Short Term Changes in the Vertical Salinity Distribution of the York River Estuary Associated with the Neap-Spring Tidal Cycle

Abstract

A multidisciplinary investigation of hydrographic-nutrient-phytoplankton interactions was undertaken in the lower York River estuary of Virginia during August, 1978. The study centered on a spring tide-associated water column destratification event predicted to occur on or soon after August 19, the date of the maximum monthly spring tide. A station in the lower York River (depth 19 m) was occupied during four different periods, August 7–10, 16–17, 21–24 and 28–30, and temperature and salinity were measured periodically at 1 m depth intervals. During August 16–20 salinities were measured through the water column at seven stations in the York River extending from the mouth to 35 km upriver. During the first two sampling periods the water column was moderately to strongly stratified. Destratification was first observed 15–20 km upriver on August 18 and the lower river was destratified by August 21. Destratification persisted in the lower river for four days at which time increasing bottom salinities indicated the beginning of the restratification process. By August 28 restratification, resulting primarily from an increase in bottom salinities, was complete. The results illustrate the highly dynamic hydrographic nature of this estuarine system and the predictability of the stratification-destratification sequence. The effects of this hydrographic cycle on nutrient distributions, phytoplankton dynamics and benthic nutrient fluxes in this estuary are discussed in accompanying papers.