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Concentrations of polycyclic aromatic hydrocarbons (PAH) were studied in 36 sediment samples collected from 29 sites in the central Adriatic Sea. The total concentration of PAH showed high variability, ranging from 42.85 µg kg−1 in open sea sediments to 28,662 µg kg−1 in the sediments of Šibenik Bay. Unsubstituted, parent PAH were dominant PAH compounds in the entire area of Šibenik Bay and most of the stations in the coastal area. In Kaštela Bay, methyl PAH concentrations were higher than the concentrations of unsubstituted PAH, whereas in the sediments along the mid-Adriatic transect, similar concentrations of both PAH fractions were determined. PAH sources were investigated by applying the Positive Matrix Factorization software developed by the U.S. Environmental Protection Agency (USEPA). The results indicate the presence of four sources, two of which can be considered petrogenic and two pyrogenic. The contribution of the sources to the total concentration PAH at each station indicates the dominance of pyrogenic sources in Šibenik Bay and at most stations in the coastal area. In the sediments along the mid-Adriatic transversal, as well as in Kaštela Bay, PAHs originate mainly from petrogenic sources. The obtained results show that PMF can be a suitable tool for control of PAH pollution and thus, for the management of various activities in the Adriatic region. Seasonal differences between the contributions of sources in the Kaštela and Šibenik bays indicate that the contribution of traffic to the total concentration of PAH was higher during the tourist season. The carcinogenic risk of PAH determined by toxicity equivalent (TEQ) calculations showed an increased carcinogenic risk in the whole area of Šibenik Bay, regardless of the number of PAH compounds considered for the calculations. A low PAH-related carcinogenic risk was found for the rest of the study area. [ABSTRACT FROM AUTHOR]

Temperature and phosphorus positively interacted in controlling picoplankton biomass production and its transfer towards higher trophic levels. Two complementary approaches (experimental and field study) indicated several coherent patterns: (1) the impact of temperature on heterotrophic bacteria was high at temperatures lower than 16°C and levelled off at higher temperatures, whereas this impact on autotrophic picoplankton was linear along the entire range of the investigated temperatures; (2) the addition of phosphorus increased the values of picoplankton production and grazing, but did not change the nature of their relationships with temperature substantially; (3) the picoplankton carbon flux towards higher trophic levels was larger during the warmer months (grazing by HNF dominated during the warmer period and by ciliates during the colder period) and also strengthened in conditions without phosphorus limitation; (4) the hypothesis that the available phosphorus can be better utilized at higher temperatures was confirmed for both autotrophic and heterotrophic picoplankton; (5) the hypothesis that the rise in temperature stimulates growth only in conditions of sufficient phosphorus was confirmed only for heterotrophic bacteria. Therefore, in the global warming scenario, an increase of the picoplankton carbon flux towards higher trophic levels can be expected in the Adriatic Sea, particularly under unlimited phosphorus conditions. [ABSTRACT FROM AUTHOR]

The structure of the microbial food web was studied in six estuary areas along the eastern Adriatic coast during March, July and October 2012. Limitation by phosphorus, not nitrogen, was a common feature for all studied estuaries. Heterotrophic bacteria and autotrophic picoplankton (APP) (particularly picoeukaryotes and Synechococcus) can reach notable abundances and biomasses, suggesting potential importance of the picoplankton community in P-limited estuarine environments. The main features of the microbial community structure in these environments included: (1) higher heterotrophic biomass in comparison to autotrophic biomass within the picoplankton community; (2) general domination of picoeukaryotes within the APP community, and increase of absolute and relative biomass of prokaryotic autotrophs (Prochlorococcus and Synechococcus) in the total APP in P-limited conditions; (3) domination of Synechococcus over Prochlorococcus biomass in all studied conditions, and common spatial distribution of these two groups of cyanobacteria, which was mostly determined by concentration of phosphorus; (4) relatively high contribution (about 50%) of LNA bacteria in the total bacterial abundance; and (5) relatively high contribution (about 33%) of heterotrophic pico-flagellates in the total flagellate abundance. [ABSTRACT FROM PUBLISHER]

