Oral Presentation Society for Freshwater Science 2025 Annual Meeting

Exploring Food Web Structures in Intermittent Streams: A Subcontinental Overview of Macroinvertebrate Community Patterns (117591)

Kierstyn T Higgins 1 , Albert Ruhi Vidal 2 , Kyle Leathers 2 , Rose Mohammadi 2 , Travis Apgar 2 , Yang Hong 3 , Stephen Cook 3 , Carla Atkinson 4 , Arial Shogren 4 , Chelsea R Smith 4 , Meryl Mims 5 , Samuel C. Silknetter 5 , Michael Bogan 6 , Daniel C Allen 1
  1. Department of Ecosystem Science and Management, The Pennsylvania State University, University Park, PA, United States
  2. Department of Environmental Science, Policy, and Management, University of California Berkeley, Berkeley, CA, United States
  3. Hydrometeorology and Remote Sensing Lab, The University of Oklahoma, Norman, OK, United States
  4. Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, United States
  5. Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
  6. School of Natural Resources and the Environment, The University of Arizona, Tucson, AZ, United States

Non-perennial streams are among the most prevalent in the globe's hydrography. Food webs in these streams are affected by periods of interrupted flow. Intermittency induced habitat fragmentation, stress to organisms, and altered food source availability can make understanding food web characteristics across an aridity gradient challenging. As a consequence, the length of the food chain and the relative importance of algal versus detrital energy sources is thought to be dependent on the alternating dry and wet cycles. Benthic macroinvertebrates are commonly used to study these food webs, given their high abundance, relatively short life cycles, and intermediate position within lotic food webs, often connecting the base of production with vertebrate predators. Here we will analyze the food web dynamics of macroinvertebrates using stable isotopes from six river networks across the continental United States. These networks were chosen to reflect the climatic and precipitation variability found throughout the southern U.S. By measuring δ15N and δ13C in both basal resources and macroinvertebrate samples, we will calculate community-wide metrics that describe food web complexity and resource utilization. Using Bayesian mixing models, we will determine various metrics including the trophic position of each taxon, food chain length, trophic niche width and diversity of carbon sources, and isotopic niche overlap. We hypothesize that in networks with increased drying, there will be a reduction in food chain length and a stronger reliance on terrestrial energy sources, as well as greater isotopic niche overlap across taxa.We contend that climate aridity and variability are key controls of food web structure in intermittent river networks.