Current Research Projects

Globally, there has been a consistent increase in the volume of hypoxic waters along coasts. Hypoxia can have numerous negative impacts on ecosystems such as modifying nitrogen and phosphorus cycling, altering food webs, degrading fisheries, and making coastal habitats uninhabitable to many economically and ecologically important fish species. Yet, hypoxia is not universally harming marine organisms. Rather some have benefitted from the effects of hypoxia since it can generate regime shifts, where certain species leave habitats since they can no longer tolerate the environmental conditions, leading to other tolerant organisms moving into those oxygen-limiting waters. The Atlantic Brief Squid, Loliguncula brevis, is one such organism.

The potential for net nitrogen removal due to oyster aquaculture is strongly related to the transport and fate of oyster biodeposits. Biodeposits exported from aquaculture sites may enhance denitrification rates elsewhere while mitigating the impacts of organic matter over-enrichment at the aquaculture site, and/or suspended biodeposit organic matter may be denitrified in the water column. Both processes are currently not well understood. We propose a 6-wk ecosystem experiment in six shear-turbulence-resuspension-mesocosm (STURM, Porter et al. 2018a) tanks with tidal resuspension to address these questions. Three tanks will receive daily oyster biodeposit additions to mimic an aquaculture site and three tanks will not in order to represent background natural conditions.

Rationale: Blue crab harvests and populations are highly variable in Maryland. Viral disease is a possible cause of blue crab mortalities, but  little is known about viruses in crabs. Interstate transport of blue crabs may introduce new viruses into the bay.

Ecosystem-based management approaches require an understanding of how environmental conditions interact with living ecosystem components to influence the productivity of harvested species. This project is structured around the central hypothesis that the intensity, duration, and spatial extent of hypoxia will have important and measurable effects on the benthic invertebrate community that anchors much of the Chesapeake Bay demersal food web and contributes to the diet of many economically and ecologically important fishery species. In addition to this central hypothesis, we will evaluate the ecological trade-offs resulting from simultaneous stimulation of food availability and habitat loss (e.g., hypoxia) associated with nutrient loading.

The recent exponential growth in established or planned US closed-containment Atlantic salmon production has been associated with over $1B investment into this aquaculture sector. The success of this dramatic expansion/investment in land-based, RAS salmon production requires a national, coordinated and interdisciplinary effort to ensure that current barriers are eliminated and efficiency and cost-effectiveness are attained. While major progress has been achieved in recent years in RAS technology, its scaling up may face biological, engineering, technological, economical and societal constraints that should be addressed via a fully integrated research, extension, outreach, education and workforce development network.

Management efforts to reduce nutrient pollution have prompted the recovery of submersed aquatic vegetation (SAV) in the Chesapeake Bay (CB), particularly in the Bay’s tidal fresh and oligohaline waters. Unfortunately, benthic filamentous cyanobacteria have also become increasingly common in some of the areas where SAV is expanding the most. Although the prevalence of cyanobacteria is increasing globally, it is relatively uninvestigated in CB where it may threaten the stability and resilience of recovering SAV, disrupt the nutrient balance of SAV beds, which are generally thought to be nutrient sinks, and potentially affect recreational and commercial activities if they produce toxic compounds.

Rationale: To meet the increasing demands of the world’s growing population under sustainability constrains, optimization of aquaculture methods will be necessary to maximize cost-effective production and minimize ecological impact. One of the supreme strategies for large-scale commercial aquaculture operations is the use of infertile/sterile populations of farmed animals. Sterility carries environmental significance, as the infertile animals are not able to propagate and/or interbreed with wild stocks. In addition, sexual maturation is associated with a substantial decrease in somatic growth due to the diversion of energy into the development of the gonads.

Triploid eastern oysters are an important component of the Maryland aquaculture industry because of their fast growth and sustained high meat yield. Commercially, triploids are produced by mating tetraploid oysters with normal diploid oysters. Developing tetraploid stock is crucial to meeting the growing demand for Maryland triploid oysters. However, it is challenging to produce and maintain excellent tetraploid lines for the benefit of industry. In short, there is a clear and pressing need for triploid and tetraploid lines that have region-specific beneficial characteristics, especially tolerance to low-salinity environments. In this project, we will establish the first generation of tetraploid stock derived from Maryland local oyster populations.