The Croatian National Monitoring Program revealed the presence of Diarrhetic Shellfish Poisoning (DSP) toxicity in Mediterranean blue mussel (Mytilus galloprovincialis) from breeding farms in southern Adriatic Sea through January to June 2011. The mouse bioassay tests (MBA; at the time the official method for DSP toxins) were accompanied by atypical symptomatology in the animals and this caused doubts about the assay results. Consequently, in parallel studies reported here, the concentration of Cd, Cr, Cu, Ni, Pb and Zn in soft tissue of DSP positive and negative mussels samples was determined. Cd, Cr, Zn and Ni show higher values in approximately 75% of the DSP positive samples, whereas for Pb and Cr the values were 26% and 34%, respectively. This trend was unchanged during the whole observation period. [ABSTRACT FROM AUTHOR]

This paper addresses the dynamics of the prokaryotic picoplankton community in the coastal and open sea areas of the central Adriatic and in the coastal area of the southern Adriatic. This involved the study, from January to December 2005, of bacteria (total number of non-pigmented bacteria; high nucleic acid content (HNA) bacteria; low nucleic acid content (LNA) bacteria), cyanobacteria ( Synechococcus and Prochlorococcus) and heterotrophic nanoflagellates. During the warmer seasons, in the mainly oligotrophic area under investigation into the Adriatic Sea, bacterial densities and bacterial production have shown an increase in values and domination of the LNA group of the bacterial population. In contrast, in those areas influenced by karstic rivers, the domination of HNA bacteria in total abundance of non-pigmented bacteria and high values of bacterial production was estimated throughout the investigated period. Our results show the importance of both HNA and LNA bacterial groups in the total bacterial activity throughout the investigated area. The biomass of bacteria was mostly predominant in the prokaryotic community, while within the autotrophic community Synechococcus biomass mostly predominated. During the warmer seasons, an increase in autotrophic biomass was observed in relation to non-pigmented biomass. The importance of predation in controlling bacteria by heterotrophic nanoflagellates was pronounced during the warmer period and in the coastal areas. [ABSTRACT FROM AUTHOR]

oka Kotorska bay is a unique coastal ecosystem in the south-eastern Adriatic Sea that has been recently under the increasing influence of human activities. In this paper, we investigated the temporal distribution of biological and environmental parameters and the trophic state of the Bay. Sampling was conducted weekly from March 2008 to February 2009 in the inner part of the Bay (Kotor Bay). The phytoplankton biomass ranged between < 1 to > 4 μg l-1 chlorophyll a (Chl a), reaching maximum values in the late winter and spring period. On the basis of Chl a and nutrient concentrations, the study area can be defined oligo-mesotrophic. Two indicators of the trophic state, trophic index TRIX and the pigment ratio Fp were calculated from the available physiochemical and biological data. The TRIX value ranged from 3.02 to 5.58 (average 4.11 ± 0.66) while the Fp ratio varied between 0.05 and 0.33 (average 0.17 ± 0.08). These results indicate a system that is in a good trophic state, where natural eutrophication still dominates over eutrophication of an anthropogenic origin. [ABSTRACT FROM AUTHOR]

In this study, we investigated the physical, chemical and biological parameters of the water column at two stations under different trophic conditions during a 1-year period (from September 2005 to September 2006) in an aquaculture area. The investigation was performed monthly at a station inside the fish farm in Maslinova Bay (middle Adriatic Sea, Croatia) and at a control station located in the Hvar Channel in the vicinity of the farm. The results showed that the concentrations of dissolved nutrients were slightly enhanced at the farm station in comparison with the control station, although those differences were not statistically significant, nor were the differences in oxygen saturation recorded during the investigation period. As opposed to the chemical parameters, considerably higher deviations were recorded for biological parameters as demonstrated by a significant increase in phytoplankton biomass and primary production (measured in situ) at the farm station, particularly during the summer season. Phytoplankton community structure analysis showed that the phytoplankton composition at the farm was mostly determined by seasonal changes rather than by the influence of fish farming. In Maslinova Bay, no causal links were identified between increased biomass and the appearance of toxic species. [ABSTRACT FROM AUTHOR]

