Istrian coastal countercurrent in the year 1997

During the 1966-1997 period the Istrian Coastal Countercurrent (ICCC), i.e. the strong southward surface current confined to the coastal belt off Istria, up to 20 Nm wide, appeared and was particularly pronounced in August of those years when mucilage or anoxia events occurred in the northern Adriatic (1977, 1988, 1989, 1991, 1997). In this paper we analyse geostrophic currents and hydrographic characteristics of the northern Adriatic in 1997. We show that the ICCC can appear in months other than August, as well as that its occurrence implies the presence of an anticyclonic gyre in the northeastern Adriatic, in which lower salinity waters, originating in the Po Delta area, are confined. Longer residence times of this nutrient-rich waters can favour eutrophication process and mucilaginous aggregate accumulation. On the basis of the prediction formula derived for the 1966-1992 period we were able to predict the intense episode of the ICCC in August 1997 from air-sea heat flux calculations with −7 months time lag and Po River discharge rate with −1 month time lag

Mechanisms of hypoxia frequency changes in the northern Adriatic Sea during the period 1972–2012

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Pojava Istarske obalne protustruje u 2000. godini, u kojoj su opažene i sluzave nakupine

The Istrian Coastal Countercurrent (ICCC) appeared in March (7 cm/s), August and September (4 cm/s) 2000, and a mucilage event occurred during late June-early July. Remarkably, previous investigations indicated that recurrent occurrences of intense ICCC coincided with mucilage and/or anoxia events in the region. In fact, already during late winter, when a sea heat gain was relatively intense, a significant transversal transport of freshened waters of Po origin occurred. Lower salinity and warmer water pool, which might be the core of an anticyclonic gyre in the northeastern Adriatic, was present also during spring and summer. This indicates the establishment of a pronounced closed circulation system in the area.Istarska obalna protustruja (IOPS) pojavila se u ožujku (7 cm/s), kolovozu i rujnu (4 cm/s) 2000. godine, a pojava sluzavih nakupina opažena je tijekom kasnog lipnja i početkom srpnja. Prema ranijim istraživanjima, povremene pojave IOPS podudarale su se s pojavom sluzavih nakupina i/ili anoksije u ovom području. Već tijekom kasne zime, kada je more iz atmosfere primalo razmjerno veliku količinu topline, opažen je značajan transverzalan prijenos zaslađenih voda porijeklom iz Poa. Bazen zaslađene i toplije vode, koji bi mogao biti središte anticiklonalnog vrtloga u istočnom dijelu sjevernog Jadrana, bio je prisutan i tijekom proljeća i ljeta. To ukazuje na postojanje zatvorenog sustava cirkulacije u promatranom području

Direct Discharges of Domestic Wastewater are a Major Source of Phosphorus and Nitrogen to the Mediterranean Sea

Direct discharges of treated and untreated wastewater are important sources of nutrients to coastal marine ecosystems and contribute to their eutrophication. Here, we estimate the spatially distributed annual inputs of phosphorus (P) and nitrogen (N) associated with direct domestic wastewater discharges from coastal cities to the Mediterranean Sea (MS). According to our best estimates, in 2003 these inputs amounted to 0.9 × 10⁹ mol P yr-1 and 15 × 10⁹ mol N yr-1, that is, values on the same order of magnitude as riverine inputs of P and N to the MS. By 2050, in the absence of any mitigation, population growth plus higher per capita protein intake and increased connectivity to the sewer system are projected to increase P inputs to the MS via direct wastewater discharges by 254, 163, and 32% for South, East, and North Mediterranean countries, respectively. Complete conversion to tertiary wastewater treatment would reduce the 2050 inputs to below their 2003 levels, but at an estimated additional cost of over €2 billion yr-1. Management of coastal eutrophication may be best achieved by targeting tertiary treatment upgrades to the most affected near-shore areas, while simultaneously implementing legislation limiting P in detergents and increasing wastewater reuse across the entire basin

Nature and Lability of Northern Adriatic Macroaggregates

The key organic constituents of marine macroaggregates (macrogels) of prevalently phytoplankton origin, periodically occurring in the northern Adriatic Sea, are proteins, lipids and especially polysaccharides. In this article, the reactivity of various macroaggregate fractions in relation to their composition in order to decode the potentially »bioavailable« fractions is summarized and discussed. The enzymatic hydrolysis of the macroaggregate matrix, using α-amylase, β-glucosidase, protease, proteinase and lipase, revealed the simultaneous degradation of polysaccharides and proteins, while lipids seem largely preserved. In the fresh surface macroaggregate samples, a pronounced degradation of the α-glycosidic bond compared to β-linkages. Degradation of the colloidal fraction proceeded faster in the higher molecular weight (MW) fractions. N-containing polysaccharides can be important constituents of the higher MW fraction while the lower MW constituents can mostly be composed of poly- and oligosaccharides. Since the polysaccharide component in the higher MW fraction is more degradable compared to N-containing polysaccharides, the higher MW fraction represents a possible path of organic nitrogen preservation. Enzymatic hydrolysis, using α-amylase and β-glucosidase, revealed the presence of α- and β-glycosidic linkages in all fractions with similar decomposition kinetics. Our results indicate that different fractions of macroaggregates are subjected to compositional selective reactivity with important implications for macroaggregate persistence in the seawater column and deposition