Assessing euphausiid homogeneity in Puget Sound scattering layers

Abstract

Euphausiids are ecologically important zooplankton in Puget Sound that vertically migrate and can form scattering layers. The depth of euphausiids across sex, species, and length affects what predator-prey interactions occur and the rate of biogeochemical cycling. Multinet tows collected euphausiids from various depths within different layers in northern Puget Sound. No significant variation in euphausiid sex or length with depth was found. Euphausiid size significantly increased with depth in the layer, with the median euphausiid length increasing from 8.3 mm to 15.3 mm over 20 m at Hazel Point. The strength of this trend varied, possibly due to the proximity of fish. Environmental modeling could be improved by better accounting for euphausiid size increase with depth even in small scales.