Impacts of Water Quality on Oyster Development to Inform Oyster Reef Restoration and Sustainability on the Mississippi Gulf Coast

Description: This project integrates field, laboratory, and policy research on the impacts of low salinity, pH, dissolved oxygen, and harmful algal blooms on the early life stages of oysters in order to inform sustainable oyster reef restoration in Mississippi coastal waters. Oyster reef conservation and restoration in the Mississippi Sound requires an understanding of where oysters can survive and thrive under present conditions. This is particularly important for the early life history stages of oysters, which are generally more sensitive to environmental stressors. Further, stressors rarely occur in isolation, and exposure to multiple simultaneous stressors has even greater effects than exposure to single stressors. For example, the sensitivity of oyster larvae to toxins is enhanced under elevated temperature or reduced salinity. To investigate these issues, the project has several components. First, we are collaborating with the MBRACE Core Research Program to collect temporally and spatially explicit data on levels of abiotic and biotic stressors at current, former, and potential oyster reef sites across the Mississippi Sound. Second, we are exposing oyster larvae and juvenile (“seed”) oysters in laboratory bioassays to a range of water quality conditions independently (Year 1) and in combination (Year 2) to assess the effects of single and multiple stressors on development, growth, and survival of oyster early life history stages. Third, we are out-planting seed oysters in the Core Research Program sensor platforms at oyster gardening, restoration, and aquaculture sites across the Mississippi Sound to evaluate in situ growth and survival after early life stage exposures to stressors. Lastly, we are analyzing the legal and policy framework governing oyster harvesting and oyster reef restoration in Mississippi and will translate our findings into a policy brief that will summarize the implications of our research results for oyster reef management. Collectively, our work will provide recommendations for management options or policy reform to improve the sustainability of oyster populations in Mississippi. The project also includes partnerships with a high school and The Nature Conservancy located on the Mississippi Gulf Coast, who are involved in our in situ experiments and outreach activities.

MBRACE Core Research Program (2020-2022)

Description: The MBRACE Core Research program for 2020 – 2022 will continue to model and assess seasonal trends in Mississippi Sound water quality, the dynamics of freshwater inflow into the Sound, and the suitability of Sound waters for sustainable oyster production. During the initial round of Core Research Program funding (2018-2020), the MBRACE partners, at USM, MSU, JSU and UM, collected essential base-line data that supported assessments of western Mississippi Sound water quality, stressors impacting water quality, oyster biology and ecology, and oyster reef health and sustainability. This new project extends the original Core Research Program’s research activity through continuing to model and assess water quality in the western Mississippi Sound while expanding our research activities into bays and other coastal waters, assessing locations with the potential for sustainable estuarine ecosystem development, and synthesizing all data from the first phase of research for distribution and use by competitively funded projects. Due to record flooding in much of the Mississippi River valley, the Bonnet Carré spillway was opened in 2018 and twice in 2019 to relieve flooding pressure on levees in New Orleans. This unprecedented event resulted in a large influx of freshwater into the Mississippi Sound through Lake Pontchartrain. This project gathers the data needed to model and assess: (1) the return of water quality conditions in the western Mississippi Sound that can support and sustain existing oyster reefs; (2) oyster spat movement and successful recruitment onto reefs; (3) the reestablishment of oyster reefs growing toward harvestable size; and (4) the overall ecosystem services of the Sound. This provides the MBRACE team with a unique opportunity to study the recovery of an estuarine ecosystem from a major event. The effort to assess the Sound’s recovery and identify potential locations for establishing new oyster reefs consist of a comprehensive, interleaved observational and modeling approach that provides a holistic view of the Mississippi Sound marine ecosystem. The research integrates water quality and ecological data with a coordinated suite of numerical models. Data are obtained by ship-based sampling, in situ sensor platforms, and spat settlement experiments. The models provide insight on water quality conditions throughout the Sound, advective pathways suitable for oyster spat transport, settlement and successful recruitment, and near real-time projection of the impact of spillway openings, flooding events, and storms. The use of high spatial and temporal resolution remotely sensed imagery provides all researchers with a synoptic view of conditions of the Mississippi Sound and the contributing land surface areas. Project results will provide a more thorough understanding of the recovery of the western Mississippi Sound and its oyster reefs, a science-based approach to selecting new areas for oyster and ecosystem restoration, and the initialization of a long-term set of data describing conditions in the Mississippi Sound.

Optical Observation for Oyster Larvae

Description: This project develops an optical observation system measuring the complete set of the inherent optical properties in the Mississippi Sound to monitor and predict oyster larvae performance as measured by growth and survival at metamorphosis. Oyster larvae feed on naturally occurring phytoplankton in the water column; the quality of this food source is critical in minimizing time to metamorphosis (growth and development rate) and success at metamorphosis. The study consists of two components: a novel optical observation system provides critical data to a cutting-edge oyster larvae model for predicting time to metamorphosis and survival at metamorphosis. All matter interacts with light, and inherent optical properties describe how the light is scattered and absorbed by the particles in a water column. We have developed state-of-the-art optical models that can: (1) quantify the concentration and the type of particles from the measurement of angular distribution of scattered light; and (2) infer the species of phytoplankton from the spectral variation of absorption. The combination of these two techniques allows rapid and accurate monitoring of key water quality parameters over extended spatial and temporal scales. The oyster larvae model is the only bivalve larval model that utilizes food quality as well as quantity in determining larval success. The model structure builds on the known biochemical repertoire of oyster larvae, in which metabolism is based on lipid rather than carbohydrates, and the lipid requirements for successful metamorphosis. The project addresses a critical research gap in understanding recruitment to oyster reefs and their sustainable management in the north-central Gulf of Mexico. In particular, our specific focus on oyster larvae is of timely relevance given the recent influx of fresh water due to the opening of the Bonnet Carré spillway that has all but destroyed the adult oyster stock in the Mississippi Sound. Consequently, recovery of the estuary and rebuilding the oyster stock depends heavily on the availability of oyster larvae and their success at metamorphosis.

