Gradients in biodiversity and macroalgal wrack decomposition rate across a macrotidal, ultradissipative sandy beach

The decomposition process of, and the meiobenthic and nematode colonization on, stranded macroalgae were studied along a macrotidal, ultradissipative sandy beach gradient at De Panne (Belgium). The horizontal patterns of macro- and meiofaunal densities and diversity in this beach have been well-documented. Defaunated Fucus detritus was buried in situ in litter bags, 10–15 cm under the sediment surface, at seven stations across the beach profile. Colonization by (meio)fauna and organic matter decomposition rates measured as carbon, nitrogen, phosphorus and dry weight loss, were studied after 10, 21 and 52 days of incubation. Algal detritus was colonized mainly by nematodes dominated by Rhabditidae, Sabatieria, Dorylaimoidea, Monhystera, Paracanthonchus and Daptonema. Organic matter weight loss was slowest at the higher and lower shore and fastest in the mid-shore, in line with the horizontal pattern of nematode diversity in the beach sediment. However, there was no consistent relationship between nematode diversity inside the litter bags and organic matter weight loss, prohibiting an unequivocal conclusion on whether the observed parallel between extant nematode diversity and organic matter decomposition rate indicates a causal relationship or follows from the fact that both are governed by the same set of physicochemical conditions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.