Matej Dolenec

Effects of fish farm loading on sea grass Posidonia oceanica at Vrgada Island (Central Adriatic): a nitrogen stable isotope study

Analyses of nitrogen stable isotopes in the marine sea grass Posidonia oceanica were used to investigate the influence of fish farming on the coastal ecosystem of Vrgada Island in the Murter Sea, Central Adriatic. The results show a statistically significant 15N enrichment (up to 4.7‰ at p < 0.005) in P. oceanica leaf and shoot tissues from fish cage sites with respect to the unaffected offshore reference site of Lumbarda Reef Flat (Kornati Islands). Heavy nitrogen enrichment was also detected in other benthic organisms analysed during this study and is attributed to the absorption and assimilation of 15N-enriched fish farm derived nitrogen waste.

Potentially toxic contamination of sediments, water and two animal species in Lake Kalimanci, FYR Macedonia: Relevance to human health

The objectives of the research were: (1) to examine the concentrations of metals in Vimba melanops and Rana temporaria and (2) to evaluate the potential risks of the contaminated organisms to human health in Makedonska Kamenica region. Analyses identified high levels of Cr, Hg, Ni and Pb in studied animals, which also exceeded their permissible levels in food. In sediment and soil samples, levels of Cd, Cu, Cr, Pb, Zn and As were perceived, while Cd, Cu, Ni, Pb, Se and As were increased in water samples. Results of transfer factor revealed that the examined animals had higher bioaccumulation rate from surrounding waters than from sediments or soils. The accomplished Health Risk Index disclosed that studied animals can have considerably high health risks for inhabitants. Conclusively, they could be considered as highly contaminated with metals and can consequently harm human health, especially children in their early development stages.

Benthic foraminifera assemblages as elemental pollution bioindicator in marine sediments around fish farm (Vrgada Island, Central Adriatic, Croatia)

Effects on sediments of fish farming activity near Vrgada Island was analysed through living and total foraminiferal assemblages and concentration of major, minor and trace elements from three sediment cores. Elemental concentrations of sediments are in accordance with carbonate characteristics of the surrounding area and show mostly natural element variations between sampling locations and throughout the cores, with no significant increases due to fish farming activity. Only phosphorus concentration shows elevate values below the fish cage, assigned to fish pellets. Foraminiferal communities are dominated by epifaunal and stress tolerant species, while diversity indices point to normal marine conditions. The type of substrate and phosphorus content in sediments principally influence foraminiferal community composition, while other elemental concentrations have no perceptible effect on the assemblages. Some foraminiferal species Ammoniatepida, Ammoniabeccarii, Elphidiumcrispum, Elphidiummacellum and genus Haynesina are confirmed to be tolerant to elevated nutrient (phosphorus) content, while Ammonia parkinsoniana shows sensitivity to pollution. Postmortem processes cause decrease of foraminiferal density and species richness with core depth. All results point to negligible influence of fish farming and relatively stable environmental conditions at all sampling locations.

Impact evaluation of the industrial activities in the Bay of Bakar (Adriatic Sea, Croatia): Recent benthic foraminifera and heavy metals

The Bay of Bakar is one of the most heavily polluted bays at the Eastern Adriatic. Three major industrial companies potentially endanger the bay. The concentration of major, minor and trace elements in surface sediments from thirteen stations was discussed in relation to the sediment type and foraminiferal assemblages. The distribution of major elements in the bay is influenced by geological nature of surroundings. Heavy metal distribution depends on pollution sources and on amount of mud fraction: fine-grained sediments are enriched by them in comparison with coarse-grained ones. Different sediment quality criteria complicate the pollution assessment in the bay. Heavy metal concentrations generally fall into allowed depositional values for marine environments; only area in front of the coke plant and the City of Bakar harbor is heavily polluted. Stress-tolerant foraminiferal species dominate at stations with higher concentrations of heavy metals and coarse-grained sediments consist of larger number of epifaunal taxa.

