Regional and seasonal variability of zooplankton collected using sediment traps in the southeastern Beaufort Sea, Canadian Arctic

Time-series sediment traps were deployed at six mooring sites in the southeastern Beaufort Sea from October 2003 to August 2004 during the cruise of the Canadian research vessel Amundsen within the framework of the Canadian Arctic Shelf Exchange Study (CASES). Trap-collected zooplankton (TCZ) at around 200 m water depth was dominated by copepods accounting for 74–93% of the total abundance throughout the year with increase in abundance at all sites during the fall. Seven distinct TCZ groups were identified through cluster analysis. Two marked seasonal shifts in TCZ composition from late fall to early winter and from spring to early summer were revealed at five sites at 200 m depth. The zooplankton was dominated by Oncaea spp., pteropods, and copepod nauplii in the late fall cluster and in the winter cluster, and by copepod nauplii in the summer cluster. A significant change in water temperature, salinity, and sea ice concentration was observed only with the spring–summer shift. The cluster analysis also revealed that TCZ composition at 200 m at a station located in the Cape Bathurst Polynya was markedly different from those at other sites through the study period by being characterized by the dominance of various copepodite stages of Metridia longa. This was probably due to a less prolonged period of sea ice cover, which provides favorable food conditions for the zooplankton community.     

Distribution, diversity and biomass of summer zooplankton from the coastal Canadian Beaufort Sea

Composition, abundance, biomass and distribution of zooplankton in the coastal Canadian Beaufort Sea were studied in the summer of 2005 and 2006. Data were collected from two cross-shelf transects (11 stations in each). Sampling was conducted with vertical hauls using a conical net of 153-μm mesh size. Our results revealed that there are three ecological zones, Intense Plume, Diffuse Plume and oceanic, which are primarily shaped by the highly variable Mackenzie River plume. The Intense Plume Grouping was located at stations influenced greatly by the Mackenzie River, where Podon leuckarti, Pseudocalanus spp., Copepoda nauplii and Limnocalanus macrurus were most abundant. The Diffuse Plume Grouping, that was located in the transitional zone between the river plume and the ocean, had the highest diversity. This grouping was characterised by high abundance of Copepoda nauplii, Polychaeta larvae, Pseudocalanus and L. macrurus. The Oceanic Grouping, located farthest from shore beyond the 85-m depth contour, was mainly inhabited by marine taxa—Calanus glacialis, C. hyperboreus, Triconia (Oncea) borealis and Microcalanus spp.—and had the greatest overall zooplankton abundance and biomass of all groupings.     

Macrofaunal crustaceans in the benthic boundary layer from the shelf break to abyssal depths in the Ross Sea (Antarctica)

The New Zealand International Polar Year–Census of Antarctic Marine Life (NZ IPY-CAML) project added to previous benthic studies in the Ross Sea by extending sampling north from the continental shelf to previously unsampled areas of the shelf break, slope, abyssal plain and seamounts in the region. The aim of the current study is to give first insights into the deep-sea community structure of the Ross Sea focussing on a component of the benthic boundary layer that is macrofaunal crustaceans collected one metre above the seafloor. We assess changes in Ross Sea crustacean community composition from the shelf break (474 m) to the abyss (3,490 m) and compare the Ross Sea crustacean fauna to areas elsewhere in the Southern Ocean. Analyses reveal high relative abundances, suggesting an important role in the food web. Among the peracarid crustaceans, there was a decline in the proportion of amphipods with increasing depth. Three of 15 isopod families (Acanthaspidiidae, Nannoniscidae and Desmosomatidae) were identified to species level and about 72 % of the species were new to science. Isopod diversity in the Ross Sea abyss appears to be comparable to that in the highly speciose Weddell deep sea. Standardised sampling of these crustacean communities allows setting the biodiversity of the Ross Sea into a global context.     

