Distribution of Arctic and Pacific copepods and their habitat in the northern Bering and Chukchi seas (original) (raw)
Frontiers in Marine Science, 2020
The Bering Strait is the only gateway to the Chukchi Sea from the Pacific Ocean and is a major route of Pacific water inflow. We recently investigated the occurrence of Pacific copepod species along with the warming of the Chukchi Sea and sought to identify the cause of the mass occurrence these copepods through an analysis of the water masses flowing through the Bering Strait. Zooplankton and Conductivity-Temperature-Depth (CTD) data collection was conducted in the Chukchi Sea and Bering Strait from 2014 to 2016. In addition, mooring systems installed in the Bering Strait were analyzed to obtain water temperature and salinity data during summer to understand the properties of the water masses. In 2015, a high abundance of Pacific copepod species (Eucalanus bungii, Metridia pacifica, and Neocalanus spp.) was observed in Bering Summer Water (BSW), which was relatively warm compared to measurements obtained from 2014 to 2016. As further confirmation, our results were consistent with 2007, 2009, and 2012 data, which showed that the abundance of Pacific copepod species was proportional to the temperature of the BSW entering the Chukchi Sea. In conclusion, we reconfirmed that Pacific copepod species are entering the Chukchi Sea along with BSW, and we newly discovered that their high abundance coincided with the relatively warm BSW, instead of other water masses. These findings suggest that the inflow of the high-temperature BSW (>3 • C) plays an important role in the mass occurrence of Pacific copepod species in the southern Chukchi Sea.
Polar Biology, 2015
The species composition of Arctic zooplankton differs greatly from that of the zooplankton of the North Pacific and Bering Sea. Particularly with greater warming from sea-ice retreat, the reproduction of North Pacific species transported into the Chukchi Sea and beyond may lead to changes in the Arctic pelagic ecosystem. We report the egg production and hatching of the Pacific copepod Neocalanus flemingeri in the Chukchi Sea based on shipboard experiments performed in September 2013. The reproductive capability of N. flemingeri observed in the Chukchi Sea resembled that reported in the Pacific, with the exception of a lower hatching success. Only 7.5 % of N. flemingeri eggs hatched compared with 93 % in Pacific experiments. Low hatching success is considered to be caused by failures of fertilization. The potential recruitment number for N. flemingeri suggests that it is unlikely to establish expatriate Arctic populations in the near future.
Frontiers in Marine Science
A remarkable early sea-ice reduction event was observed in the northern Bering Sea during 2018. In turn, this unusual hydrographic phenomenon affected several marine trophic levels, resulting in delayed phytoplankton blooms, phytoplankton community changes, and a northward shift of fish stocks. However, the response of the zooplankton community remains uncharacterized. Therefore, our study sought to investigate the zooplankton community shifts in the northern Bering Sea during the summers of 2017 and 2018 and evaluate the effects of early sea-ice melt events on the zooplankton community, population structure of large copepods, and copepod production. Five zooplankton communities were identified based on cluster analysis. Further, annual changes in the zooplankton community were identified in the Chirikov Basin. In 2017, the zooplankton community included abundant Pacific copepods transported by the Anadyr water. In 2018, however, the zooplankton community was dominated by small cope...
Polar Science, 2019
In recent years, marine ecosystems have changed due to the drastic sea ice reduction in the Arctic Ocean, but the relationship between copepod phenology and environmental drivers is unclear. To reveal the relationship, seasonal changes in the flux (abundance of swimmers), population structure, lipid accumulation and gonad maturation of four dominant copepods (Calanus hyperboreus, Metridia longa, Paraeuchaeta glacialis and Heterorhabdus norvegicus) were studied using a sediment trap deployed at a depth of 222 m in the Pacific-Arctic sector from October 2010 to September 2013. C. hyperboreus, mostly comprising copepodid stage 6 females (C6F), exhibited several peaks in flux in spring and autumn. C. hyperboreus C6Fs were dominated by lipid-rich specimens year-round, and gonad development was observed in these samples from February to April. The M. longa flux showed no clear seasonality. Gonad maturation of M. longa C6Fs occurred from February to September. P. glacialis flux exhibited two peaks in autumn of 2011 and 2012. In contrast to the former two species, lipid-rich, mature P. glacialis C6Fs occurred year-round. H. norvegicus copepodid stage 6 males (C6Ms) also occurred throughout the year, likely because H. norvegicus has functional feeding appendages, even in C6Ms. From generalized additive models, C. hyperboreus, M. longa and P. glacialis showed relationships with daytime length and/or sea ice concentrations, but the relationship patterns were different. These findings suggest that the response (e.g., vertical migration) to the environmental parameters could vary with species and the drastic sea ice reductions may affect the copepod phenology in the Pacific-Arctic sector.
