engleski

Biometry and leaf lepidochronology of the seagrass Posidonia oceanica in the Croatian Adriatic

The endemic Mediterranean marine phanerogam Posidonia oceanica (L.) Delile forms dense beds characteristic of the photic infralittoral zone. As elsewhere in the Mediterranean, they are considered to be the most important shallow benthic habitat in the Adriatic Sea. This complex habitat/biocoenosis, with high primary production and high biodiversity, is important for the oxygenation of the seawater and stabilization of the sediment. However, in the Croatian part of the Adriatic the biocoenosis is poorly known. The aim of this research was to compare biometry and leaf lepidochronology of seven Posidonia meadows in the Middle and South Adriatic studied from 2002 to 2006 (on Islands Dugi otok, Krapanj, Vis and in the Lastovo Archipelago). In well-developed meadows, 20-50 Posidonia shoots per meadow were taken along the depth gradient. The upper and the lower bathymetric extension of the meadows and the number of shoots along the depth/light gradient (in 10 quadrats 40 x 40 cm per each depth) were determined in situ. Variables measured included shoot density, leaf area index, biomass, and estimated annual primary production. Meadow density and the effect of depth on estimated primary production were compared among the researched meadows as well as with the published data for Posidonia beds in the Mediterranean. Generally, meadows under the influence of open Adriatic clear waters showed the highest primary production: in Lojisce cove (Dugi otok) and Rukavac cove (Vis). Estimated primary production in our studied Posidonia meadows was similar to the estimated primary production of other meadows in the Mediterranean Sea. However, meadows in enclosed bays (Cuska Dumboka, Sascica) showed remarkably lower primary production, probably due to natural eutrophication and lower water clarity.

Adriatic Sea; Posidonia oceanica; lepidochronology; leaf biometry

nije evidentirano