Occurrence of a Deep Nitrite Maximum in Lake Michigan

Abstract

A nitrite maximum with concentrations up to 10 μg NO 2 − -N∙L −1 was observed at depths between 30 and 60 m during summer in oxygen-saturated waters of Lake Michigan. The extracellular release of nitrite by phytoplankton concentrated below the thermocline appears to account for this maximum. In fall, when phytoplankton were no longer concentrated in this zone, no nitrite maximum was observed. It appears that the deep nitrite maximum in Lake Michigan is found only in association with high densities of phytoplankton.Key words: Lake Michigan, nitrite, nitrogen, phytoplankton