Spawning of the colonial coral <Emphasis Type="Italic">Cladocora caespitosa</Emphasis> (Anthozoa,Scleractinia) in the Southern Adriatic Sea

Data on sexual reproduction of scleractinian coral species living in temperate zones, particularly in the Mediterranean Sea, are quite scarce. This paper describes sexual reproduction of the colonial coral Cladocora caespitosa from Veliko jezero (Mljet Island) in the Adriatic Sea. Spawned orange eggs and white sperm bundles were observed on the coral bank of C. caespitosa two nights before the full moon (20 June 2005) coinciding with increasing water temperature and correlated with the lunar cycle. Spawning was observed during five nights, involving about 30% of the colonies from the coral bank. Different colonies on the bank released only one type of gamete during the reproductive period. The diameter of the sperm bundles ranged from 100 to 200 μm (average 163 μm; SD = 47.08), while the female gametes diameter ranged from 300 to 500 μm (average 416 μm; SD = 73.12).     

Identity of Squalius (Actinopterygii, Cyprinidae) from Istra Peninsula in Croatia (Adriatic Sea basin)

A chub of previously ambiguous identity from the Boljunscica and Pazincica rivers (south-eastern Istra Peninsula) was studied and compared with geographically close Squalius squalus, Squalius zrmanja, and Squalius janae recently described from the Dragonja River drainage in the Adriatic Sea basin in Slovenia. It was shown that the chub from the south-eastern Istra Peninsula differs from all know species of Squalius but one: Squalius janae. Three samples examined from Boljunscica and Pazincica rivers and Squalius janae from its type locality, Dragonja River, show the following characters typical for the latter species: a long head (the head length 27–32% SL); a pointed conical snout with a clearly projecting upper jaw; a long straight mouth cleft, the lower jaw length (39–45% HL) exceeding the caudal peduncle depth; a large eye; commonly 9? branched anal-fin rays; commonly 44 total vertebrae (24+20 or 25+19); bright silvery colouration, scales easily lost; iris, pectoral, pelvic and anal fin pigmentation with yellow shades. The data on the distribution of Squalius chubs in the northern Adriatic basin support the assumption that the range of Squalius janae is determined by the geology of the Trieste Flysch Basin and the Pazin Flysch Basin forming the base of the Istra Peninsula. The distribution pattern of this species does not support a simple model of fish dispersal and a complete connectivity within the whole Palaeo-Po historical drainage. Indeed, it indicates a disrupted surface palaeohydrography that was heavily fragmented by karstification in the whole Dinaric area.     

Characterisation and differentiation of oligotrophic waters by culturable particle-attached and free-living bacterial communities

This study reports the development of a tool to characterise and differentiate northern Adriatic waters, particularly oligotrophic, high-salinity waters, based on the cellular fatty acids of culturable heterotrophic bacterioplankton. The growth abilities and population dominance were observed for particle-attached and free-living bacteria cultured in three types of media: Marine Broth, diluted Marine Broth (1:10) and R2 broth. Three groups of water layers were distinguished by hierarchical clustering analysis: eutrophic, oligotrophic and oligotrophic nutrient-selected. Significant differences between the resulting groups were tested by two-way ANOVA (with replication). Eutrophic layers were characterised by readily culturable particle-attached and free-living fractions of the bacterial community in all three media, all dominated by fast-growing γ-Proteobacteria. In contrast, oligotrophic water layers with low productivity had a much weaker culturability and a different population dominance for the free-living community, as compared to their attached or growth-arrested counterparts, for all media. The free-living bacteria from strictly oligotrophic environments demonstrated minimum culturability in Marine Broth, while those from selective oligotrophic environments were culturable and were dominated either by Cytophaga–Flavobacter complex, α-Proteobacteria or γ-Proteobacteria. The conclusive evidence regarding the selective and refractory nature of organic compounds in these waters demonstrates the dominant culturability of the Cytophaga–Flavobacter complex and α-Proteobacteria in free-living communities in all growth-media. The response of fatty acid dominance ratios depends significantly on the trophic state and fraction (p < 0.05), although the effect of the trophic state is completely different in attached and free fractions. Both fractions were tested separately, demonstrating a significant influence of the trophic state (p < 0.05), while the effect of the media on the fatty acid response was not significant (p > 0.05). An interaction between media and trophic status was present in the attached fraction (p < 0.05), yet this was not observed in the free fraction (p > 0.05), indicating that any systematic difference between trophic states was the same for each media tested. Accordingly, the free-living fraction of bacterioplankton is a more informative attribute and can be used solely as an indicator of the water layer trophic condition.     