Spatial and temporal variation of photosynthetic parameters in natural phytoplankton assemblages in the Beaufort Sea, Canadian Arctic

During summer 2008, as part of the Circumpolar Flaw Lead system study, we measured phytoplankton photosynthetic parameters to understand regional patterns in primary productivity, including the degree and timescale of photoacclimation and how variability in environmental conditions influences this response. Photosynthesis–irradiance measurements were taken at 15 sites primarily from the depth of the subsurface chlorophyll a (Chl a) maximum (SCM) within the Beaufort Sea flaw lead polynya. The physiological response of phytoplankton to a range of light levels was used to assess maximum rates of carbon (C) fixation (P _m^*), photosynthetic efficiency (α ^*), photoacclimation (E _k), and photoinhibition (β ^*). SCM samples taken along a transect from under ice into open water exhibited a >3-fold increase in α ^* and P _m^*, showing these parameters can vary substantially over relatively small spatial scales, primarily in response to changes in the ambient light field. Algae were able to maintain relatively high rates of C fixation despite low light at the SCM, particularly in the large (>5 μm) size fraction at open water sites. This may substantially impact biogenic C drawdown if species composition shifts in response to future climate change. Our results suggest that phytoplankton in this region are well acclimated to existing environmental conditions, including sea ice cover, low light, and nutrient pulses. Furthermore, this photoacclimatory response can be rapid and keep pace with a developing SCM, as phytoplankton maintain photosynthetic rates and efficiencies in a narrow “shade-acclimated” range.     

Distribution and microhabitats of living (stained) benthic foraminifera from the Canadian Arctic Archipelago

The geographic distribution of live (Rose Bengal stained) foraminifera from ☐ cores taken in the Canadian Archipelago shows a dominance of agglutinated species in the western study area and an abundance of calcareous forms in the east. This distribution is attributed to the presence of differing water masses. The western channels are shallow and permit entrance only of the Arctic water mass whereas the eastern channels allow passage of the more saline and warmer Atlantic water mass. In habitat depth, both calcareous and agglutinated species exhibit highly variable vertical faunal distributions. Of the 6 cores studied, the depth above which 95% of the individuals occur ranges from 2.5 to 13 cm. Species microhabitat preference between localities also was found to be variable. Several factors are suggested to contribute to this variability. The cores were taken in shallow-water environments where physical and chemical conditions are less stable. Seasonal differences in ice cover affects productivity and thus the amount of food reaching the benthos. Sedimentation rates also are affected by differences in ice cover. Both of these factors control the rate of food burial which in turn must influence species vertical distribution patterns and microhabitat preferences. Although it has not been investigated, the role played by benthos in modifying sediment texture and in oxygenating subsurface layers may be an additional factor contributing to the variability observed in this study.     

Trophic variability of Arctic fishes in the Canadian Beaufort Sea: a fatty acids and stable isotopes approach

Trophic ecology of most demersal Arctic fishes remains one of the major knowledge gaps for understanding food web dynamics and connectivity among ecosystems. In this study, fatty acids (FA) and stable isotopes (SI) were used to study the feeding ecology of seven species (n = 106) of the most abundant benthic fishes (eelpouts, sculpins and agonids) in the Canadian Beaufort Sea from shallow (20–75 m), slope (200–350 m) and deep (500–1000 m) habitats. Both FA and SI results revealed among- and within-species variability in diet composition. Correspondence analysis of FA signatures identified high within-species variability in diet, resulting in high overlap among species. Calanus-derived FA were present in all species (Calanus markers up to 13 % of total FA) and were particularly important in Ribbed Sculpin, Adolf’s and Longear Eelpout collected in deep habitats, suggesting a strong contribution of pelagic-derived FA to benthic fish communities. Incorporation of this signal in the benthos may result from either direct consumption of deep overwintering copepods (i.e., off-bottom feeding) or through detrital accumulation in benthic invertebrate prey. Mean SI values differed among species and indicated that a large range of trophic positions (δ¹⁵N varied from 14.09 to 17.71 ‰ for Canadian Eelpout and Adolf’s Eelpout, respectively) and carbon dietary sources are preyed upon (δ¹³C range from ?21.13 to ?23.85 ‰ for Longear Eelpout and Ribbed Sculpin, respectively). SI analyses suggested that most species examined were low- to mid-trophic generalist benthic carnivores, with the exception of Ribbed Sculpin, which was a low-trophic pelagic predator.     