Recent Sediments of Makirina Cove (Northern Dalmatia, Croatia): Their Origin Viewed Through a Multidisciplinary Approach

Makirina Cove was formed by the Holocene sea-level rise which caused a marine ingression into the depression formed within Albian– Cenomanian dolomites at approximately 4.5 ka B.P. At present, Makirina Cove represents an restricted, stressed, shallow-marine (<2 m) ecosystem characterized by varying seawater temperatures (0–35°C) as well as fluctuating salinities (up to 41‰) affected by seasonally enhanced evaporation, continuous freshwater supply through on-shore and submarine springs associated with the coastal karst area and surface run-off episodes. These environmental conditions have been conducive to high primary production of organic matter resulting in the formation of organic-rich deposits which contain up to 5 wt.% of organic carbon. Up to the present times, 3.5 m of sediments have been deposited indicating a relatively high sedimentation rate estimated at 0.75 m/1.0 ka in the northern central part of the Cove. The sediments are being deposited mostly as poorly sorted clayey–sandy silts. The distribution and concentration of most of the chemical elements is dependant on the mineralogical composition and granulometric features of the Makirina sediments, which show values more or less similar to those from the Central Adriatic. Accordingly, there is a positive correlation with Al and K concentrations increasing off-shore and with the depth being associated with increasing concentrations of clay minerals within the clay fraction. The same holds true for concentrations of some trace elements, especially Mo and Se which is consistent with the distribution pattern of sulphides. Selenium is preferentially enriched in authigenic pyrite and it is probably the major source of Se in the Makirina Cove sediments. The concentrations of Ca, Mg and Sr decrease off-shore and they are linked to the composition of the surrounding carbonate rocks. The saturation indices show that the water is supersaturated with respect to carbonates enabling the precipitation of authigenic amorphous or crystalline carbonate phases from the pore water in the upper segment of the sediment column. According to the oxygen isotopic (δ18O) composition, molluscs precipitated their carbonate shells mostly during warmer periods (May to November) at or near isotopic equilibrium with their ambient waters. The carbon isotopic δ13C composition of mollusc carbonate shells is environmentally affected due to oxidation and decomposition of organic matter as well as influxes of fresh water into the Cove, indicating their formation out of the predicted isotopic equilibrium with atmospheric CO2. Palynological and organic carbon isotopic (δ13C) composition shows that the sedimentary organic matter (SOM) is 70–90% lipid- and hydrogen-rich and on average 2/3 marine derived (mainly phytoplankton, bacteria and marine macrophytes) and 1/3 terrestrially derived (mainly woody tissue). The variations in composition of SOM have been noted as a function of the distance from the shore. The type and the preservation state of SOM and pyrite as well as the measurements of Eh, pH, total alkalinity, dissolved inorganic carbon (DIC) and the enrichment of redox-sensitive trace elements, indicate oxygen-depleted depositional conditions and that the sediment is highly reductive even in the uppermost segment at the sediment/water interface. According to the results obtained from the applied methods, the features of Makirina sediments strongly reflect the given depositional conditions within this restricted, stressed, shallow- marine environment where these organic-rich sediments originate, and may therefore serve as a calibration standard in further investigations

Stable Isotope Event Markers Near the Permo-Triassic Boundary in the Karavanke Mountains (Slovenia)

Permo-Triassic (P/Tr) boundary events, which took place approximately 250 Ma ago, led to the most extensive mass extinction in the history of life. A number of possible explanations for this profound break in the evolution of life have been proposed, such as volcanic activity, sea-level fluctuation, changes in sea-water chemistry, an extra-terrestrial impact event and various related factors (YOICHI, 1994). The most recently proposed cause of the mass extinction at the end of the Permian is a combination of these more or less co-occurring events operating in three phases (ERVIN, 1996). The first began with the marine regression during the Late Permian and resulted in the destruction of many marine basins, reduction in the habitat area of many organisms and increased climatic instability. The second phase involved the eruption of the Siberian Traps and further environmental degradation. The final phase may have started immediately prior to the boundary when the Late Permian regression ended and the earliest Triassic transgression begun. The global events outlined above coincide with isotope and elemental anomalies recorded in several P/ Tr boundary sections all

Seasonal differences of stable isotope composition and lipid content in four bivalve species from the Adriatic Sea