The Maryland shellfish aquaculture industry has grown rapidly in the last decade. However, the industry currently consists of only a single species, the Eastern oyster. The monoculture approach leaves the industry vulnerable to disease, climate change, and market fluctuations which pose threats to sustainable industry growth. The soft-shell clam (Mya arenaria) is a commercially important shellfish species harvested in Northeast U.S. coastal waters. This species can grow and reproduce in low salinity waters, which makes it a strong candidate species for culture in Maryland’s portion of the Chesapeake Bay. Further, several Maryland growers have stated their interest in culturing this species.

Shoreline erosion is a major issue globally and in Chesapeake Bay, leading to increased shoreline-stabilization efforts. Recent efforts have focused on living shorelines living shorelines as the preferred method to reduce erosion, but questions remain regarding their effectiveness and potential impacts to adjacent shallow-water benthic habitats over the long term (~10 years). These are pressing management issues in the Chesapeake Bay, where two key open questions challenge widespread adoption of living shorelines: 1) how well living shorelines reduce erosion and persist over time; and 2) how installation impacts SAV habitat and distributions over time. While we have examined these questions at some Chesapeake Bay sites, we have been limited to one design type.

Coastal ecosystems are vulnerable to short term anthropogenic changes such as nutrient loading and longer-term changes such as sea level rise. Together these changes can alter these systems in ways that change the ecosystem services these systems provide. For example, estuaries bury carbon over time which in turn is a major controller for a habitable atmosphere. Carbon can enter estuaries through a number of processes such as photosynthesis, respiration, air-sea exchange, terrestrial runoff, and groundwater input. As it gets buried, it will undergo a series of microbially mediated processes which terminates in the production of methane, a potent greenhouse gas.

The Chesapeake Bay mouth plume is an important yet understudied system that transports large amounts of nutrients and organic matter to the continental shelf. The role of this dynamic plume in structing the population and diet of juvenile fish species that migrate through and (or) reside in this ecotone for at least part of their juvenile stage is largely unknown.

Urbanization has negative environmental impacts, including increasing the export of eutrophying pollutants, such as nitrogen, that reach downstream water bodies. In response, efforts are underway to use “green” stormwater infrastructure (GSI) that enhances infiltration of stormwater and increases retention and removal of pollutants. However, the effectiveness of GSI regarding nitrogen is questionable: there is evidence that some GSI provides no more nitrogen (or sometimes, less) retention than traditional stormwater management. The reason for this apparent limitation of GSI is uncertain and is the focus of the proposed research.

Though fish populations typical experience spatially varying mortality, abundance, and fishing pressure, stock assessments commonly model a population that is assumed to be well-mixed. When assumptions about population mixing are not met, these models can result in biased estimates. Spatial population estimates are particularly beneficial to the Chesapeake Bay as this region faces unique challenges as a result of climate change, fishing pressure, and land use within the watershed. Though the Chesapeake Bay supports many important commercial and recreational fisheries, few assessments have estimated abundance of fish within the bay. However, use of spatial models for fisheries management relies on the ability of these models to reliably estimate biological parameters.

Oyster aquaculture is a rapidly growing industry in Maryland’s Chesapeake waters which stimulates economic activity and may provide a host of ecosystem benefits. A potential concern associated with the intensification of the oyster aquaculture is the local production and accumulation of oyster biodeposits, which can lead to a porewater sulfide accumulation and declining bioturbation, symptoms of declining ecosystem function. Sulfide is naturally removed from the seafloor by the interactions between bioturbating infauna and sulfide oxidizing bacteria. Here, we propose exploring the feasibility of using benthic microbial fuel cells (BMFCs) to accelerate sulfide oxidation in areas of high biodeposit accumulation, below oyster aquaculture cages.

The existence of spatial structure in populations of exploited marine fishes challenges our ability to develop reliable stock assessments. Using the northern stock of Black Sea Bass (BSB - Centropristis striata) on the US Atlantic coast as a model species, I will combine empirical and analytical approaches to explore the impacts of the spatial resolution of population and assessment models on the reference points generated by assessments. In this region, the distribution of BSB is highly structured during summer months when the fish are inshore, but the distribution is more widely dispersed when offshore in the winter.

The Ostreid herpesvirus 1 (OsHV-1) and its microvariants are highly virulent pathogens that cause mass mortalities of oysters and pose a threat to the shellfish aquaculture industry globally. OsHV-1 causes economically devastating mass mortality events up to 100% in the Pacific oyster (Crassostrea gigas). However, OsHV-1 and its variants lack host specificity and are known to infect a range of bivalve species and be carried by the European green crab (Carcinus maenas). There is a lack of testing and research on the East coast of the United States, including in the Chesapeake and Maryland Coastal Bays where aquaculture is an important industry for food production and restoration efforts.