First record of the dinoflagellate Tripos rotundatus in the Adriatic Sea

This report presents the first record of Tripos rotundatus (Jørgensen) Gómez in the Adriatic Sea. The species was found in a net sample in the 50 – 100 m depth layer, taken on July 2021 off the southern coast of the Adriatic Sea. The species T. rotundatus was probably previously misidentified as the morphologically similar species T. digitatus (Schütt) Gómez

Relationship between marine epilithic diatoms and environmental variables in oligotrophic bay, NE Mediterranean

The taxonomic composition and structure of a marine epilithic diatom community were sampled from the bottom of the two sites at monthly intervals from January to December 2011 in the small semi-enclosed oligotrophic Neum Bay in Bosnia and Herzegovina (Middle Adriatic). Altogether, 264 diatom taxa (species and infraspecific taxa) within 69 genera were identified. Among them, 149 and 203 taxa occurred in samples from the shallow (0.5 m depth) and deep (8 m depth) sites, respectively. The monthly distribution of most of the diatoms was irregular and high numbers of sporadic taxa were found. SIMPER analysis indicated that the difference between shallow and deep sites could be largely attributed to the frequently recorded diatom taxa and those with high percentage abundances. They were Halamphora coffeiformis, Caloneis excentrica, Cocconeis scutellum var. scutellum, Licmophora flabellata, Licmophora gracilis, Licmophora sp., Navicula abunda, Rhabdonema adriaticum, and Striatella unipunctata. Canonical Correspondence Analysis (CCA) showed that temperature, oxygen saturation (O2/O2′), silicate concentration (SiO4), and salinity were the most important factors influencing diatom community structure in the bay

Colonization of bacteria and diatoms on an artificial substrate in a marine lake (eastern Adriatic Sea, NE Mediterranean)

The initial colonization of bacteria and diatoms on a immersed artificial substrate and the development of diatom assemblages in relation to physico-chemical parameters were investigated on a weekly basis at one station in the marine Lake Mrtvo More, South Croatia, from April to October 2016. According to TRIX trophic index, lake showed different trophic character: (i) oligotrophic (at the beginning and the end of the study), (ii) mesotrophic (the end of June to mid-July), (iii) eutrophic (the end of July to mid-September). Heterotrophic bacteria increased to peak abundances (69,268 cells cm–2) at the beginning of June when the diatoms abundances start to increase. The lake has high diatom species richness (285 diatom taxa within 72 genera), with the highest species diversity index in August. Among diatoms, adnate were the primary colonizers, particularly Cocconeis dirupta W.Gregory var. flexella (Janisch and Rabenhorst) Grunow and Cocconeis scutellum Ehrenberg var. scutellum, while motile taxa joined the fouling communities from July to September. This study showed close relationship between diatom species composition and changes of physico-chemical parameters, particularly the nutrient concentrations

Usporedba struktura zajednica bentoskih dijatomeja na prirodnim i umjetnim podlogama u morskom jezeru (Jadransko more)

In this study, the diatoms of three alternative habitats (epilithon, epiphyton and artificial sub- strate) were compared to understand the differences in composition on artificial and natural sub-strates. For this purpose, the samples were collected weekly between 11th August and 2nd Septem-ber 2016 at a sampling site in a shallow marine lake, Mrtvo More (Dead Sea) on Lokrum Island near Dubrovnik (South Adriatic, Croatia). In addition to detailed light microscopic analysis, ultrastructural analysis of benthic diatoms from Lake Mrtvo More was performed for the first time using scanning electron microscopy (SEM). A total of 97 taxa were identified in 12 samples. Cocconeis scutellum Ehrenberg and Halamphora coffeiformis (C.Agardh) Levkov were the most frequent taxa in the samples. Shannon-Wiener diver-sity index (H’) values varied from 1.78 (in September on Padina sp.) to 4.52 (in August on glass). According to non-metric multidimensional scaling ordination, there were two groups: epilithon and artificial glass substrate as Group1 and macroalgae as Group2. The results of the analysis showed that the diatom communities developing on artificial sub-strates accurately corresponed to the diatom community of a rock substrate and thus can be used as a representative alternative tool for studies of epilithic diatoms in further experiments.Kako bi se razumjele razlike između naseljavanja na umjetnim i prirodnim podlogama, u ovom istraživanju uspoređivani su sastavi dijatomeja s tri alternativna staništa (epiliton, epifiton i umjetni supstrat). U tu svrhu uzorci su sakupljani tjedno između kolovoza i rujna 2016. na jednoj lokaciji u plitkom morskom jezeru Mrtvo More na otoku Lokrumu kod Dubrovnika (Južni Jadran, Hrvatska). Osim detaljne analize svjetlosnim mikroskopom, po prvi put je provedena i ultrastrukturna analiza bentoskih dijatomeja iz jezera Mrtvo More pomoću elektronske mikroskopije (SEM). U 12 uzoraka identificirano je ukupno 97 vrsta dijatomeja. Vrste Cocconeis scutellum Ehrenberg i Halamphora coffeiformis (C.Agardh) Levkov bile su najčešće vrste u uzorcima. Vrijednosti Shannon-Wiener (H’) indeksa varirale su od 1,78 (u rujnu na vrsti Padina sp.) do 4,52 (u kolovozu na staklu). Prema nMDS ordinaciji, razlikuju se dvije skupine zajednica bentoskih dijatomeja: epiliton i umjetna staklena podloga kao Grupa 1 i makroalge kao Grupa 2. Rezultati analize pokazali su da zajednice bentoskih dijatomeja koje se razvijaju na umjetnim podlogama, odgovaraju dijatome-jskoj zajednici kamene podloge i da se stoga mogu koristiti kao reprezentativni alternativni alat za proučavanje epilitskih dijatomeja u daljnjim eksperimentima

