Changes in species richness with stocking density of marine bivalves

Abstract

Summary1. Monocultures of mussels might alter the infaunal benthic community of adjacent and interstitial sediments through provision of a complex habitat, input of organically rich material and larval removal through filter feeding. At a site of commercial seabed mussel cultivation, we aimed to determine the effect of mussels on the infaunal community of an intertidal mudflat at different spatial scales and under different stocking strategies. 2. Mussels were laid at four different densities (2, 3, 5 and 7·5 kg m − 2 ) on 400-m 2 plots in a 4 × 4 Latin square. Benthic samples were collected within and 10-100 m distant from the cultivation area c . 7 months prior to and 18 months after seeding the plots with blue mussels. Benthic community characteristics were related to initial seeding density and to the actual surface area of mussels associated with each set of samples collected within replicate plots. 3. The presence of mussels significantly changed the occurrence of some species of the infaunal community within the cultivated area. The infaunal communities supported fewer individuals and species than control treatments at all but the lowest mussel cover. 4. Species richness and the abundance of individuals per unit area also declined with increased area of mussel cover. The abundance of cirratulids and amphipods declined strongly with increasing mussel surface area. 5. Although the species composition and abundance of individual invertebrate species were altered by the presence of mussels, the distribution of individuals among species remained relatively unchanged. 6. Synthesis and applications . Overall, mussel beds changed the infaunal community, but the effects were localized (0-10 m) and not detectable at larger scales (10-100 m). Changes in benthic community composition could be reduced (but not eliminated) by lowering the stocking density of mussels to either 2 or 3 kg m − 2 . Given the small edge effects associated with cultivated mussel beds, the use of larger mussel beds would be preferable to many smaller mussel beds.

Changes in geochemical foreshore attributes as a consequence of intertidal shellfish aquaculture: a case study

“…Previous studies (Sorokin et al 1999, Bartoli et al 2001, Beadman et al 2004, Bendell-Young 2006 have shown that netted farmed sites tend to have more of organic matter and silt as compared to reference sites. Intensive shellfish farming also leads to loss of benthic diversity and changes in species composition towards netted regions being dominated by bivalves and deposit feeding worms as compared to paired reference beaches (Spencer et al 1997, Bendell-Young 2006.…”

Manila Clam (Tapes philippinarum Adams & Reeve, 1852) in the Lagoon of Marano and Grado (Northern Adriatic Sea, Italy): Socio-Economic and Environmental Pathway of a Shell Farm

“…In this way, there has been increasing recent interest in evaluating the collateral effects of commercial cultivation of bivalves on the marine environment (Sorokin et al, 1999;Bartoli et al, 2001;Jie et al, 2001;Dame et al, 2002), especially on macrobenthic communities (Kaiser et al, 1996;Drake & Arias, 1997;Spencer et al, 1997;Gaspar et al, 2002;. The main effect on non-target species is a reduction in species richness and abundance (Commito, 1987;Dittman, 1990;Guenther, 1996;Ragnarsson & Raffaelli, 1999;Beadman et al, 2004;Pranovi et al, 2004), although in some cases the opposite effect has been recorded (Mantovani et al, 2006). This latter may be caused by the use of plastic nets to protect juvenile clams from predation by shorebirds and crabs (Spencer et al, 1992), which increased sedimentation rates and consequently the density of some species of infaunal deposit-feeding worms (Spencer et al, 1997).…”

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

“…Crooks 1998, Ragnarsson & Raffaelli 1999 or inhibit the presence of and/or exclude others (Commito 1987, Beadman et al 2004). The mussel shells provide secondary hard substratum, which in sedimentary habitats may be the only hard substratum available for settlement of sessile organisms and algae (Albrecht 1998, Buschbaum 2000.…”