Patterns and drivers of Submersed Aquatic Vegetation in Chesapeake Bay (SAVSyn)
Submersed aquatic vegetation (SAV) is a hugely important foundational habitat across both freshwater and marine ecosystems. As part of the SAV Synthesis Working Group (SAVSyn), I’m helping to describe the patterns and drivers of SAV abundance and diversity in the Bay. Moreover, we intend to directly and indirectly link management efforts, including Best Management Practices (BMPs), to SAV cover to understand how to most effectively SAVe the Bay.
Trajectories of eelgrass in Chesapeake Bay (SAVSyn)
Eelgrass is an important coastal ecosystem that provides a variety of critical services, including nursery habitat, shoreline buffering, and carbon storage. Unfortunately, eelgrass has undergone catastrophic declines (>80%) in the Chesapeake Bay since 1972.
I’m integrating high resolution aerial photography conducted since 1984 with long-term water quality monitoring data to understand the drivers of this decline, and disentangle the contributions of declining water clarity with episodic extreme warming.
The outcome of this project will help us better understand the factors driving the distribution and abundance of eelgrass in the Bay, and how to best conserve this valuable habitat in a rapidly changing world.
Are Coastal Habitats Nurseries?
The idea that coastal habitats like seagrasses, mangroves, marshes, and biogenic reefs provide nurseries for many species of fishes and invertebrates has gained increasing traction since the early 2000s, with many local examples. Yet, we still do not understand whether these habitats generally enhance growth, survival, and recruitment of juveniles. I am working with students at the Virginia Institute of Marine Science and collaborators at the University of California Santa Cruz and The Nature Conservancy to conduct a quantitative synthesis of all available evidence for the nursery habitat hypothesis with the goal of understanding whether this phenomenon is broadly applicable, or only holds in a few select instances.
Patterns in Marine Predation
Predation is among the most important processes structuring ecological communities, but little is known about how predation varies along marine and estuarine gradients, among habitats, and through space and time.
We are employing a novel standardized assay, the Squidpop, to characterize marine predation in restored oyster reefs versus aquaculture sites in North Carolina, Virginia, and Massachusetts. I am also a partner in Ocean Bitemap, to create a global map of marine predation.
Animal functional diversity and its utility to explain ecosystem functioning
Variation in the number of species is only one aspect of biodiversity. In the past, I have applied organismal functional traits — morphological, ecological, and behavioral indicators of how animals interact with one another and their environment — to understand patterns of biomass production in experimental estuarine assemblages (read more here).
I’m now working with researchers at the University of California Davis and Swansea University to generalize these results using a series of parallel experiments. Our goal is to identify a core set of easy-to-measure but relevant traits that can be used to better and more mechanistically link the diversity of animals to ecosystem processes.
The human footprint on global marine foodwebs: interactions between biodiversity, body size and ecosystem function in inshore ecosystems (Reef Life Survey)
Understanding global patterns in diversity is arguably the driving question in ecology, reaching back as far as Darwin. Yet, the number of species tells us basically nothing about what species are doing or how they are related, or how individuals are distributed among functional types or along phylogenetic trees, and this information may be important for conserving and managing unique or important ecosystems.
I’ve been working with the Reef Life Survey network to use an unprecedented dataset surveying >2,500 sites worldwide to:
- Show that fish richness and functional diversity are among the premminent drivers of biomass at the global scale (read more here).
- Revisit and test the strength of evidence for and against classic hypotheses in macroecology relating to the latitudinal diversity gradient.
- Understand the factors that drive species coexistence, and how these drivers change across global-scale gradients.
Biodiversity and complex forcing of ecosystem functioning in the marine foundation species, eelgrass: A global experimental network (Zostera Experimental Network)
Top-down vs bottom-up control is a tenant of ecological research, and many have used seagrasses as model systems to investigate the relative strength of these processes. However, many of these experiments have been conducted in mesocosms, which are important to identify whether these processes can occur, but it remains unclear whether conclusions drawn from such experiments extend to real-world systems.
