Struktura populacije i brojnost fitoplanktonske zajednice u tri zaljeva na istočnoj obali Jadrana, Šibenskom zaljevu, Kaštelanskom zaljevu i Malostonskom zaljevu

Present study describes the phytoplankton community structure and phytoplankton abundance in three bays on the eastern Adriatic coast (Šibenik Bay, Kaštela Bay and Mali Ston Bay) during 2005. The highest phytoplankton biomass (expressed as chlorophyll a) were recorded at one station in Šibenik Bay (4.73 mg m-3), and in Kaštela Bay (2.79 mg m-3), while at all other stations recorded values were generally below 1 mg m-3. At the investigated area of Šibenik Bay a total of 114 phytoplankton taxa have been determined. The most diverse were diatoms with 61 and dinoflagellates with 37 taxa. Coccolithophorids contributed with 6, cryptophytes with 3, silicoflagellates, euglenophytes and chlorophytes with 2 taxa. In the area of Kaštela Bay 193 phytoplankton taxa have been recorded. Dinoflagellate group was the most diverse with 92 taxa, followed by diatoms (80), coccolithophorids (9), silicoflagellates and euglenophytes (4), cryptophytes (2) and chlorophyte (1). In the area of Mali Ston Bay a total of 88 phytoplankton taxa have been found, with 39 diatoms, 36 dinoflagellates, 2 silicoflagellates, 4 coccolithophorids, 2 euglenophytes, 1 chllorophyte and 3 chrisophyte taxa. Abundance of dinoflagellates was very low in this area. Coccolithophorids contributed more to the community composition in Mali Ston Bay, then in other areas of research. A diverse microflagellate group was present in the whole area of investigation with a high frequency of findings. During the investigated period a relatively small number of monospecific blooms in all areas have been recorded. The largest numbers of taxa were recorded at stations that are under an influence of freshwater input from rivers and strong anthropogenic influence.U ovom radu je analizirana struktura fitoplanktonske zajednice i brojnosti fitoplanktona u tri zaljeva na istočnoj obali Jadrana (Šibenski zaljev, Kaštelanski zaljev i Malostonski zaljev) tijekom 2005. Najveća biomasa fitoplanktona (izražena preko klorofila a) je zabilježena na jednoj postaji u Šibenskom zaljevu (4,73 mg m-3), te jednoj postaji u Kaštelanskom zaljevu (2,79 mg m-3), dok su na svim ostalim postajama zabilježene vrijednosti bile niže od 1 mg m-3. Na istraživanom području Šibenskog zaljeva određeno je ukupno 114 taksonomskih kategorija fitoplanktona. Najraznovrsnije su bile dijatomeje sa 61 i dinoflagelati sa 37 taksonomskih kategorija. Kokolitoforidi su pridonijeli sa 6, kriptofiti sa 3, silikoflagelati, euglenofiti i klorofiti sa 2 taksonomske kategorije. Na području Kaštelanskog zaljeva su zabilježene 193 taksonomske kategorije. Dinoflagelati su bili najraznovrsniji sa 92 taksonomske kategorije, slijede dijatomeje (80), kokolitoforidi (9), silikoflagelati i euglenofiti (4), kriptofiti (2) te klorofiti (1). U području Malostonskog zaljeva ukupno je pronađeno 88 fitoplanktonskih taksonomskih kategorija; dijatomeje 39, dinoflagelati 36, silikoflagelati 2, kokolitoforidi 4, euglenofiti 2, klorofiti 1, te krizofiti 3. Brojnost dinoflagelata u ovom području je bila niska dok su kokolitoforidi više doprinijeli sastavu zajednice u ovom području nego na drugim istraživanim područjima. Raznorodna grupa mikroflagelata je bila prisutna sa visokom frekvencijom pojavljivanja na svim istraživanim područjima. Za vrijeme istraživanog perioda pojavljuje se relativno mali broj monospecifičnih cvatnji. Statistička obrada okolišnih parametara i sastava fitoplanktonske zajednice je ukazala na najveći broj vrsta na postajama koje su pod snažnim utjecajem slatkovodnih dotoka i jakim antropogenim utjecajem

Prvi nalaz proizvodnje domoične kiseline u kulturama vrste Pseudo-nitzschia calliantha iz srednjeg Jadrana

