Denitrification Rates in the Low-Oxygen Waters of the Stratified Baltic Proper

Denitrification activity was shown in the deep, low-oxygen waters of the Baltic proper by both in vitro and in situ methods. The vertical distribution of NO(3) in the water column showed nitrate consumption and NO(2) and N(2)O maxima in the deep waters when O(2) was below 0.2 ml liter, which is suggestive evidence for denitrification. Direct in situ evidence for denitrification was obtained by finding an N(2) saturation of up to 108% in the deep waters. When these waters were incubated with NO(3), N(2) was produced. Quantification of the denitrification rate done by the addition of C(2)H(2) to water samples from the active depths showed a rate of about 0.10 mumol liter day.