engleski

The relative importance of autochthonous and allochthonous sources of organic matter in the northwestern Adriatic sediment

The sediment is expected to have an important role in the organic matter cycle of the shallow northern Adriatic ecosystem, but the question of the relative importance of the autochtonous production vs. allochthonous (mainly terrestrial material) sources of the sediment organic matter unresolved. For this reason, organic matter in sediment were characterized, taking into account that the original lipid compositions of marine algae (and bacteria) and land plants are different. Sediment cores (120-180 cm long) were collected with a "vibrocorer" in the northwestern Adriatic, 25 km E (station 101), 25 km SE (108), and 40 km S (201) from the delta of the Po River. Organic carbon was analysed with a CH analyser, organic phosphorus spectrophotometrically, and geolipids by capillary GC. The vertical distributions of the clay fraction (<4 ľm ; 10-70%), organic carbon (4-32ˇ10-3), organic phosphorus (11-220ˇ10-6), fatty acids (2-25ˇ10-6), n-alkanes (2-13ˇ10-6), and unresolved hydrocarbon complex mixture (UCM ; 0-86ˇ10-6) were determined. While the lowest value ranges were measured at station 101, the most pronounced vertical changes were measured at station 108. The geolipid compositions and ratios suggested that these changes in sedimentation mechanisms (due to diversions of the Po river course and increasing eutrophication) might have influenced the quantities of deposited organic matter, but not significantly the relative importance of the autochthonous and allochthonous sources. Contributions of marine organic production prevailed over terrestrial sources to more recent sediment. In contrast, prevailing of terrigenous input was inferred from the parameter distributions in the sediment several centuries old. The UCM distribution in the upper parts of the cores was typical for anthropogenic oil pollution.

organic matter ; origin ; northern Adriatic ; sediments

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