The effects of shrimp grazing on the microbial communities of Hawaiian anchialine habitats
Justin C Havird*, Alan E Wilson, Scott R Santos.
Department of Biological Sciences, College of Sciences and Mathematics
Shrimp in the family Atyidae have been shown to influence the benthic environment in freshwater streams through grazing. Furthermore, it has been hypothesized that grazing by the atyid shrimp Halocaridina rubra maintains a diverse microbial community in Hawaiian anchialine habitats (coastal, landlocked ponds and pools), because habitats with invasive fishes and lacking shrimp have been reported to have altered, low diversity benthic communities. To explore this hypothesis, a series of field observations and laboratory experiments were performed. Firstly, shrimp densities were quantified in fish-invaded and fishless habitats, although shrimp were only present in invaded habitats at night. Utilizing these shrimp densities, aquaria (n = 24) were established containing: 1) tiles cultured with algal growth and 2) varying, ecologically relevant densities of shrimp. Chlorophyll a concentration (a proxy for algal abundance) was measured in aquaria over 2 months. After one month of grazing, tiles in aquaria without shrimp had significantly greater algal abundances than those with high densities of shrimp (representative of fishless habitats). These results indicate that H. rubra grazing can influence microbial communities, and that fishes may alter this process. Ongoing studies are using high-throughput sequencing profiling of prokaryotic and eukaryotic microbial taxa to address these and related questions.