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Abstract. The origin and temporal variation in composition of sedimented particulate organic matter (POM) in the Gulf of Trieste (northern Adriatic) was studied over the year with special reference to the composition and sedimentation of macroaggregates in summer of 1991 using sediment traps.Suspended and sedimented POM, comprising a minor part of the largely inorganic total particulate matter, was prevalently of marine origin and composed mostly of humic substances followed by carbohydrates and proteins. Seasonal variations of particulate proteins and carbohydrates were correlated with variations of phytoplankton biomass. 'New' production, occurring in late spring as a consequence of massive riverine inputs of N, Si and P nutrients in the surface layer of the Gulf, produced high particulate carbohydrate and protein concentrations. Subsequent depletion of introduced nutrients caused the decrease of particulate protein concentration but not that of particulate carbohydrate. The prolonged plankton biosynthesis of carbohydrates successively produced marine snow and later macroaggregates. The macroaggregates were characterized by 613C value of -19.%0 and their carbohydrates were mostly composed of glucose followed in decreasing order by mannose, fructose, galactose, arabinose, ribose, xylose and fucose, suggesting a prevalent origin from phytoplankton structural heteropolysaccharides. Sedimentation of particulate organic constituents in the summertime, characterized by the massive presence of macroaggregates in the surface layer above the pycnocline, was the highest at a depth of 10 m at the end of this phenomenon, about six weeks after its first appearance. Sedimented macroaggregates were clearly traced by a characteristic 613C signal and higher carbohydrate concentrations. The monosaccharide composition was influenced by selective degradation in the water column. Sedimented POM in the bottom layer was, on the other hand, more affected by sediment resuspension. The mean yearly decrease of particulate protein-C and carbohydrate-C by 40-50% in the water column between the depths of 10 and 20 m indicates the preferential utilization of these constituents by microorganisms. The decrease of particulate humic-C is probably more the result of the export of particulate matter from the Gulf. This study also indicates that the macroaggregate formation has little impact on the annual C and N budget in such coastal areas.

ABSTRACT. 613C and 14C activity measurements were made on terrestrial, marsh and aquatic plants growing in their natural habitat of the Plitvice Lakes in northwest Yugoslavia. &3C values were ca -47%o for aquatic mosses, which indicate that the carbon source was dissolved inorganic carbon (DIC) from alkaline karst waters, following a C3 pathway, and ca -25%o for marsh plants, indicating the carbon source was atmospheric CO2.

Kratka vsebina Nadrobne raziskave rude rudnega telesa Grübler so dale vrsto novih podatkov o živosrebrovem rudišču Idrija. Metasomatska ruda v spodnjeskitskem dolomitu je seveda povezana s srednjetriasno magmatsko aktivnostjo. Toda ta ruda je bila kasneje tektonsko pretrta in zdrobljena. Nastale so žilice, žile in rudne breče. Vezivo sestavlja predvsem beli zrnati dolomit, kateremu se v spremenljivih, toda manjših količinah pridružujejo cinabarit, organska snov, kremen in pirit. Te sestavine se pojavljajo v več generacijah, ki so po našem mnenju povezane z delovanjem podtalnice, medtem ko je alpidska orogeneza dvigala rudišče proti površju. Raziskave so dopolnjene z masnospektrometrično analizo izotopske sestave žvepla v cinabaritu ter kisika in ogljika v različnih generacijah dolomita.