The Size Driven Variations in Physiological Responses of the Bearded Horse Mussel Modiolus barbatus and the Noah’s Ark Shell Arca noae

Bearded horse mussel and Noah’s ark shell are sometimes observed to live together in groups. Oxygen consumption, ammonia excretion and clearance rate were investigated on these species under laboratory conditions considering different size of individuals divided into three size groups (less than 25 mm; 25 to 50 mm and larger than 50 mm). Body size of both species significantly influenced oxygen consumption, ammonia excretion and clearance rate of the Noah’s ark shell. In both species, respiration and clearance rate decreased with body size while excretion rate increased with body size. For Noah’s ark shell groups of 25 to 50 mm and smaller than 25 mm, the atomic ratio between oxygen consumption and ammonium excretion i.e. O:N ratio was detected to be greater than 30. The same applies to a group of the bearded horse mussels smaller than 25 mm. Animals of both species larger than 50 mm have O:N ratio smaller than 30 indicating use of proteins as metabolic substrate, compared to use of lipids and carbohydrates in younger animals

Rast, učestalost dužinskih klasa promjerskih veličina i reprodukcijski ciklus hridinskog ježinca (Paracentrotus lividus) (Lamarck, 1816) iz uvale Bistrina, Južni Jadran

This paper presents research data on the growth, size class frequency and reproduction of the sea urchin Paracentrotus lividus in Bistrina Bay, eastern Adriatic Sea coast, Croatia. The population was sampled on a monthly basis and from depths ranging between 0 and 3 m from the surface. Size class frequency of the test diameter showed that the population size ranges between 10 and 65 mm in the area with the main population in the class 30-45 mm. The von Bertalanffy growth parameters were found: TD∞=7.07 cm, K=0.182, to=-1.403 years. The estimated longevity was found to be 15.06 years. The gonad somatic index annual distribution showed that the peak of reproduction occurs in April. The average GSI values range between 1.33±0.96% in September and 4.83±2.02% in April.U ovom radu prikazani su rezultati istraživanja populacije hridinskog ježinca, Paracentrotus lividus iz uvale Bistrina, Malostonski zaljev. Istraživani parametri su: rast, učestalost dužinskih klasa i reprodukcijske značajke. Uzorkovanje je obavljano jednom mjesečno, ronjenjem do dubine od 3 metra. Učestlost dužinskih klasa kućice kolebala je između 10 i 65 mm, gdje je glavnina populacije unutar razreda, 30-45 mm. Izračunati su Von Bertalanfijevi parametri rasta: TD∞=7.07 cm, K=0.182, to=-1.403 godine. Procijenjena najveća starost je 15.06 godina. Godišnja raspodjela gonadosomatskog indeksa pokazala je maksimalnu vrijednost u travnju, a GSI je kolebao između 1.33±0.96% u rujnu do 4.83±2.02% u travnju

Epilithic diatom communities from areas of invasive Caulerpa species (Caulerpa taxifolia and Caulerpa cylindracea) in the Adriatic Sea, NE Mediterranean