Environmental influences on benthic fauna associations of the Kara Sea (Arctic Russia)

Macrobenthic faunal associations, hydrography and sediment structure were examined at 14 stations in the Kara Sea. The stations were located in an area influenced by huge runoff from the Ob and Yenisei Rivers and in areas influenced by Barents Sea water. Sampling depths varied from 17 to 43 m, with one station at 195 m. The sediments were predominantly muddy but some stations were sandy. Three hundred and eighty-seven taxa were identified and Polychaeta, Crustacea and Mollusca were the most conspicuous. Species number, abundance and biomass varied widely among stations, and were generally higher in the more marine waters. Boreal-arctic species predominated, but an increase of arctic species from marine to the estuarine areas was evident. Five faunal associations were delineated by cluster analysis and suggested quite heterogeneous sampling areas. The most conspicuous species of each faunal association were Spiochaetopterus typicus, Tridonta borealis, Serripes groenlandicus, Portlandia arctica, and Marenzelleria arctia, respectively. The sedimentation rate, as well as depth, sediment structure and salinity, apparently influenced the main differences in the fauna. Accepted: 29 June 1999     

Oceanographic characteristics of the habitat of benthic fish and invertebrates in the Beaufort Sea

We relate the spatial variability in the distribution of benthic taxa of the Beaufort Sea to oceanographic characteristics of their habitat with the goal of illustrating potential mechanisms linking climate change to Arctic marine communities. Offshore fish of the Beaufort Sea have not been surveyed since 1977 and no synchronous measures of fish distribution and the oceanographic characteristics of their habitat have been made previously. A survey was conducted during August 2008 in the western Beaufort Sea, Alaska. The distribution and abundance of benthic fish and invertebrates were assessed with standard bottom trawl survey methods. Oceanographic data were collected at each trawl station and at several locations between stations. The dominant benthic taxa, Polar cod (Boreogadus saida), eelpouts (Lycodes sp.), and snow crab (Chionoecetes opilio) were associated with cold (<?1.5°C), high salinity (>33) water found offshore of the shelf break, derived from the Chukchi Sea. These waters are expected to be high in secondary productivity, such that we hypothesize that the distribution of fish and crab was driven by conditions favorable for successful foraging. Predictions of the impacts of climate change require an understanding of the mechanisms linking the distribution and abundance of marine organisms to their oceanographic habitat. Our study documents the association of dominant benthic fish and invertebrates of the Beaufort Sea with specific water mass types and is thus a step toward this understanding.     

夏季黄海一断面底边界层动物多样性初步研究

2002年8月4日在黄海从青岛至济州岛断面的4个站位上,进行了底边界层动物昼夜连续采样, 对底边界层动物的多样性及其昼夜变化进行了分析。共鉴定出底边界层动物32种, 其中桡足类19种,端足类3种,涟虫3种,糠虾2种,毛颚类2种,枝角类2种,磷虾1种, 可划分为中型浮游动物、大型浮游动物和超底栖动物三个生物类群。主要种类有尖额真猛水蚤(Euterpina acutifrons)、挪威小毛猛水蚤(Microsetella norvegica)、戴氏猛水蚤(Danielssenia sp.)、小拟哲水蚤(Paracalanus parvus)和双刺纺缍水蚤(Acartia bifilosa)等。超底栖动物和中型浮游动物是两个主要类群。此外,桡足类幼体（无节幼体和桡足幼体）也是底边界层动物的重要组成部分。多样性分析显示: 底边界层动物在4个调查站位的均匀度（d）皆较高(0.728-0.915), 但种类较少(19-33), 故多样性指数(H′)较低(2.248-2.827)。超底栖动物的多样性指数相对较高, 中型浮游动物次之, 大型浮游动物较低。各类群的多样性指数在白天和夜间无显著性差异(P>0.05)。底边界层动物的丰度在细砂底质环境的1-3站最低, 在其他3个具有粉砂-粘土底质环境的站位皆较高。通过聚类分析, 可将这两种底质环境上的底边界层动物在26.6%相似性水平上分为两个类群。生物-环境匹配分析显示, 底边界层动物的种类及丰度除了与水深、水温有关外, 还与近底层颗粒有机碳(POC)、颗粒有机氮(PON)的沉降通量以及沉积物中值粒径密切相关。     

Parasitic infection of the hyperiid amphipod Themisto libellula in the Canadian Beaufort Sea (Arctic Ocean), with a description of Ganymedes themistos sp. n. (Apicomplexa, Eugregarinorida)

