Benthic Oxygen Production in the Choptank Estuary

Abstract

Microphytobenthos (MPB) represent an important component of primary production in many coastal estuarine systems. The aim of this study is to determine which variables in the Chesapeake Bay are positively correlated with MPB oxygen production, and based on this correlation to develop a predictive relationship for estimating benthic primary production. Furthermore, this study estimates the proportion of MPB primary production to total primary production in the Chesapeake Bay. Oxygen flux rates were measured in the dark and in the light from sediment cores taken from three sites on the Chesapeake Bay. Flux rates ranged from 6000 mol O2 m-2 h-1 in the light to -3800 mol O2 m-2 h-1 in the dark treatment. From these rates and other measurements, we developed multiple linear regressions using sediment grain type and depth to predict oxygen production seasonally. We applied these relationships to sediment grain-size and bathymetry data using ArcMap software to create a spatial dimension to our predictive relationships. Based on our derived relationship, we estimated summer average benthic daily net production to be 123 ± 962 mg O2 m-2 d-1 between 0-3 meters. For the winter, we estimated the rate to be 152 ± 413 mg O2 m-2 d-1. For spring we had a weaker relationship, but we estimated benthic production to be -257 ± 123 mg O2 m-2 d-1. Using published pelagic data, we created a proportion of benthic to pelagic primary production, and we estimate that MPB provide approximately 12% of total primary production in the mid-bay region. Shallower depths contained a higher proportion of benthic O2 productivity to pelagic O2 production with the contrast peaking during the summer months.