Carachilo, Isaac, Department of Ecosystem Science and Management, The Pennsylvania State University, 221 Forest Resources Building, University Park, PA 16802, ikc5068@psu.edu; Croke, Megan V., Department of Ecosystem Science and Management, The Pennsylvania State University, 221 Forest Resources Building, University Park, PA 16802, mvc6374@psu.edu; Wagner, Tyler, U.S. Geological Survey PA Cooperative Fish and Wildlife Research Unit, The Pennsylvania State University, University Park, PA 16802, txw19@psu.edu; Keagy, Jason, Department of Ecosystem Science and Management, The Pennsylvania State University, 410 Forest Resources Building, University Park, PA 16802, keagy@psu.edu.
Riparian buffers are a best management practice (BMP) consisting of vegetated areas planted along the banks of streams, rivers, and other water bodies. Riparian buffers are used as part of watershed management plans for improving stream habitat for cold-water species of fish, including recreationally important brown trout (Salmo trutta). The planting of riparian buffers has been encouraged to improve water quality by mitigating adverse environmental effects of urbanization and agricultural activities. Water quality goals often include the reduction of nonpoint pollution and stream water temperatures. Although various aspects of the effectiveness of riparian buffers to improve water quality have been studied, the impact of riparian buffers on the thermal physiology of coldwater fishes is understudied. To address this research gap, we are examining brown trout gene expression (gill transcriptomics) to assess the efficacy of riparian buffers to reduce thermal stress. To accomplish this, we are conducting a space-for-time substitution study, in which we are monitoring eleven riparian stream buffer sites of varying age classes (three young [5-10 years], four intermediate [5-20 years], and four mature sites [15+ years]) to understand how buffer development (age) influences thermal tress in naturally reproducing brown trout. Brown trout sampling will occur during three seasons (fall 2024, spring 2024, and summer 2025) to assess population density and for non-lethal gill biopsies used for gene expression. Three HOBO temperature monitors are deployed at each site, two instream loggers and one air logger, to monitor temperature variation at 30-minute intervals. Physical stream and riparian buffer assessments will be conducted. Gill tissues will be used to assess individual brown trout thermal stress through analysis of transcriptomes. Increased riparian buffer development (e.g., leading to increased percent canopy cover) is expected to be associated with a decrease in thermally stressed brown trout as indicated by heat shock protein expression. We also expect genes that are responsive to stress generally (e.g., immune response) to be upregulated in both summer fish due to thermal stress and fall fish due to preparing for reproduction, but for this stress to be reduced in summer fish in more developed riparian buffer sites. This research will address a critical gap in our understanding of how riparian buffers influence brown trout, an ecologically important species in Pennsylvania streams.
Riparian buffers, Pennsylvania, Thermal stress, Transcriptomics