Interannual variability of the primary production in the middle Adriatic Sea for the period 1961–2002 was examined and correlated to the various atmospheric and oceanographic parameters. The sequential t-test analysis of regime shift (STARS) method and locally-weighted scatter plot smoothing (LOWESS) method were applied to the primary production, revealing the new regime with significantly different mean productivity ranging from 1980–1996. Moreover, this period with the highest primary production, consists of the two distinguished sub-periods: periods of increasing (1980–1986) and decreasing (1987–1996) primary production. Whereas in the first period the ecosystem was under the influence of warmer and nutrient richer Levantine Intermediate Water (LIW) intrusions into the Adriatic, in the second period, which started with a cold winter in 1987, the Eastern Mediterranean Transient (EMT) occurred. The EMT established a new circulation regime which prevented the LIW intrusions in the Adriatic, causing its reduced productivity. Reduced LIW inflow in the Adriatic was evidenced in the lower than normal sea temperature, salinity and oxygen concentrations below the thermocline depth. Precipitation and wind regime also arose as important local factors for the primary production variability. Our analysis connected the shifts in primary production with hemispheric and regional scale climate variations, and supports the hypothesis that atmospheric variability can trigger the ecosystem changes. [ABSTRACT FROM PUBLISHER]

Physical and chemical characteristics of the water column and sediments at sea bass/sea bream farm located on the middle Adriatic island of Brač were investigated during the 2001-2006 period. Measurements and samplings were performed at stations inside the farm area and at reference station, approximately 1 km distant from the farm. Investigated parameters in the water column were temperature, salinity, transparency, suspended matter concentration, oxygen saturation and nutrient concentrations. Parameters measured in the sediments were granulometric composition, redox-potential, organic matter organic carbon and total nitrogen content, phosphorus (P) species concentration (biogenic apatite P, authigenic apatite P, detrital apatite P, P bound to iron oxides and hydroxides and organic P). Transparency in the water column at all stations followed the natural seasonal course, although constantly lower values at the farm stations relative to the reference site indicate a certain impact offish farming on this parameter. Impact on chemical parameters was moderately expressed in the surface and middle layer of the water column through the deficiency of oxygen and increased concentrations of dissolved inorganic nitrogen, orthophosphate and urea due to fish excretion and degradation of their metabolic products. Sediment inorganic P concentrations were enhanced under the cages compared to the reference site, while organic P was mainly within the range of "natural" middle Adriatic concentrations. Sequential analysis of inorganic P species showed an increased portion of biogenic apatite P and decreased detrital apatite P at the farm stations with respect to the inorganic P pool at the reference station as a direct consequence offish farming. Sediment redox-potential, granulometric composition, organic matter content, carbonates as well as organic carbon and total nitrogen content reflected natural sediment characteristics rather than fish farm influence. [ABSTRACT FROM AUTHOR]

Annual dynamics and ecological characteristics of the genus Dinophysis spp. and associated shellfish toxicity events were studied from 2001 to 2005 during monitoring fieldwork in the coastal waters of the eastern Adriatic Sea. Analysis of the seasonal occurrence of Dinophysis species identified D. acuminata and D. sacculus as typical spring species, D. caudata, D. fortii and D. rotundata as summer and late summer species and D. tripos as a winter species. The highest abundances occurred when there were large differences between surface and bottom temperatures and salinities. D. caudata, D. sacculus and D. rotundata abundances had significant relationships with Δt, while the highest abundances of D. acuta, D. fortii and D. tripos were associated with high Δs values. Much higher abundances of D. caudata and D. fortii in offshore compared to inshore waters of the northern Adriatic Sea and the significant inverse relationship of these species' abundances with salinity suggested the possibility of their transport by Italian river-influenced coastal waters towards the eastern Croatian coast during the summer season and under stratified conditions. Toxicity events occurred more frequently in the more eutrophicated northern Adriatic Sea than in the southern Adriatic Sea and mostly succeeded the rainfall periods. Diarrhetic shellfish poisoning (DSP) toxin profile analyses identified okadaic acid and yessotoxin as the main DSP toxins occurring in Croatian waters. [ABSTRACT FROM AUTHOR]

