engleski

Phytoplankton driven distribution of dissolved and particulate lipids in the northern Adriatic (Mediterranean) : Spring to summer situation

Connection between changes in lipid classes and phytoplankton composition and abundance in the northern Adriatic was studied during spring and summer 2008 at two stations with different nutrient levels, i.e. western mesotrophic and eastern oligotrophic. Changes in the phytoplankton community depended on temporal surface nutrient depletion and bottom accumulation ; that is, microphytoplankton, mainly diatoms Pseudo-nitzschia spp. developed at nutrient richer surface layers of mesotrophic area in spring and at deeper layers of oligotrophic site at late summer. In other periods nanophytoplankton dominated. Dissolved organic carbon (DOC) and lipid content were comparable for the two stations, while particulate organic carbon (POC) was richer at mesotrophic side. Total lipid concentrations varied in the range of 8.0 to 92.2 g l–1 and 16.9 to 76.9 g l–1 in the dissolved and particulate fractions, respectively. DOC and POC contents were in ranges from 0.77 to 1.58 mg l–1 and 0.06 to 0.56 mg l–1, respectively. Lipid and organic carbon distribution did not follow phytoplankton progression, indicating decoupling between organic matter production and decomposition through the investigation period. The main sources of lipids were marine phytoplankton and bacteria. Low nutrient conditions caused increased biosynthesis of lipids rather than protein or carbohydrate. Also, increasing oligotrophy led to increasing number of phytoplankton taxa. The synthesis and accumulation of glycolipids of the developed taxa were enhanced during nutrient exhaustion, contributing at late summer on average 20.2 and 22.0% at the mesotrophic and oligotrophic station, respectively, in the particulate fraction. The distribution of bacterial lipids and lipid breakdown products imply that bacterial lipid degradation was significant in spring, while very probably lipid abiotic degradation took place during summer.

lipids ; phytoplankton ; DOC ; POC ; nutrients ; oxygen ; northern Adriatic Sea

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