Horizontal distribution of calanoid copepods in the western Arctic Ocean during the summer of 2008
Polar Science, 2012
The horizontal distribution of the epipelagic zooplankton communities in the western Arctic Ocean was studied during AugusteOctober 2008. Zooplankton abundance and biomass were higher in the Chukchi Sea, and ranged from 3,000 to 274,000 ind. m À2 and 5e678 g WM m À2 , respectively. Copepods were the most dominant taxa and comprised 37À94% of zooplankton abundance. For calanoid copepods, 30 species belonging to 20 genera were identified. Based on the copepod abundance, their communities were classified into three groups using a cluster analysis. The horizontal distribution of each group was well synchronized with depth zones, defined here as Shelf, Slope and Basin. Neritic Pacific copepods were the dominant species in the Shelf zone. Arctic copepods were substantially greater in the Slope zone than the other regions. Mesopelagic copepods were greater in the Basin zone than the other regions. Stage compositions of large-sized Arctic copepods (Calanus glacialis and Metridia longa) were characterized by the dominance of late copepodid stages in the Basin. Both the abundance and stage compositions of large copepods corresponded well with Chl. a concentrations in each region, with high Chl. a in the Shelf and Slope supporting reproduction of copepods resulting in high abundance dominated by early copepodid stages.
Regional comparison of seasonal changes on copepod community structure in the Arctic Ocean
Polar Science, 2020
The Arctic Ocean is characterized as the greatly variable oceanic environment both seasonality and regionally. Such environmental variability would affect regional differences in the respective copepod community structures, though it has not been reported so far. In this study, we analyzed time-series zooplankton samples with focus on large copepods collected by sediment traps moored in three different regions of the Arctic Ocean at approximately 72-260 m water depth, and seasonality of copepod community structures were compared. Remarkable seasonality in the copepod community structure around Molloy deep in the eastern Fram Strait were due to the influence of endemic species transported by the West Spitsbergen Current. In contrast, in the southern Canada Basin (Northwind Abyssal Plain, Hanna Canyon and Barrow Canyon), the community structure of predominant large copepods showed less seasonality due to low primary production. In the MacKenzie Trough, the number of copepod swimmers were greater than those in all other regions investigated, which cooccur with much higher primary production in that area. These spatial differences in seasonality of copepod swimmer community structure were thought to be caused by various factors, not only sea ice seasonality but also differences in current patterns, endemic species and the magnitude of primary production.
Ambio
The changing Arctic environment is affecting zooplankton that support its abundant wildlife. We examined how these changes are influencing a key zooplankton species, Calanus finmarchicus, principally found in the North Atlantic but expatriated to the Arctic. Close to the ice-edge in the Fram Strait, we identified areas that, since the 1980s, are increasingly favourable to C. finmarchicus. Field-sampling revealed part of the population there to be capable of amassing enough reserves to overwinter. Early developmental stages were also present in early summer, suggesting successful local recruitment. This extension to suitable C. finmarchicus habitat is most likely facilitated by the long-term retreat of the ice-edge, allowing phytoplankton to bloom earlier and for longer and through higher temperatures increasing copepod developmental rates. The increased capacity for this species to complete its life-cycle and prosper in the Fram Strait can change community structure, with large cons...
