Flow reversals as a driver of ecosystem transition in Florida’s springs

Abstract

AbstractThe springs of northern Florida have degraded dramatically over recent decades, and filamentous algal mats have replaced submersed macrophytes. The unique temporal stability of these spring ecosystems has prompted narratives about the mechanisms of change in which authors focused entirely on press disturbances, such as NO3− enrichment and flow reduction. We tested the hypothesis that pulse disturbances, in the form of episodic flow reversals, are a key component of spring degradation. During flow reversals, acidic floodwaters rich in dissolved organic C (DOC) from adjacent blackwater rivers dramatically alter the light environment, and DOC respiration depletes dissolved O2 (DO), thereby creating a trophic cascade wherein negative effects on algae consumers enable algal proliferation. Synthesis of river and aquifer stages from springs in the Suwannee River basin indicates that reversal events have become more frequent with time in response to aquifer declines attributed to climate variability and g...