Local & watershed drivers of macroinvertebrate assemblages in lentic & lotic waters across the conterminous US

The relative role of natural and anthropogenic drivers on freshwater biodiversity across different aquatic ecosystem types is not well understood. The U.S. Environmental Protection Agency’s National Aquatic Surveys (NARS) offers a unique opportunity to compare lentic and lotic ecosystems at a continental scale.  We compared patterns and key drivers of macroinvertebrate diversity and composition in streams and lakes across the conterminous US, using machine learning methods. For both streams and lakes, multivariate random forest (MVRF) models performed better than stacked single random forest models. The MVRF models explained about 40% of the spatial variation in macroinvertebrate richness in both streams and lakes. Based on the MVRF models, many macroinvertebrate genera were strongly influenced by geography, temperature, and the amount of runoff, regardless of ecosystem type. Multiple genera were common in both streams and lakes. Two common genera, the mayfly Caenis and the damselfly Agria, were more likely to be found in streams and lakes in the Western US with warmer maximum temperatures (>20°C). However, the extent of forest cover and nitrogen deposition was more important for macroinvertebrates in lakes than in streams. Stream macroinvertebrates were more influenced by the extent of row crops and elevation. Varying key anthropogenic drivers of biodiversity between streams and lakes may suggest prioritizing different management strategies such as stream buffers in agricultural areas and air pollution mitigation for lakes. The views expressed in this abstract are those of the author(s) and do not necessarily represent the views or policies of the U.S. EPA

Impact/Purpose

It is not well understood how human activity in watersheds differs in their influence on stream and lake biological conditions. Understanding the relative impacts of watershed activities on these different ecosystem types could improve the way we prioritize management of these systems at the national scale. Further, this understanding will help support current work by EPA economists to improve the way EPA captures the existence value of freshwater ecosystems and our understanding of the factors influencing this value. In this talk, we describe work to compare the relative roles of different watershed factors on stream and lake macroinvertebrate communities. We found that different human-related activities are associated with communities in these ecosystems, implying that management of each ecosystem could benefit from consideration of these different watershed stressors. Specifically, stream communities were more influenced by the amount of nearby row crops, whereas lake communities were more strongly associated with extent of forest cover and nitrogen deposition. ovel multivariate machine learning models. The results of this work will support efforts by NCEE economists to improve national valuation of freshwater ecosystems when conducting analysis of proposed Clean Water Act regulations and contributes to StRAP subproduct SSWR.401.3.2.2 – Empirical models to interpolate benthic macroinvertebrate observed/expected ratios, or other biological indicator(s) of aquatic ecosystem health, from NARS stream and lake condition to HUC12 or HUC8 units over CONUS under Product SSWR.401.2.2 – Interpolation and stressor-response analyses that extend the use of NARS data to support regulatory program needs.

Citation

Jansen, L., R. Hill, D. Kopp, S. Rumschlag, AND L. Yuan. Local & watershed drivers of macroinvertebrate assemblages in lentic & lotic waters across the conterminous US. Annual Meeting of the Society for Freshwater Science, Philadelphia, PA, June 02 - 06, 2024.