Microbial Ecology in Invasive Hosts

I am working on a project that involves characterizing and investigating the microbial community associated with an invasive aquatic crustacean (the copepod Eurytemora affinis). This copepod species has invaded inland freshwater lakes, rivers, and reservoirs from saline estuary environments multiple independent times within the last century; probably as a result of the dumping of ship ballast water. My lab is interested in how E. affinis can cross the saltwater/freshwater barrier; a major biogeographic hurdle for most species. These multiple replicate invasions from different source populations make E. affinis a powerful system to study evolution in response to rapid environmental change and in particular the shift from saltwater to freshwater.

When E. affinis is introduced to freshwater it does not do so alone, however, but carries with it a diverse and complex host-associated microbial ecosystem (the host “microbiome”). The importance of host microbial communities is only beginning to be understood, but other studies have shown that such communities are critical for host survival via nutrient provision, defense against pathogens, and even reproduction. Additionally, in coastal ecosystems, up to 40% of the microbial biomass is thought to be associated with zooplankton. Zooplankton have been hypothesized to account for a significant proportion of microbial metabolic processes in aquatic habitats (such as nitrogen fixation and denitrification) and also to be important vectors of waterborne disease.

By characterizing the microbial community associated with these copepods across freshwater-to-saltwater invasions, I hope to identify host-symbiont associations that persist during habitat invasion and those that are specific to either fresh- or saltwater environments. Furthermore, I can identify functional changes in the copepod microbial “metagenome” that occur during invasions. My data will provide novel insights about uncharacterized symbiotic microbial diversity and function in zooplankton, components which may be critically important to aquatic ecosystem processes and potentially to host adaptation to novel environments.