Vallius, H.
Sediment and carbon accumulation rates off the southern
coast of Finland
Abstract. The southern coast of Finland encompasses about
one third of the coasts of the Gulf of Finland. It is a mosaic of hundreds if
not thousands of islands, peninsulas and bays, which also are reflected in the
seabed of the coast. The sea floor is composed of a patchy and fragmented
mosaic of mainly quite small basins separated from each other by thresholds of
islands, peninsulas or submarine ridges. This affects transport and near bottom
currents such that deposition of suspended particles is restricted to certain
areas only. Linear sediment accumulation rates along the southern coast of
Finland were studied from 28 cores of a sampling campaign in 2000–2004 through
gamma spectrometry of 137Cs. Sediment accumulation in this environment with
such diverse character was found very patchy and net sedimentation rates
varying from less than 0.5 cm/a to values of nearly 3 cm/a as well as mass
accumulation rates from 0.5 kg/m2/a to 8.8 kg/m2/a were found. The sediment
accumulation rates were observed to be higher in shallower water in coastal
sheltered or semi-sheltered bays. Total carbon concentrations varied from 1.3 %
to 12.6 % and carbon accumulation rates from 20 g/m2/a to 355 g/m2/a such that
the highest carbon concentrations were usually found in deeper water with some
distance from the coast, while the highest carbon accumulation rates were found
in the coastal shallow basins where sediment accumulation was found strongest.