Vol. 382: 265–278, 2009 MARINE ECOLOGY PROGRESS SERIES Published April 30 doi: 10.3354/meps07955 Mar Ecol Prog Ser OPENPEN Contribution to the Theme Section ‘Large-scale studies of the European benthos: the MacroBen database’ ACCESSCCESS Biological geography of the European seas: results from the MacroBen database C. Arvanitidis1,*, P. J. Somerfield, H. Rumohr, S. Faulwetter, V. Valavanis, A. Vasileiadou, G. Chatzigeorgiou, E. Vanden Berghe, J. Vanaverbeke, C. Labrune, A.Grémare, M. L. Zettler, M. Ke˛dra, M. W8odarska-Kowalczuk, I. F. Aleffi, J. M. Amouroux, N. Anisimova, G. Bachelet, M. Büntzow, S. J. Cochrane, M. J. Costello, J. Craeymeersch, S. Dahle, S. Degraer, S. Denisenko, C. Dounas, G. Duineveld, C. Emblow, V. Escavarage, M. C. Fabri, D. Fleischer, J. S. Gray, C. H. R. Heip, M. Herrmann, H. Hummel, U. Janas, I. Karakassis, M. A. Kendall, P. Kingston, L. Kotwicki, J. Laudien, A. S. Y. Mackie, E. L. Nevrova, A. Occhipinti-Ambrogi, P. G. Oliver, F. Olsgard, R. Palerud, A. Petrov, E. Rachor, N. K. Revkov, A. Rose, R. Sardá, W. C. H. Sistermans, J. Speybroeck, G. Van Hoey, M. Vincx, P. Whomersley, W. Willems, A. Zenetos 1Institute of Marine Biology and Genetics, and Institute of Marine Biological Resources, Hellenic Centre for Marine Research, PO Box 2214, Heraklion 71003, Greece ABSTRACT: This study examines whether or not biogeographical and/or managerial divisions across the European seas can be validated using soft-bottom macrobenthic community data. The faunal groups used were: all macrobenthos groups, polychaetes, molluscs, crustaceans, echinoderms, sipun- culans and the last 5 groups combined. In order to test the discriminating power of these groups, 3 criteria were used: (1) proximity, which refers to the expected closer faunal resemblance of adjacent areas relative to more distant ones; (2) randomness, which in the present context is a measure of the degree to which the inventories of the various sectors, provinces or regions may in each case be con- sidered as a random sample of the inventory of the next largest province or region in a hierarchy of geographic scales; and (3) differentiation, which provides a measure of the uniqueness of the pattern. Results show that only polychaetes fulfill all 3 criteria and that the only marine biogeographic system supported by the analyses is the one proposed by Longhurst (1998). Energy fluxes and other interac- tions between the planktonic and benthic domains, acting over evolutionary time scales, can be asso- ciated with the multivariate pattern derived from the macrobenthos datasets. Third-stage multi- dimensional scaling ordination reveals that polychaetes produce a unique pattern when all systems are under consideration. Average island distance from the nearest coast, number of islands and the island surface area were the geographic variables best correlated with the community patterns pro- duced by polychaetes. Biogeographic patterns suggest a vicariance model dominating over the founder-dispersal model except for the semi-closed regional seas, where a model substantially mod- ified from the second option could be supported. KEY WORDS: Marine biodiversity · Biogeography · Macrobenthos · Polychaetes · Europe Resale or republication not permitted without written consent of the publisher INTRODUCTION (e.g. Croizat 1958, MacArthur & Wilson 1967, Heads 2005). By integrating knowledge from the disciplines Biogeography is useful for identifying patterns of of ecology and taxonomy, biogeography is equipped to biological diversity and mechanisms (e.g. vicariance play a central role in exploring the relationship vs. founder-dispersal), determining their occurrence between biodiversity and ecosystem functioning on many scales, from local to continental or even larger through identifying large-scale background patterns *Email: [email protected] © Inter-Research 2009 · www.int-res.com Addresses for other authors are given in the Electronic Appen- dix at www.int-res.com/articles/suppl/m382p221_app.pdf 266 Mar Ecol Prog Ser 382: 265–278, 2009 against which some of the hypotheses formulated in safeguarding of human health and for the sustainable the context of the proposed relationships (e.g. Solan et use of resources. Into this category fall the systems sug- al. 2004, Raffaelli 2006) can be tested. Large-scale gested by the Oslo-Paris Commission (OSPAR 2003) for approaches are particularly useful for European Union the European seas and by the Helsinki Commission policies, which usually have to be implemented on (www.helcom.fi, HELCOM 2007), for the Baltic Sea. On scales larger than the ecosystem. Examples include the a larger scale, the International Council for the Explo- Common Fisheries Policy (Berg 1999) and the Com- ration of the Seas (ICES) (www.ices.dk/abouts/icesareas. mon