groundwater seepage exists. Recent hydrogeological models developed by the U.S. Geological Survey have predicted locations in Peconic Bay where groundwater seepage occurs with a coarse spatial resolution. This project seeks to identify shoreline segments where groundwater discharge may provide cool water temperature refugia and conduct eelgrass restoration demonstrations in these areas. Previous research in Peconic Bay has demonstrated that eelgrass is unable to acquire sufficient carbon during the warmest month of the year in much of the interior of Peconic Bay. In addition to cooler water temperatures, groundwater is also enriched in pCO 2 which may provide carbon enrichment to the belowground biomass alleviating this metabolic deficiency. This project is a demonstration of a potential region-wide habitat restoration strategy in the face of continued warming. The conservation of coastal ecosystems depends on management and restoration practices that reinforce ecosystem resilience (ie. the ability to resist and recover from disturbance). The increasing frequency and intensity of marine heatwaves is a major threat to coastal ecosystems and is commonly associated with the decline of foundation species (ie. seagrass) and disruption of the ecosystem services they provide.
Lab personnel: Bradley Peterson