Evaluating the Impacts of Nutrient Enrichment and Connectivity on Freshwater Bacterioplankton Community Composition

It is increasingly important to understand the response of freshwater ecosystems to fertilizers given their widespread usage and the propensity for these fertilizers to runoff into rivers and lakes. At the foundation of these freshwater ecosystems are bacterioplankton which play important roles as primary producers and in recycling organic matter and nutrients back into the ecosystem. To investigate the impacts of nutrient enrichment on freshwater bacterioplankton communities, we treated freshwater mesocosms–supplied with freshwater and native planktonic communities from a nearby lake–with different concentrations of nutrients (KH₂PO₄, K₂HPO₄, KNO₃). We likewise tested the simultaneous impacts of connectivity/dispersal which, through the steady reintroduction of unaffected communities, is thought to have potentially remediating effects. We found that nutrient enrichment, even at its lowest levels, strongly structures the native bacterioplankton community. We further found that nutrient enrichment significantly lowers the alpha-diversity of bacterioplankton communities irrespective of the level of connectivity from an unenriched source. Taken together, our results demonstrate that nutrient enrichment significantly impacts freshwater bacterioplankton communities with enrichment favoring nutrient-tolerant taxa such as cyanobacteria. Furthermore, our results ultimately put into question the ability of connectivity and dispersal to counteract the effects of nutrient enrichment and other stressors. 

Presentation Preference: Oral

Primary Presenter: Akhil Kholwadwala, McGill University (akhil.kholwadwala@mail.mcgill.ca)

Authors:

Akhil Kholwadwala, McGill University  (akhil.kholwadwala@mail.mcgill.ca)

Rowan Barrett, McGill University  (rowan.barrett@mcgill.ca)

B. Shapiro, McGill University  (jesse.shapiro@mail.mcgill.ca)

Egor Katkov, McGill University  (egor.katkov@mail.mcgill.ca)