Microphytobenthic Primary Production and Sedimentary Carbohydrates Along Salinity Gradients in the Lagoons of Grado and Marano (Northern Adriatic Sea)

Primary production of the microphytobenthic community and carbohydrates concentrations were studied in the lagoonal system of Grado and Marano, located in the Northern Adriatic coast. Sediment samples were collected along a salinity gradient. Abundance and species composition of the microphytobenthic communities were analysed and the benthic microalgal biomass was estimated as Chlorophyll a (Chl a). Primary production of benthic diatoms was estimated using ¹⁴C-tracer. Extracellular carbohydrates were extracted from the sediment and separated in two operationally defined fractions (colloidal and EDTA-extractable). Salinity was higher in the Grado lagoon, where the benthic microalgal community was mainly composed of marine diatoms. In the Marano lagoon, which has a lower salinity, freshwater species were also found. In both lagoons, photosynthetic efficiency showed an inverse relationship with salinity and a direct relationship with the main biological variables. Photosynthetic activity was directly related to Chl a and abundance of benthic microalgae, suggesting that in the benthic system microalgal community is responsible for primary production. Overall, salinity was also influent on the microphytobenthic primary production, which was greater in the more saline Grado lagoon.     

Phytoplankton population density and volume as indicators of eutrophication in the eastern part of the Adriatic Sea

Population density and volume-biomass of microplankton, nanoplankton and total phytoplankton were analyzed at 14 stations along the eastern part of the Adriatic Sea. Based upon data frequency distribution, four categories of ecosystems were established in the investigated area. Criteria for ecosystem categorization and biological evaluation of eutrophication are proposed.     

Genetic evidence for the identity of Caulerpa racemosa (Forsskål) J. Agardh (Caulerpales,Chlorophyta) in the Adriatic Sea

Three taxa of Caulerpa racemosa that differ morphologically and genetically have been reported in the Mediterranean Sea. The ‘invasive variety’ was recorded for the first time in the early 1990s in Libya. In less than 10 years, it was found in almost all parts of the Mediterranean. The first record of C. racemosa in the Croatian part of the Adriatic Sea was in 2000 and as many as 35 different localities were established by the end of 2004. In terms of morphology, the specimens from the Adriatic Sea resemble the ‘invasive variety’. To confirm this, we analysed populations from two different localities (the island of Mljet and the peninsula of Pelje?ac) using the ITS1-5.8S-ITS2 region of 18S-5.8S-26S rDNA unit as a molecular marker. The ITS1-5.8S-ITS2 region from nine individual plants was amplified by PCR, cloned in a pCR 2.1 vector and sequenced. Phylogenetic comparison of sequences from specimens found in the Adriatic Sea with specimens of the same and similar taxa, found both inside and outside the Mediterranean, provided genetic evidence that C. racemosa populating the Adriatic Sea corresponds to the Mediterranean C. racemosa var. cylindracea (Sonder) Verlaque, Huisman?&?Boudouresque, i.e. to the ‘invasive variety’.     

Diatom distribution in the Southern Adriatic Coastal waters

Abstract

Data on the horizontal and vertical distribution of diatom species, collected between April 1995 and March 1996 in coastal waters of the Apulian Adriatic Sea are presented. A total number of 120 species belonging to 51 genera were identified. Diatoms were dominant in the major part of the examined samples, constituting up to 90% of the total cell numbers during the spring period.     

Plant species diversity of Adriatic islands: An introductory survey

Abstract

The European Mediterranean region is one of the world's major centres of biodiversity. Research on plant species diversity in this region has neglected the area along the eastern part of the Adriatic basin in comparison to the other Mediterranean areas. The main aim of this study was to focus on this neglected area, by supplying data which is at present lacking in order to discuss the species-area relationship (SAR), floristic richness and endemism of the Adriatic islands and coast. Floristic data for 106 Croatian islands collected by different authors were integrated, systematised and presented in a form usable by other researchers worldwide. The Power (Arrhenius) function was used for modelling (by non-linear regression) the SAR. Residuals around the regression curve (as indicators of floristic diversity without the influence of island area) were calculated for each island. The proportion of endemics in the total island flora varies from 0% up to 28.6%, and 17.5% for narrow endemics. Floristic richness of the broader region was estimated (on the basis of SAR extrapolation) on 1807 species for all Croatian islands, and on 2797 species for the entire Mediterranean area in Croatia.     

Nutrient (N,P, Si) fluxes between marine sediments and water column in coastal and open Adriatic

Nutrient benthic fluxes, as well as sediment phosphorus concentration at the open sea and coastal water stations of the Central and South Adriatic were studied during 1997–98. The fluxes were in the ranges: 0.16–2.67 mmol m^–2 d^–1 (silicate); –0.031–0.164 mmol m^–2 d^–1 (phosphate); –0.51–2.03 mmol m^–2 d^–1 (ammonia); and –1.32–1.62 mmol m^–2 d^–1 (nitrate + nitrite). Silicate flux showed a gradient from the coastal area to the open sea. Ammonia was the main nitrogen species in the flux at the estuary and bay stations, while the sum of nitrate and nitrite was predominant at the open sea stations. Relationships between phosphate and ammonia fluxes (r = 0.699, p<0.01) as well as phosphate and silicate (r = 0.529, p<0.01) were established.