Based on satellite images in the visible range, the boundaries of ice zones of various ages in the Sea of Okhotsk and the Tatar Strait for mid-February and mid-March in the period from 2000 to 2020 ...were delineated. Zone's areas were calculated using microwave range satellite imagery considering ice concentration. Average ice thickness was calculated based on the hummocking coefficient of ice extent. Based on these data, ice volume at the phase of maximum development of ice extent in the studied water areas was calculated using the “ICE” software package as average value for February and March. From the analysis of inter-seasonal variations, it was concluded that for the studied period the volume of ice in the Sea of Okhotsk decreased by ∼56%, or 292 km³. The average rate of ice decrease in the Sea of Okhotsk was ∼27%/10 years, in region I ∼18%/10 years, in region II ∼34%/10 years and in region III ∼29%/10 years. The ice volume change was ∼42% due to decrease in ice cover and ∼58% due to decrease in ice thickness. In the Tatar Strait, the volume of ice decreased by ∼30% (∼3.4 km³). Since the ice cover of the strait remained constant during the period under study, the ice volume declined solely due to decrease of the ice thickness.
•Based on the interpretation and analysis of data obtained from passive and active microwave spectroradiometers the boundaries of the ice extent zones in the Sea of Okhotsk with different age characteristics for the period from 2000 to 2020 have been defined.•At the start of the 21st century, the volume of ice in the Sea of Okhotsk at the phase of maximum ice extent development (average for February and March) decreased by 52%.•For the 2000 to 2020 changes in the volume of ice in the Sea of Okhotsk have been due to decrease in its thickness by ∼56% and ice cover by ∼44%.
Based on the interpretation and analysis of data obtained from passive and active microwave spectroradiometers installed on artificial Earth satellites, the boundaries of the ice extent zones in the ...Sea of Okhotsk with different age characteristics for the period from 2000 to 2020 have been defined and discretized into monthly components. Weighted average ice thickness in the selected zones has been calculated for three dominant age groups of ice according to World Meteorological Agency Nomenclature without adjustment for ice deformation. Analysis of the estimated characteristics has allowed us to conclude that in the XXI century there was a decrease in the volume of ice in the Sea of Okhotsk by 162 cub.km (or 51.9%). Ice volume decreased at average speed of 7.7 cub.km (or 24.7%) per decade, while ice extent decreased by 11.2% per decade (or 23.6%), and weighted average ice thickness – by 14.1% per decade (or 29.6%). For the 2000 to 2020 research period, changes in the volume of ice have been due to decrease in its thickness by ~ 56% and ice cover by ~ 44%. It has been established that the nature of the development of the ice regime parameters within the boundaries of the regions of the first hierarchical level varies significantly.
•Based on the interpretation and analysis of data obtained from passive and active microwave spectroradiometers installed on artificial Earth satellites, the boundaries of the ice extent zones in the Sea of Okhotsk with different age characteristics for the period from 2000 to 2020 have been defined and discretized into monthly components.•At the start of the 21st century, the volume of ice in the Sea of Okhotsk at the phase of maximum ice extent development (average for February and March) decreased by 51.9%.•The change of volume occurred to a greater extent due to decrease in ice thickness (~ 56%) and to a lesser extent due to decrease in ice cover (~ 44%).•For the 2000 to 2020 changes in the volume of ice in the Sea of Okhotsk have been due to decrease in its thickness by ~ 56% and ice cover by ~ 44%.
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.
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.
PDF
