Environmental controls on zooplankton composition and distribution in Muchalat Inlet, Nootka Sound, B.C., Canada

Senior thesis written for Oceanography 445

[author abstract] This study investigates environmental controls on zooplankton populations within the estuarine Muchalat Inlet fjord basin in Nootka Sound, B.C., Canada. Five stations were sampled along an ecological gradient from exposed Nootka Sound towards the head of Muchalat Inlet. At each station, four samples were collected at different depth ranges of the upper 100 meters to distinguish vertical distribution of zooplankton, and environmental conditions were measured by CTD casts. Abundances of nine zooplankton groups were identified, including euphausiids, hyperiids, gammarids, chaetognaths, larvaceans, ostracods, Oithona, other small copepods, and large copepods. Principal component analysis was used to identify correlation of sample composition and environmental conditions. Vertical distributions of zooplankton groups were strongly associated with salinity and dissolved oxygen limitations, while horizontal distributions were likely controlled by water mass transport. This study assists future conservation efforts and ecological modeling of dynamic estuarine systems.

University of Washington School of Oceanography