Nutrient Fluxes in the Microalgal-dominated Intertidal Regions of the Lower Yaquina Estuary, Oregon (USA)

Abstract

The effects of benthic microalgae on sediment nutrient fluxes were investigated at three sites across the intertidal zone of lower Yaquina Bay. Study sites were selected where microalage were present but where seagrass and mud shrimp were absent. Sediment columns were collected seasonally from one to three stations from September 1999 through August 2000 to determine the seasonal and spatial range in benthic fluxes. Collected sediments were carried to the nearby laboratory for light and dark incubation experiments. Nitrate fluxes ranged from −122 to −4 μmol N m−2 hr−1, whereas ammonia fluxes ranged from −52 to 101 μmol N m−2 hr−1. The ranges for orthophosphate and silicate were −7.4 to 12 μmol P m−2 hr−1 and −93 to 283 μmol Si m−2 hr−1. The sediments were always a net sink for nitrate. Nitrate uptake rates were highest during the warmest month (August) and lowest during the coldest months (November and January). Nitrate fluxes were not statistically different for light and dark conditions. Ammonium was ge...