engleski

Biotopes patterns based on distribution of recent benthic foraminifera in the eastern Adriatic Sea

The distribution of recent benthic foraminifera in 129 samples from four bays in the Eastern Adriatic has been studied. Sediment samples were taken with corer or by hand collecting, during the spring and fall seasons of the years 2006, 2007 and 2008. Samples were treated with Rose Bengal and washed on the 63μ sieve ; granulometrical analysis was done using method of wet sieving, and organic matter concentration (OM) was determined gravimetrically. All interpretations are based on total assemblages (living and dead specimens). Using cluster analysis, two main foraminiferal associations were identified reflecting different ecological conditions. The first, Haynesina-Ammonia association, described from Nin and Soline Bay (Krk Island), developed in organic matter poor sediments down to 20 m of water depth. Characteristic species are Haynesina germanica, Ammonia beccarii, Elphidium macellum, Ammonia tepida, Neoconorbina terquemi, Asterigerinata mamilla, Elphidium depressulum, Haynesina depressula and Ammonia inflata. The second, Haynesina-Epistominella association, in Mala Luka (Drvenik Island) and Boka Kotorska Bay, characterizes sediments with >5% of organic matter and water depths between 13 and 108 m, dominated by specimens of Bulimina aculeata, H. germanica, Stomatorbina concentrica, Nonionella opima, A. inflata, Brizalina striatula, H. depressula, Epistominella exigua, Bulimina marginata, Elphidium translucens, Brizalina dilitata and Globocassidulina subglobosa. Foraminiferal associations span through environments with different hydrological conditions, represented by biotopes. Haynesina-Ammonia association comprises two biotopes: Ammonia inflata biotope, inhabiting enclosed lagoon (Nin Bay), and Ammonia tepida biotope, occupying lagoon with entrance channel and distinct water circulation (Soline Bay). Samples from Soline Say taken in 2008 are classified into Ammonia inflata biotope, as a consequence of seasonal and annual changes in meteorological and hydrological conditions in the Bay. Haynesina-Epistominella association encloses Epistominella-Neoconorbina biotope, spread in bay with wide channel (Mala Luka Bay), and Brizalina-Bulimina biotope, inhabiting restricted lagoon (Boka Kotorska Bay). Each biotope has varieties due to differences in sediment type and OM ; sandy substrates with low OM are characterized by epifaunal species, whereas infaunal species dominate assemblages at muddy bottoms with higher OM. Established associations and biotopes have good correspondence with biofacial units, associations and biotopes, previously defined in the Adriatic.

Foraminifera; Adriatic Sea; Biotopes

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