The first experiment with nonnative oysters in Maryland water was launched in late April, as scientists lowered trays containing thousands of sterile Crassostrea ariakensis to the bottom of three rivers.
Over the next year and a half, scientists will watch the oysters to see if they survive as well in the state’s lower salinity water—and grow as fast—as the Asian oysters have in Virginia tests.
“Maryland waters are fundamentally different from Virginia waters,” said Kennedy Paynter, of the University of Maryland’s Center for Environmental Science, who is conducting the study. “We hope that this study will help to provide important insight into the population potential for the Asian oyster in Maryland’s portion of the Chesapeake Bay.”
It is one of more than a dozen research projects under way this year seeking to gain information about the nonnative oyster so state and federal officials can make a decision about whether a reproducing population of the oysters should be introduced into the Bay, possibly as soon as next year.
Paynter’s project, funded by Maryland Sea Grant College, placed oysters confined within plastic cages into the Choptank, Patuxent and Severn rivers. Oysters were also placed in the York River in Virginia to compare results between the states.
At each site, about 1,300, 1-inch sterile Asian oysters were deployed alongside sterile native oysters, C. virginica, to compare their growth, disease susceptibility and survival.
Previous tests funded by the Virginia Seafood Council have shown that C. ariakensis grows much faster than the native oysters and resists the diseases that have devastated the native population.
But most past comparisons between the two species have used sterile C. ariakensis and reproductive C. virginica oysters. Some scientists say the results of such comparisons may be misleading as the sterile oysters are able to put all their energy into growth, rather than reproduction.
Also unlike the Virginia projects, the cages in Paynter’s project will be placed only a few inches off the bottom rather than high up in the water column.
“We want to do it in a non-floating device to test how they would do in a completely sub-tidal exposure,” Paynter said. Some scientists have speculated that oysters grown closer to the bottom, where water quality is usually poorer, may not fare as well, although Paynter said it is not clear that will be the case.
Findings from that and other research taking place this year, as well as those from previous Virginia studies, will be used in the development of an Environmental Impact Statement, which could be completed as early as next spring. The EIS will allow policy makers to determine whether a proposal by the states of Maryland and Virginia to proceed with an introduction is ecologically responsible, or if more study is needed.
Many scientists have been critical of the accelerated time frame for the decision, saying it is not adequate to assess complex issues, such as whether a reef developed by C. ariakensis oysters over a period of years would provide the same ecological benefits as those created by native oysters.
A report prepared by the Bay Program’s Scientific and Technical Advisory Committee in February, drawing on input from scientists from both around the region and across the nation, said it would likely take about five years of research to answer key questions.
State officials disagree, saying that the most crucial information needed for a decision can be gained more rapidly.
But there is increasing demand for the nonnative oyster, especially as Maryland oyster harvests this year hit a new record low of 19,000 bushels, down from last year’s record low of 53,000 bushels.
The ongoing Virginia Seafood Council study placed a total of nearly 1 million sterile oysters spread over nine sites in the water last fall, but most of the new work is being funded by the Maryland Department of Natural Resources and the Potomac River Fisheries Commission.
Ultimately, the information developed by the research projects will be used in an ecological risk assessment model being developed by scientists from the University of Maryland and Versar Inc., an environmental consulting firm.
The model would be used to estimate the likelihood of establishing a population of nonnative oysters that would meet the states’ goals of supporting “sustainable harvests comparable to harvest levels during the period 1920–1970” and restoring “the ecological role of oysters in the Bay.”
The model would also be used to evaluate the level of risk that C. ariakensis would become a nuisance species within the Bay.
Among the research project taking place this year:
Economists from the University of Maryland and the Virginia Institute of Marine Sciences are estimating the economic benefits of the oyster fishery with native and nonnative species. They will also examine the the economic benefits of a C. ariakensis population to other fisheries, and to water quality, as well as the potential harm from an introduction.
Further research on the susceptibility of C. ariakensis to various pathogens in the Bay is being undertaken by the Center of Marine Biotechnology, University of Maryland Biotechnology Institute.
Scientists from the University of Maryland Center for Environmental Science are developing models to estimate the potential rate and distance that both C. ariakensis and C. virginica oyster larvae will disperse in the Bay.
Scientists from UMCES and VIMS are conducting laboratory studies to determine how larvae from C. ariakensis behaves under different combinations of salinity, temperature and dissolved oxygen compared with larvae from C. virginica. They will also examine how successfully the larvae are able to settle onto a substrate under different conditions.
A population model that uses the results of other research will be developed by VIMS researchers to help estimate the growth of C. ariakensis in a variety of habitats in the Bay.
Under quarantined conditions, scientists from VIMS and UMCES will estimate the reproductive timing and productivity for yearling C. ariakensis under low and medium salinities, including examining the temperature and salinity cues which lead the oysters to spawn. The project will also breed new C. ariakensis in anticipation of increased brood stock needs in future years.
C. ariakensis has been shown to be vulnerable to the oyster parasite Bonamia in North Carolina. VIMS researchers are working to determine whether C. ariakensis would be susceptible to the parasite in temperatures and salinity conditions typical of the Bay in the event Bonamia were to reach the Chesapeake.
Scientists from VIMS, UMCES and the Smithsonian Environmental Research Center are examining differences in substrate preferences between C. ariakensis and C. virginica under different conditions.
Competition between C. virginica and C. ariakensis from larval settlement to their development of reefs will be examined by researchers from UMCES, VIMS, SERC and the Cooperative Oxford Laboratory. The studies are examining the reef-building capabilities of C. ariakensis and how it interacts with C. virginica at different life stages.
Scientists from VIMS will lead a team of experts to a C. ariakensis reef in China’s Laizhou Bay to improve their understanding of the oyster’s ability to produce and survive on reefs under specific environmental conditions and relate those findings to the Chesapeake.
Scientists from Versar are examining the potential for C. ariakensis to foul water intakes at power plants that withdraw water from the Bay.
An anthropologist from the University of Maryland is examining the social and cultural implications of the proposed introduction, as well as possible alternative actions, for watermen communities.
Laboratory studies at the Center of Marine Biotechnology, University of Maryland Biotechnology Institute, are examining environmental tolerances, such as maximum and minimum temperature and salinity tolerances, that may limit where C. ariakensis is distributed in the Bay, as well as identifying the regions where they will fare best.