Project: MO: Assembly of Marine Microbial Communities

Abstract: 

The USC Microbial Observatory was established in 2000. The research focus of this observatory is an investigation of the microbial diversity and microbial community composition at a study site in the San Pedro Channel and Basin off the coast of southern California. The Channel area encompasses a diversity of coastal ocean habitats. The near-coast region borders one of the most highly urbanized areas of the country (greater Los Angeles) while open ocean waters impinge on the Channel Island archipelago that extends to within 30 km of the mainland. The San Pedro Basin is a deep-water environment (approximately 890 m) that exhibits very low oxygen concentration. The overarching objective of this project is the derivation of fundamental understanding of how microbial communities in the ocean are organized spatially (with depth) and temporally (at scales of months-to-years), and how environmental and biological factors shape this organization. The basic premise of the research is that "guilds" or "consortia" of microbial species exist that constitute functional subunits within the huge diversity of taxa that comprise planktonic microbial communities. The microbial species forming these guilds are functionally interdependent, and act as ecological units that replace one another in time and space as environmental conditions change. The program consists of monthly sampling at four depths in order to document the abundance, biomass and species composition of all planktonic microorganisms at the mid-channel sampling station. A variety of microscopical and molecular biological approaches are employed to examine archaeal, bacterial and microeukaryote (microalgal, protozoan, micrometazoan) diversity. The observatory is unique in that it entails an assessment of the complete spectrum of microorganisms (from viruses to the largest protists) in the water column. Genetic fingerprinting of the total microbial community is the primary tool for revealing the trophic roles and relationships among microbial taxa (predation, mutualism, commensalism, parasitism/infection), and to generate hypotheses on the interdependences among these species. Experimental studies involve manipulative food web experiments to test hypotheses concerning the relationships and interactions among the various microbial species. The data support extensive statistical analyses to identify relationships between microbial taxa, and with environmental parameters.

This research program strives to develop a fundamental understanding of the factors controlling the structure of microbial communities in aquatic ecosystems. Therefore, the results have far-reaching consequences for predicting biogeochemical processes mediated by microbial activities in nature. The project also incorporates a strong educational component aimed at reaching students ranging from elementary school children to graduate students. The information resulting from the research is incorporated into undergraduate and graduate courses taught by the principal investigators, and both types of students participate actively in the research. In addition, the principal investigators and graduate students supported by this project participate directly in an ongoing teacher education program (Centers for Ocean Science Education Excellence; COSEE-West) that reaches middle and high school students, many of whom are Hispanic, African-American or other ethnic minorities and most of whom are economically disadvantaged. This education/outreach goal is accomplished through an existing teacher enhancement and student enrichment program that incorporates the research from this microbial observatory into a learning experience that enhances student awareness of environmental science, microbiology and the natural world. The observatory principal investigators work is featured and publicly available on the internet as a part of the USC Microbial Observatory Website at http://www.usc.edu/microbialobservatory)