engleski

Benthic biocoenoses of the Sv. Marko islet (Rijeka Bay)

Researches of marine flora and fauna of the Rijeka Bay and the whole Kvarner Gulf have been going on for a century and a half. Despite numerous sampling locations in the coastal, open-water and channel zone of the region, the submarine littoral of the Sv. Marko islet remained almost unexplored. Because of the fact, our goal was to describe some biocoenological features of this "blank" area. In the submarine area of the islet of Sv. Marko we have found all together 47 taxa of macroalgae, two species of blue-green algae, 1 phanerogam species and 101 macrofauna species. According to the current data, the benthic communities of Sv. Marko are rich and diverse, but do not differ from other locations of the Rijeka Bay and Kvarner region. An exception is the excessive growth of red algae Polysiphonia spp. that cover comprehensive parts of a bottom surface at some localities. A thick layer of algae obviously reduces the water near- bottom circulation causing anoxic conditions beneath the layer. Such phenomenon was neither recorded during previous researches in the Kvarner nor was noticed in the biocoenologic literature of the eastern Adriatic coast. We believe that there are reasons for establishment of the distinct ruderal biocoenosis of movable stony bottom of infralittoral step. The inclination of the unconsolidated bottom is one of main factors leading to the development of the particular scree community. We consider the present research just as preliminary because of the minimal number of stations which were visited and investigated only once. The well-like submarine cave between stations RI-18 and RI-76 has remained completely uninvestigated.

macroflora; macrofauna; Polysiphonia; marine cave; benthic biocoenoses; Rijeka Bay; Croatia

nije evidentirano