Occurrence of Pesticides in Oregon Coastal Waters and Effects on the Intertidal Sea Anemone, <i>Anthopleura elegantissima</i>

Pesticides are used globally for a wide range of applications including agricultural, forestry, roadsides, freshwater systems, and personal use. While pesticides have ensured efficient crop production, they are frequently transported away from application sites and are ubiquitous in terrestrial and aquatic environments. Pesticides are often detected in watersheds and rivers globally, which can have unintentional toxic effects on non-target organisms by interfering with cellular processes, behavior, feeding, reproduction, and disrupting endocrine processes. The aggregating anemone, Anthopleura elegantissima, is an important species along the North American Pacific coast due to its symbiotic relationships that contribute to high productivity, and its clonal abundance that structures the rocky intertidal habitat. Despite frequent detection in inland water bodies, pesticide contamination in marine environments is less understood, and studies examining effects on sea anemones are limited. To address these data gaps, this study investigated pesticides presence in Oregon coastal waters, and based on the most frequently detected compounds, a toxicology study was conducted to examine their effects on A. elegantissima at environmentally relevant concentrations. Polar organic chemical integrative samplers (POCIS) were deployed at six sites along the Oregon coast to examine the occurrence of pesticides. Between two and seven different pesticides were detected at every site, with herbicides diuron, and atrazine, and fungicides carbendazim, propiconazole, and tebuconazole being the most frequently detected at three sites. These findings provide new insights into the presence of pesticides in coastal nearshore and offshore waters and suggest that a comprehensive monitoring effort could enhance our understanding of sources, transport, and pesticide risks for marine species both nearshore and offshore. The detected pesticides, atrazine, diuron, and carbendazim, were used to examine potential effects on reproduction, symbiont concentrations, and behavior of A. elegantissima over an eight-week period. Most pesticides individually and in combination led to a decrease in male gonad development across atrazine (p < 0.001), carbendazim (p < 0.001), two-way mixture (p = 0.05), and three-way mixture (p = 0.08) treatments. All pesticide treatments significantly increased cloning behavior compared to the control, suggesting that cloning is an important stress response. This study is the first to document behavioral changes in anemones from pesticide exposure, as tentacle retraction significantly increased, and movement significantly decreased, suggesting possible metabolic or energy impairments. All three pesticides significantly impacted a non-target marine invertebrate at environmentally relevant concentrations, which underscores the importance of studies that focus on effects on marine invertebrates, paired with comprehensive pesticide monitoring in coastal areas.