In this study, three isolates of the potentially toxic diatom genus Pseudo-nitzschia were analysed for morphological and toxicological features. Cultures of Pseudo-nitzschia were established from seawater samples collected from the southern part of the Velebit Channel (central Adriatic Sea) during February 2019. All culture isolates were identified by scanning electron microscopy (SEM) as Pseudo-nitzschia calliantha. Domoic acid (DA) production was confirmed in all isolates analysed. The highest concentrations of cellular DA were found in early culture stages, with the lowest cell abundance, for all P. calliantha isolates. This study is the first to report DA production by P.calliantha isolated from the Adriatic Sea.Ovim istraživanjem analizirane su morfološke i toksikološke osobine potencijalno toksičnog roda dijatomeja Pseudo-nitzschia. Tri stanične kulture Pseudo-nitzschia uspostavljene su iz uzoraka morske vode prikupljenih iz južnog dijela Velebitskog kanala (srednji Jadran) tijekom veljače 2019. Pretražnim elektronskim mikroskopom (SEM) utvrđeno je da sve izolirane kulture pripadaju vrsti Pseudo-nitzschia calliantha. Proizvodnja domoične kiseline (DA) potvrđena je za sve analizirane izolate. Najviše koncentracije stanične DA u svim izolatima vrste P. calliantha određene su u ranoj uzgojnoj fazi, s najmanjom brojnošću stanica. Ovo istraživanje je prva potvrda proizvodnje DA u kulturama vrste P. calliantha izoliranim iz Jadranskog mora

High proliferation of Pseudo-nitzschia cf. arenysensis in the Adriatic Sea: ecological and morphological characterisation

The aim of the present study isto characterise the diatom Pseudo-nitzschia community during a bloom period together with environmental conditions. High proliferation of Pseudo-nitzschia spp. was observed in September 2017 at the shellfish breeding area in the Krka River estuary (Central eastern Adriatic Sea). The peak of abundance (1.8 x 106 cells L-1) was recorded at 7 m depth, and the increased abundance persisted for four weeks.Morphological analyses of field samples based on scanning electron microscopy (SEM) revealed that Pseudo-nitzschia cf. arenysensis was prevailing (94%) in the Pseudo-nitzschia assemblage. Several strains were successfully isolated from net samples in order to better define morphological features and phylogenetic characterisation. The isolated Pseudo-nitzschia strains corresponded morphologically to the P. cf. arenysensis from the field samples, based on our SEM observations. Phylogenetic analysis demonstrated that the Croatian strains grouped with P. arenysensis using the ITS and LSU rDNA sequences. Spearman rank correlation showed that salinity was an important environmental factor affecting the vertical distribution of Pseudo-nitzschia spp. in this highly variable area. Availability of increased concentration of orthophosphates and ammonium and low Si: TIN ratio may have promoted the bloom of P. cf. arenysensis in the estuary

Morfologija i ekologija slabo poznatog dinoflagelata Prorocentrum arcuatum (Dinophyceae) iz Medulinskog zaljeva (istočni dio Jadranskog mora)

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 19.6 oC – 20.4 oC, 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.Na području Medulinskog zaljeva, u razdoblju od srpnja 2013. do listopada 2014. godine, zabilježena je pojava rijetke i slabo poznate vrste dinoflagalata Prorocentrum arcuatum. Prisutnost vrste P. arcutum u fitoplanktonskoj zajednici Medulinskog zaljeva tijekom 15- mjesečnog razdoblja omogućila je istraživanje promjene u brojnosti vrste i okolišnih parametara koji uvjetuju dinamiku populacije vrste P. arcuatum u prirodnim uvjetima, a ujedno nam je omogućilo i prvi detaljni opis P. arcuatum temeljen na SEM metodologiji. Tijekom istraživanja zabilježili smo sezonsku varijabilnost u veličini stanica P. arcuatum. Optimalni fizikalni uvjeti za povećanu brojnost P. arcuatum zabilježeni su u jesen 2013. pri rasponu temperature od 19.6 oC do 20.4 oC i salinitetu 36.7 - 37.7. Unatoč činjenici da su slični okolišni uvjeti zabilježeni i naredne godine, u jesen 2014, povećanje brojnosti P. arcuatum se nije ponovilo, što može biti povezano s većom kompetitivnošću drugih vrsta uslijed godišnjih promjena fitoplanktonske zajednice

