By Ayla Skorupa, Postdoctoral Researcher 

December 16, 2024

Let us begin by thinking about our favorite stream inhabitants. A mix of vertebrates, such as a particular fish species or even a river otter, may come to mind. Rarely will someone jump at the opportunity to exclaim their enthusiasm for a net-spinning caddisfly or a clam that slowly lays a track across the streambed with its single foot. Yet, aquatic macroinvertebrates (invertebrates that you can see without magnification) are essential to stream ecosystems. Within macroinvertebrates, there is immense taxonomic and functional biodiversity that encompasses varying feeding tactics and life history strategies. Some even emerge into beautiful (albeit more well-known) flying insects, such as dragonflies! Macroinvertebrates can influence upper trophic levels; in other words, they support the persistence of fishes as a food source and contribute to stream ecosystems through biogeochemical cycling (e.g., filtering water and depositing nutrients). 

The Midwest Landscape Initiative is a collaboration of federal and state agencies that work across state boundaries to identify priority species needing regional protection. Of the species identified as needing regional protection, more than two-thirds were aquatic species. Within the aquatic taxa, most are macroinvertebrates, with freshwater mussels having the highest number of Regional Species of Greatest Conservation Need (RSGCN) and caddisflies having the highest number of RSGCN and Proposed RSGCN species. Other aquatic macroinvertebrates included in the assessment were crayfish, dragonflies, mayflies and stoneflies. All taxa contain stream specialists adapted to survive under specific stream conditions. Unfortunately, in many cases, these stream conditions are being altered by climate change. 

The popular phrase, “Rain, we needed it,” is generally true. Precipitation is necessary for sustaining life. However, how heavy, for how long, when, how quickly and how frequently precipitation occurs directly impacts the habitats of stream macroinvertebrates. For example, most mussel species use fish to complete their life cycle by infesting a host with their larvae (glochidia). Mussels have different methods of infesting fish; Lampsilis mussels form a lure from their tissue to attract predatory fish. When the fish attacks the mussel’s lure, it initiates the release of glochidia, which clamp to the fish, where the glochidia will develop until metamorphosing into a juvenile and dropping to the river bottom. Imagine an adult mussel has exerted energy to move from a deep pool to a shallow bank to better position itself to attract a fish. This movement from deeper to shallower water may occur at a specific time of year under typical climate conditions when lower stream flows would not dislodge the adult. With the changing precipitation regime, a surprise flood could potentially wipe out many gravid females, severely effecting a population.

For the past year, our team at the Illinois Natural History Survey, a division of the Prairie Research Institute at the University of Illinois Urbana-Champaign, has been working with macroinvertebrate experts across the Midwest to gather data to understand how RSGCN species may be affected by climate. We are assessing species’ sensitivity to climate by looking at the variation in precipitation and temperature throughout their Midwest ranges. This way, we can calculate a standardized index that categorizes how sensitive species may be to climate. By further including species traits that may aid their adaptation to temperature and precipitation, we can better understand how species react to changing conditions. For species with enough data, we can project their distributions into the future under new precipitation regimes to further test if traits are contributing to adaptation. By identifying climate-sensitive species, we can inform bio-monitoring efforts and identify watersheds with a high number of these vulnerable species.

Ayla Skorupa is a postdoctoral researcher working on MW CASC-funded research at the University of Illinois Urbana-Champaign. Her work in applied aquatic conservation spans multiple research disciplines, from developing decision frameworks that link science and management, to understanding species ecological needs that govern their persistence. She specializes in field biology, quantitative ecology, and has extensive aquaculture experience. While she has a broad background, her degrees are malacology focused. She earned a MSc. studying planktonic mollusks and a PhD researching freshwater mussel conservation.