Species abundance and conditions of plankton blooms in Possession Sound

• Main Author: Larsen, Maci
• Format: Text
• Language: English
• Published: Western CEDAR 2022
• Subjects: Orca
• Online Access: https://cedar.wwu.edu/ssec/2022ssec/allsessions/174; https://cedar.wwu.edu/context/ssec/article/3336/viewcontent/194_416f23ecf2cc4a4ab082097c1be37843.pdf

Harmful algal blooms (HABs) can threaten the health and stability of an ecosystem. They occur when there is a significant increase in the abundance of toxin-producing phytoplankton. Paralytic shellfish toxins are just one example of how these massive blooms can be lethal to marine life and even humans if the poisoned shellfish are consumed. HABs are seen as a considerable threat to the ecosystem, but what about the non-HAB-forming plankton that make the waters of the Salish Sea their home? Plankton of many kinds do not require complex conditions for blooming to occur; it can be as simple as temperature and time of year fitting the ideal requirements needed for plankton to reproduce rapidly. Do these other types of blooms also pose a threat, which could even be more prominent than HABs due to the frequency of occurrence? This study investigates phytoplankton blooms occurring in Possession Sound, Washington for the last four years to figure out if this is possible. Two sites in Possession Sound, encompassing the Snohomish River Estuary, were selected for study: one site farther out in the sound and one site closer to shore, potentially with more influence from human activity. Using data from the Ocean Research College Academy (ORCA), we examine the conditions in which an overabundance of phytoplankton occurred at these two sites. Water temperature, chlorophyll levels, and plankton counts completed by ORCA students are used to compare bloom and non-bloom conditions. Additionally, we investigate which species dominate these blooms and whether there is any correlation between season or other conditions and the species most prevalent. By investigating this, a possible conclusion can be drawn about the overall threat that phytoplankton blooms may pose, even if they are not under the label of HABs.