Two parasites were found in the hyperiid amphipod Themisto libellula sampled with nets and collected by sediment traps over the annual cycle in the Canadian Beaufort Sea. The trophozoites of the newly described gregarine Ganymedes themistos sp. n. infected the digestive tract of 60.2% of the T. libellula analyzed from net collections. An unidentified ciliate infected the body cavity of 4.4% of amphipods. G. themistos possessed the ball-like structure at the anterior end and the cup-like invagination at the posterior end that are typical of the genus Ganymedes. The frequency and severity (number of parasites host⁻¹) of infection by G. themistos increased with the length of T. libellula in the range 8–20 mm, and leveled off at ca. 94% and 186 trophozoites host⁻¹ on average in the range 20–34 mm. Spatially, gregarine infection was less severe (63 ± 100 G. themistos host⁻¹) on the Slope than on the Mackenzie Shelf (110 ± 160) and in the Amundsen Gulf (132 ± 157). No evidence of an impact of trophozoite infection on the feeding and sexual maturation of the host was found. For a given size of T. libellula, infection by both parasites was more frequent in the traps than in the nets (G. themistos: 91.0% vs. 82.7%; ciliates: 16.3% vs. 6%). The 2.7 times higher infection frequency in the traps suggested that the ciliate parasite may kill its host.     

Effect of salinity and temperature on the growth of yearling Arctic cisco (Coregonus autumnalis) of the Alaskan Beaufort Sea

The growth of 1-year-old Arctic cisco ( Coregonus autumnalis ) was monitored under laboratory conditions for fish acclimated to one of two temperatures (5 and 10° C) and one of five salinities (6, 12, 18,24, 30‰). Fish were maintained for 43 days at rations of 3% wet body weight per day at 5° C and 5% wet body weight per day at 10° C, with rations adjusted for weight gain every 7–12 days. Fish increased 9–11% in length and 55–71% in weight at 5° C, and 23–27% in length and 141–161% in weight at 10° C. Length and weight increased linearly over 43 days. There was a statistically significant effect of temperature on growth but no statistically significant effect of salinity. Higher growth rates at 10° C were partially attributable to significantly greater gross conversion efficiency at the higher temperature. Over the course of the experiment, the condition (weight per unit length) of all fish increased by 3·2 to 63·6% at 5° C and by 5·6 to 46·0% at 10° C. There was no discernible effect of salinity on condition at either temperature. These results demonstrate that, with salinity acclimation and high food ration, 1-year-old Arctic cisco can grow at equivalent rates across salinities ranging from 6 to 30‰. The ecological implications of the results are discussed.     

Potential impact of the main benthic amphipods on the eastern Weddell Sea shelf ecosystem (Antarctica)

As they represent one of the most diversified taxonomic groups on Antarctic bottoms, amphipods are likely to play a complex role in biogeochemical fluxes that occur within benthic ecosystems. The aim of this paper is to present, using both digestive tract analyses and relative species abundance data, the impact of amphipod feeding on different potential preys of the Weddell Sea. The study is based on data obtained for 29 representative amphipod species collected at 130 stations distributed along the eastern shelf of the Weddell Sea (depth range: 60-2,000 m) during three summer cruises, from 1989 to 1998. Sedimenting plankton particles (10-27%), crustaceans (22-32%) and fish carrion (5-18%) are the main food resources. Other abundant potential preys, such as molluscs or tunicates, do not seem to be consumed. Variations in the proportions of the different preyed food items are observed, mainly related to differences in relative amphipod species composition in samples. Presented results will help in refining ecological models of the prospected area, but also underline the need for accurate and reliable measurements of the feeding rates of Antarctic benthic organisms.     