Polar Biology, 2021
The process of climate change by which global temperatures increase and seasonal shifts occur is more pronounced at higher latitudes. These changes induce shifts in the phenology of biota, including zooplankton. Regression analysis revealed significant advance of the spring–summer water warming in the sub-Arctic White Sea (Chupa Inlet, Kandalaksha Bay), which occurs 3 weeks earlier in the last decade compared with 1961. The shift of timing of phenological events of Calanus glacialis, Pseudocalanus spp., Microsetella norvegica, Oithona similis, Acartia spp., Centropages hamatus, and Temora longicornis is particularly pronounced. These shifts were accompanied by a significant increase in Calanus and Microsetella abundance with an observed decrease in Acartia abundance. No correlation between population abundance and year-to-year changes in the species phenology was determined. We propose hypotheses to explain species adaptation to these phenological shifts in the ecosystem: (1) flexib...
Copepods in sea ice of the western Weddell Sea during austral spring 2004
Deep Sea Research Part II: Topical Studies in Oceanography, 2008
In the framework of the R.V. Polarstern expedition ''Ice station POLarstern'' (ISPOL) spatial and temporal trends in composition, abundance and age structure of sea ice inhabiting copepods were investigated in the western Weddell Sea during the transition from the spring to the summer state. For the spatial scale, sea-ice coring was performed at six locations on a transect from the ice edge to the icedrift station between 14 and 24 November 2004. The temporal changes were investigated in a time series study on a drifting sea-ice floe from 29 November to 30 December 2004. A relatively large number of copepod species (15) were found in the ice with a higher number at the time station (13) than at the transect (9). Drescheriella spp. was by far the most abundant taxon encountered in the sea ice throughout the present study (72-87%). On the transect, Idomene antarctica ranked second in abundance (7%) followed by Stephos longipes (2%) and Ectinosoma sp. (2%). In contrast, Diarthrode cf. lilacinus, which was not found on the transect, was the second most abundant species (11%) at the time station, followed by I. antarctica (9%), Ectinosoma sp. (6%) and S. longipes (1%). Naupliar stages dominated the populations of Drescheriella spp. and S. longipes both on the transect and during the time series. The Ectinosoma sp. population was dominated by nauplii only at the stations of the transect, while copepodite stages made up the largest fraction during the time series. Copepodids always predominated the I. antarctica populations, and it was the only species in which adults occurred in high densities contributing significantly to the abundance. Only Drescheriella spp. and S. longipes occurred throughout the sea-ice cores, while the occurrence of all other species was restricted to the bottom layer of the ice. The distribution of all species was very patchy and varied greatly between the sampling sites. r
2019
Increasing numbers of Pacific copepods are being transported from the Bering Sea to the Arctic Ocean, so there is clear potential to affect the structure and composition of the Arctic food web. We investigated the grazing impacts of Arctic and Pacific copepods in the western Arctic Ocean using shipboard experiments during autumn. Ingestion rates for both Arctic and Pacific species were low and linked to low food availability. The ingestion rates varied with species, but were not related to chlorophyll a. The maximum ingestion rates calculated by the Michaelis-Menten equation were higher in the Arctic species (3.6% body carbon day−1) than in the Pacific species (0.10% body carbon day−1). The community grazing impacts were 0-0.57% remove day−1, and the Pacific copepods contributed 0.1-17% for this parameter. Even if Pacific copepods are transported into the Arctic Ocean and ingest the natural protist assemblage, their impact is spatially and seasonally limited, and, at present, Pacifi...