Phytoplankton Dynamics in the Middle Adriatic Estuary, with a Focus on the Potentially Toxic Genus Pseudo-nitzschia

The Krka River estuary is a karstic, permanently stratified estuary due to the strong freshwater inflow. It is a special environment in which to study the phytoplankton community, especially because this area is an important aquaculture site. Among other potentially toxic phytoplankton species, the diatom genus Pseudo-nitzschia occurs frequently and is a potential source of domoic acid (DA), causing shellfish toxicity and human intoxication. The main objective was to examine the dynamics of the phytoplankton community and, in particular, the genus Pseudo-nitzschia in the upper part of the Krka estuary, through monthly sampling over two years. The phytoplankton community was analysed using light microscopy and scanning electron microscopy to determine the diversity of Pseudo-nitzschia species and characterise the environmental parameters associated with a high abundance of Pseudo-nitzschia species. Seven Pseudo-nitzschia species were identified in the investigation, with higher frequencies and abundances in the less variable layer, at a 7 m depth. Blooms of Pseudo-nitzschia were noted in the late summer/early autumn, dominated by P. delicatissima/arenysensis. Winter assemblages were characterised by P. pseudodelicatissima/cuspidata, P. calliantha, and P. subfraudulenta, and were associated with domoic acid occurrence in shellfish

Competitive feeding interactions between native Ostrea edulis and non-native Crassostrea gigas with implications of introducing C. gigas into commercial aquaculture in the eastern Adriatic Sea

Highlights: • Feeding overlap was highly expressed between native and non-native oyster. • Differences were recorded in zooplankton but not in phytoplankton consumption. • O. edulis larvae in C. gigas stomach content was confirmed by DNA analysis. • O. edulis had broader isotopic niche than C. gigas. Abstract: In order to detect the possible regulatory effect of non-native C. gigas on the native O. edulis, under aquaculture conditions, feeding interactions between them were investigated in a highly productive environment of Lim Bay (Adriatic Sea). The present study uses a multi-methodological approach, including stomach content, DNA barcoding and stable isotope analysis to elucidate the feeding ecology of two oyster species. The research confirmed a high overlap throughout the year in the feeding traits among native and non-native oyster species. Competition for food was not the only relationship that exists between the investigated species as the presence of O. edulis larvae in C. gigas stomach content was confirmed by DNA analysis. Findings are not in favour of introducing C. gigas to commercial aquaculture in any new areas in the Adriatic Sea and support the need to improve the existing O. edulis aquaculture and conserve its wild stocks

Massive Occurrence of the Harmful Benthic Dinoflagellate <i>Ostreopsis</i> cf. <i>ovata</i> in the Eastern Adriatic Sea

In September 2015, a massive occurrence of the Ostreopsis species was recorded in central Adriatic Ka&#353;tela Bay. In order to taxonomically identify the Ostreopsis species responsible for this event and determine their toxin profile, cells collected in seawater and from benthic macroalgae were analyzed. Conservative taxonomic methods (light microscopy and SEM) and molecular methods (PCR-based assay) allowed the identification of the species Ostreopsis cf. ovata associated with Coolia monotis. The abundance of O. cf. ovata reached 2.9 &#215; 104 cells L&#8722;1 in seawater, while on macroalgae, it was estimated to be up to 2.67 &#215; 106 cells g&#8722;1 of macroalgae fresh weight and 14.4 &#215; 106 cells g&#8722;1 of macroalgae dry weight. An indirect sandwich immunoenzymatic assay (ELISA) and liquid chromatography&#8722;high-resolution mass spectrometry (LC-HRMS) were used to determine the toxin profile. The ELISA assay revealed the presence of 5.6 pg palytoxin (PLTX) equivalents per O. cf. ovata cell. LC-HRMS was used for further characterization of the toxin profile, which showed that there were 6.3 pg of the sum of ovatoxins (OVTXs) and isobaric PLTX per O. cf. ovata cell, with a prevalence of OVTXs (6.2 pg cell&#8722;1), while the isobaric PLTX concentration was very low (0.1 pg cell&#8722;1). Among OVTXs, the highest concentration was recorded for OVTX-a (3.6 pg cell&#8722;1), followed by OVTX-b (1.3 pg cell&#8722;1), OVTX-d (1.1 pg cell&#8722;1), and OVTX-c (0.2 pg cell&#8722;1)