engleski

The spatial and vertical distribution of benthic foraminifera from the Boka Kotorska Bay, Adriatic Sea, Montenegro

Sediment cores (10 cm) were taken at eight stations in Boka Kotorska Bay in order to study foraminiferal assemblages. Foraminifera are unicellular organisms that live in a wide range of marine environments ; their tests make a substantial portion of sediments, while different abundances and diversity come from different ecological conditions. Dominant species have been identified and diversity indices were calculated ; sediment types were determined and organic matter sediment content (OM) was measured. Based on foraminiferal community composition, principal component analysis (PCA) was carried out. The association in the bay is characterized by infaunal species: Epistominella exigua, Brizalina dilitata, Brizalina spathulata, Brizalina striatula, Globocassidulina subglobosa, Bulimina aculeata, Bulimina elongata, Bulimina marginata, Stomatorbina concentrica, Nonionella opima, Ammonia inflata, Elphidium translucens, Elphidium depressulum and Haynesina germanica. The assemblage at the reference station (at the bay entrance) is dominated by epifaunal species: Bigenerina nodosaria, Textularia agglutinans, Textularia bocki, Adelosina sp., Quinqueloculina seminula and Cibicides refulgens. There are no significant community changes throughout the top 10 cm of the sediment. Sewage disposal of neighbouring cities causes high values of OM in the bay (9.5%), while at reference station OM values remain low (2.5%). Sediment type in the bay is mud, whereas at reference station is muddy sand. Diversity indices indicate high biodiversity: Shannon-Wiener index varies from 2.75 to 3.53 and equitability index from 0.5 to 0.79. Fisher index is representative for normal marine lagoons (from 9.6 to 18.41). PCA separates bay samples from reference station samples. Bay species abundances decrease toward the reference station, indicating their dependence on food availability and sediment type. The assemblage at the reference station reflects sandy bottom and lower OM values. Different sediment type and OM values cause changes in foraminiferal community composition, but do not affect foraminiferal biodiversity in the Boka Kotorska Bay.

foraminifera; sediment; organic matter; Boka Kotorska Bay

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