|Breaking open the black boxes of marine microbial communities|
Rebecca Gast, David Caron, Peter Countway, Julie Ellis, Jed Fuhrman, Michael Moore, Jeff Shimeta, Joshua Steele
Planktonic communities are complicated systems with a myriad of interactions among organisms and with their physical and chemical environment. A traditional and successful approach to study ecosystem dynamics involves high-level grouping of organisms into assemblages such as ?phytoplankton,? ?zooplankton? and ?bacteria,? then examining rate processes and interactions among these large sets. This approach has yielded a wealth of information about ecosystem-level processes and gained a greater understanding of the ecology of marine ecosystems. However, it is widely recognized that using this ?black box? approach to characterize a system has limitations, because frequently organismal interactions within these groups have a significant effect on the group as a whole.
Recent technological advancements have made it relatively easy for biological oceanographers and molecular ecologists to obtain a more detailed picture of whole communities of organisms within these large black boxes. I am very interested in the synthesis of this extensive information to address basic questions about interactions within communities and with their physical and chemical environment. Through the use of multivariate statistical analyses for data visualization and hypothesis testing, I have been able to link changes in microbial community composition with either naturally fluctuating physicochemical factors or with treatment amendments in field studies of natural populations. Recent projects have included linking changing protistan community composition to grain size rather than flow rates in estuarine sediments, demonstrating the cohesive nature of protistan assemblages at depth in the western North Atlantic that were distinct and not correlated with corresponding surface water assemblages, and illustrating consistently rapid and dramatic shifts in protistan community composition unrelated to measured physical and chemical factors at a series of inland bays in the northeastern United States. Currently I am working on a project examining patterns of antibiotic resistance within pathogenic bacteria isolated from marine vertebrates of the coastal northeastern US. This project centers on a database of over a thousand bacterial isolates from over a hundred marine mammals, seabirds and sharks. About 50% of the bacteria isolated were of clinical interest, and approximately 1/3 were screened for resistance to a suite of 16 antibiotics. We have determined from this data set that antibiotic resistant bacteria were widespread in marine vertebrates, geographically and taxonomically. I have been able to identify groups of antibiotics with similar resistance patterns across samples. I have also identified groups of samples with similar antibiotic resistance and am now investigating the factors correlating with these observed patterns. Preliminary results suggest the patterns of antibiotic resistance are linked to overall animal health (based on sample type: live/stranded/bycaught) rather than animal type (mammal/bird/shark).