Temporal and spatial variability of micro and mesozooplankton was studied in 1998 and 1999 at four stations in the Neretva Channel area influenced by the Neretva river and the open waters of the south Adriatic Sea. The area is orthophosphate limited, but an excessive accumulation of land derived nitrogen is prevented by phytoplankton uptake and the general circulation pattern. Microzooplankton was dominated by ciliates, with average abundances comparable to other Adriatic channel areas (122-543 ind. l). Non-loricate ciliates (NLC) generally peaked in the warmer periods, but a winter increase was evident towards the inner part of the channel. Tintinnid abundances generally increased in autumn. A significant relationship with temperature was not recorded for either protozoan group. An inverse relationship between NLC and salinity might be indirectly caused by their preference for the food abundant surface layer. Mesozooplankton was dominated by copepods, with distinct summer maxima throughout the area and pronounced winter maxima of >10,000 ind. m at the inner stations. The community was predominantly neritic but the open sea waters were important in structuring the mesozooplankton assemblage at all stations during the autumn-winter period. Although temperature regulated the seasonal dynamics of most metazoans and the species succession in the copepod community, small omnivorous copepods ( Oncaea media complex, Oithona nana and Euterpina acutifrons) dominated regardless of the season. A trophic link between copepods and ciliates was evident in winter during low phytoplankton biomass. [ABSTRACT FROM AUTHOR]

This paper presents monitoring results of the impacts of a tuna breeding farm on physical and chemical parameters in sediment and water column. The results showed permanently more negative sediment redox-potential at the station under the cage than at the referential station, as well as higher organic carbon and total nitrogen sediment content. The average sediment total phosphorus concentration (TP) in surface sediment for the station under the cage (G1) was 24.1±7.9 μmol g-1 d.w., which is almost twofold higher than at the station 200 meters far from the cage (G2) and the referential station (REF) distanced 500 meters. These concentration values were similar to those recorded for highly eutrophicated bays in the Middle Adriatic area. SEDEX analysis showed an increased "fish debris phosphorus" concentration at the station under the cage (31% of TP concentration) in relation to G2 and REF station (20% and 12% of TP). This increase is directly influenced by fish farming activities (fish bones and fish tooth remains, originated from uneaten fish food settled at the seabed). The bottom layer of the water column showed occasionally an enhancement of nutrient concentrations at the station under the cage in relation to REF station (orthophosphate: 1.423 to 0.028 mmol m-3, organic phosphorus: 0.577 to 0.146 mmol m-3 and ammonia: 2.41 to 0.71 mmol m-3, respectively). [ABSTRACT FROM AUTHOR]

A recent analysis of the Mediterranean Sea surface temperature showed significant annual warming. Since small picoplankton microorganisms play an important role in all major biogeochemical cycles, fluxes and processes occurring in marine systems (the changes at the base of the food web) as a response to human-induced temperature increase, could be amplified through the trophic chains and could also significantly affect different aspects of the structure and functioning of marine ecosystems. In this study, manipulative laboratory growth/grazing experiments were performed under in situ simulated conditions to study the structural and functional changes within the microbial food web after a 3 °C increase in temperature. The results show that a rise in temperature affects the changes in: (1) the growth and grazing rates of picoplankton, (2) their growth efficiency, (3) carrying capacities, (4) sensitivity of their production and grazing mortality to temperature, (5) satisfying protistan grazer carbon demands, (6) their preference in the selection of prey, (7) predator niche breadth and their overlap, (8) apparent uptake rates of nutrients, and (9) carbon biomass flow through the microbial food web. Furthermore, temperature affects the autotrophic and heterotrophic components of picoplankton in different ways. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAH) were investigated in the sediments at 24 locations in the coastal area of Adriatic Sea. Total PAH concentrations ranged from 14,98 to 26145,62 µg kg-1, with the highest levels determined in the sediments of Šibenik Bay and the lowest in the sediment near Island of Pag. Unsubstituted PAH were prevailing PAH group in the sediments from the Šibenik Bay and in the Coastal area, while methyl-substituted PAH were dominant group in the sediments of the Kaštela Bay. In order to estimate the possible toxicological significance of PAH concentrations, Sediment Quality Assessment was done according to three different sets of sediment quality guidelines. A high environmental risk was calculated for each station in Šibenik Bay; for the station in vicinity of the Industrial port of Split and for the two stations in Coastal zone. Low environmental risk was determined in less urbanised areas such as Island of Pag. Sediment extracts were further analysed for acute toxicity by measurements of decrease in bioluminescence upon exposure to sediment extracts. Obtained results show disagreement between sediment toxicity predicted upon PAH levels in sediment and experimentally obtained sediment toxicity. Sediment extracts in which low PAH levels were measured showed high acute toxicity indicating that concentrations of PAH alone are a poor indicator of sediment toxicity. Correlation analysis between concentrations of specific PAH compounds and toxicity revealed the strongest association between acute sediment toxicity and sulphur-containing PAH suggesting the S-PAH should be considered in sediment toxicity assessment. [ABSTRACT FROM AUTHOR]

