Mussel beds — amensalism or amelioration for intertidal fauna?

Abstract

The faunal assemblages of a mussel bed (Mytilus edufis L.) and ambient sand_flat were compared to study how a bioherm of suspension feeding organisms affects benthic communities in a tidal flat. During a survey of mussel beds in the Wadden Sea at the island of Sylt {North Sea}, a total of 52 macrofaunal species and 44 meiobenthic plathelminth species were detected. They occupied different microhabitats in the mussel bed. 56 % of the macrofauna species were dwelling in the sediment beneath the mussels and 42 % were epibenthic or epiphytic. The latter were restricted in their occurrence to the mussel bed. Along a transect from the sandflat to the mussel bed the mean species densities of macrofauna did not differ significantly, while abundances were significantly lower in the mussel bed than in the sandflat. The composition of the assemblages shifted from a dominance of Polychaeta in the sandflat to Oligochaeta in the mussel bed. Surface filter-feeding polychaetes of the sandflat (Tharyx mariom) were displaced by deposit feeding polychaetes under the mussel cover (Capitella capitata, Heteromastus filiformis}. The total meiobenthic density was lower and single taxa (Ostracoda, Plathelminthes, Nematoda} were ~ignificantly less abundant in the mud of the mussel bed. The plathelminth assemblage was dominated by grazing species (Archaphanostoma agile}, and differed in community structure from a sandflat assemblage. An amensalistic relationship was found between the suspension-feeding mussels and suspensionfeeding infauna, while deposit-feeders were enhanced. The presence of epibenthic microhabitats results in a variety of trophic groups co-occurring in a mussel bed. This is hypothesized as trophic group amelioration and described as an attribute of heterotrophic reefs.

Benthic assemblages associated with native and non-native oysters are similar

“…Historically, however, these regions would have supported widespread populations of O. edulis (Reise et al, 1989;Riesen and Reise, 1982 edulis may have formed massive reefs in historic periods (Todorova et al, 2009) there are no contemporary records of it forming reefs. Species diversity is related to habitat heterogeneity, generally following a unimodal curve, with greatest diversity usually in habitats with intermediate levels of heterogeneity (Allouche et al, 2012;Dittmann, 1990;Snover and Commito, 1998). Although no decrease of diversity was associated with increasing oyster cover in the present study, previous studies have shown lower species richness in experimental plots with high oyster cover compared to those with low oyster abundance (Green and Crowe, 2013).…”

Subtidal and intertidal mussel beds (Mytilus edulis L.) in the Wadden Sea: diversity differences of associated epifauna

“…Dittmann 1990;Obert and Michaelis 1991;Albrecht and Reise 1994;Günther 1996;Albrecht 1998) or subtidal mussel beds (e.g. Dekker 1989;Dankers and Zuidema 1995).…”

Effects ofFucus vesiculosus covering intertidal mussel beds in the Wadden Sea

“…These mussel beds are abundant in the lower tidal zone and subtidally (Verwey, 1954;Riesen & Reise, 1982;Dankers & Koelemaij, 1989;Obert & Michaelis, 1991), constituting ecological elite structures in terms of the high number of associated species (Dittmann, 1990), biomass and secondary production (Asmus, 1987), foraging site for birds (Swennen et al, 1989;Zwarts, 1983), remineralization, and oxygen consumption (Dame & Dankers, 1988;Asmus et al, 1990).…”