Sezonska promjenjivost površinske temperature mora duž istočne obale Jadrana

Time series of sea surface temperature (SST), measured over some 20-year interval at 21 stations along the east Adriatic coast, are analyzed. By means of the Fourier analysis the average annual cycle of temperature is documented and the year-to-year variability of various SST-related parameters is described. It is shown that amplitudes of the first harmonic of the annual cycle are decreasing and its phases increasing in an offshore direction. The amplitudes range from 5.4 to 8.0 °C, the phases vary from 7.2 to 7.5 months (implying maximal time lag of nine days). The variability is mostly controlled by the autumn/winter cooling process. Amplitude of the first harmonic is anomalously low at Senj, whereas the corresponding phase does not depart from the typical coastal values. The finding is due to the exceptionally low summer SSTs that occur in the vicinity of Senj. At the Sv. Ivan station (near Rovinj) the spring/summer heating is significantly faster than the autumn/winter cooling. This can be ascribed to the influence of the Po River waters, which spread over the open Adriatic in spring/summer, but are mostly confined to the western coast in autumn/winter. The year-to-year changes of all parameters considered are found to be much smaller than the multi-year average values, and in some cases prove to be small even if compared with the spatial variations of the long-term averages

Hidrografska svojstva sjevernog Jadrana od listopada 2002. do rujna 2003. godine, u razdoblju s anomalno toplim ljetom

CTD data were collected during 38 cruises in the northeastern Adriatic from October 2002 to September 2003 and were analyzed in the context of long-term variability (from data collected over a period of 38 years). A prognostic statistical model was created to fit the long-term data and predicted values were compared to those of the in situ CTD measurements. As with air temperatures, values attained by the sea in summer 2003 far exceeded those expected by predictive models and were induced by very large heat input from the atmosphere. In conditions of very low regional freshwater input and intrusions of more saline water masses from the south, salinity values in the spring/summer period lay far outside typical salinity values for the area.Analizirani su podaci o temperaturi, salinitetu i gustoći skupljani na 38 krstarenja u sjeveroistočnom Jadranu od listopada 2002. do rujna 2003. godine i uspoređeni s prognoziranim vrijednostima iz statističkog modela. Model je načinjen na temelju podataka sakupljanih u ovom području u tridesetosmogodišnjem razdoblju. Površinske su temperature mora ljeti 2003. godine bile daleko iznad očekivanih, što je bila posljedica pojačanih površinskih protoka topline iz atmosfere u more. U proljeće i ljeto 2003. godine vrijednosti saliniteta bile su također značajno iznad prosjeka, zbog niskih dotoka slatke vode i intruzije slane vode iz srednjeg Jadrana

Factors favouring phytoplankton blooms in the northern Adriatic: Towards the northern Adriatic empirical ecological model

Influenced by one of the largest Mediterranean rivers, Po, the northern Adriatic (NA) production is highly variable seasonally and interannually. The changes are especially pronounced between winters and seemingly reflect on total Adriatic bioproduction of certain species (anchovy). We analysed the long-term changes in the phytoplankton production in the region, as derived from monthly oceanographic cruises, in relation to concomitant geostrophic currents distribution in the area and to Po River discharge rates in days preceding the cruises. In winter and early spring the phytoplankton abundances depended on existing circulation fields, in summer and autumn they were related to Po River discharge rates 1–15 days earlier and on concomitant circulation fields, while in late spring phytoplankton abundances increased 1-3 days after high Po River discharge rates regardless of the circulation fields. During the entire year the phytoplankton abundances were dependent on forcing of the previous 1-12 months of surface fluxes and/or Po River rates. The role of wind was uncertain but that was partly due to unmatched sampling time frames between meteorological and sea data. Low evaporation rates in November reflected significantly on the next February circulation pattern and, although with somewhat lower significance, on large phytoplankton blooms in the same month. We showed that the role of wind in evaporative flux enhancements is not straightforward as evaporative fluxes are highly dependent on other factors, e.g. air-sea temperature difference. Wind-induced vertical mixing was only sporadically related to phytoplankton abundances. From 1990 to 2004 a shift towards large winter bioproduction induced by circulation changes appeared. The investigations performed represent the preliminary actions in the construction of an empirical ecological model of the NA which can be used in the sustainable economy of the region, as well as for validation of the numerical ecological model of the region, which is currently being developed

Mechanisms of hypoxia frequency changes in the northern Adriatic Sea during the period 1972–2012

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Geostrophic Circulation Patterns in the Northeastern Adriatic Sea and the Effects of Air-Sea Coupling: May-September 2003

CTD data were collected weekly during 20 cruises from May to September 2003 over a 19 station grid in a coastal region of the northeastern Adriatic Sea as part of Project ADRICOSM. Relative geostrophic velocities indicated fine scale circulation patterns in in the area consisting of two pronounced circulation cells, of cyclonic and anti-cyclonic character, and that were present in the area for most of the investigated period.. These motions were induced primarily by spatial variations in the temperature field and may be strengthened during episodes of very strong northeasterly bora wind, when the investigated region is not heated (cooled) uniformly

Pojava Istarske obalne protustruje u 2000. godini, u kojoj su opažene i sluzave nakupine