Journal of Marine Systems, 2008
Global warming is presently a widely accepted phenomenon with a broad range of anticipated impacts on marine ecosystems. Alterations in temperature, circulation and ice cover in Arctic seas may result in changes in food chain dynamics, beginning with planktonic processes. As part of the Shelf-Basin Interactions (SBI) program, we conducted zooplankton surveys during summer 2002 to assess the biomass, distribution and abundance of copepods and other pelagic zooplankton over the Chukchi and Beaufort shelves, slope regions and the adjacent Canada Basin. The motivation for our fieldwork was the question, "Will global change, particularly warming, result in more large-sized zooplankton which support a pelagic food web of fish, birds, and certain mammals over the Chukchi and Beaufort shelves or in more smaller-sized zooplankton which will diminish the fish, birds and mammals and favor sedentary benthic organisms?" The objectives of the present study were 1) to census the regional zooplankton community and establish a baseline for comparisons with historical and future studies and 2) to determine whether large-bodied copepods associated with deep waters of the Bering Sea or the Canada Basin were transported to the shelves in sufficient numbers to modify the food web in a region where smaller copepods often dominate the zooplankton numerically. Spatial distributions of zooplankton communities were clearly associated with hydrographic habitats determined by the chemical, physical and biological characteristics of the upper water layer. Smaller taxa dominated the shelf communities while offshore zooplankton assemblages were characterized by large-bodied copepods. The mesozooplankton community was numerically dominated by copepod nauplii and small-bodied juveniles, including Pseudocalanus spp. and Oithona similis. We observed very few large-bodied copepods from the Bering Sea. However, much of the shelf region surveyed included relatively numerous Calanus glacialis juveniles and adults, suggesting that these copepods were advected onto the shelf and possibly reproducing there. Juvenile stages of the large-bodied copepod Calanus hyperboreus were found in relative abundance on the Chukchi shelf in the vicinity of Hanna Canyon. These observations suggest that large-bodied, deep-water species from the basin are advected onto the Chukchi Shelf where they may impact the fate of shelf-derived primary production and alter the food webs of the shelves. Regional comparisons of abundances of selected taxa enumerated in the present study with sample data from the early 1950s suggested that some taxa were more abundant in the SBI region in 2002 than ca. 50 years ago. Long-term changes in planktonic populations are expected to have significant implications for shelf-basin exchange of biogenic material in the Chukchi and Beaufort Seas and the adjacent Arctic Basin.
Chinese Journal of Oceanology and Limnology, 2011
Population dynamics of four dominant Antarctic copepods, Calanoides acutus, Calanus propinquus, Metridia gerlachei and Rhincalanus gigas were studied based on zooplankton samples collected in the Prydz Bay during austral summer from 1999 to 2006. We found that C. acutus was the most abundant species among these four copepods, followed by C. propinquus, M. gerlachei and R. gigas. R. gigas occurred mainly in the warmer oceanic regions and showed distribution patterns discrete from the other three species, whose distribution in the whole survey area overlapped. By December 15 th (about one month before our sampling) of the years 1999, 2003 and 2006, sea ice retreated earlier and polynyas existed in the neritic region one month before sampling. These periods were characterized by numerical dominance of C. acutus, C. propinquus and M. gerlachei, elevated proportions of Copepodite I and Copepodite II stages especially in the neritic region. While for the years 2000, 2002, and 2005, the ice edge located more northerly and polynyas did not exist in the neritic region, the copepods abundance was lower, indicating poor recruitment. Population structure of R. gigas was mainly composed of advanced stages Copepodite V and female during all cruises. Log 10 (x+1) transformed densities of C. acutus, C. propinquus and M. gerlachei showed positive correlation with temperature and chlorophyll a concentration, while mean population stages of these copopods were negatively correlated with these environmental variables. Younger copepodite stages of C. acutus, C. propinquus and M. gerlachei appeared more often in neritic regions. We confirmed that the polynyas had a great contribution to phytoplankton blooms, which promote copepods reproduction and recruitment success. The study suggested that population dynamics of the four copepods have good correspondence with sea ice and polynya variations during all cruises of the Prydz Bay.
