Biogeochemical conditions and ice algal photosynthetic parameters in Weddell Sea ice during early spring

Physical, biogeochemical and photosynthetic parameters were measured in sea ice brine and ice core bottom samples in the north-western Weddell Sea during early spring 2006. Sea ice brines collected from sackholes were characterised by cold temperatures (range −7.4 to −3.8°C), high salinities (range 61.4–118.0), and partly elevated dissolved oxygen concentrations (range 159–413 μmol kg⁻¹) when compared to surface seawater. Nitrate (range 0.5–76.3 μmol kg⁻¹), dissolved inorganic phosphate (range 0.2–7.0 μmol kg⁻¹) and silicic acid (range 74–285 μmol kg⁻¹) concentrations in sea ice brines were depleted when compared to surface seawater. In contrast, NH₄ ⁺ (range 0.3–23.0 μmol kg⁻¹) and dissolved organic carbon (range 140–707 μmol kg⁻¹) were enriched in the sea ice brines. Ice core bottom samples exhibited moderate temperatures and brine salinities, but high algal biomass (4.9–435.5 μg Chl a l⁻¹ brine) and silicic acid depletion. Pulse amplitude modulated fluorometry was used for the determination of the photosynthetic parameters F _v/F _m, α, rETR_max and E _k. The maximum quantum yield of photosystem II, F _v/F _m, ranged from 0.101 to 0.500 (average 0.284 ± 0.132) and 0.235 to 0.595 (average 0.368 ± 0.127) in the sea ice internal and bottom communities, respectively. The fluorometric measurements indicated medium ice algal photosynthetic activity both in the internal and bottom communities of the sea ice. An observed lack of correlation between biogeochemical and photosynthetic parameters was most likely due to temporally and spatially decoupled physical and biological processes in the sea ice brine channel system, and was also influenced by the temporal and spatial resolution of applied sampling techniques.     

Living benthic foraminifera of the Okhotsk Sea: Faunal composition, standing stocks and microhabitats

Live (Rose Bengal stained) benthic foraminifera were investigated in surface sediment samples from the Okhotsk Sea to reveal the relationship between faunal characteristics and environmental parameters. Live benthic foraminifera were quantified in the size fraction > 125 µm in the upper 8 cm of replicate sediment cores, recovered with a multicorer at five stations along the Sakhalin margin, and at three stations on the southwestern Kamchatka slope. The stations are from water depths between 625 to 1752 m, located close or within the present Okhotsk Sea oxygen minimum zone, with oxygen levels between 0.3 and 1.5 ml l^- 1. At the high-productivity and ice-free Kamchatka stations, live benthic foraminifera are characterized by maximal standing stocks (about 1700-3700 individuals per 50 cm²), strong dominance of calcareous species (up to 87-91% of total live faunas), and maximal habitat depths (down to 5.2-6.7 cm depth). Vertical distributions of total faunal abundances exhibit a clear subsurface maximum in sediments. At the Sakhalin stations, which are seasonally ice-covered and less productive, live benthic foraminifera show lower standing stocks (about 200-1100 individuals per 50 cm²), lower abundance of calcareous species (10-64% of total live faunas), and shallower habitat depths (down to 2.5-5.4 cm depth). Faunal vertical distributions are characterized by maximum in the uppermost surface sediments. It is suggested that 1) lower and strongly seasonal organic matter flux, caused by the seasonal sea ice cover and seasonal upwelling, 2) lower bottom water oxygenation (0.3-1.1 ml l^- 1), and 3) more pronounced influence of carbonate undersaturated bottom water along the Sakhalin margin are the main factors responsible for the observed faunal differences. According to species downcore distributions and average living depths, common calcareous species were identified as preferentially shallow, intermediate and deep infaunal. Foraminiferal microhabitat occupation correlates with the organic matter flux and the depth of the oxygenated layer in sediments.     

The size composition of the pelagic eggs of walleye pollack <Emphasis Type="Italic">Theragra chalcogramma</Emphasis> in spawning areas of the northern Sea of Okhotsk

The data on the size composition of the pollack developing eggs of walleye pollack collected in the northern Sea of Okhotsk in 2001 during mass spawning are given. The eggs caught in western Kamchatka and in Shelikhov Bay had the greatest diameter; they were somewhat less in the northern Okhotsk Sea area; and the smallest eggs were found in eastern Sakhalin. The clinal variability of the size composition of walleye pollack eggs was observed in the northern Sea of Okhotsk, and in the western and eastern parts it had a local pattern. Parameters such as spawning female size composition, temperature, and salinity, as well their influence on the size composition of eggs, were considered.Original Russian Text Copyright © 2004 by Biologiya Morya, Ovsyannikov.     