Environmental Policy (McCormick 2001). asp, Rozwadowski 2002) has adopted a grid of rectangles Large-scale biodiversity patterns are the central for the reporting of the catch data of commercially im- issue in Theme 1 of the European Network of Excel- portant species. Finally, the International Hydrographic lence on marine biodiversity, Marine Biodiversity and Organization (IHO 1953), actively engaging all inter- Ecosystem Functioning (MarBEF) (www.marbef.org). ested states to improve maritime safety and efficiency A suite of (bio)geographic systems dividing the seas of in support of the protection and sustainable use of the globe into sectors, regions and provinces has been the marine environment, divides the world seas into proposed by various scientists and by several regula- sectors according to their physical characteristics. tory organizations. These systems can be divided into 2 Until recently, most scientific efforts to explain pat- broad categories if one takes into account the basis on terns of multi-species distributions were, with very few which they have been proposed. exceptions — such as Ekman (1967), Fredj (1974), Por (1) Systems proposed largely on the basis of empiri- (1989), and Longhurst (1998) — directed towards the cal relationships between the distribution of taxa and experts’ favoured taxon. For example, the provinces of environmental (geological, hydrographical, physical) Briggs (1995) were primarily defined using fish species variables. Into this category fall systems such as those distributions, those of Pierrot-Bults & Nair (1991) using proposed by Ekman (1967) and by Fredj (1974). Ekman chaetognaths, whereas Van Soest & Hajdu (1997) used (1967) summarized the knowledge on the distribution sponges, Glasby (2005) used polychaetes, and Deprez and reproductive physiology of individual species and (2006) used hyperbenthic mysids. However, even in tried to integrate this information with the hydro- the studies using multi-taxon distributions, rigorous graphy of the regions. The study used information on hypothesis testing to validate findings has rarely been both planktonic and benthic species, such as cnidari- attempted. ans, crustaceans, molluscs, polychaetes, echinoderms, The objective of the present study was to test the chordates, nemerteans, rotifers and bryozoans, and validity of the proposed systems for the division of the considered that temperature was the main factor in European seas based on soft-bottom macrobenthic influencing multi-species distributions, in association community data, an important component of the ben- with salinity and depth. Nevertheless, he did not at- thic ecosystem, against pre-determined criteria. The tempt to set the limits of the provinces and sectors he patterns so derived can serve as background informa- proposed. Fredj (1974) focused on the influence of tion for further testing of hypotheses concerning links depth on benthic communities, rather than individual between biodiversity and ecosystem functioning. species, and set geographic limits to the provinces defined by Ekman (1967). The large marine eco- systems (LME) concept of Sherman (1992), which DATA AND METHODS divides the oceans into relatively large regions (ca. 200 000 km2) characterized by bathymetry, hydrogra- Biogeographic systems. The system of Longhurst phy, productivity, and trophic groups, is another exam- (1998) was tested both as originally defined and in a ple of the systems included in this category. In addi- slightly modified version by excluding the Baltic and tion, Longhurst (1998) suggested a division of the seas Black Seas from their corresponding provinces of the based on the oceanographic characteristics of large Northeast Atlantic continental shelves and the Medi- water masses and their associated plankton com- terranean Sea, respectively, and treating them as sep- munities. Finally, Por (1989) proposed a division of the arate regional seas. The same modification was also Mediterranean and Black Sea region into sectors followed in the case of the systems used by OSPAR, based on relationships between geological formations, while in the case of the ICES rectangles, the Mediter- hydrographic and physical/chemical variables and ranean and the Black Seas were taken as separate faunal distributions. provinces, since ICES does not include these 2 regional (2) Systems that, at least implicitly, acknowledge a seas. This modification to the biogeographic provinces political as well as a scientific dimension to the setting of was made in order to emphasize the distinctive nature geographical boundaries aimed at promoting the conser- of the above sea areas when characterized, for exam- vation and protection of the marine environment, for the ple, according to salinity