Diatoms are one of the main groups of phytoplankton that form the base of the food web in aquatic systems and make up a large portion of the phytoplankton assemblage in the estuaries and sounds of the Pacific Northwest. Diatoms have a silica-based cell wall and lack flagella, limiting mobility. Due to silica being a significant element of their cell walls, diatoms have a greater silica requirement than dinoflagellates or other phytoplankton groups. As climate change progresses, ocean temperatures rise, and marine heat waves (MHWs) are becoming more frequent. Prior research has found that, in the North-Eastern Pacific Ocean, the relative abundance of diatoms compared to dinoflagellates decreases during these events. Two main hypotheses proposed to explain this trend are that 1) dinoflagellates are more temperature tolerant and 2) silicate availability may decrease with increased temperature, and diatoms are more reliant on silicate than dinoflagellates. For this study, I propose to examine the diatom/dinoflagellate ratio relative to changes in temperature and silicate availability in Tofino Inlet in Clayoquot Sound on the west coast of Vancouver Island BC, Canada from 2013-2023, during which time there were multiple marine heat waves. University of Washington Tacoma researchers have been collecting water property data in Clayoquot Sound in the late summer/early fall annually since 2001 and phytoplankton samples since 2007. These data include CTD profiles of temperature, salinity, density, oxygen, fluorescence and transmissivity and discrete water samples for nutrients and phytoplankton. Phytoplankton 10-meter vertical net tows (20 um mesh) were collected in addition to bottle samples at the surface and 10 m at the same stations every year. These samples were fixed with formalin and counted in the lab using a research grade compound microscope. I will be using these data for my study.

The spatial and temporal distribution of select harmful algae species in Clayoquot Sound on the west coast of Vancouver Island, BC, was investigated to understand their prevalence and potential risks to human health, aquaculture, and local economies. Harmful algae species, such as Alexandrium spp. (producing saxitoxins), Pseudo-nitzschia spp. (physically harmful to fish gills and producing domoic acid), and Dinophysis spp. (producing okadaic acid and dinophysotoxins), are known to cause harmful algal blooms (HABs) where toxins can accumulate in bivalves, leading to paralytic shellfish poisoning, amnesic shellfish poisoning and diarrhetic shellfish poisoning in humans when consumed. These blooms can disrupt aquaculture industries and result in serious economic repercussions. In addition, harmful algae can cause significant damage to marine animals, including fish kills and the disruption of trophic interactions, thereby threatening ecosystem stability. UWT researchers have been collecting water property data in Clayoquot Sound in the late summer/early fall annually since 2001 and phytoplankton samples since 2006. These data include CTD water property profiles and discrete water samples for nutrients and phytoplankton. Phytoplankton 10-meter vertical net tows (20 um mesh) were collected in addition to bottle samples at the surface and 10 m at the same stations every year. Samples were fixed and counted in the lab. This project aims to compile and map the distribution patterns of the three harmful algae species mentioned above and assess how that distribution has changed over the last 17 years. These results will also be compared with historical phytoplankton data for this region from Fisheries and Oceans Canada to compare distribution pattens.  We hypothesize that HABs will become more prevalent as water temperature increases. The study will provide valuable insights into the location and prevalence of select HABs in Clayoquot Sound, informing future monitoring plans and management strategies to mitigate potential negative effects.