Seasonal and spatial variations of carbon and nitrogen distribution in thesurface sediments of the Gulf of Riga, Baltic Sea

The variations in concentrations of carbon and nitrogen in surface sediment s of the Gulf of Riga were investigated between December 1993 and January 1 995. The sediment samples were taken nine times during this period at two s ampling sites. One sampling site, G5, exhibited high abundance of burrowing amphipods, whereas at the second site, T3, the number of macrozoobenthic o rganisms was comparatively small. Similar vertical profiles of mean sediment dry-weight concentrations of tot al carbon (TC) and total nitrogen (TN) were obtained at both sites G5 and T 3. However, during autumn-winter considerable differences of TC and TN conc entrations in surface sediments (0-2 cm) between sites were observed. This was probably the effect of differences in the bioturbation level. During su mmer, when decline in numbers of amphipods were recorded, the vertical prof iles of TC and TN at site G5 were similar to those at site T3. Significant differences between months were detected for TN at site T3 refl ecting sedimentation of spring and autumn blooms in April and late October- early November, respectively. This was supported also by lower atomic C/N r atios in surface sediments during corresponding sampling events. (C) 2001 E lsevier Science Ltd. All rights reserved.