The massive disruptions to the oyster industry caused by the Covid-19 pandemic creates an opportunity to rethink how oyster habitat can be restored and created. Oyster reef restoration and enhancement projects have focused on replacing or supplementing cultch material in the hopes of gaining a natural spat set. Despite these considerable efforts, oyster reproduction has varied wildly over the last 5 years from Florida to Texas causing nearly catastrophic consequences to the Gulf oyster community. The use of aquaculture as a tool for restoration or enhancement has been limited, with any efforts primarily focused on the use of spat on shell. We seek to determine the ecosystem service benefits provided using large, single oysters, obtained from the private commercial aquaculture sector. The objectives are to: 1. Partner with the Alabama Marine Resources Division and the Mississippi Department of Marine Resources to identify appropriate sites to place oysters. 2. Purchase oysters from farmers in Alabama and Mississippi to provide up to 450,000 3-plus inch farm-raised oysters for enhancement. 3. Monitor the farmed oysters’ growth and survival and the ecosystem services they provide. 4. Conduct stakeholder engagement about the program. Participating oyster farmers are providing oysters to the appropriate state agencies (AL MRD and MS DMR) for deployment at designated sites. Working in cooperation with the state agencies, oysters stocked will be monitored by Auburn University Shellfish Lab (AUSL) personnel to assess oyster growth and survival, natural recruitments, and estimates of associated ecosystem services. In addition to the direct support to oyster farmers during the pandemic by paying a net price of $0.33 per oyster, this project will also provide critical ecosystem services through improved water quality, increased biodiversity, creation of more diverse habitat and cultural services provided by productive oyster reefs.

Oyster reefs are important ecosystems that provide invaluable services for coastal communities. Crassostrea virginica populations in the northern Gulf of Mexico have suffered heavy losses in the 21st century due to alterations in water quality from various disasters, including openings of the Bonnet Carré Spillway. These flooding events reduce salinity, increase nutrient and pollutant levels, and introduce freshwater harmful algal species into coastal waters where oysters live. Significant resources have been invested to restore oyster reefs, but recovery is reliant on the survival of early oyster life stages. We assessed the effects of stressors associated with flooding events on larval and juvenile oyster development to better understand the tolerances of early oyster life stages. We exposed D-stage larvae to a range of dissolved oxygen (1-8 mg/L O2), microcystin (0-20 μg/L), pH (7.1-8.1), and salinity (3-15 ppt) concentrations in 96-hour single stressor experiments. Larvae were not affected by any microcystin or pH concentrations tested, but low salinity and hypoxia reduced shell growth. Using concentrations informed by the results of the larval assays, we then exposed juvenile oysters to the same water quality stressors for 24 days in the lab. Juvenile wet weight and shell growth were decreased by hypoxia, low pH, and low salinity, but microcystin had no effect. These laboratory-exposed juveniles were then transplanted to the field to assess how prior exposure to stressors affects growth and survival in natural conditions. Larval and juvenile oyster survival was relatively unaffected for the duration and stressor concentrations tested, but the negative impact on growth of early life stages may limit the recovery and resilience of oyster reefs. Further research is needed to determine the combined impact of multiple stressors across all life stages of oysters, as the frequency and intensity of extreme flooding events rise.

Oysters in Mississippi Sound are important to the ecosystem and to the local economy, or they used to be. In the early 1900s, over 2 million pounds of oysters from Mississippi Sound were processed each year. From the year 2000 to 2013, the oyster harvest decreased from 1.5 million pounds to 0.5 million pounds. The harvest has decreased significantly each year since then. Recognizing their importance, the Mississippi Gulf Coast Restoration Plan considers “Restoring and protecting existing oyster reefs in Mississippi [is] critical to the ecological and economic sustainability of the region.” The plan focuses on increasing the density and acreage of oyster reefs in the Mississippi Sound. The Governor’s Oyster Council has set of goal of producing one million sacks of oysters from Mississippi Sound by 2025. To this end, tens of millions of dollars have been devoted to oyster research and especially restoration by the State of Mississippi using primarily federal funds. While over harvesting may have contributed to the decline, the influence of increasing amounts of freshwater in Mississippi Sound cannot be discounted. From 1937 to 2007 (70 years), the Bonne Carre Spillway was opened 8 times. Since 2007 (13 years), the spillway has been open 7 times, as recently as April 2020. Each time the spillway is open, fresh water diverted from the Mississippi River can flood Mississippi Sound potentially lowering the salinity to a level deleterious to oysters. Restoration efforts must consider whether oysters reefs can survive and whether restoration efforts will be effective considering how the current conditions of river water diversion differ from times when oyster harvests were abundant.

