UW Aquatic & Fishery Sciences Quantitative Seminar

Neil Banas

UW Oceonagraphy

Dynamics of Willapa Bay, Washington: A tale of raging tides, ravenous oysters and extremely unbalanced salt fluxes

Abstract

Willapa Bay is a shallow, macrotidal, coastal-plain estuary where  Pacific oysters (Crassostrea gigas) are intensively cultivated. A  high-resolution numerical model of the bay is used to map this tidal  exchange process in detail. A Lagrangian particle-tracking method  reveals coherent lateral exchange flows interwoven with discontinuous,  small-scale dispersion, as well as tidal-residual currents that in  some locations sharpen rather than smooth gradients between water  masses. Results from a version of the tidal model modified to include  a non-conservative, phytoplankton-like tracer suggest that oysters and  other intertidal benthic grazers may be sufficient by themselves to  explain the net loss of phytoplankton within the estuary in summer.  These grazers appear to be close to carrying capacity: as bay-total  filtration capacity increases, the chlorophyll intrusion shortens and  food intake per individual grazer declines. Even in this well-flushed  system, the small-scale structure of the tidal circulation, rather  than total oceanic supply, controls overall food availability for the  benthos.