The seasonal and spatial distributions of particulate phosphorus (PP) in the water column of the coastal area and open sea of the middle Adriatic Sea area were investigated for the first time. The relationship between PP and two other important forms of phosphorus (dissolved inorganic phosphorus (DIP), and organic phosphorus (P-ORG)), and the relationship between PP and other nutrients (nitrogen and silicon salts) and oceanographic parameters (temperature, salinity, oxygen saturation, chlorophyll a) from the water column were also examined. PP concentrations ranged from 0.007 μmol dm-3 in the open sea near Palagruža archipelago to 0.589 μmol dm-3 in the Krka River estuary. In the coastal area, PP concentrations were highest in autumn and lowest in winter. The vertical distribution of PP concentrations in the water column of the coastal area were highest in the surface layer during most of the year due to input of PP by freshwater inflows. In the open sea area, there were no significant seasonal or vertical differences in the distribution of PP concentrations in the water column. Seasonal analysis of the total phosphorus pool (PP, DIP and P-ORG) in the water column indicated that PP and P-ORG concentrations were higher in the coastal area compared to the open sea, while DIP concentrations were comparable. The results further demonstrate that PP can be an important fraction of the total phosphorus pool. A significant positive correlation was found between PP and chlorophyll a, indicating that PP was mainly of biological origin, and with nutrient salts of nitrogen and silicon, while a negative correlation was found with salinity [ABSTRACT FROM AUTHOR]

In order to test the response of phytoplankton to anthropogenic pressure, data of chlorophyll a concentration, phytoplankton abundance, and composition are analyzed in relation to anthropogenic pressure gradient and environmental variables such as temperature, salinity and nutrients. Investigated sites encompassed wide tropic range according to a preliminary determination of anthropogenic pressure, quantified through the LUSI index. Statistical analyses indicated nitrates and silicates as proxies of freshwater influence, and phytoplankton single metrics such as concentrations of chlorophyll a and abundances as indicators of anthropogenic pressure. Boundary values for different water quality classes for coastal waters under indirect freshwater influence (Type II) are obtained according to gradient between concentration of chlorophyll a and pressure index (LUSI), which empirically fit to exponential equation. The response of phytoplankton diversity was not linear, as the highest diversity was observed in the area with intermediate disturbance level. CCA analysis identified Skeletonema marinoii , Scrippsiella trochoidea , Guinardia flaccida , Leptocylindrus spp., Prorocentrum spp., Proboscia alata , Eutreptiella spp., and Pseudonitzschia spp. as local eutrophication indicators, whose abundances increased with nutrients loads. [ABSTRACT FROM AUTHOR]