The Distribution of Submarine Groundwater Discharge and its Effect on Coastal Water Quality in Mississippi

Description: Submarine groundwater discharge (SGD) is an important, but poorly constrained, hydrologic process that affects coastal water quality by transporting environmental stressors, such as nutrients, contaminants, and pathogens, into the ocean. Although SGD water flux to the coastal ocean is usually lower than that of rivers and streams, it can often represent an equivalent or greater contribution to local nutrient budgets because solutes are highly concentrated in SGD relative to surface waters. Published hydrologic models and preliminary results indicate that SGD occurs in the Mississippi coastal waters and may directly contribute to degradation of water quality including eutrophication, harmful algal blooms, and ultimately hypoxia. However, the spatial and temporal variability of SGD in Mississippi coastal waters, as well as its specific chemical composition, are poorly constrained. Additionally, published results indicate that spatial heterogeneity in subsurface hydraulic conductivity created by infilled paleochannel drainage networks, such as those that underlie the Mississippi Sound (MS) and Mississippi Bight (MB), can control the location of SGD. This project uses geophysical profiling, geochemical tracer surveys, and SGD sampling in the MS and MB to quantify the spatial distribution and temporal variability of SGD as well as its chemical composition. The research evaluates the role of paleochannel features in mediating SGD distribution, the sources of chemically distinct SGD in the study area, and the effect of SGD on water quality with emphasis on nutrient loading and the onset of hypoxia. The results of this research will contribute to an improved understanding of the contribution of SGD to nutrient budgets and water quality degradation in the MS and MB. Additionally, they will constrain the spatial and temporal variability of this poorly understood nutrient transport pathway, which may inform improved management of water quality and the multiple commercial fisheries in coastal Mississippi. Finally, we anticipate that these data will be directly relevant to the multiple productive commercial finfish and shellfish fisheries in the study area, particularly oyster reef sustainability and the optimal siting of future oyster cultch deployments.

Dataset for: Effects of flood-associated stressors on growth and survival of early life stage oysters (Crassostrea virginica)

Water quality data collected in the northern Gulf of Mexico from 2021-05-01 to 2021-07-31 and Eastern oyster (Crassostrea virginica) growth and survival responses during multistressor exposures

Seismic profiles of subsurface stratigraphy in the Mississippi Sound, from 2020-11-10 to 2021-12-07

Chemical tracers in Mississippi Sound water samples collected from 2018-10-28 to 2021-12-07

Chemical composition data of Mississippi Sound surface seawater and groundwater samples collected along the coastline, from 2017-07-28 to 2019-11-13

Water and food quality data collected on oyster reefs in the Mississippi Sound, 2021-05-14 to 2021-10-25

Water and food quality data collected on oyster reefs in the Mississippi Sound 2022-05-12 to 2022-10-27

Optical and water column oceanographic data collected as part of Optical Observation for Oyster Larvae (O3L) in Mississippi Sound, from 2021-05-14 to 2022-10-27

Water quality data collected from Wolf River and Jourdan River from 2022-01-05 to 2022-12-20

Water quality data collected from Wolf River and Jourdan River, 2021-02-22 to 2021-12-22

Water quality data collected from northern Mississippi Sound, 2021-07-23 to 2021-08-19

CTD and spectroradiometer data in the Mississippi Sound from 2020-11-12 to 2021-09-29

Oyster recruitment in Mississippi Sound from 2019-09-10 to 2021-10-12

CTD and spectroradiometer data, Mississippi Sound from 2022-04-01 to 2022-09-16

Surface water quality data obtained from Mississippi Sound from 2021-06-02 to 2021-09-29

Surface water quality data of the Mississippi Sound sampled from 2022-09-12 to 2022-09-16

Water quality data from three depths in Mississippi Sound from 2020-11-12 to 2021-07-29

Water quality data from three depths of the Mississippi Sound obtained from 2022-04-01 to 2022-09-16

Remote sensing data and imagery collected in Mississippi Sound by UAS, from 2021-07-26 to 2021-07-29

Remote sensing data and drone imagery obtained by UAS, Mississippi Sound, 2022-09-12 to 2022-09-16

Water quality data collected from northern Mississippi Sound, Mississippi from 2022-02-25 to 2022-03-16

Water quality data collected from northern Mississippi Sound and effects on oyster populations, 2022-03-17 to 2022-04-12

Ocean Circulation Model of the Mississippi Sound and Bight from 2015-04-01 to 2015-12-31