The degradation of stranded carrion on a Baltic Sea sandy beach

Litterbags of two mesh sizes (0.5 mm and 0.02 mm) were employed to assess the role of faunal and physical components in carrion breakdown on sandy beaches. Field experiments were undertaken on two sandy beaches in Poland. The tissue of Gadus morrhua L. and the white of a hen's egg were used as substrata to be decomposed in the litterbags. The bags, together with control bags, were distributed in three trials in different beach locations (medium water-mark, strandline, backshore, and dune) and at appropriate depths (5, 20 and 50 cm deep). Each trial was run for 20 days and was set up on the beach profile. The litterbags were retrieved after 3, 6,10, 15 and 20 days. The remaining material was then dried and weighed, and analysed using a C11N Analyser. Organic material was rapidly lust from the litterbags. From 4 to 56 % of the original dry mass remained after 20 days in the field in the coarse-mesh bags. However, between llic low and higW-beach stations there were some differences in the decay process. At the former, degradation proceeded rapidly in the initial stages and then stabilised, at the latter it did so linearly throughout the study period. The fact that fauna were excluded from the carrion by the use of finer mesh litterbags had an appreciable effect on the rate of dry matter loss. Microbial decay, abiotic leaching and fragmentation were thought to be major causes of carrion weight loss from the litterbags. The rate of dry mass loss, expressed as loss of organic material, ranged from 1 to 14% per day. At the same time, the C/N ratio increased, which was evidence of the earlier use of nitrogen as an energy source. These results suggest that differences in organic matter degradation in high and low-beach areas can be explained by differences in moisture regime and nutrient status and not by differences in the decay processes themselves.