Sedimentation of organic and inorganic particulate material in Lindaspollene, a stratified, land-locked fjord in western Norway

Abstract

Sedimentation of particulate material to the bottom (90 m) was measured in Lindåspollene, a land-locked, highly stratified, west Norwegian fjord, receiving fresh water from a small glacier free watershed. Five cylindrical sediment traps positioned at 10, 20, 40, 70, and 85 m below the surface were exposed from April to November. Organic material comprised 40 to 60 % of the sedimented matter. Sedimentation rates of particulate inorganic material (PIM) and particulate organic carbon (POC) decreased from 229 and 111 at 20 m to 71 and 22 g m-2 yr-1 respectively, in the deeper water. Possible reasons for the low sedimentation in the stagnant water below 40 m are high mineralization rates in the upper 40 m and the lack of resuspension in the water below. Three pulses of POC and PON (particulate organic nitrogen) reached the bottom related to phytoplankton blooms in April and May. The pulse in April was the largest and the sedimented material consisted of unidentified aggregates, diatoms and some few fecal pellets. Few recognizable structures were found in the samples below 20 m except in April. This might indicate a low zooplankton grazing efficiency in April, but a high efficiency during the rest of the investigation period.