The purpose of this paper is to identify likely ranges of costs, market returns, and ecosystem benefits associated with three different oyster (Eastern oyster, Crassostreia virginica) production methods: extensive bottom harvest, intensive off-bottom aquaculture, and non-harvested reefs. As part of this endeavor, this paper also compiles the limited and disparate literature on costs, yields, and returns associated with commercial oyster production. I use Monte Carlo simulation to estimates the likely distribution of gross market returns, gross nonmarket benefits associated with four ecosystem services, and net benefits. I find that extensive bottom harvest has the lowest and least variable per-acre cost, whereas intensive off-bottom aquaculture and non-harvested reefs have much higher and more variable per-acre costs. Gross market returns are lower but also less variable for bottom harvest, whereas they are higher but more variable for off-bottom aquaculture. I find that gross nonmarket benefits for non-harvested reefs are relatively high with relatively little variability, whereas those of off-bottom aquaculture are relatively low with low variability. Gross nonmarket benefits for bottom harvest are estimated to be highly variable. These results are driven by the contribution of market returns, and consequently, gross benefits associated with non-harvested reefs are much lower. When market returns, nonmarket benefits, and costs are considered together, bottom harvest is net positive, with moderate upside potential. Off-bottom aquaculture has the greatest upside potential, but also substantial downside potential, with mean returns at or near zero. Because non-harvested reefs have no market benefits, and because of the relatively high cost, most of the distribution of net benefits lies in the negative range.

In addition to suitable substrate and physical conditions, successful oyster recruitment requires an adequate supply of planktonic larvae from local and remote source areas, followed by the subsequent survival and growth of early post-settlement stages. Recruitment limitation arises when the stock size is constrained below some threshold density by the supply of larvae. Above the threshold density, stock size should reflect post-settlement processes such as growth and predation more than larval supply rates. Low abundances of adult oysters in some areas of Mississippi Sound in the summer of 2018 were likely caused by the combined effects of multiple stressors. Thus in 2018, local recruitment was potentially limited within certain areas of Mississippi Sound. Despite low abundances of adults in some areas, spat settlement appeared sufficient to support oyster recruitment throughout western Mississippi Sound in 2018. However, subsequent sustained freshwater inflow for 122 d in 2019 extensively devastated adult oyster stocks, apparently even including more remote sources of larval supply. Consequently, the recruitment limitation threshold was exceeded, as spat settlement was effectively eliminated in Mississippi Sound during the oyster spawning season of 2019. Thus, recruitment limitation now presents a major challenge to oyster restoration efforts in Mississippi.

The Mississippi Based RESTORE Act Center of Excellence (MBRACE) was designated as Mississippi’s Center of Excellence in September 2016. MBRACE is a consortium of Mississippi’s four research universities (Jackson State University [JSU], Mississippi State University [MSU], University of Mississippi [UM], and The University of Southern Mississippi [USM]), with USM serving as the lead institution. The mission of MBRACE is to seek sound comprehensive science-and technology-based understanding of the chronic and acute stressors on the dynamic and productive waters and ecosystems of the northern Gulf of Mexico and to facilitate sustainable use of the Gulf’s important resources. Since its designation as Mississippi’s Center of Excellence in 2016, MBRACE has funded research projects totaling over $5M. Four projects were funded in Fall 2017 under the Core Research Program (Core 1) that examined how ecological conditions relevant to oysters vary over time and between restored and unrestored oyster reefs in Mississippi Sound. In Spring 2020, MBRACE funded three new projects through the Competitive Research Program, focused on water quality and oyster sustainability in Mississippi, as well as a second round of the Core Research Program (Core 2) to support the original four projects for continued work. Research funded by MBRACE contributes to scientific discovery within the Gulf of Mexico and, through the Center’s close partnership with state managers, provides science-based guidance for state restoration and management priorities. This presentation will provide information and updates on MBRACE and MBRACE-funded research activities, including new projects, products, and other developments.