Spring-to-summer changes and regional variability of benthic processes in the western Canadian Arctic

Seasonal dynamics in the activity of Arctic shelf benthos have been the subject of few local studies, and the pronounced among-site variability characterizing their results makes it difficult to upscale and generalize their conclusions. In a regional study encompassing five sites at 100–595 m water depth in the southeastern Beaufort Sea, we found that total pigment concentrations in surficial sediments, used as proxies of general food supply to the benthos, rose significantly after the transition from ice-covered conditions in spring (March–June 2008) to open-water conditions in summer (June–August 2008), whereas sediment Chl a concentrations, typical markers of fresh food input, did not. Macrobenthic biomass (including agglutinated foraminifera >500 μm) varied significantly among sites (1.2–6.4 g C m⁻² in spring, 1.1–12.6 g C m⁻² in summer), whereas a general spring-to-summer increase was not detected. Benthic carbon remineralisation also ranged significantly among sites (11.9–33.2 mg C m⁻² day⁻¹ in spring, 11.6–44.4 mg C m⁻² day⁻¹ in summer) and did in addition exhibit a general significant increase from spring-to-summer. Multiple regression analysis suggests that in both spring and summer, sediment Chl a concentration is the prime determinant of benthic carbon remineralisation, but other factors have a significant secondary influence, such as foraminiferan biomass (negative in both seasons), water depth (in spring) and infaunal biomass (in summer). Our findings indicate the importance of the combined and dynamic effects of food supply and benthic community patterns on the carbon remineralisation of the polar shelf benthos in seasonally ice-covered seas.     

An investigation into the zooplankton composition of a prominent 38-kHz scattering layer in the North Sea

This study aims to determine the contribution made by zooplanktonto acoustic scattering layers, which are particularly strongat 38 kHz, in the northern North Sea in summer. It uses a combinationof net sampling and forward and inverse acoustic modelling ofdata collected at 38, 120 and 200 kHz in July 2003. Zooplanktonsamples were collected from regions of strong acoustic scatteringin depths to 50 m, using a undulating towed (U-tow) vehicle.Acoustic data recorded simultaneously were scrutinized to determineactual backscattering, expressed as mean volume backscatteringstrength (MVBS) (dB). This observed MVBS (MVBS_obs) was comparedwith backscattering predicted by application of appropriateacoustic models (MVBS_pred) to sampled densities of zooplankton.In all instances, MVBS_obs was greater than MVBS_pred, with thedifference considerably more pronounced at 38 kHz. There wasa weak correlation between MVBS_pred and MVBS_obs at all threefrequencies, with the greatest correlation (r = 0.450, P = 0.545)at 120 kHz. A number of candidate acoustic models were invertedin order to infer the most likely type of scatterer. In mostcases, scatterers with a gas inclusion were predicted by thismethod. Potential sources of inconsistencies between MVBS_predand MVBS_obs were identified which, when considered alongsidethe presented forward and inverse solutions, indicate that 38kHz scattering in particular must be due to sources other thansampled zooplankton.     

The composition and structure of the benthic diatom taxocene (Bacillariophyta) near Cape Fiolent (the Crimea,the Black Sea)

For the first time in the waters of the Cape Fiolent Reserve, a high species richness of benthic diatoms was revealed on natural substrates, 290 species and infraspecific taxa (IT), belonging to 281 species, 68 genera, 32 families, 19 orders, and 3 classes. A total of 68 species and 3 genera were previously registered as new for the flora of the Black Sea; 3 species and 1 taxonomic combination were previously described as new to science, as well as 4 species that did not occur in the Black sea in the past 50 and 100 years of research. Navicula (41 species and IT), Amphora (30), Nitzschia (29), Fallacia (20), Cocconeis (17) and Diploneis (16) were the most represented genera. Only one representative was identified in each of the orders Anaulales, Ardissoneales, Thalassionematales, Rhaphoneidales, and Rhopalodiales. The diversity assessment that was carried out using taxonomic distinctness indices, TaxDI, revealed that the structure of the phylogenetic diatom tree was formed by branches with various species saturation levels and different hierarchical subordination, but with the predominance of polyspecific taxa up to at genera level. The TaxDI values (Δ⁺ = 76.71; Λ⁺ = 361.52) indicate the low evenness and high variability of the structure of the benthic diatom taxocene near Cape Fiolent.     

The composition and distribution of benthic amphipods (Crustacea: Amphipoda) in the southern Barents Sea

The composition and distribution of near-bottom amphipods in the southern part of the central Barents Sea were studied based on quantitative materials collected by expeditions of the Murmansk Marine Biological Institute in 1996–1997. A total of 144 amphipod species (on average 13 ± 1 species per station) were found; the average biomass was 0.49 ± 0.07 g/m², average abundance 106 ± 15 specimens/m². Boreal-Arctic (46%), Arctic (17%), and boreal (21%) species were predominant among the amphipod fauna. The present results were compared with the data for 1968–1970.     

