The burrows of macro-infaunal organisms are generally sites of intense microbial activity and often harbor abundant populations of microorganisms. Since the various infaunal species differ greatly in their biology (e.g., feeding guild, motility) and specifically, in aspects of their burrow construction and ventilation, it is reasonable to anticipate that the microbiology of their burrows will also vary. This project will test whether a burrows' increased microbial abundance and activity simply represents enhancement of ambient microorganisms or whether there are specific microbial populations that predictably occur in burrows, independent of the ambient microbial community. A comprehensive assessment of these complex microbial communities will require non-selective methods; the microbes' phospholipid, ester-linked fatty acids (PLFA), the chief constituent of membrane lipids in eubacteria and eukaryotes will be examined. These PLFA, which have already been extracted from field samples of burrows and ambient sediments, are powerful, discriminating tools for determining microbial biomass, composition, and even physiological condition. These biochemical markers will be used to compare the burrow microbes of five infaunal species, representing three phyla, sampled across six sites. Comparisons will be made at interspecific and intraspecific levels using multivariate analysis. This project will test an intriguing biogeochemical hypothesis and impinge on the very attractive concept of "microbial gardening".
