POTENTIAL EFFECTS OF EUTROPHICATION-INDUCED CYANOBACTERIAL BLOOMS AND INVASIVE MUSSEL SPECIES ON CARBON CYCLING AND BURIAL IN GREAT LAKES REGION LAKES AND RESERVOIRS

Lakes and reservoirs may sequester organic carbon ~ 1.4 to 5 times the rate of the world’s oceans, but biogeochemical carbon cycling in these ecosystems is more susceptible to anthropogenically driven forcing (e.g., nutrient inputs leading to eutrophication, increasing temperatures due to global climate change). The enrichment of nutrients in lakes and reservoirs coupled to rising global temperatures is leading to an increase of eutrophication-induced blooms (EIBs) of cyanobacteria and associated harmful cyanobacterial blooms (blooms with elevated toxin production). Collectively, blooms increased water column biomass, alter food webs and biogeochemical cycles, and negatively impact water quality. However, the effects of EIBs on carbon cycling and sequestration in lakes and reservoirs may be obfuscated by the presence of invasive non-native mussel species (i.e., Dreissena spp.). To help elucidate the influence of harmful cyanobacterial blooms and invasive mussel species on carbon cycling and sequestration, we conducted a preliminary study examining geochemical attributes (including carbon stable isotopes) and microbial community composition in eutrophic lakes, reservoirs, and rivers in western Ohio, eastern Indiana, and northern Kentucky during the cyanobacterial bloom period of the summer of 2015. Results of the single time point sampling indicate the occurrence of EIBs and the presence of invasive mussel species do not result in changes in overall microbial community composition and support previous reports of increased cyanobacterial biomass during seasonal blooms. However, EIBs and invasive mussels may alter the δ¹³C signal of carbon pools in the water column and sediments. Furthermore, this pilot study suggests the presence of EIBs only or of both EIBs and invasive mussel species may diminish the carbon sequestration potential of lakes/reservoirs by 2.9 and 3.5 times, respectively. The results of this study highlight the need for more intensive study of the effects of EIBs and invasive mussel species on the carbon sequestration potential of lakes and reservoirs.