Biogenic reefs affect multiple components of intertidal soft-bottom benthic assemblages: the Lanice conchilega case study

Abstract

International audienceBiogenic reefs composed of the tube-building polychaete Lanice conchilega are important from a conservationpoint of view because they noticeably increase the biodiversity in otherwise species poorenvironments. However, up to now, little or no attention has been paid to the intertidal epi- andhyperbenthic communities associated with the reefs. Therefore, this is the first study which focuses onthe effect of L. conchilega reefs on the entire bentho-pelagic community at two different locations.Environmental variables were measured and macro-, epi- and hyperbenthic communities were sampledwithin a L. conchilega reef and a control area at two locations in France: the bay of the Mont Saint-Michel(BMSM) and Boulogne-sur-Mer (Boulogne). The effect of the reef presence on the benthic communitywas studied with a 3-factor (Reef, Location and Period) Permanova. In addition, the relationship betweenthe benthic community and the environmental variables was investigated using Distance-based linearmodels (DistLM). Most collected organisms were sampled in the reef area (macrobenthos: 91%, epibenthos:81% and hyperbenthos: 78.5%) indicating that, independent of the location, the L. conchilegareefs positively affect all three associated benthic communities. However, the extent of the effect seemsto be most pronounced for the macrobenthos and less distinct in case of the hyperbenthos. The macro-,and epibenthos are mainly structured by biotic variables (L. conchilega density and macrobenthic foodavailability respectively), while the hyperbenthos is rather structured by environmental variables. Ingeneral, L. conchilega reefs do not only affect abundances and diversity but they substantially steer thestructure of the intertidal benthic sandy beach ecosystem

Lanice conchilega structures carbon flows in soft-bottom intertidal areas

“…In the present study, the intertidal L. conchilega reefs are similar to the bivalve reefs with respect to their largescale engineering affects. The facilitated OM trapping by the reefs and the consequential impacts on the macrobenthic community and the fish and wading bird populations (De Smet et al 2013, 2015a demonstrate that the spatial impact of L. conchilega reefs is much larger than their size suggests.…”

“…This study focusses on the bentho−pelagic community of the soft-bottom intertidal food web, as described by De Smet et al (2015a). The most abundant species, ranging from smaller polychaetes up to fish, were included as separate compartments interconnected by flows ( Fig.…”

“…Macro-, hyper-and epibenthic organisms were collected, identified to species level and counted. Species that could not be distinguished with certainty were grouped at the genus level (see De Smet et al 2015a for a detailed description of the sampling design and processing). Wet mass of the organisms was determined and subsequently converted to dry mass and carbon units (mmol C m −2…”

“…S1 in the Supplement). The species compartments were selected out of all species occurring in the areas based on their abundance and biomass in the system (De Smet et al 2015a). Due to a lack of data on meiofaunal and detrital compartments, the focus of this model therefore lies on the macrofaunal component of the L. conchilega reef and bare sand food webs.…”

“…As a result, L. conchilega affects the community composition, abundance and species richness within the reef (Zühlke et al 1998, Rabaut et al 2007, Godet et al 2008, Braeckman et al 2011, De Smet et al 2013. Moreover, intertidal L. conchilega reefs are important from a conservation point of view due to their central role in the link between benthic, pelagic and air-borne parts of the intertidal food web (De Smet et al 2013, 2015a. Despite their structuring role on the meio-and macro fauna, these reefs seem to have a minor effect on the overall structure of the soft-bottom intertidal food web.…”