Showing papers by "Sonja Lojen published in 2014"

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 pe...

Aquaculture Assessment of Noah's Ark (Arca noae Linnaeus, 1758) in the Central Adriatic Sea (Croatia)

Abstract: In support of aquaculture development and sustainable fisheries, survival, condition index, and stable isotope composition of the commercially important bivalve species Arca noae were investigated on individuals suspended in the water column at 2 distances from fish cages and those collected from natural populations. Significant differences were recorded in temperature and chlorophyll a with respect to season, and temperature and salinity values differed significantly with respect to sampling site. Mortality was greatest at the beginning of the experiment, probably as a result of the stress associated with collection of A. noae and the shell-marking process. The relatively small numbers of individuals that survived the experiment did not allow for a detailed statistical analysis of growth rates at the 3 study sites. Condition index showed a pronounced seasonal variation, with greater values recorded between April to July (CI, ∼24) and lesser values noted during November and December (CI, ∼20). St...

Variability of Stable Isotope Fingerprints of the Serpulid Ficopomatus enigmaticus Within a Permanently Stratified Estuary: Implications for (Palaeo)environmental Interpretations

Abstract: This paper examines how the mixing of freshwater and seawater, and related mixing of freshwater and marine particulate organic matter (POM) in the permanently stratified estuary of the River Krka, Croatia, are reflected in the stable isotope fingerprints of soft tissues and tubes of the serpulid Ficopomatus enigmaticus The carbon stable isotope composition (δ13C values) of the river-borne POM is retained over long distances, causing a depletion in 13C of POM in brackish waters A trophic depletion in 13C was recorded in serpulid soft tissues The serpulid carbonate tubes were depleted in 13C even at locations with salinity close to that of the sea and were subject to large isotope fractionation between dissolved inorganic C (DIC) and carbonate caused by vital effects, making carbonate depleted in 13C by several per mil compared with DIC These effects, though large in the freshwater zone, fade towards the sea The carbonate δ18O values of tubes reflect the δ18O values of the water The temperature-related differences in δ18O values of tubes from different sites are masked by source-related differences in the δ18O values of water arising from mixing of freshwater and seawater in the estuary Therefore, in serpulide tubes, the terrestrial component can easily be overestimated because of vital effects during biomineralisation and trophic depletion in 13C in freshwater and brackish environments

Makirina bay peloid (N Dalmatia, Republic of Croatia) – its potential use in balneotherapy

Abstract: Recent marine sediments from Makirina bay are according to their organoleptic properties, treated as peloid or healing mud, already frequently used by local people and tourists as pomades. The application of peloids in balneotherapy is mainly intended for therapeutic treatment generally related to muscle-bone skin pathologies and purposes of wellness and relaxation. Recent studies point out that one of the main factors determining the final characteristics of peloids are grain size distribution, mineralogy, cation exchange capacity (CEC), elemental and microbiological composition of initial »geological material«. As reported by previous studies Makirina Bay peloid is represented mostly by sandy silt with relatively high CEC value (63.82 meq/100g). Peloid mineral composition is dominated by dolomite and quartz, followed by illite/muscovite, aragonite, halite, calcite, and pyrite. The average concentrations of potentially toxic elements (PTE) in Makirina bay peloid determined in this research are: As (17.6 mg/kg), Cr (92.09 mg/kg), Cu (44.5 mg/ kg), Mo (31.8 mg/kg), Pb (28.9 mg/kg) and Zn (69.2 mg/kg) and are comparable to previous results. PTE contents in benthic algae Codium bursa (C. bursa) are: As (8.8 mg/kg), Cr (15.7 mg/kg), Cu (5.6 mg/kg), Mo (0.7 mg/kg), Pb (3.6 mg/ kg) and Zn (16.3 mg/kg). Calculated Transfer factors (TF) from surficial peloid (0-5 cm) to benthic algae C. bursa are <1 for all analysed PTE, indicating no PTE transfer or bioaccumulation of PTE in C. bursa. Results of microbiological research correspond to previous studies and showed no coliforms and E. coli presence in Makirina bay peloid. Our studies have shown the adequate comparability of Makirina Bay peloid with peloids already successfully used in various spa centres around the world in purposes related to wellness and therapy, but additional researches (determination of Cr and Mo mobilities) are necessary before potential use of Makirina bay peloid. 168 Darja KOMAR et al.

Sources of dissolved ammonia and iron in Borovnica alluvial fan groundwater

Abstract: The article deals with chemical and isotopic properties of Borovnica alluvial fan groundwater. Increased concentrations of ammonium and iron were detected in well VB-3 of the Borovnica alluvial fan pumping station. On the basis of analyses it was found out that increased concentrations of both elements are linked to the hydrogeological conditions in the aquifer area. In the upper part of the Borovnica alluvial fan aquifer, layers of clay prevent the access of oxygen to groundwater. This fact, together with the presence of organic matter in the aquifer, creates reduction conditions causing the mobility of iron and manganese in groundwater and the transformation of nitrogen from nitrate into ammonium form. Water from the lower aquifer contains more dissolved oxygen, and on the basis of tritium presence it can be concluded that the water is old up to 50 years. Wells VB-5 and VB-6 capture water from the lower pleistocene aquifer, while well VB-3 recharges also with water from the upper holocene aquifer.