The first iteration of the Zostera Experimental Network (ZEN) manipulated top-down control using a novel exclusion, with bottom-up fertilization at 15 sites all over the world to address the generality of this ecological paradigm. We found that biodiversity (species richness) was the single strongest predictor of ecosystem properties across all fifteen sites. Also, we made a music video.
The second round of ZEN will broaden the scope of the network by incorporating dozens of new partners and performing detailed surveys, from the plants and animals, to their genetic and functional attributes, down to the microbial communities they harbor.
Recovery of community structure and function with the successful restoration of a foundational species
Eelgrass was once dominant in the coastal bays of Virginia, until disease and hurricanes completely eradicated it in the 1930s. Sixty years later, researchers at the Virginia Institute of Marine Science began a seed-based program to restore this important foundational species. In just over a decade, they have generated more than 2,500 hectares of restored eelgrass, representing one of the most drastic state shifts in marine systems.
Despite this unequivocal success, virtually nothing is known about the recovery of associated plant and animals communities that depend on this newly re-established habitat. I used a 12-year dataset collected during the active restoration in these coastal bays to understand patterns in animal community recovery, and applied organismal traits to illuminate the functional recovery of the bed.
We showed that invertebrate richness, evenness, and functional trait diversity were all higher in the restored bed than a nearby reference bed, which we directly link to the ongoing restoration efforts. You can find a paper describing the outcome of this work here.
Biodiversity and the functioning of ecosystems: Translating results from model experiments into functional reality (NCEAS)
A huge amount of empirical evidence exists investigating the relationship between diversity and ecosystem processes, and meta-analysis has shown that diversity matters for many of these functions individually, such as standing stock biomass, resource use efficiency, and nutrient cycling. But natural ecosystems are not driven by a single function, nor are functions independent entities, as we often treat them in analyses. Rather, functioning ecosystems are supported by a network of multiple interacting processes, and this reality must be addressed moving forward.
We recently published a framework for quantifying the effect of diversity on ecosystem multifunctionality that takes into accounts interactions and trade-offs among multiple functions, and tested it using data from a pan-European grassland manipulation. Next, we incorporated data from nearly 100 published experiments to show that the positive association between biodiversity and ecosystem multifunctionality is quite general across systems and trophic levels.
Patterns and drivers of components of biodiversity in a Chesapeake Bay groundfish assemblage (NSF Dimensions of Biodiversity Distributed Graduate Seminar)
Reconciling local and regional processes is a fundamental question in ecology, and diversity can help us better understand and address this question. More importantly, we are beginning to realize that different aspects of diversity, including taxonomic, functional, and phylogenetic, can better elucidate the drivers of diversity across spatial scales. Along with several other graduate students at VIMS, we have been using data from long-term fisheries stock assessments in the Chesapeake Bay to address ecological questions, integrating morphological, life historical, and genetic data to describe diversity in this dynamic and important estuarine system. We found that the evenness with which biomass is distributed along functional and phylogenetic trees has large implications for patterns of groundfish diversity, sustaining peaks well into the fall, after many species have migrated out of the Bay.
This work has been done as part of the NSF Dimensions of Biodiversity Distributed Graduate Seminar, a novel educational model that unites graduate students at 15 universities globally to integrate research on biodiversity. You can read more about the network in this interview with Nature Jobs.
Impacts of micropredators on recently settled bay scallops (Virginia SeaGrant)
Seagrasses have been missing from Virginia’s coastal bays since the 1930s until recently, when efforts to restore this important foundational species have been massively successful. Now that the seagrass has been re-established, focus has turned to restoring other organisms that once relied on the seagrass habitat. The bay scallop, Argopecten irradians, was at one time a thriving fishery in these coastal bays, but has not been seen since the pandemic loss of seagrass. Successful restoration of the scallop requires knowledge of both the aquaculture and ecology of this species. Using a series of experimental assays, I showed for the first time that small invertebrate grazers can control populations of juvenile bay scallops through direct predation, with mortality reaching as much as 60% per day.