CYCLOPHEOPHORBIDE A IN SUSPENDED PARTICLES IN THE META‐ AND HYPOLIMNION DURING OXYGEN DEPLETION IN A SUBTROPICAL LAKE

Abstract

Ostrovsky, I. & Yacobi, Y. Z.Israel Oceanographic and Limnological Research, Kinneret Limnological Laboratory, P.O. Box 345, Tiberias 1402, IsraelCyclopheophorbide a (CPP) was the most abundant degradation product of chlorophyll a (Chl a) in the hypolimimnion, benthic boundary layer and sedimenting particles in Lake Kinneret in June‐July 1997, when a prolonged period of residual oxygen concentration was found below the thermocline. The highest concentration of CPP was found in the benthic boundary layer, where it reached as high a concentration as 2 *g liter‐1. In sediment traps positioned below the thermocline CPP constituted from about 5 to 20% of the Chl a concentration and in bottom sediments from 5 to 185%. CPP was not detected in epilimnetic water samples, but was found in sediment traps located within the oxygenated water column, within the range of surface wave action. Comparison of regular traps, with traps poisoned by formaldehyde indicates that the importance of CPP‐containing particles in the sedimentation flux is relatively low, and that the bulk of CPP found in the bottom sediment is apparently a result of Chl a transformation in situ by biological activity. The timing and location of CPP appearance coincided with the lake compartments where denitrification apparently took place. This suggests that CPP can be used as a target pigment to trace organic matter processing under transient conditions in the water column and on the bottom sediments.