Abstract The feeding ecology of four bivalve species co-occurring in the Mali Ston Bay, the most important bivalve aquaculture area of the Eastern Adriatic, were investigated by analysing the stable isotope composition and lipid content in two tissue types. Analyses included two cultured species: Mytilus galloprovincialis and Ostrea edulis, and two naturally occurring species: Modiolus barbatus and Arca noae. Total lipid concentrations were higher in the digestive gland than in the adductor muscle in all species studied. The study confirmed seasonal variability of stable isotope signatures. Observed seasonal changes were more pronounced in the digestive gland than in the adductor muscle, suggesting that the former better reflects seasonal trophic patterns. The results obtained indicate isotopic niche overlap in the investigated species with the highest degree of overlap (~60%) among two cultured species during the spring–summer period, and between two naturally occurring species during the autumn–winter period (~60%). A lower degree of overlap between other species might suggest utilization of different additional food sources during certain times of the year. This study contributes to our understanding of trophic interactions between different bivalve species and is important for future modelling of food webs and sustainable management of wild and cultured populations.

Major, minor and trace element content derived from aquacultural activity of marine sediments (Central Adriatic, Croatia)

Introduction and purposeStudies examining the environmental impact of marine aquaculture have increased significantly in number during the last few decades. The present paper investigates a region of rapid growth in intensive aquaculture and its influence on the local marine ecosystem.DiscussionThis study was undertaken with the specific aim of assessing the effect of fish farming on marine sediment at a farm near the island of Vrgada in the Central Adriatic. Data obtained regarding major (Si, Al, K, Na, Fe, Ca, Mg), minor (Mn, P, Ti) and trace (As, Au, Ba, Cd, Co, Cr, Cs, Cu, Ga, Hf, Hg, Mo, Nb, Ni, Pb, Rb, Sb, Sc, Se, Sr, Ta, Th, Tl, U, V, Y, Zn, Zr) elements were used to estimate the spatial and temporal distribution of metals in the sediment and their possible relationship with local aquacultural activity.ResultsAlthough the measured concentrations of heavy metals in sediment below fish cages were notably different and potentially a result of farming activity, the values were generally lower than background concentrations observed in the Central Adriatic. In contrast, concentrations of heavy metals at a reference site unaffected by aquaculture varied from lower levels to values even higher than those observed below the high-production cages. Furthermore, calculated environmental index values indicate that the sediment below the farm is either uncontaminated or suffers from only low levels of contamination.ConclusionSuch results suggest that the effect of observed fish farm activity on the local marine ecosystem is practically negligible.

Use of Stable Nitrogen Isotope Signatures of Anthropogenic Organic Matter in the Coastal Environment: The Case Study of the Kosirina Bay (Murter Island, Croatia)

In this study stable nitrogen isotope ratios of particulate matter POM, zooplankton and selected biota such as Mytilus galloprovincialis were used to assess the impact of anthropogenically derived organic matter from the untreated domestic sewage, municipal and industrial effluents on the coastal ecosystem of the Kosirina Bay (Murter Island). The differences in δ15N values observed in POM and organisms collected in Kosirina Bay as compared to POM and biota sampled at unaffected sites from the southern part of the Kornati Island and highly impacted Pirovac Bay revealed only a very minor effects of anthropogenic inputs of nutrients and organic matter which is most probably derived from a sewage outfall south of the Tužbina Island.

Use of stable isotope composition variability of particulate organic matter to assess the anthropogenic organic matter in coastal environment (Istra Peninsula, Northern Adriatic)

Nitrogen and carbon stable isotope analysis of particulate organic matter (POM) was used to assess the impact of anthropogenically derived organic matter in coastal parts of the Istra Peninsula (Northern Adriatic). The investigation was conducted in areas potentially impacted and enriched with different amounts of organic matter. Elevated δ15N values in POM reflect enrichment of organic matter near the coast due to inadequate municipal infrastructure in cities and local septic systems as well as inputs from riverine terrestrial material. On the contrary, negative δ15N values reflect the depleting effect of purification plants. Significant differences in nitrogen stable isotope ratios were observed between western and southeastern coasts. The δ13C values show small depletion at sites with potentially greater anthropogenic impact. A weak temporal increase of δ15N from spring to late summer was observed. The results for nitrogen and carbon isotope ratios of POM and their comparisons with other areas suggest diverse amounts and sources of organic matter as well as differences in movement of floating POM within the water column. The δ15N and δ13C values reflect the ratios of marine and terrigenous organic matter, the latter being mainly anthropogenically influenced. The results finally suggest precaution in applicability of POM as tracers for detecting anthropogenic organic matter in marine coastal ecosystem.