Investigating change in toxic algae in Scottish coastal waters
Toxin-producing algae naturally occur in Scottish coastal waters. Despite decades of research into harmful algal blooms (HABs), the environmental drivers remain uncertain and inconclusive. Further understanding and knowledge of the relationships between environmental variables and HAB occurrence has the potential to better protect consumer health from contaminated shellfish and the aquaculture industry from financial losses through site closures and/or product toxicity. In this PhD project, the ecology of toxin-producing taxa and impacts of environmental parameters on them were explored nationally, regionally, and locally through monitoring data, field surveys, and experimentation. Using a 13-year dataset (2006-2018), no single catalyst was determined but some combinations and trends could be pinpointed. Nationally, diatoms appeared to decrease, while some dinoflagellates increased. Regional trends could be identified, and individual taxa were shown to respond to combinations of variables. In northern waters, salinity and toxicity were inversely correlated with signals that non-toxic species of Pseudo-nitzschia and Alexandrium dominated in high salinity summer water temperatures. The growing season of Alexandrium spp. in Loch Creran was shown to be lengthening, and a germination experiment on Lingulodinium polyedra cysts from the same loch found its ecology differed from A. catenella, another harmful cyst-forming dinoflagellate studied in Maine, USA, by not entering full dormancy or having a chilling requirement. Overall, comparisons between cyst-forming dinoflagellates indicated limited overlaps in response to environment but mostly that responses were taxa-, or species-, and/or location-specific. This study demonstrated the benefits of a multi-layered, interdisciplinary approach, examining national, regional, and local scales, combining microbiological and biogeochemical investigations, and highlighted the potential advantages to be gained from widespread, rapid, species-level identification of phytoplankton.
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