Abstract
Laboratory experiments using six macrobenthic invertebrates from a brackish habitat were performed to test the organisms escape reaction after burial at 4 °C and a salinity of 13 PSU. All three bivalves Arctica islandica (Linnaeus), Macoma balthica (Linnaeus), Mya arenaria (Linnaeus) and the polychaete Nephtys hombergii (Savigny) successfully re-burrowed to the sediment surface through a covering layer of 32 – 40 cm of till or a sand/till mixture. These high escaping potential could partly be explained by an inhomogeneous texture of the till and sand/till mixture with “resting holes”. The polychaete Bylgides sarsi (Malmgren) successfully burrowed through a covering layer of 15 cm whereas the polychaete Lagis koreni (Malmgren) showed almost no escaping reaction. No general differences in escape behaviour after burial were detected between test species from brackish and marine habitats. However, a size-dependence in mobile polychaetes was apparent within our study. Generally, thin covering layers increase the chance of the organisms to reach the sediment surface after burial. High burrowing velocities of up to 8.0 cm d-1 were observed for the bivalves and up to 20.0 cm d-1 for N. hombergii. Survival rates varied between 0 and 50 % and the percentage of organisms which showed burrowing activity after burial ranged between 15 and 81 %. In combination with multibeam echosounder measurements of the elevated sea floor level at two disposal sites in Mecklenburg Bay (western Baltic Sea) laboratory survival rates were extrapolated to the field, yielding survival rates of 68 and 77 % for the two disposal sites. A comparison of these rates with results from a simultaneously field study of the macrofauna using grab sampling shortly before and shortly after a disposal event in June 2001 reveals slightly lower values in the present study. Reasons for discrepancies are discussed.
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