Journal of Natural History, 2015
Seasonal changes in the population structure of dominant planktonic copepods collected using a sediment trap moored in the western Arctic Ocean Winter ice cover of the Arctic Ocean makes year-round zooplankton sampling by plankton net a difficult task. Therefore, the collection of copepods with a sediment trap can be a powerful tool. In the present study, we analyzed the seasonal changes in the population structures of five dominant planktonic copepods (Oncaea parila Heron, 1977, Calanus hyperboreus Krøyer, 1838, Metridia longa (Lubbock, 1854), Paraeuchaeta glacialis (Hansen, 1887) and Heterorhabdus norvegicus (Boeck, 1872)), which were collected using a sediment trap rotated at 10−15 day intervals moored at 184−260 m in the Northwind Abyssal Plain (75°00´N, 162°00´W) of the western Arctic Ocean from October 2010−September 2012. Oncaea parila C6F with egg sacs occurred throughout the year, and the total abundance and composition of early copepodid stages (C1−C3) had two peaks each year. Calanus hyperboreus was dominated by C6F throughout the year, and their maturation was observed during February to May. Metridia longa C6F had a clear seasonality in lipid accumulation and gonad maturation: high lipid accumulation was obse rved from October−February, whereas gonad maturation occurred from March−September. Paraeuchaeta glacialis C6F also showed seasonality in lipid accumulation and gonad maturation, although their seasonal patterns varied from those of M. longa: high lipid individuals were abundant from February−April and mature individuals dominated from October−November. Heterorhabdus norvegicus showed seasonal changes in population structure as well: C1, C5, and C6M dominated from April−May, November−February and 3 August−October, respectively. The life cycle patterns of these species are compared with those reported from other areas. While the results obtained by a sediment trap are inevitably subject to collection bias (i.e., passive collection at a fixed depth), a sediment trap should be considered as a powerful tool for the evaluation of the life cycle of planktonic copepods, especially in ice-covered oceans.
Deep Sea Research Part II: Topical Studies in Oceanography, 2013
On the southeastern Bering Sea shelf, mesozooplankton play an important role in material transfer between primary producers and fisheries resources. The biomass of mesozooplankton in this region is known to vary annually, but little is known about annual changes in community structure and species composition. In the present study, regional and long-term changes in abundance, biomass and community structure of copepods and chaetognaths on the shelf were evaluated based on NORPAC net samples collected during summers of 1994-2009. During the study period, regime shifts occurred from high interannual variability regime (1994-1999) to low interannual variability regime with high temperature (2000-2005), then to a low interannual variability regime with low temperature (2007-2009). A total of 24 calanoid copepod species belonging to 21 genera were identified from samples. Copepod abundance ranged from 150 to 834,486 inds. m-2 , was greatest on the Middle shelf, and was higher in cold years, than in warm years. Copepod biomass ranged from 0.013 to 150 g DM m-2 , and was also higher in cold years than in warm years. Based on the results of cluster analysis, the copepod community was divided into six groups (A-F). The regional and interannual distributions of each group were distinct. Interannual changes in abundance of the dominant copepod on the Outer shelf and Middle shelf were highly significant (p < 0.0001), and their abundances were negatively correlated with temperature and salinity. Interannual changes in copepod community that occurred between cold and warm years are thought to have been caused by differences in the magnitude and timing of the spring phytoplankton bloom between the two regimes. Abundance and biomass of the chaetognath Parasagitta elegans ranged from to 15,180 inds. m-2 and from 11 to 1,559 mg DM m-2 , respectively. Chaetognath abundance was significantly correlated with the abundance of the dominant copepods (p < 0.0001). Differences in cold and warm years may also affect recruitment of walleye pollock. We conclude that on the southeastern Bering Sea shelf, the magnitude and timing of primary production, which is related to climate change, may significantly affect how it is transferred through the food web.
2002
The timing of copepodite recruitment and population development of copepods in spring and early summer (April-July) were compared between the North Water polynya and Barrow Strait, a non-polynya region in the Canadian Archipelago. In the North Water, young copepodites (CI-CIII) of calanoid herbivores were concentrated in the cold and chlorophyll-rich water at the base of the Arctic surface layer, while later stages (CIV-CV) invaded the warmer surface layer. The phytoplankton bloom and the recruitment of the first cohort of copepodites of Calanus hyperboreus, C. glacialis, and Pseudocalanus spp started in May-June, some 1.5-3 months earlier than in Barrow Strait. Consistent with a precocious summer recruitment, population stage structure of these species in early spring (April-May) was more advanced in the North Water than in Barrow Strait. The recruitment in June of CI of the omnivore Metridia longa was advanced by at least 5 weeks in the polynya relative to Barrow Strait. We found no evidence for an acceleration of the population development of the small Microcalanus pygmaeus, Oithona similis or Oncaea borealis in the polynya.
