engleski

Temporal dynamics of epibiontic meiofauna in the Caulerpa taxifolia settlement

Caulerpa taxifolia (Vahl) C. Agardh is a tropical green alga accidentally introduced in the Western Mediterranean in 1984. Due to its exceptional competitive and expansionistic abilities, benthic communities in areas colonized by C. taxifolia suffered great alterations and impressive decrease in macrobenthic diversity. Only a few information is available on the influence of algal spread on sediment living meiofauna, and almost nothing is known about community structure and dynamics of epibiontic assemblages. The aim of the study was to reduce this lack of information. For that purpose, qualitative and quantitative composition of epibiontic meiofauna was studied in the C. taxifolia settlement recently recorded on the silty-sand sediment in the Malinska port (Krk Island, northern Adriatic Sea). The sampling was performed in monthly intervals from June 1998 to April 1999 and covered a complete life cycle of C. taxifolia including both its active and latent phases. Each sample contained 20 fronds with associated meiobenthos, and was taken as triplicate. All together 14 meiofaunal taxa were recorded. The meiofauna assemblage was characterized by an expressive dominance of copepods (58%), a subdominant position of nematodes (27%), and proportionally low participation of other taxa, i.e. Hydrozoa, Polychaeta, Bivalvia, Amphipoda, Ostracoda, Gastropoda, Chaetognatha, Kinorhyncha, Isopoda, Decapoda, Pantopoda and Bryozoa (all together15%). The latter five taxocoens noted were observed sporadically, or seasonally. The results of monthly monitoring pointed out four distinctive periods, and indicated a seasonal trend of meiofaunal distribution. The first period (June - August 1998) had started with a low meiofaunal abundance (139 ind./sample) but proceeded with an exponential increase. The second period was distinguished by fairly high abundances (~1000-1500 ind. per sample) and its moderate variation on the constitutive taxa level. In the third period (December '98 - February '99) exponential growth (to about 10000 ind./sample) and high faunal diversity occurred, while in subsequent months meiofaunal abundance overreached 19000 ind./sample - remaining extremely high until May when C. taxifolia fronds disappeared. The increase of abundance and diversity of meiofauna was positively correlated with the increase of algal frond's surface, due to the increasing quantity of sediment particles and organic detritus accumulated on fronds during the C. taxifolia vegetative cycle.

Caulerpa taxifolia; meiofauna; Adriatic Sea

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