This work takes a multi-disciplinary approach to ocean and human health research by investigating illness/climate relationships through time series modeling and evaluating two microbial source tracking tools for human specificity. In each case the subject of the work is the California coast. In the first project, associations were characterized and modeled between four gastrointestinal illnesses and a number of climate factors across an eleven-year time series of data from Orange County, CA. The results suggest that incidence of gastrointestinal illness in Orange County may increase as a result of rising temperatures due to global climate change. The second project evaluated the use of Enterococcus species differentiation as a microbial source tracking tool in California recreational waters. The results indicate that no single Enterococcus species is a reliable indicator of the host fecal source; however, Enterococcus species composite 'fingerprints' may offer auxiliary evidence for bacterial source identification. The third project evaluated the distribution of the enterococcal surface protein (esp) gene in E. faecium in the Pacific coast environment as well as the distribution and diversity of the gene in Northern California animal hosts. The gene was found to be widespread in non-human animal feces and DNA sequence analysis revealed that esp gene sequences were not divergent between hosts. Overall, the work presented here indicates that gastrointestinal illness rates in California may increase over time, and that Enterococcus-based microbial source tracking methods are insufficient tools to assess risk from recreational water exposure.