Nitrate and ammonium uptake in Antarctic waters1

Abstract

Nitrate and ammonium uptake rates were measured by the ¹⁵N tracer technique in Antarctic waters. The ratio urn:x-wiley:00243590:media:lno19802561064:lno19802561064-math-0001 averaged 0.54 in the Scotia Sea in early spring and 0.40 in the Ross Sea in summer, indicating that NO₃⁻ and NH₄⁺ contribute about equally to primary production in these regions and that a large proportion of the primary production is exported from the surface layers. Uptake rates in laboratory experiments increased with increasing temperature and the relative uptake of NH₄⁺ was positively correlated with increasing mean ambient NH₄⁺ concentration and depth in the water column.