Exploring Linkages Between Landscape Patterns and Freshwater and Estuarine Bivalves in the Coast Range of Oregon

• Main Author: Scully-Engelmeyer, Kaegan Michael
• Format: Text
• Language: English
• Published: PDXScholar 2021
• Subjects: Landscape ecology; Bivalves > Effect of pesticides on > Oregon > Pacific Coast; Ecosystem management; Forest management > Environmental aspects > Oregon; Western pearlshell > Oregon > Pacific Coast; Freshwater mussels > Oregon > Pacific Coast; Environmental monitoring; Ecology and Evolutionary Biology; Environmental Sciences; Natural Resources Management and Policy; Pacific; Crassostrea gigas
• Online Access: https://pdxscholar.library.pdx.edu/open_access_etds/5754; https://doi.org/10.15760/etd.7625; https://pdxscholar.library.pdx.edu/context/open_access_etds/article/6826/viewcontent/ScullyEngelmeyer_psu_0180D_12796.pdf

Spatial configurations of landscape variables (biotic, abiotic, and socio-ecological) affect and are affected by ecological processes and species in watersheds. This dissertation explores relationships among landscape patterns, ecosystem processes and bivalve species dynamics in coastal watersheds in Oregon, USA. I approached this broad topic through two primary avenues of research: investigating cross-ecosystem threats from pesticide use in forestland management to downstream aquatic environments, and the landscape ecology of an at-risk freshwater mussel species. Terrestrial land use activities present cross-ecosystem threats to riverine and marine species and processes. Specifically, pesticide runoff can disrupt hormonal, reproductive, and developmental processes in aquatic organisms, yet non-point source pollution is difficult to trace and quantify. In Oregon, state and federal forestry pesticide regulations, designed to meet regulatory water quality requirements, differ in buffer size and pesticides applied. To identify exposure and uptake of contaminants in coastal watersheds, I collected freshwater and estuarine bivalves Margaritifera falcata, Mya arenaria, and Crassostrea gigas from eight Oregon Coast watersheds to examine forestry-specific pesticide contamination. Additionally, during a 45 day period in the spring of 2019, I sampled sixteen coastal watersheds for current-use water-borne herbicides commonly used in forestland vegetation management. In 38% of bivalve samples, one or more of twelve unique pesticides were detected (two herbicides; three fungicides; and seven insecticides). Frequency and maximum concentrations varied by season, species, and watershed, with indaziflam (herbicide) the only current-use forestry pesticide detected. At 80% of sampling locations integrative passive water samplers detected at least one of four commonly used herbicides, with hexazinone and atrazine most commonly detected. An additive effects model using slope, herbicide activity notified during the sampling window, ...