Floods and droughts can cause pools and riffles—and the bugs that live in them—to become more homogenous. – Estuary News Magazine

For years, scientists monitoring water quality in streams and rivers have collected mixed samples of aquatic invertebrates from riffles, pools, and transition zones. But UC Santa Barbara stream ecologist David Herbst and his colleagues recently finished a 15-year study of the benthic life in small streams of the central Sierra that examined pools and riffles separately. They found that during flood and drought events, these habitats and their inhabitants become more uniform. But while floods come and go, droughts can have longer-term effects on the biodiversity in the stream. “As stream flows go down, the riffles go dry first,” says Herbst. “The riffle habitat, the richest place in the stream, can be depleted during drought conditions. The habitat itself is lost and so you lose that biodiversity normally harbored in the riffle.” Herbst says his study also points to the importance of habitat type in restoring straightened, engineered channels to a more natural sinuous shape. “The sinuosity creates higher flows at bends and variety in the riffles and pools. It’s restoring that ecological function that restores the hub of the food web, the bugs.” LOV

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Floods and droughts can cause pools and riffles—and the bugs that live in them—to become more homogenous. For years, scientists monitoring water quality in streams and rivers have collected mixed samples of aquatic invertebrates from riffles, pools, and transition zones. But UC Santa Barbara stream ecologist David Herbst and his colleagues recently finished a 15-year study of the benthic life in small streams of the central Sierra that examined pools and riffles separately. They found that during flood and drought events, these habitats and their inhabitants become more uniform. But while floods come and go, droughts can have longer-term effects on the biodiversity in the stream. “As stream flows go down, the riffles go dry first,” says Herbst. “The riffle habitat, the richest place in the stream, can be depleted during drought conditions. The habitat itself is lost and so you lose that biodiversity normally harbored in the riffle.” Herbst says his study also points to the importance of habitat type in restoring straightened, engineered channels to a more natural sinuous shape. “The sinuosity creates higher flows at bends and variety in the riffles and pools. It’s restoring that ecological function that restores the hub of the food web, the bugs.” LOV

About the author

Lisa Owens Viani

Lisa Owens Viani is a freelance writer and editor specializing in environmental, science, land use, and design topics. She writes for several national magazines including Landscape Architecture Magazine, ICON and Architecture, and has written for Estuary for many years. She is the co-founder of the nonprofit Raptors Are The Solution, www.raptorsarethesolution.org, which educates people about the role of birds of prey in the ecosystem and how rodenticides in the food web are affecting them.