Beach morphology and food web structure: comparison of an eroding and an accreting sandy shore in the North Sea |
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Authors: | Iris Menn |
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Institution: | (1) Alfred-Wegener-Institut für Polar und Meeresforschung, Wattenmeerstation Sylt, 25992 List, Germany, |
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Abstract: | Food web components and inorganic nutrients were studied on two sandy shores of the adjacent barrier islands of Sylt and
R?m? in the North Sea, differing in morphodynamics. Implications of high and low wave energy on the food web structure were
assessed. The Sylt shore represents a dynamic intermediate beach type, while the R?m? shore is morphologically stable and
dissipative. On the steep-profiled, coarse-grained Sylt shore, strong hydrodynamics resulted in erosion and high fluxes of
organic material through the beach, but prevented any storage of food sources. In contrast, the flat-profiled, fine-grained
R?m? shore, with low wave energy and accretion, accumulated organic carbon from surf waters. At Sylt, oxic nutrient regeneration
prevailed, while anoxic mineralization was more important at R?m?. Macrofauna on the Sylt shore was impoverished compared
with the community at R?m?. Correspondingly, abundances of epibenthic predators such as shrimps, crabs, fish, and shorebirds
were also lower at Sylt. Meiofauna was abundant on both shores, but differed in taxonomic composition. Several major taxa
were represented in fairly equal proportions of individual numbers on the well-oxygenated Sylt shore, while nematodes strongly
dominated the assemblage at R?m?. Thus, on cold-temperate, highly dynamic intermediate shores with high wave energy and subject
to erosion, the "small food web" dominates. Organisms are agile and quickly exploit fresh organic material. Larger organisms
and nematodes abound under stable, dissipative and accreting shore conditions, where some food materials may accumulate and
zoomass builds up to support numerous visitors from higher trophic levels.
Electronic Publication |
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Keywords: | Sandy shore Food web Wave energy Beach morphology |
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