Copepods in spring annual sea ice at Terra Nova Bay (Ross Sea, Antarctica)
Polar Biology, 2007
The aim of this study was to investigate patterns of abundance, distribution, temporal changes and species composition of the dominant ice-associated copepods in the spring annual pack ice, platelet ice and water column at Terra Nova Bay, Ross Sea, during late spring 1997. Ice cores were drilled for temporal and spatial scales. Stephos longipes and Harpacticus furcifer dominated the sea ice meiofauna in terms of numbers in the lower few centimeters of the bottom ice associated with high chlorophyll a and phaeopigment levels. Nauplii dominated the S. longipes population (91.6%) and occurred in extremely high concentrations. In contrast, copepodids were the dominant stages in H. furcifer. How H. furcifer carries out its entire life cycle and how it diVers from ecologically similar species such as Drescheriella glacialis should be examined in more detail.
Plankton and Benthos Research, 2013
Stratified zooplankton sampling was conducted in the subarctic Pacific in June 2009 at four stations along 47°N from 0 to 3,000 m depth to evaluate longitudinal changes in population structure and vertical distribution of the dominant copepod species. At the westernmost station (160°E), the population structure of Eucalanus bungii and Metridia pacifica was dominated by early copepodid stages. In E. bungii, nauplii were abundant and adult females had developed ovaries at 160°E, while at the three stations to the east (167°E, 174°E and 179°W), no E. bungii nauplii were collected, and the resting stages were dominant. This suggests the species was reproducing near 160°E and in diapause in the east. In all three Neocalanus species analyzed (N. cristatus, N. flemingeri and N. plumchrus), late copepodid stages were dominant at the eastern three stations. Lipid accumulation in the fifth copepodid stage of Neocalanus spp. was greater in the west than in the east. This probably resulted from better food conditions and lower temperatures in the west, where copepods could consume more food during development than in the east.
Polar Biology, 2013
ABSTRACT This research explores the distributions and community composition of pelagic species in the sub-Arctic and Arctic waters of the northern Bering and central and southern Chukchi seas during September 2007 by linking pelagic zooplankton and fish assemblages to water masses. Juvenile saffron cod (Eleginus gracilis), polar cod (Bore-ogadus saida), and shorthorn sculpin (Myoxocephalus scorpius) were most abundant in warm, low salinity Alaska Coastal Water (ACW) of the central Chukchi Sea, charac-terized by low chlorophyll, low nutrients, and small zoo-plankton taxa. Adult Pacific herring (Clupea pallasii) were more abundant in the less stratified Bering Strait waters and in the colder, saltier Bering Shelf Water of the northern Bering and southern Chukchi seas, characterized by high chlorophyll, high nutrients, and larger zooplankton taxa. Juvenile pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon were most abundant in the less stratified ACW in the central Chukchi Sea and Bering Strait. Abun-dances of large zooplankton were dominated by copepods (Eucalanus bungii, Calanus glacialis/marshallae, Metridia pacifica) followed by euphausiids (juvenile Thysanoessa raschii and unidentified taxa), whereas small zooplankton were dominated by bivalve larvae and copepods (Centro-pages abdominalis, Oithona similis, Pseudocalanus sp.). Pelagic community composition was related to environ-mental factors, with highest correlations between bottom salinity and large zooplankton taxa, and latitude and fish species. These data were collected in a year with strong northward retreat of summer sea ice and therefore provide a baseline for assessing the effects of future climate warming on pelagic ecosystems in sub-Arctic and Arctic regions.