Long-term biodiversity trends of macroinvertebrates and fish in rivers and streams of the United States (2024-11-15)

Abstract

Documenting long-term trends in communities can lead to new insights regarding how the quality of streams has changed across the US. The National Aquatic Resource Surveys (NARS) is a major national program aimed at understanding the state of the nation�s waters and provides critical data on stream macroinvertebrates and fish across the contiguous U.S. We analyzed biodiversity and composition of assemblages of stream macroinvertebrates and fish and their drivers. We found total densities of macroinvertebrates over the past 27 years have decreased by 11%. Urban and agricultural streams lost the few disturbance-sensitive taxa they once had and gained disturbance-tolerant taxa, indicating ongoing environmental degradation. Changes in stream temperature and the management of fish communities influence fish biodiversity. Warming is associated with diverging trends in biodiversity in cold and warm streams, with a disproportionately large impact on cold streams. In cold streams, fish abundance and richness declined by 21.7% and 13.3% per decade, respectively, and uniqueness increased. In warm streams, abundance increased by 25.2% per decade, and communities have homogenized. The presence of introduced and game fish can obscure the effects of temperature change on local biodiversity. These results suggest that current efforts to protect and restore streams are not sufficient to mitigate anthropogenic effects.