Extremophile Bacteria Populate Shellfish Shell Surfaces Despite a High Ph Unstirred Layer

Extremophile bacteria populate shellfish shell surfaces despite a high pH unstirred layer. University of New England Biddeford and Southern Maine Community College Joseph G. Kunkel, Kristin Burkholder, and Brian Tarbox Total with ship cost (and without) $950,000 ($920,000) Sep 1, 2015-Aug 31, 2018 (3) Abstract/Project Summary The American lobster, Homarus americanus, existed for centuries on the Northeast American coastal shelf with a small incidence of Epizootic Shell Disease (ESD). After 1996 the incidence south of Cape Cod rose and quickly reached rates that had dramatic effects on the lobster industry. No precise cause has been determined but suspicions were cat on global warming, ocean acidification and marine polution. Now ESD is increasing in the Gulf of Maine. Can careful analysis allow implicating the same factors unproven for south of Cape Cod? Adult American lobsters and blue mussels are protected from the environment by a shell which is commonly thought to be a physical barrier to assaults by microbes and predators. It is suggested that this shell is much more than a physical barrier. The physical barrier is a structure which is elegantly designed to dissolve slowly creating a thin (~100 micron) unstirred surface layer of high pH. This high pH is established by a standing gradient of dissolved carbonate that reacts quickly with water releasing a hydroxyl which will effectively scavenge protons that are needed for bacterial locomotion and metabolism. Bacteria do not move or grow well in a high pH environment. Despite this some extremophile bacteria species have learned to thrive in this environment and cause erosion of the shells of crustaceans and mollusks. It is asserted that one needs to understand extremophile bacteria that specifically populate shellfish shells in order to understand the future vulnerability of shellfish. In addition, the defense afforded by the carbonate shells of shellfish makes theme particularly vulnerable to ocean acidification which may have its most dramatic effects in the nearshore gulfs, bays and estuaries of the Gulf of Maine. There is now great interest in the Gulf of Maine, which has lobster and other shellfish populations that are vulnerable to shell erosion. Study is needed on the shell defense vulnerability to decreasing pH and how the extremophile bacteria that populate the shells may be encouraged by the acidification in the various environments in which they live. To do this the collaboration of a physiologist, a microbiologist and a field ecologist are needed in investigating the ways that the lobster, other decapods and blue mussel shells interact with bacteria. The lobsters of Casco Bay are currently exhibiting an alarming increase in shell disease which should be followed and correlated with environmental factors. Collection of candidate extremophile bacterial strains from the lobster trap-line established in a transect of Casco Bay may allow correlation with explanatory variables in the benthos. Other candidate lobster shell extremophile bacteria will be collected from trawl collected lobsters on NOAA Fall and Spring Groundfish Surveys through the Volunteer Scientist program. The variability of the populations of inshore lobsters of Casco Bay and offshore lobsters of Downeast Maine Coast, Georges Bank and the Scotian Shelf can be estimated by applying morphometric landmark analysis of carapace shape and genetic barcoding of the lobster populations and their shell-surface microbes. The genetic and phylogenetic connectedness of the populations studied will be ascertained in order to know the potential of the proposed defense mechanisms being breached in the broader population of shellfish. The CaCO3 dissolution rate of lobster and mollusk shells will be examined in the laboratory under conditions varying about those observed in Casco Bay to establish at what population level temperature and pH variance have effects. Does an antimicrobial effect of the unstirred layer benefit only the individual shellfish; or does shell dissolution need to be integrated over species and individuals in the entire Gulf of Maine for its significance in the carbonate balance of the Gulf floor to be recognized? .

Load more