Oceanologia (Dec 2002)
Spatio-temporal decay 'hot spots' of stranded wrack in a Baltic sandy coastal system. Part I. Comparative study of the pattern: 1 type of wrack vs 3 beach sites
Abstract
The significance of distance along the beach-dune transectand different moisture conditions as regards the decay ofZostera marina leaf litter was investigated in simple fieldexperiments in three temperate, medium- to fine-quartz-sediment,sandy beaches of the Gulf of Gdansk in Poland. 1800 replicatelitterbags of freshly stranded Zostera marina leaves wereplaced in beach sediments at different strata and levels on eachof the beaches. The litterbags were sampled after 5, 10, 50, 100and 150 days in the field and the remaining material was thendried and weighed. Under similar conditions of sediment composition,salinity and wave inundation, ANOVA tests revealed significantdifferences in breakdown through time and site. Thus there weresome differences in the decay process between the low and high beach.In the former, degradation proceeded rapidly in the initial stagesand then stabilised, while in the latter it remained linearthroughout the study period. Matter loss in each stratum was alsoseasonally dependent. This may, however, be more closely linkedto successional changes in the chemistry and/or microflora of thebeach wrack than to its physical breakdown. Differences betweenorganic matter degradation in the high and low beaches may beexplained by differences in the moisture regime and nutrient status,and not by differences in the decay processes themselves. Therefore,two decay centres were found in the beach-dune system: the lowbeach together with the strandline (wrack consumption 12-21% day-1in the warm season, and 4-10% day-1 in the cold season) and the dune(active consumption 2-6% day-1 in the warm season only).
