Patches of the mussel Mytilus sp. are islands of high biodiversity in subtidal sediment habitats in the Baltic Sea

Abstract

Mytilus sp. is a habitat-modifying species that can influence biodiversity by facilitation and inhibition of species. We investigated the relationship between size of Mytilus patches, sediment characteristics and species richness of associated macrofauna, meiofauna and macroalgae on sandy sediments at 7 m depth in the Askö area, northern Baltic proper. A total of 24 associated macrofauna species were identified, 11 of which were not present on bare sediment outside the patches. The bare sediment had on average 5 species, which increased to 6 associated species at a mussel patch size of 5 cm 2 and 17 species at 314 cm 2 , which was > 85% of the associated species in a nearby large mussel bed. The diversity of macro-infauna was higher in mussel patches compared to sediment. Macroalgae, being dependent on mussel shell as substrate or on attachment by byssus threads, were not found outside patches. Sediment contents of total carbon and nitrogen were significantly higher within patches than outside, mainly due to the mussels' filtration and biodeposition of small nutrientrich particles. Diversity of meiofauna did not change with patch size, but total abundance of Nematoda was higher within patches. As patch size increased, the effects of Mytilus on the sediment characteristics became stronger, but few negative effects of increased biodeposition were seen on species richness. The results show that mussel patches represent islands of high biodiversity in sediment areas and belong to the most species-rich habitats in the Baltic Sea, due to structural and functional effects.

Invertebrate communities associated with blue mussel beds in a patchy environment: a landscape ecology approach

“…These findings are in contrast with many terrestrial studies (e.g. Simberloff & Wilson 1969, Diamond 1975 and smallscale studies of patches of blue mussels, seagrass and coral reefs (Sale et al 1994, Hovel & Lipcius 2001, Norling & Kautsky 2008. The result might be a consequence of scale since the study islands were bigger than most previously studied habitats.…”

Spatially Extended Habitat Modification by Intertidal Reef-Building Bivalves has Implications for Consumer-Resource Interactions

“…However, in soft-bottom systems, their effects on sediment conditions typically extend beyond the direct surroundings of the reefs and may be detectable up to several hundreds of meters (Krö ncke 1996;Bergfeld 1999). Many studies have demonstrated that reef builders have an important effect on the local benthic community (Dittmann 1990;Norling and Kautsky 2008;Markert and others 2009) and that the reefs themselves are important foraging grounds for avian consumers (for example, Nehls and others 1997;Caldow and others 2003). However, the spatially extended effects of such reef builders on this community remain largely unstudied.…”

Influence of environmental factors and biogenic habitats on intertidal meiofauna

“…In fact, biogenic habitat plays a key role in structuring the meiofaunal communities through provision of shelter and food (Gibbons, 1988a,b;Danovaro & Fraschetti, 2002;Arroyo et al, 2004;Danovaro et al, 2007;Logan et al, 2008;Urban-Malinga et al, 2008). While there are a few studies discussing the facilitation role of mussels on meiofauna-and most of the focus is on biodeposition effects, with sometime contrasting results-the general outcome is that organic matter emitted into mussel beds increases meiofaunal abundances (Norling & Kautsky, 2008). Some of our descriptors of quality and quantity confirmed this pattern: higher concentrations of CPE and PRT:CHO ratio in the sediment organic matter in the sites characterised by the presence of mussels more than in those with algae coverage.…”