Deposition of large organic particles (macrodetritus) in a sandy beach system (Puck Bay, Baltic Sea)

The aim of this study was to evaluate the amount of organic macrodetritus deposited on the sandy shores of the southern Baltic,an d to determine the type of washout material and their chemical composition (carbon and nitrogen). Over 900 samples of macrodetritus (particles retained on a 0.5 mm sieve) were collected from seven sampling locations along a 120 km stretch of coastline in Poland at monthly intervals in 2002. Analysis of the C and N content of several categories of detritus supplied information about seasonal changes in and the ageing of algal debris,an d indicated that the amount of carrion is constant; the latter is apparently always metabolised very rapidly. The annual deposition of macroalgal detritus on this coast was estimated at 15 000 tonnes fresh weight,t hat is around 75% of the primary production of filamentous macroalgae in Puck Bay. In comparison with the amounts of kelp deposited on sandy beaches in South Africa (Griffiths & Stenton-Dozey 1981),t he massive seaweed washouts on Mediterranean beaches (Morand & Briand 1996),or the deposition of algal mats in the northern Baltic (Norkko & Bonsdorff 1996a),t he quantities of macrodetritus on the shore in the study area are average,ev en allowing for the fact that the Baltic Sea is highly eutrophic (HELCOM 2005).