The aggregation of polar cod (Boreogadus saida) in the deep Atlantic layer of ice-covered Amundsen Gulf (Beaufort Sea) in winter

During the Circumpolar Flaw Lead System Study (CFL, 2007–2008), large aggregations of polar cod were detected in winter in the Amundsen Gulf (Western Canadian Arctic) using the EK60 echosounder of the CCGS Amundsen research icebreaker. Biomass estimated over 10 months reached a maximum of 0.732 kg m⁻² in February. Aggregations were encountered only in the presence of an ice cover from December to April. The vertical extent of the aggregations was dictated by temperature and zooplankton prey distribution. In winter, polar cod generally occupied the relatively warm deep Atlantic Layer (>0°C), but a fraction of the densest aggregations occasionally followed zooplankton prey up into the cold Pacific Halocline (−1.6 to 0°C). The diel vertical migration of polar cod was precisely synchronized with the seasonally increasing photoperiod. Throughout winter, polar cod aggregations migrated to progressively deeper regions (from 220 to 550 m bottom depths) in response to increasing light intensity, presumably to avoid predation by visual predators such as the ringed seal. Comparing Amundsen Gulf and Franklin Bay indicates that the entrapment of polar cod in embayments during winter is an important mechanism to provide marine mammal predators with dense concentrations of their main prey within their diving range.     

Feeding ecology of Pseudalibrotus (=Onisimus) litoralis kröyer (Crustacea: Amphipoda) on the Beaufort Sea inner continental shelf

Summary In polar waters ice microalgae are the important food source for under-ice amphipods in the late spring; however, earlier, the algal primary productivity is low. This study relates the feeding ecology of the dominant lysianassid amphipod Pseudalibrotus litoralis to its life history and its use of the under-ice substrate for a concentrated food supply and nursery ground early in the year. Gut contents and fecal pellets in April consist primarily of crustacean parts, and in late May-early June, of diatom frustules. Pseudalibrotus litoralis is welladapted to live at the ice undersurface before and during the spring diatom bloom as a result of its omnivorous feeding behavior.     

Introduction to the special issue on the biology of the circumpolar flaw lead (CFL) in the Amundsen Gulf of the Beaufort Sea (Arctic Ocean)

The sea-ice cover of the Arctic Ocean is decreasing in areal extent and volume more rapidly than model predictions of its response to continued warming of earth’s lower atmosphere. Reflecting this decrease is the spatial and temporal widening of the circumpolar flaw lead, a zone of open water and unconsolidated ice along the coastlines of the shallow seas that surround the deep Arctic Ocean basins. As part of the International Polar Year, the Circumpolar Flaw Lead System Study deployed the research icebreaker Amundsen from October 2007 to August 2008 in the flaw lead segment bordering Banks Island in the Canadian Beaufort Sea. With participation from Canada, the USA, Spain, Germany, China, Russia, the UK, Norway, Belgium, the Netherlands, France, and Sweden, the multi-disciplinary overwintering expedition logged 9,812 scientist-days in an effort to decipher key aspects of the ecosystem of the flaw lead. Highlights of the scientific achievements documented in this special issue on the biology of the circumpolar flaw lead system help to capture the depth, breadth, and novelty of this remarkable exploration.     

Seasonal changes in zooplankton composition in the Barents Sea, with special attention to Calanus spp. (Copepoda)

The Barents Sea is an important area with respect to fisheriesresources (i.e. capelin and cod). In May, June and August 1981zooplankton biomass was measured along a transect at 30°E,from the ice border southwards. A maximum was recorded in Atlanticwater by the end of June (>100 g wet weight m^–2 InAugust the biomass values were relatively low south of the Polarfront and increased northwards into Arctic water (–50g m^–2 The species composition was influenced by the distributionof cold Arctic water and warmer Atlantic water. The zooplanktonwas dominated by the copepods Calanus finmarchicus and C. glacialis;the former is regarded as an Atlantic species and C. glacialisas an Arctic species.