Coupling biogeochemical process rates and metagenomic blueprints of coastal bacterial assemblages in the context of environmental change

Abstract

Bacteria are major drivers of biogeochemical nutrient cycles and energy fluxes in marine environments, yet how bacterial communities respond to environ- mental change is not well known. Metagenomes allow examination of genetic responses of the entire micro- bial community to environmental change. However, it is challenging to link metagenomes directly to bio- geochemical process rates. Here, we investigate metagenomic responses in natural bacterioplankton communities to simulated environmental stressors in the Baltic Sea, including increased river water input, increased nutrient concentration, and reduced oxy- gen level. This allowed us to identify informative pro- karyotic gene markers, responding to environmental perturbation. Our results demonstrate that metage- nomic and metabolic changes in bacterial communi- ties in response to environmental stressors are influenced both by the initial community composition and by the biogeochemical factors shaping the func- tional response. Furthermore, the different sources of dissolved organic matter (DOM) had the largest impact on metagenomic blueprint. Most prominently, changes in DOM loads influenced specific trans- porter types reflecting the substrate availability and DOC assimilation and consumption pathways. The results provide new knowledge for developing models of ecosystem structure and biogeochemical cycling in future climate change scenarios and advance our exploration of the potential use of marine microorganisms as markers for environmen- tal conditions.