COS 45-2 - Community-based, socio-ecological lens improves understanding of harmful algal bloom impacts and shellfish harvester perceptions in coastal Oregon

Abstract: Harmful algal blooms (HABs) occur when certain species of toxin-producing microalgae reach high abundance and enter the food chain where they can contaminate shellfish, making them unsafe for human consumption due to the risk of shellfish poisoning. These events often lead to coastal fishery closures to protect human health. Despite the maturity of the fields of HAB monitoring and prediction, a socio-ecological lens is rarely employed to understand the human dimensions of this issue. The goal of this research is to assess HAB-related health risks to shellfish harvesters and how they perceive HABs in order to more effectively target management and outreach efforts.

We conducted monthly HAB monitoring from October 2020 – August 2022 and toxin testing monthly in 2021 and 2022 in the South Slough and Coos estuaries on the Southern Oregon Coast. HAB species in estuarine water were identified using light microscopy, and toxins (particulate domoic acid (pDA), saxitoxins, and microcystins) were measured using enzyme-linked immunosorbent assay (ELISA). To link HAB-associated health risks with recreational harvesting practices, we conducted in-person and online surveys of local shellfish harvesters monthly from June 2022 - February 2023, collecting standard demographic information, harvesting practices, and knowledge and perceptions of HAB threats.

We observed bloom concentrations (105 cells/L or greater) of Pseudo-nitzschia spp. in both estuaries during the summer of 2021, with pDA detected in water samples at popular shellfish harvesting sites, typically in concentrations below alert levels (200 ng/L). One sample from a known crab harvesting site contained pDA concentrations high enough to accumulate in shellfish. Preliminary survey findings (n=140) suggest that intensity of shellfish harvest is highest in summer, with 80% of survey participants reporting at least one summer harvest, compared to a range of 29 - 41% during other seasons. Only 6% of participants reported ever experiencing illness following the consumption of recreationally harvested shellfish, while 64% agreed or strongly agreed that they were concerned about HABs. Future analyses will assess differences in responses between demographic groups using logistic regression.

This study of the socio-ecological system of HAB management allows us to pinpoint overlap between general algal toxin risk and human exposure factors to streamline future HAB monitoring. By combining ecological monitoring with information about community natural resource use and perceptions, we can more accurately estimate risk of environmental exposures and understand how to best improve management practices.