The Istrian Coastal Countercurrent (ICCC) appeared in March (7 cm/s), August and September (4 cm/s) 2000, and a mucilage event occurred during late June-early July. Remarkably, previous investigations indicated that recurrent occurrences of intense ICCC coincided with mucilage and/or anoxia events in the region. In fact, already during late winter, when a sea heat gain was relatively intense, a significant transversal transport of freshened waters of Po origin occurred. Lower salinity and warmer water pool, which might be the core of an anticyclonic gyre in the northeastern Adriatic, was present also during spring and summer. This indicates the establishment of a pronounced closed circulation system in the area.Istarska obalna protustruja (IOPS) pojavila se u ožujku (7 cm/s), kolovozu i rujnu (4 cm/s) 2000. godine, a pojava sluzavih nakupina opažena je tijekom kasnog lipnja i početkom srpnja. Prema ranijim istraživanjima, povremene pojave IOPS podudarale su se s pojavom sluzavih nakupina i/ili anoksije u ovom području. Već tijekom kasne zime, kada je more iz atmosfere primalo razmjerno veliku količinu topline, opažen je značajan transverzalan prijenos zaslađenih voda porijeklom iz Poa. Bazen zaslađene i toplije vode, koji bi mogao biti središte anticiklonalnog vrtloga u istočnom dijelu sjevernog Jadrana, bio je prisutan i tijekom proljeća i ljeta. To ukazuje na postojanje zatvorenog sustava cirkulacije u promatranom području

Nalazi meduze Aequorea cf. forskalea u Jadranskom moru: usporedba povijesnih i recentnih podataka

Jellyfish are becoming an increasingly important component of studies of the global marine environment, as their frequent mass phenomena affect ecosystem performance and have economic and health consequences. Recent research has focused primarily on mass occurrences of scyphozoans and ctenophores, while less attention has been paid to hydromedusae blooms, which can also have significant impacts on the marine ecosystem with economic consequences. Like many members of the Scyphozoa and Ctenophora, Aequorea species can be numerous and form blooms. Based on surveys from 2000 to 2020 and information provided by marine professionals, we examine the (multiannual) variability, seasonality, and spatial distribution patterns of the poorly studied temperate species Aequorea cf. forskalea (Hydrozoa: Leptothecata). We hypothesized that this macrogelatinous jellyfish with a bipartite life cycle (benthic polyps and planktonic medusae) is sensitive to seasonal and long-term temperature fluctuations, particularly because temperature has been shown to play a critical role in mediating transitions in the life cycle of cnidarians. The cold-water affinity of A. cf. forskalea was confirmed by a significant negative correlation with temperature and the most frequent occurrence during the winter-spring period. For the northern Adriatic (Gulf of Trieste), sea temperature data and semi-quantitative plankton data are available for the first decade of the 20th century, allowing comparison of the historical data (1900-1911) with our current data set. Compared to historical records, the current occurrence of A. cf. forskalea differs significantly. With the warming of the northern Adriatic Sea since the beginning of the 20th century, the current phenology of A. cf. forskalea has changed, probably related to the delayed production of medusae by hydroids in autumn, the absence of medusae in this season and their less frequent occurrence in winter.Meduze postaju sve važnija komponenta globalnog proučavanja morskog okoliša, budući da njihove česte masovne pojave utječu na održanje ekosustava, a imaju ekonomske i zdravstvene posljedice. Najnovija su istraživanja usmjerena prvenstveno na masovnu pojavu režnjaka (Scyphozoa) i rebraša (Ctenophora), dok se manje pažnje posvećuje masovnim pojavama hidromeduza, koje također mogu imati veliki utjecaj na morski ekosustav sa značajnim ekonomskim posljedicama. Poput mnogih pripadnika Scyphozoa i Ctenophora, vrste roda Aequorea se mogu javljati u visokim brojnostima te njihovu pojavu možemo opisati kao masovnu („bloom“). Na temelju podataka prikupljenih tijekom istraživanja Jadrana u razdoblju od 2000. do 2020. godine te informacija dobivenih od stručnjaka koji se bave istraživanjem mora, razmatrali smo višegodišnju i sezonsku varijabilnost kao i obrasce prostorne raspodjele slabo proučavane vrste Aequorea cf. forskalea (Hydrozoa: Leptothecata) koja nastanjuje umjerena klimatska područja. Pretpostavili smo da je ova makro-želatinozna meduza, s bipartitnim životnim ciklusom (bentoski polipi i planktonske meduze), osjetljiva na sezonske i dugoročne promjene temperaturne, budući da temperatura igra ključnu ulogu za izmjenu generacija u životnom ciklusu žarnjaka (Cnidaria). Afinitet A. cf. forskalea prema hladnoj morskoj vodi potvrđuje značajna negativna korelacija s temperaturom te učestalo pojavljivanje tijekom zimsko-proljetnog razdoblja. Podaci o temperaturi mora i abundancijama vrste su dostupni za sjeverni Jadran (Tršćanski zaljev) za prvo desetljeće 20. stoljeća, što je omogućilo usporedbu povijesnih podataka (1900.-1911.) s novim setom podataka. U usporedbi s povijesnim zapisima, recentna se pojava A. cf. forskalea značajno razlikuje. Sa zatopljenjem sjevernog dijela Jadranskog mora od početka 20. stoljeća se mijenja sadašnja fenologija vrste A. cf. forskalea, što je vjerojatno povezano sa zakašnjelom proizvodnjom meduza u jesen, izostankom tijekom jeseni i njihovom rjeđom pojavom tijekom zime