Resource heterogeneity structures aquatic bacterial communities

Mario E Muscarella,Claudia M Boot,Jay T Lennon,Corey D Broeckling

doi:10.1038/s41396-019-0427-7

Abstract

Microorganisms are strongly influenced by the bottom-up effects of resource supply. While many species respond to fluctuations in the concentration of resources, microbial diversity may also be affected by the heterogeneity of the resource pool, which often reflects a mixture of distinct molecules. To test this hypothesis, we examined resource-diversity relationships for bacterioplankton in a set of north temperate lakes that varied in their concentration and composition of dissolved organic matter (DOM), which is an important resource for heterotrophic bacteria. Using 16S rRNA transcript sequencing and ecosystem metabolomics, we documented strong relationships between bacterial alpha-diversity (richness and evenness) and the bulk concentration and the number of molecules in the DOM pool. Similarly, bacterial community beta-diversity was related to both DOM concentration and composition. However, in some lakes the relative abundance of resource generalists, which was inversely related to the DOM concentration, may have reduced the effect of DOM heterogeneity on community composition. Together, our results demonstrate the potential metabolic interactions between bacteria and organic matter and suggest that changes in organic matter composition may alter the structure and function of bacterial communities.

Highlights

Resource supply has strong bottom-up effects on the diversity of consumer communities
The variation in dissolved organic matter (DOM) composition, based on the PCoA, was significantly related to dissolved organic carbon (DOC) (r2 = 0.68, p = 0.01), total nitrogen (TN) (r2 = 0.70, p = 0.01), Chl a (r2 = 0.69, p = 0.02), and pH (r2 = 0.58, p = 0.03), but there were no significant relationships with total phosphorus (TP) (r2 = 0.27, p = 0.34), altitude (r2 = 0.31, p = 0.74), or surface area (r2 = 0.30, p = 0.26) (Fig. 1)
This study revealed that DOM resources were heterogeneous across lakes—on average lakes were 37% dissimilar in their DOM composition; and resource heterogeneity may help explain the variation in resource–diversity relationships along resource concentration gradients

Summary

Introduction

Resource supply has strong bottom-up effects on the diversity of consumer communities. Theory suggests that resource enrichment can promote diversity and food-web complexity [1,2,3,4]. Diversity can increase linearly with resource concentration [13], but it can exhibit more complex, non-linear relationships where diversity peaks at intermediate concentrations [14]. Such patterns have been attributed to a range of processes including variation in competitive ability among consumers [14], shared limitations across species [13], and trophic interactions [15, 16]

Methods

Results

Conclusion