SEDIMENTATION AND CARBON FLUX IN A SCOTTISH SEA LOCH, LOCH- LINNHE

Sediment traps were deployed in the upper basin of Loch Linnhe in 120 m of water at depths of 20, 60, 90 and 110 m below the surface. They were serviced over 13 months during 1991-92 at intervals ranging from a week to a month and the following parameters measured: dry weight and concentrations of carbon, nitrogen and chlorophyll. The average sedimentation rates of total dry weight over a year at 20, 60, 90 and 110 m were 12.4, 20.4, 31.0 and 48.5 gm(-2) day(-1) respectively. The historical net sedimentation rate, calculated from the depth profile of (210)pb, was 12.7 g m(-2) day(-1), suggesting that the sedimentation rate at 20 m is probably a good estimate of the present net sedimentation rate. On this basis the (estimated) sedimentation at the sediment surface (120 rn) was composed of approximately 80% resuspended material. The estimate of input of organic carbon of phytoplankton origin was based on chlorophyll sedimentation rates and yielded a figure of 0.082 g C m(-2) day(-1) A summary diagram indicating our estimate of the pathways of particulate organic carbon is presented. (C) 1995 Academic Press Limited