Content area
Full Text
Mar Biol (2008) 153:405420 DOI 10.1007/s00227-007-0819-5
RESEARCH ARTICLE
Temporal variation of Tubularia indivisa (Cnidaria, Tubulariidae) and associated epizoites on artiWcial habitat communitiesin the North Sea
Vincent Zintzen Alain Norro Claude Massin Jrme Mallefet
Received: 8 December 2006 / Accepted: 7 September 2007 / Published online: 28 September 2007 Springer-Verlag 2007
Abstract We have analyzed the composition, diversity, density and biomass of a temporal series of samples taken in a Tubularia indivisa community, which dominates a shipwreck in the North Sea waters (N 5123[H11032],730E 0229[H11032],790, 17 nautical miles from the coast, 30 m depth). This shipwreck has structures emerging up to 8 m above the seabed. Water temperature ranged from 4.2C in March to 20.3C in August. Salinity showed few variations around33.9 psu. Bottom tidal currents followed a semi-diurnal cycle and were preferentially NE oriented with 84% of them in the range 0.250.75 m s1. The mean value for total suspended matter was 6.2 mg l1 with large variations on a monthly scale. The species richness of samples varied from 15 in October to 42 in August with a mean value of 33 species. Diversity indices were higher during autumn and winter because of the strong dominance of a few crustacean species during the warmer months. The total density of
individuals ranged from 6,500 ind m2 in October to 445,800 ind m2 in July, most of these individuals belonging to the amphipod species Jassa herdmani. The biomass of the T. indivisa community varied from 9 g AFDW m2
in October to 1,106 g AFDW m2 in July, with T. indivisa itself constituting between 59 and 82% of the total biomass. The biomass of T. indivisa was positively correlated with species richness and with the density of 23% of the species identiWed on this community, suggesting that T. indivisa plays an important structural role in this habitat. This was further conWrmed by the number of species associated withT. indivisa which was generally superior to 55% of the sorted species. Multivariate analysis indicated strong diVerences between spring/summerautumn/winter assemblages mostly but not solely due to the abundance patterns of species. These Wndings support the conclusion that shipwrecks in Belgian waters allow the development of assemblages dominated by a high biomass of T. indivisa which in turn provides shelter for...