Impact of Surface Temperature and Salinity on the Ratio of Marine Diatoms to Dinoflagellates in the Trevor Channel Area

Abstract

In an effort to illuminate the factors that influence surface phytoplankton community composition with respect to marine diatoms (Class Bacillariophyceae) and dinoflagellates (Phylum Dinoflagellata), temperature and salinity data were collected. Phytoplankton samples were collected at six surface water locations along the Trevor channel near Bamfield, British Columbia where sampling locations were of known gradients of salinity and temperature. Each sample was analysed under a light microscope, where 2 µL volumes of seawater were counted for both dinoflagellate and diatom abundances. The ratio of diatoms to dinoflagellates was determined by averaging multiple counts of well-mixed samples from each station. Surface temperature and salinity data were collected using individual CTD (Conductivity, Temperature, Depth) casts, where only the surface values were considered. The phytoplankton ratios were then correlated to each of temperature and salinity. It was found with strong positive correlation that conditions with higher salinity favoured dinoflagellate-dominant communities (r = 0.97, p = 0.00013) and conditions with higher temperature favoured diatom-dominant communities (r = 0.92, p = 0.0035). This data may prove useful in studies regarding how small and large scale climatic changes affect phytoplankton community composition, and proves interesting directions in research as to how bottom-up controls on community structure can impact abundances of macro-organisms.