The zooplankton assemblage was investigated in April 2006 at 9 stations along, and in front of the highly stratified salt-wedge Krka river estuary, using 53- and 125-μm mesh Nansen nets. Tintinnids, copepods and their developmental stages and mollusc larvae dominated the zooplankton community, with 28 tintinnid and 41 copepod taxa recorded in the investigated area. Both tintinnid and copepod communities showed a general decrease in abundance and increase in species number from the head to the mouth of estuary, with a clear dominance of estuarine-neritic species. The most abundant tintinnids were Tintinnopsis campanula and Favella ehrenbergii. Small cyclopoid copepod Oithona nana dominated in the upper reaches, presumably feeding opportunistically on abundant organic matter accumulated at the permanent halocline. The contribution of calanoids intensified towards marine stations, except in the eutrophicated Šibenik harbour area in the middle reaches, where cyclopoid Oithona nana again proliferated. An assessment of the sampling performances of the 53- and 125-μm nets and data on zooplankton population structure indicated that the 125-μm mesh size plankton net in combination with Niskin bottles would give the optimal insight into the ecology of all zooplankton components in future investigations of this and similar highly stratified estuaries. [ABSTRACT FROM AUTHOR]

Distribution and abundance of two Synechococcus ecotypes, phycocyanin-rich cells (PC-SYN) and phycoerythrin-rich cells (PE-SYN) were studied in the surface layer of the central Adriatic Sea during the 2015-2016 period. The studied area included several estuarine areas, and coastal to open sea trophic gradients, covering a wide range of seawater temperatures (11.82 - 20.75oC), salinity (4.47 - 38.84) and nutrient concentration. The abundance of PC-SYN ranged from 0 to 79.79 x 103 cell mL-1 and that of PE-SYN from 5.01 x 103 to 76.74 x 103 cell mL-1. Both ecotypes coexisted in the studied waters with PC-SYN cells dominating during spring and PE-SYN during winter and autumn. PC-SYN showed a significant positive relationship with temperature and strong positive responses to nitrogen nutrients, whereas PE-SYN positively responded to phosphate availability. The relative ratio of phosphorus availability and total inorganic nitrogen nutrients (N/P ratio) affects the spatial distribution of the two Synechococcus ecotypes. [ABSTRACT FROM AUTHOR]

Phytoplankton assemblages and pigment distribution were determined in the transitional Boka Kotorska Bay. Samples were collected four times from three stations in the inner part of the Bay between April 2008 and March 2009. Microscopic analysis revealed that the phytoplankton was composed of marine diatoms, dinoflagellates, cryptophytes, chlorophytes and coccolithophorids. Aside from fucoxanthin as the dominant biomarker pigment, alloxanthin, 19′-hexanoyloxyfucoxanthin, peridinin and chlorophyll b provided indicative contributions. Fucoxanthin and alloxanthin showed significant correlation with the phytoplankton chlorophyll a biomass throughout the investigated period. In November 2008, the diatoms were outcompeted by coccolithophorids, which probably efficiently absorbed nutrients during a period of their reduced supply. Due to the reduced nutrient input, in the summer, the phytoplankton community in the Bay was composed mostly of marine dinoflagellates, cryptophytes, and chlorophytes. [ABSTRACT FROM AUTHOR]

The unusual and prolonged occurrence of rare and poorly known dinoflagellate Prorocentrum arcuatum in the phytoplankton of the shallow aquaculture site in Medulin Bay was recorded from July 2013 to October 2014. This enabled us to investigate changes in abundance and environmental drivers of P. arcuatum population dynamics in natural conditions, and to provide first detailed description of P. arcuatum from field samples based on SEM images. During 15 months of observations we also recorded seasonal variability in P. arcuatum cell size. The optimum physical conditions for P. arcuatum proliferation were reached in autumn 2013, during the narrow temperature range between 19.6oC - 20.4oC, and salinity between 36.7 - 37.7. Despite the general similarity in physical conditions in autumn 2014, this increase in the abundance of P. arcuatum was not repeated, which might be connected to higher competition due to observed interannual changes in phytoplankton population structure. [ABSTRACT FROM AUTHOR]

