Effects of tidal phase on zooplankton abundance in Cattle Pass, WA

Abstract

Zooplankton in Cattle Pass are advected from two water sources. Water from the Juan de Fuca Strait enters the pass from the South during flooding tides, while water from the Strait of Georgia enters from the North during ebbing tides. The questions I am interested in answering are: how does the marine influence of the Juan de Fuca Strait and the estuarine influence the Strait of Georgia affect the abundance of zooplankton in Cattle Pass? Do tidal processes affect the abundances of zooplankton in Cattle Pass? Is zooplankton abundance correlated with upper trophic level foraging? I based my hypothesis on several assumptions based on conclusions of a study from 1995 to 1997 by Zamon: water density fluctuations in San Juan Channel are evidence that tidal currents affect the source from which plankton is derived. Flooding tides mix colder, saltier water from Juan de Fuca into San Juan Channel. Tides create predictable patters of zooplankton availability for planktivorous animals (Zamon 2000). I hypothesized that ebbing tides advect zooplankton from the Juan de Fuca Strait. Zooplankton will be more numerous in the more oceanic waters during flood tide. I tested this hypothesis by analyzing zooplankton tows collected during flooding and ebbing tides.