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; 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) often used as part of watershed management plans for improving stream habitat for cold-adapted fish species, including recreationally important brown trout (Salmo trutta). The effectiveness of riparian buffers for reducing nutrient and sediment inputs to streams has been well studied, but the impact of riparian buffers on cold-adapted fish physiology is largely underexplored. To address this research gap, we are examining brown trout gene expression (gill transcriptomics) to assess the efficacy of riparian buffers to reduce environmental stress. To accomplish this, we are conducting a space-for-time substitution study in Pennsylvania by monitoring eleven riparian stream buffer sites of varying age (three young [5-10 years], four intermediate [5-20 years], and four mature sites [15+ years]) to understand how buffer development influences stress in naturally reproducing brown trout. Brown trout sampling occurred during three seasons to capture times when different types of stress are expected (fall 2024 – reproductive stress, spring 2025 – low stress, and summer 2025 – thermal stress). During sampling, we conducted non-lethal gill biopsies for gene expression and indexed fish abundance (catch per unit effort). Stream and riparian buffer physical assessments were also conducted following each fish sampling period. HOBO temperature loggers were deployed at each site to continuously monitor water and air temperature variation at 30-minute intervals. 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 expression of certain heat shock proteins. We also expect genes that are responsive to stress generally to be upregulated in fish sampled in both the summer and fall. This research will address a critical gap in our understanding of how riparian buffers affect brown trout, an ecologically and socioeconomically important species in Pennsylvania streams.
Riparian buffers, Pennsylvania, Environmental stress, Transcriptomics