Aggregations of brittle stars can perform similar ecological roles as mussel reefs

• Published in: Marine Ecology Progress Series
• Main Authors: Geraldi, Nathan, Bertolini, C, Emmerson, MC, Roberts, D, Sigwart, JD, O’Connor, NE
• Other Authors: Red Sea Research Center (RSRC), Queen's University Marine Laboratory, 12-13 the Strand, Portaferry, BT22 1PF, United Kingdom, Institute of Global Food Security, School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, United Kingdom
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Inter-Research Science Center 2016
• Subjects: Benthic-pelagic coupling; Biogenic habitat; Bivalve; Brittle star; Foundation species; Ophiuroids; Organic matter; Reef; Modiolus modiolus
• Online Access: http://hdl.handle.net/10754/623486; https://doi.org/10.3354/meps11993

Biogenic habitats, such as coral reefs, facilitate diverse communities. In aquatic systems, aggregations of mobile benthic species may play a similar ecological role to that of typically sessile biogenic habitats; however, this has rarely been considered. We quantified the abundance of sessile horse mussels Modiolus modiolus and aggregating brittle stars Ophiothrix fragilis and tested for correlations between the density of mussels (live and dead) and brittle stars each with (1) abundance, biomass, diversity, and assemblage structure of associated benthic macrofauna; and (2) percent organic matter of the sediment. We found that the abundance of live M. modiolus was positively associated with the abundance and biomass of macrofauna. The positive association between M. modiolus and macrofaunal abundance was further amplified with an increase in brittle stars and a decrease in dead mussel shells. Macrofaunal biomass was lower with a higher percentage of dead mussel shells, and macrofaunal diversity increased with greater abundances of live M. modiolus and brittle stars. Sediment organic matter was positively related to brittle star density, but not to the abundance of live or dead mussels. The positive relationship between brittle stars and sediment organic matter suggests that brittle stars could enhance rates of benthic- pelagic coupling. Given the importance of understanding the functional role of threatened habitats, it is essential that the underlying community patterns be understood through robust observational studies to then derive testable hypotheses to determine drivers. These findings provide novel insight into the ecological role of aggregations of mobile species, which is essential to prioritize conservation and restoration strategies. We thank all those who assisted with the organization and collection of data for this project, including H. Van Rein, T. Mackie, M. Service, R. Schneider, M. Allen, J. Breen, and the captain and crew of the FPV ‘Banrion.’ The manuscript was improved by comments from A. ...