Resource constraints highlight complex microbial interactions during lake biofilm development

Abstract 1. This study evaluated how the availability of nutrients and organic carbon interact to influence the associations between autotrophic and heterotrophic microorganisms during lake biofilm development. Considering that decomposers are often better competitors for nutrients than producers in aquatic environments, we hypothesized that heterotrophs would outcompete autotrophs for available nutrients unless heterotrophs were limited by organic carbon provided by autotrophs. 2. To test our hypothesis, we evaluated autotrophic (algae) and heterotrophic (fungi, bacteria) biomass in response to a factorial enrichment of nutrients (nitrogen and phosphorus in combination) and glucose using nutrient diffusing substrates with either inorganic or organic discs in a subalpine lake. In the field, nutrient diffusing substrates were exposed to either natural sunlight or placed under a darkened experimental canopy to evaluate the response of heterotrophs to nutrients and carbon subsidies in the ...