Data in Action: What Keeps Stream Critters in Sync (or Not)?

What’s the question? When stream environments fluctuate, do aquatic macroinvertebrate communities respond together—or does each species follow its own pattern?

The big picture: Streams are constantly changing systems, shaped by shifts in temperature, water flow and available resources. Scientists use aquatic macroinvertebrates—organisms like insect larvae, snails and small crustaceans—as indicators of ecosystem change because they respond quickly to local conditions. Understanding how these communities fluctuate over time helps reveal how stable and resilient stream ecosystems may be.

NEON data products used:

• Aquatic macroinvertebrate collection (DP1.20120.001)
• Temperature (PRT) in surface water (DP1.20053.001)
• Continuous discharge (DP4.00130.001)  

Researcher(s): Anthony Pignatelli and Dr. Tad Dallas, University of South Carolina

What they did and what they learned

Using NEON’s standardized, long-term data products, researchers analyzed aquatic macroinvertebrate communities across 18 streams in the United States from 2014 to 2022. They were interested in community synchrony: whether species increase and decrease in abundance together or fluctuate independently over time.

The team compared the patterns in community abundance to differences in stream conditions, including temperature variability, discharge (streamflow) variability and species turnover (the rate at which species appear and disappear in a community).

They expected that more variable conditions would lead species to respond differently, resulting in less synchrony. But that’s not what they found. Across sites, community synchrony was not related to temperature variability, discharge variability or species turnover. Even streams with very different environmental conditions showed similar patterns in how species fluctuated over time. Instead, the clearest differences emerged when researchers looked at how species feed.

• Feeding strategy helped explain which species contribute most to overall community dynamics
  • Scrapers (which graze algae) and filterers (which capture particles from the water) were more likely to fluctuate in sync with other species
  • Shredders (which break down leaf litter) were less likely to move in step with the community

These findings suggest that biological roles—particularly how organisms acquire resources—may be a key factor shaping how communities change over time. By combining NEON’s long-term environmental data with species traits, this study highlights a more nuanced view of stream ecosystems.  

“Our results show just how complex freshwater ecosystems can be and how the life history of these critters is important to consider when trying to understand large-scale dynamics. This research underscores just how important it is to have continuous monitoring of ecological populations over multiple years. NEON is the reason we can ask large-scale temporal questions in our research.” 

-Anthony Pignatelli, Department of Biological Sciences, University of South Carolina

Note. Figure that provides a summary of the functional feeding group analysis including a stacked histogram of z-scores for each functional feeding group, a heat map showing contributions to community synchrony, example images of taxa found in each functional feeding group provided by The Atlas of Common Freshwater Macroinvertebrates of Eastern North America and a heat map showing the number of taxa for each group that were used to estimate functional feeding group contributions to community synchrony. Full description available from "Community synchrony in aquatic macroinvertebrates is unrelated to environmental variability but differs among functional feeding groups," by A. J. Pignatelli and T. A. Dallas, 2026, Ecology & Evolution, V16(2), https://doi.org/10.1002/ece3.72999. CC BY 4.0. Reprinted with permission.

Read more: Pignatelli, A. J., & Dallas, T. A. (2026). Community synchrony in aquatic macroinvertebrates is unrelated to environmental variability but differs among functional feeding groups. Ecology & Evolution, 16(2). https://doi.org/10.1002/ece3.72999