There Roscovitine are also artificial shallow areas that appeared in 1989–1997, after sediment had been dredged to feed beaches on the open-sea side of the Hel Peninsula so as to protect them from abrasion. The Outer Puck Bay, which is directly connected with the open sea is much more dynamic. One of the main sources of sediment feeding the Bay’s seabed is the discharge of material weathered and eroded in its catchment area. In situ measurements of the rate of sediment accumulation were carried out in 2007–2008 at station MH1, situated in the eastern part of Puck Bay at a depth of about 20 m (Figure 1). To determine the rate of accumulation a measurement

setup was prepared. This consisted of four cylindrical traps fixed to a single rod at a depth of about 0.5 m above the seabed. The traps were made from 50 cm long PVC pipes with an internal diameter of 9.5 cm, i.e. an aspect ratio of 5.3 (Figure 2). This type of trap was selected on the basis of earlier in situ investigations of sediment deposition processes in the sea (Hargrave and Burns, 1979, Blomqvist and Kofoed, 1981, Hakanson et al., 1989, White, 1990 and Kozerski, 1994). All the sediment traps were deployed in September 2008 and were retrieved after 4, 7, 10 and 14 months of exposure. During the investigations trap no. 4 may have been damaged by a drifting log and begun to leak; in addition, in the difficult weather conditions during its retrieval, some INCB024360 of sediment may have been

lost. For this reason, trap no. 4 was excluded from further analysis. Seabed sediment samples were taken with a Niemistö corer (i.d. = 8 cm) in the form of 20 cm long cores, extracted from the spot where the in situ measurement setup was deployed. Near-bottom water samples were obtained with a small tube, and the core was sliced into 1 and 2 cm long sub-sections. The slices were then dried at room temperature, put into plastic bags and sent to the Institute of Meteorology and Water Management – National Research Institute, Marine Branch, Gdynia, for radioisotopic analysis. Near the sedimentation

traps additional surface sediment samples were taken with a van Veen grab for granulometric analysis. The 4-litre near-bottom water samples were acquired with a bathometer prior to the installation of measurement setup and also after the exposure time of consecutive to sediment traps had ended. The water samples were necessary for calculating the sediment concentration near the sediment traps. To calculate the concentration of suspended particulate matter (SPM) in the near-bottom water, the seawater samples were passed through preweighed Whatman GF/F glass fibre filters. Before filtration, the filters were dried at 105 °C for about 60 minutes to remove hygroscopic humidity; they were also weighed to 0.00001 g accuracy. The near-bottom water was filtered on a quadruple Sartorius filtering unit, with about 4 litres of water being passed through each dried filter.

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