Mariculture is a rapidly growing industry in Alaska, and includes farmed Pacific oysters (Magallana gigas). Harmful algal blooms (HABs), which can cause paralytic shellfish poisoning (PSP), are a major challenge for Alaska oyster farmers, along with choosing farm sites for optimal oyster growth. This project seeks to determine environmental factors associated with HABs and oyster health in the high-latitude estuarine environment of southeast Alaska with the goal of predicting HAB events and aiding in site selection for future farms as the industry grows.
We conducted weekly water column, phytoplankton, and oyster tissue sampling at an oyster farm in Juneau, AK. We observed significant seasonal variation in both environmental variables and phytoplankton community composition in southeast Alaska over the four years of monitoring (Figure 1A and 1B). Preliminary results suggest that higher lipid content in oysters may align with peaks in phytoplankton biomass, and that lipid content tends to be higher at higher water temperatures and lower salinities (Figure 1C). Thus far, toxin levels in sampled oysters have been below safe thresholds for consumption, but analyses are ongoing to identify drivers of toxicity. Determining which factors contribute most strongly to the health of farmed oysters, as well as to toxin levels in oyster tissue, is critical in allowing oyster mariculture to expand in a safe and profitable way in southeast Alaska.