Maryland Stream Data Shows Hidden Effects of Management Practices

US Geological Survey study shows that management can have positive and negative impacts

DNR staff holds a bluegill during a stream survey. A new study looks at the effects management practices are having on fish and other stream life. DNR photo

Many management practices aim to reduce nutrient and sediment pollution entering the watershed, and a new study looked at what unintended effects these practices are having on Maryland streams.

The study, led by scientists with the United States Geological Survey using data from the Maryland Department of Natural Resources’ Maryland Biological Stream Survey, assessed the effects that urban and agricultural management practices in the state could be having on the living things in streams, namely fish and benthic macroinvertebrates—aquatic animals including insect larvae and crustaceans.

“That’s why we did our paper,” Kelly Maloney, a USGS research ecologist and co-author of the study, said. “We realized no one connected the dots, at least at this scale. And we need more and more data to answer this question.”

By comparing data on a range of management practices—including riparian forest buffers, cover crops, bioretention, and septic system denitrification—with Maryland Biological Stream Survey data on fish and invertebrate communities, the scientists found that management practices can have both hidden costs and benefits.

In areas with poorer stream health, management practices tended to have more positive effects, according to the study. Management practices also benefited species that were sensitive to sedimentation.

However, in streams that were already healthier, management practices could have negative effects, increasing the amount of dissolved material in the water, which can be detrimental to fish and invertebrates.

The study did not look at specific streams, but brought together large amounts of data and used modeling techniques to determine causal inferences, or likely cause-and-effect relationships between management practices and aspects of stream health. This modeling technique is also often used in epidemiology, where researchers can employ vast data sets to draw out conclusions about the spread of disease.

Sean Emmons, a USGS research ecologist and lead author of the study, said more research is needed to connect particular management practices to specific effects on stream biology, but that the study highlights how these biological benefits can be considered while designing management approaches.

He said the breadth of Maryland Biological Stream Survey data on streams was critical to taking this step in determining effects of management practices.

“We knew that the Maryland MBSS data was a powerful and extensive dataset we could use to answer this question,” Emmons said. “So I think partnering with the Maryland MBSS team was a natural progression.”

The study was published in June in the Journal of Environmental Management.

Read the USGS Science Summary on the study and its additional findings here.

By Joe Zimmermann, science writer with the Maryland Department of Natural Resources