Phytoplankton pigments and dissolved organic matter distribution in the Gulf of Riga

The results of field studies of phytoplankton and dissolved organic matter (DOM) in the Gulf of Riga in August-September 1993, June 1994 and April 199 5 are presented. Actively excited fluorescence in UV- and visible spectral regions was used to investigate spatial distributions of DOM, Chl a, carote noids and phycoerythrin in surface water. The fluorescent data were collect ed by means of laser remote sensing spectrometer (LIDAR), spectrofluoromete rs in underway flow-through mode and in the measurements of the water sampl es. Pronounced variable spatial structures of phytoplankton were observed i n spring 1995 and late summer 1993, while in early summer 1994 the pigment distribution was rather homogeneous. The spatial modulation of high-resolut ion profiles of phytoplankton with the period 3.5-5 km was detected across the gulf in all seasons probably caused by variability of hydrophysical con ditions. A negative correlation of DOM concentration in surface waters and salinity was revealed in August-September 1993 and June 1994. (C) 1999 Else vier Science B.V. All rights reserved.