Ammonia Excretion Rates of Oceanic Copepods and Implications for Estimates of Primary Production in the Sargasso Sea

Abstract

AbstractAmmonia excretion rates of oceanic copepods were measured on three cruises to the Sargasso Sea in August-September 1980, August-September 1981, and March-April 1982. Twenty experiments were conducted using ten species representing genera abundant in the tropical/subtropical Northwest Atlantic: Calanus, Clausocalanus, Undinula, Microsetella, Macrosetella, Oncaea, Farranula, Candada, and Pleuromamma. Remineralization rates of separate species were calculated by linear regression of time series (6–12 h) of net NH4 release, after correction for uptake in control bottles. Changes in chlorophyll a in the total and <10 μm size fractions indicated that these excretion rates are representative of feeding animals. Excretion rates were significantly related to body dry weight, with small copepods releasing more NH4 for their size than large species. The small harpacticoid and cyclopoid copepods excreted NH4 at rates equivalent to their entire body nitrogen every three days. The size frequency distribution of...