Epilithic diatom community structures are compared among three locations of the eastern Adriatic Sea coast (Croatia), in the presence of two different invasive Caulerpa species, C. taxifolia and C. cylindracea, which have spread rapidly in the Mediterranean in the last decades. Forty samples were taken seasonally at three sites (island of Hvar, island of Mljet, and Dubrovnik) between November 2008 and October 2010. Light and electron microscopy examinations were used for qualitative analysis. Altogether 310 epilithic taxa belonging to 65 genera were identified. The highest number of these taxa belonged to Mastogloia (48) and Amphora (32), followed by Diploneis (24), Nitzschia (23), Navicula (22), and Cocconeis (19). A similar seasonal shift in growth form structure was observed for epilithic communities at the three sampling sites, where the number of erect group diatoms doubled (Hvar, Mljet) and tripled (Dubrovnik) in spring. Apart from erect forms, Dubrovnik and Mljet were characterised by adnate forms, while Hvar was characterised by tube-dwelling forms. The highest values of the Shannon-Wiener Diversity Index were recorded in autumn and ranged from 5.26 to 5.34. ANOSIM tests performed on species relative abundance data confirmed that the diatom communities differed significantly between the sampling sites, and that the differences were correlated with the presence of the two species of invasive macroalgae (Hvar – area of C. taxifolia; Mljet and Dubrovnik – areas of C. cylindracea). As revealed by SIMPER analyses, the group of taxa contributing the most to variance between diatom assemblages from sites of different invasive alga included Cocconeis scutellum var. scutellum, Rhopalodia pacifica, Navicula ramosissima, and Berkeleya rutilans. Although the spatial variation in communities may also reflect the effects of unmeasured environmental variables, the results suggest the possible influence of invasive seaweeds of the genus Caulerpa which may affect the habitat by competing with autochthonous algae. This study contributes to the knowledge of diatom diversity both at regional and at broader scales in these challenged environments

Influence of Salinity on Physiological Response of the Bearded Horse

Bearded horse mussel Modiolus barbatus and Noah’s ark shell Arca noae are a species of interest for the diversifying shellfish aquaculture on the south-eastern coast of the Adriatic. In this study, oxygen consumption (OC), total ammonia excretion (TAM) and clearance rate (CR) responses to the changes in seawater salinity (37, 30, 25 and 20) were investigated in the laboratory. There is a statistically significant influence of salinity on oxygen consumption and TAM excretion of Noah’s ark shell, while the time of exposure to different salinities is significantly correlated to TAM excretion by the bearded horse mussel. Mean OC of Noah’s ark shell ranged from 0.14 ± 0.06 to 0.54 ± 0.27 mg O2g-1h-1 and that of bearded horse mussel from 0.18 ± 0.17 to 0.26 ± 0.14 mg O2g- 1h-1. Mean values of TAM excretion of Noah’s ark shell ranged from 2.14 ± 1.52 to 7.22 ± 6.04 μmol g-1 h-1 and for bearded horse mussel from 0.98 ± 0.53 to 2.78 ± 2.96 μmol g-1 h-1. Salinity and exposure time have a significant influence on the CR of Noah’s ark shell, whilst salinity has been found to be the determining factor for the bearded horse mussels’ CR. Mean values of Noah’s ark shell CR ranged from 0.96 ± 0.54 to 4.18 ± 1.15 l h-1g-1 and for bearded horse mussel from 2.43 ± 0.99 to 4.23 ± 0.84 l h-1g- 1. Higher oxygen consumption to total ammonia excretion (O:N) ratios at lower salinities indicated the use of proteins as a metabolic substrate for both species. Noah’s ark shell has greater energy expenditure related to respiration and TAM excretion than the bearded horse mussel

Biochemical and fatty acid composition of Arca noae (Bivalvia: Arcidae) from the Mali Ston Bay, Adriatic Sea

Biochemical and fatty acid composition of the bivalve Arca noae were investigated in the Mali Ston Bay in relation to environmental conditions. Sampling was carried out monthly, from December 2001 to November 2002. Wet shellfish meat consists on average of 77.61% water and 22.39% dry matter, while dry shellfish meat consists on average of 89.04% organic and 10.96% inorganic matter. PCA analysis identified temperature, nitrate, silicate, MICRO, Chl a and salinity as the most important environmental factors influencing biochemical composition of A. noae. An increase of dry weight content of A. noae was observed during the spring when both the sea temperature and food supply increased rapidly. Contents of protein (54.39-62.06% of dry weight), carbohydrate (4.13-8.07% of dry weight) and lipid (3.46-8.58% of dry weight) varied significantly during the year. Protein and lipid level reached the maximum value in June. The fatty acid profiles of total lipids extracted from A. noae showed high level of unsaturation (UNS/SAT 1.9-3.4). Total polyunsaturated fatty acids (PUFA) represented the majority of total fatty acids (40.3-59.9% of total fatty acids) and the most abundant were eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) acid. n-3/n-6 PUFA ratio value varied between 2.1 and 5.0 and was the highest during the spring (April to June). Due to their low lipid and high percentages of healthy polyunsaturated fatty acids A. noae can be evaluated as a quality seafood product. The most suitable period of the year for its consumption is in the spring when it reaches its highest nutritional values