Streambed Microbial Activity and Its Spatial Distribution in Two Intermittent Stream Networks

TL;DR

This study explores how microbial activity varies in different parts of two intermittent streams, showing how drying and rewetting affect organic matter and nutrient cycling.

Contribution

The study reveals spatial patterns of microbial enzyme activity and stoichiometric limitations in intermittent streams under different environmental conditions.

Findings

Microbial activity was higher in Gibson Jack Creek compared to Pendergrass Creek.

Enzyme activity in leaf litter varied along the stream network in Gibson Jack Creek.

Microbial activity in both streams was primarily limited by carbon and phosphorus.

Abstract

Headwater streams comprise almost 90% of global river networks, and their microorganisms play critical roles in organic matter decomposition and nutrient cycling. These functions, however, are affected by recurrent drying and rewetting. This study examined spatial variation in microbial enzyme activity tied to organic carbon degradation (β-glucosidase, phenol oxidase, and peroxidase) and nitrogen (N-acetylglucosaminidase) and phosphorus (phosphatase) mineralization in water, epilithic biofilm, leaf litter, and sediment in two intermittent streams: Gibson Jack Creek (Idaho, USA) and Pendergrass Creek (Alabama, USA), representing different climactic and physiographic settings. Microbial activity was greater in Gibson Jack Creek, where the activity of leaf litter enzymes varied along the stream network, and there were strong correlations in microbial activity between different stream habitats. Microbial activity in Pendergrass Creek showed primarily within-habitat associations. Activity in water, sediment, and biofilm showed broader spatial heterogeneity in both stream networks. Ratios of microbial activity (enzyme stoichiometry) suggested that microbial communities in both systems were primarily limited by carbon and phosphorus, although there was more spatial variation in nitrogen limitation, particularly in water and sediment at Pendergrass Creek and in biofilm at Gibson Jack Creek. These findings underscore the spatial heterogeneity and environmental sensitivity of microbial processes in intermittent streams.

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