In recent highly variable climate, a combined effect of a large-scale northern hemisphere climate and regional-scale Adriatic hydroclimate changes significantly reflected in the Adriatic Sea ecosystem. To clarify this statement we set up in connection two inter-annual systems: the air-sea interconnected system and pelagic ecosystems for the period 1961 to 2010. Within this period, significant changes occurred through 1987-1998 period, characterized by a drop of temperature, salinity and oxygen concentration in the middle Adriatic intermediate layer as consequence of a weaker ventilation of the Adriatic Sea. The pelagic ecosystem reacted to these changes. Large fluctuations in marine biota (from plankton to pelagic fish) revealed significantly different regimes before and after the late eighties. Different patterns observed through analyzed biotic parameters seem linked to modification in thermohaline circulation related to the Eastern Mediterranean Transient (EMT), whose effects prevented warmer and saltier water mass intrusions into the Adriatic Sea. These results provide evidence on connections between the shifts in the middle Adriatic pelagic ecosystem and the northern hemisphere climate via changes in regional atmospheric conditions, and highlight the importance of northern hemisphere climate changes for physical and biological regimes of the Adriatic Sea. [ABSTRACT FROM AUTHOR]

The objectives of this paper were to determine the main environmental drivers of zooplankton variability in coastal waters adjacent to urban areas and to evaluate the differences in zooplankton abundance and population structure in relation to chemical and biological parameters in the water column. Samples were collected seasonally from May 2006 to January 2009 at 8 sampling sites in the bays and channels along the eastern Adriatic coast. Zooplankton population structure showed high similarity withir, the investigated region, especially evident in the homogeneity of copepod community composition, where relative importance of the individual species showed characteristic high ranking of small and medium-sized taxa. Zooplankton numerical variability primarily responded to seasonal variation in water temperature and spatial variation in salinity, but spatial distribution of the collected data showed that abundances were also linked to chemical and biological parameters generally used as descriptors of water quality. This indicates that zooplankton community size reflects the trophic status of an area and supports the use of zooplankton studies as an auxiliary method in the evaluation of the trophic state of coastal waters. [ABSTRACT FROM AUTHOR]

A one-year survey of HNA and LNA heterotrophic bacteria abundance and its relation to bacterial production was conducted in the middle and southern Adriatic. The average abundance of heterotrophic bacteria in the central and southern coastal areas of the eastern coast of the Adriatic Sea ranged from 0.24x106 to 2.39x106 cells mL-1 and in the open sea area ranged from 0.23x106 to 0.63x106 cells mL-1. Elevated average abundances were found in the coastal area of Sibenik and in Kastela Bay. The average monthly percentage of HNA bacteria in the central and southern coastal areas investigated ranged from 21.48 to 93.18%, while in the open sea HNA ranged from 28.62 to 65.62%. The seasonal distribution in the coastal areas mostly showed simultaneously the prevalence of LNA bacteria in the bacterial community and high values of bacterial production, respectively, during spring and summer. The prevalence of the HNA group in the bacterial community was found during colder seasons together with low values of bacterial production. Exceptions are identified in the areas influenced by rivers with the highest bacterial production, where HNA bacteria were dominant in the microbial community during all four seasons. On the open sea during the periods with the highest values of bacterial production, when viewed seasonally and vertically, the water column was dominated by LNA bacteria indicating the importance of both groups of bacteria in the marine ecosystems of the waters studied. [ABSTRACT FROM AUTHOR]

The abundance of Synechococcus and Prochlorococcus were determined at twenty-one stations located along the eastern coast of the central and southern Adriatic and at three stations located in the open central Adriatic Sea. Synechococcus abundance ranged from 10² to 105 cells mL-1 in the coastal area, and from 10³ to 104 cells mL-1 in the open sea Prochlorococcus abundance in the coastal area ranged from 0 to 104 cells mL-1, and from 10³ to 104 cells mL-1 in the open sea The seasonal distribution of Synechococcus and Prochlorococcus mostly showed an increase in abundance during the warmer period and a decrease during winter. The highest abundance of Synechococcus was found in Kaštela Bay with values at 4. 6 x 1 05 cells mL1, while the highest abundance of Prochlorococcus was determined in the Sibenik area and recorded as 7.1 x 104 cells mL-1. Synechococcus was found to be more abundant than Prochlorococcus in most cases. The abundance of Synechococcus was influenced more by temperature than nutrient availability. The abundance of Prochlorococcocus was influenced by nutrient availability and the movement of water masses more than by HNF. [ABSTRACT FROM AUTHOR]