Evaluating benthic macroinvertebrate populations in response to scouring events in the Trinity River, CA
River systems across California have been impacted by appurtenant structures such as dams and diversions. These structures have had an adverse impact on Benthic invertebrate (BMI) communities by regulating river systems and changing the natural hydraulic pulses that follow seasonal precipitation. Benthic invertebrates are a critical food resource for salmonids and serve as an indicator of ecosystem health. Our study was interested in seeing the effects of scouring events on BMI in the Trinity River of Trinity County, C.A. Following a large precipitation event that occurred in the region in December 2022, an influx of water entered the river through flood releases from Lewiston Dam, natural storm runoff, and accretion from regional tributaries along the Trinity River. The BMI samples from the Pear Tree Gulch site were used to measure the effects of the scouring event that occurred between January 8 and January 14, 2023. Our results showed that the Shannon Diversity Index (SDI) increased after the scouring event, the composition changed, and overall abundance decreased after the scour event. This study suggests that an isolated period of scouring in a regulated system does not result in BMI metrics associated with unregulated systems that experience frequent scouring events.
Environmental Science & Management
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