PS 36-6 - Green goo and fish slime: Investigating impact of algal blooms on fish skin mucosal microbiome

Abstract: The Great Lakes are home to an array of unique species which are threatened by the recurring formation of harmful algal blooms (HABs). Freshwater blooms are predominantly caused by cyanobacteria which can directly impact organisms through the release of toxins or indirectly through alteration of water conditions and habitat. Though not well studied, HABs have the potential to alter the microbial community in the water as well as the mucosal microbiome of fish. The mucus coat on the surface of fish is the first defense against disease. These mucosal surfaces are cultivated by the host to allow for colonization of beneficial microorganisms which prevent infection by harmful pathogens. Changes in environmental conditions associated with HABs can upset the delicate balance, which can leave fish vulnerable to infection by opportunistic pathogens and impact overall fitness. We hypothesize that sites with recent histories of cyanobacterial blooms will exhibit differences in the fish mucosal microbiome. In this study, the mucosal microbiome on the surface of yellow perch was investigated at three sites in Lake Superior that have had recurrent HABs and three sites that have not had documented HABs. At each site, five yellow perch of similar size were collected by electrofishing and swabbed for DNA-based identification of the skin mucus microbiome. For comparison, water quality metrics and water samples were also collected for the identification of the microbial community in the environment. Each site was sampled twice, once in August and September. During the September sampling we collected samples a week after a bloom had occurred at one of our sampling locations. Though we did not observe any signs of the HAB during sampling, we did observe a thick film of algae covering vegetation; the site also had the highest pH (8.46), conductivity (204.7 µS/cm), and dissolved oxygen (11.27 mg/L) of all the sites measured. We also observed a higher frequency of fish collected with external parasites in HAB sites. This preliminary study will be a key first step in understanding the relationship between the microbial community, water quality, and fish health. This study will determine if areas impacted by HABs show variation in the surface mucosal microbiome of fish and provide insight into long-term impacts of HABs on the ecosystem.