Expansion of the macroalga Caulerpa racemosa and changes in softbottom macrofaunal assemblages in Moni Bay, Cyprus

The recent expansion of the Red Sea macroalga Caulerpa racemosa and its impact on the diversity and abundance of macrobenthos were examined and compared in the summers of 1992 and 1997, in Moni Bay, Cyprus. The phytobenthic community of the bay in 1992 was dominated by the seagrass Posidonia oceanica while, in 1997, the Lessepsian migrant C. racemosa became the most dominant, forming extensive mars. Changes in the vegetation system in Moni Bay have caused significant compositional changes in macrofaunal assemblages. A total of 178 individuals of 62 species are recorded. The composition of the macrofauna in 1992 was dominated by gastropods (44 %), crustaceans (22 %), bivalves (17 %), polychaetes (11 %) and echinoderms (6 %). In 1997, the gastropods and crustaceans had decreased to 13 % and 16 % respectively, while, polychaetes had increased to 38 % becoming the mast dominant taxon. Bivalves and echinoderms also increased to 22 % and 11 %, respectively, in 1997. The proliferative growth of C. racemosa imposed successional changes on the macrofaunal assemblages in Moni Bay, Cyprus, between 1992 and 1997. It remains to be tested whether the expansion of C. racemosa is related to the increase of water temperature associated with global warming or nutrient inputs or with the differences in the life history characteristics of this migrant vs. native algal species. (C) 1999 Ifremer / CNRS / IRD / Editions scientifiques et medicales Elsevier SAS.