Research
Oyster Ecology and Aquaculture
Oysters are vital coastal resources - they are a valued food product while also providing a number of important ecosystem services, including creating habitat for other organisms, improving water quality, and buffering shorelines, among others. Unfortunately, their populations have declined dramatically due to overharvest and disease. Because they are so important to coastal economies, numerous agencies invest in restoration and management of oyster reefs. A number of biotic and abiotic stressors may affect oysters and limit restoration and management success. Biotic factors, including pests, parasites, predators, and diseases, can all limit oyster abundance, growth, and reproduction, affecting populations. Similarly, abiotic factors, including temperature, salinity, aerial exposure, sedimentation, substrate availability and groundwater impact oysters. Getting a better understanding of these factors, how they interact, and how they might change in the future, is important for successful management. My lab has explored a number of this issues, primarily biotic, including predator-prey relationships, pests such as boring sponges, and parasites including 'oyster mosquitos' and pea crabs. We are currently investigating some abiotic factors, including sedimentation and groundwater flux. In addition, I work closely with hatcheries in both North Carolina and Georgia to explore issues related to expanding and improving oyster aquaculture.
Restoration Ecology of the Bay Scallop
The bay scallop once supported a vibrant fishery on Long Island, where I currently reside, as well as fisheries all along the east coast. For a variety of reasons, scallop populations crashed, mostly linked to harmful algal blooms, but also associated with loss of habitat in some locations. Over the past decade, many restoration efforts have been undertaken to restore scallops to their previous densities - these efforts have taken place in Florida, North Carolina, Massachusetts, and, of course, New York. Unfortunately these restoration efforts have met with mixed success. One of the biggest issues facing restoration efforts such as these is that the environment has also changed considerably over time. Understanding how these changing environments - diminished habitats, invasive species, etc - impact scallop recruitment, survival and growth is paramount for successful restoration. I have been involved with a large bay scallop restoration effort in the Peconic Estuary System, on the east end of Long Island, New York. Working with collaborators from Stony Brook University, Long Island University and the Cornell Cooperative Extension since 2006, we have produced the most successful scallop restoration project in the country, in part, due to the science-driven approach to the efforts. Specifically, knowledge of the interaction between scallops and diminished seagrass habitats (their 'preferred' habitat), alternative habitats, and dominant predators, has allowed this restoration project to use better site selection and deployment strategies.
Seascape Ecology
An emerging field in marine systems, more attention is being given to sizes and shapes of complex habitats, proximity to other structured habitats, geological positions within an estuary or watershed, among others, and how those factors influence ecological processes. The location within the seascape can play a significant role on which geophysical factors – such as flow, sedimentation and turbidity – and biotic factors – such as recruitment, competition and predation. As such, both trophic transfer and secondary production are likely affected by the seascape. Much of my previous research has examined questions related to seascape ecology. For bay scallops, I demonstrated a larval shadow within seagrass patches, where larval settlement is diminished with increasing distance from the edge of a seagrass patch, which was inversely related to scallop survival, because predatory mortality was also greatest at patch edges. Further, I also demonstrated trade-off between growth and survival for scallops associating within patchy seagrass habitats, and determined that for scallops, any seagrass patch, regardless of size or shape, was valuable, and that patchy seagrass might even be beneficial. Similarly, oyster reefs can form either intertidally or subtidally, as reefs fringing the shoreline or as isolated patches. These different locations can affect a number of ecological processes that ultimately determine the population structure on each type of reef. Intertidal reefs in southeast North Carolina exist primarily in two configurations - as fringing or patch reefs. With collaborators from the University of North Carolina Wilmington, we have demonstrated that where oysters are located within the overall seascape (fringing salt marshes vs. isolated on mud flats) affected both survival, larval supply, and recruitment. There are a number of other avenues to pursue based on observations from this study, including how pests and parasites may vary within a landscape context, and since predator behavior may also differ, examining whether the strength of non-consumptive effects may change within a marine seascape.
Larval Settlement and Recruitment
Larval settlement and recruitment play a major role in population size and structure of benthic invertebrates, like the bay scallop. The supply of larvae plays a crucial role in year-to-year variability in population size of many invertebrates. Larval supply is largely determined by fertilization success, larval survival and transport. Many invertebrate larvae have rather long durations that allow them to be dispersed great distances. In addition, once larvae are ready to metamorphose and settle, many are capable of choosing a suitable substrate. After settlement, a variety of factors impact the survival of benthic invertebrate larvae. This post settlement period is extremely critical, and the period between settlement and recruitment to adult populations is a period of high predatory mortality. While there is literature that suggests high rates of mortality, and size refuges from predation, there is little research on the early 6 week period after settlement for bay scallops. My research demonstrated up to 3 orders of magnitude difference in settlers vs. recruits over this relatively short time period. Likewise, working with oysters, we were able to demonstrate significant differences between oysters available to settle and actually recruiting, and how that changed based on location. Based on both these projects, one major conclusion is that the processes resulting in recruitment can be incorrectly identified if measuring recruitment without controlling for predation. Further, understanding the role that habitat plays on this post-set mortality is also important, and will help in understanding why certain restoration efforts are working and why some are not.
Functional Redundancy
The problem with many management and restoration efforts is that they target specific species and ignore that the ecosystem has changed considerably since the baseline the efforts are striving to attain. A field that should be investigated more thoroughly to increase the success of such efforts is functional redundancy. In marine systems, numerous species are capable of performing similar ecosystem functions, and each species might differ in their ability to withstand natural and anthropogenic stressors common in degraded ecosystems. Much of the success of the bay scallop restoration effort in New York is owed to the fact that we threw out the early paradigm that seagrass is the preferred scallop habitat; a macroalgal species is providing the same role and is much more abundant. In addition, during my dissertation, suction surveys in beds of Crepidula fornicata, the common slippershell snail, suggested a complex habitat capable of supporting the diversity and density of fauna typical of other structured estuarine habitats such as seagrasses and oyster reefs. Ecological and functional redundancy can be necessary to ensure ecosystem functioning in future, degraded systems. It is important to start to investigate this further by identifying functionally similar species, mapping their distributions, and conducting lab studies to examine how those similar species might differ in their tolerance to stressors such as harmful algal blooms, climate change and ocean acidification. Currently, we have a proposal to use Crepidula fornicata to restore water quality and habitat in degraded portions of Great South Bay, New York.
