Poster Presentation Society for Freshwater Science 2025 Annual Meeting

Controls on terrestrial arthropod inputs and impacts to benthic communities in ephemeral streams in the San Antonio region. (118743)

Cidney Williams 1 , Brian Laub 1
  1. University of Texas at San Antonio, HELOTES, TEXAS, United States

Urbanization has a global impact on stream environments and aquatic communities by altering riparian habitats. Urban development can alter stream food webs by altering terrestrial invertebrate inputs. This influence is important, especially for drift-feeding fish, because terrestrial invertebrate inputs can contribute up to half of their annual energy intake. Ephemeral systems, dependent on seasonal variation in precipitation events, enable habitat connectivity between aquatic and terrestrial ecosystems and become corridors for migratory species of invertebrates. However, the impacts of urbanization on food webs in ephemeral systems are less studied, particularly in subtropical regions such as south-central Texas. Our study area of San Antonio, Texas, is a region experiencing rapid urban sprawl, becoming the fastest-growing city in the United States between 2016 and 2017. This study has two objectives. The first is measuring the diversity and abundance of terrestrial, aquatic, and emerging invertebrates in urban and non-urban pools within ephemeral stream channels. To accomplish the first goal, we will sample benthic aquatic, emergent, and terrestrial invertebrates in and around ten urban-impacted pools and ten non-impacted pools. We will use a D-net to sample aquatic invertebrates from the substrate, emergence traps to estimate aquatic invertebrate production, and malaise traps to measure the abundance of aerial invertebrates around pools. The second objective is to identify controlling factors influencing terrestrial inputs and aquatic invertebrates. We will measure multiple land use and habitat variables in each pool, including percent impervious cover upstream, percent canopy cover, and riparian vegetation types within a 100-meter buffer around the pool to accomplish this goal. This study tests whether terrestrial arthropods are a significant energetic subsidy into ephemeral pools to determine potential trophic cascades that could reshape the benthic arthropod communities. Furthermore, the study will quantify urbanization factors that may influence the type and amount of terrestrial arthropods in ephemeral pools.

 

 

 

 

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