New Data About Seasonal Distribution and Migrations of Whales and Dolphins in the Sea of Okhotsk

This paper presents new data about the seasonal distribution of whales and dolphins in the Sea of Okhotsk including the ice period. Even under the most severe ice conditions, the migrating species of whales and dolphins may be encountered in the Sea of Okhotsk. In all seasons the density of cetaceans is higher in the eastern part of the sea, which is more abundant in fish.     

Species Structure of Plankton Microalgae on the Coast of the Sea of Okhotsk on Sakhalin Island

The results of long-term studies of the species structure of microalgae plankton of the coast of the Sea of Okhotsk of Sakhalin Island were summarized. There were 227 species and 4 intraspecific taxa attributed to 8 divisions. The greatest number of species was represented by the divisions Bacillariophyta (112 species and 3 intraspecific taxa) and Dinophyta (96 and 1 respectively). For the first time 5 diatom, 4 dinoflagellate, and 1 euglenophyte species were recorded for the Sea of Okhotsk.     

Microbian Indication of Pollution of the Coastal Zone of the Sea of Okhotsk and Avacha Bay

The results of microbiological analysis of a number of microorganisms of various ecological–trophic groups in plankton microbial communities of some water areas of the Sea of Okhotsk and Avacha Bay are presented. The data were compared to the hydrochemical parameters (temperature, salinity, BOD₅, dissolved oxygen, phosphates, organic phosphate, detergents) determined simultaneously. The microbian indication method is used for express assessment of water pollution of the surveyed areas. The data demonstrated that Avacha Bay was subjected to heavier anthropogenic impact than the water areas of the ports of Kholmsk and Magadan.     

A device for remote sampling of benthic algae under ice

A benthic algae sampling device designed for use through surface ice, uses the principle of pivoting arms. It is designed to be activated below ice sheets and is capable of passing easily through a hole of 11 cm diameter bored by a SIPRE ice auger.     

Autotomy and regeneration of limbs in the male blue king crabParalithodes platypus from the Bering Sea and the Sea of Okhotsk

Limb loss and the frequency of regeneration was investigated in the male blue king crabParalithodes platypus collected in the Sea of Okhotsk and the Bering Sea. TheP. platypus population in the Bering Sea is characterized by an anomalously high proportion of crabs with missing limbs, which is largely due to the intensive fishing. The present approach to the exploitation of the Bering Sea population, in which large intact crabs are removed and injured crabs are left to recover to the normal state, may result in a decline in the reproductive potential of this population as early as this coming year.     

夏季鄂霍茨克海公海区狭鳕渔场环境特征

根据鄂霍茨克公海区狭鳕资源声学评估调查资料,研究了狭鳕分布状况及渔场环境特征,并分析了狭鳕行动分布与环境的关系．结果表明,8月公海区狭鳕密集群位于55°N以北、水深小于500m的海域,其主要分布水层在150～300m之间;调查期间狭鳕只为索饵群体,主要摄食太平洋磷虾,狭鳕密集区一般也为太平洋磷虾高密度分布区;8月公海区水温跃层大致在0～50m之间,强度为0．25℃     

The rotifer fauna of arctic sea ice from the Barents Sea,Laptev Sea [2pt] and Greenland Sea

Hydrobiologia - Samples from arctic sea ice were studied for their rotifer fauna. Ice core samples were collected in the northern Barents Sea and the Laptev Sea from August to October 1993 and in...     

Distribution,Feeding, and Some Physiological Parameters of the Pacific Herring from the Gizhigin and Okhotsk Populations in the North Part of the Sea of Okhotsk in the Spring Season

The distribution of the Pacific herring of various sizes from the Okhotsk and Gizhigin-Kamchatka populations is discussed. The dependence of herring food composition on the condition of the plankton community is demonstrated. In the spring season the feeding rate of juveniles and fattening adult herring depended on the degree of its fatness and on the maturity of the gonads in the prespawning period.     

Sea ice seasonality during the Holocene, Adélie Land, East Antarctica

Thin sections of laminated cores from different Antarctic coastal areas have demonstrated the potential of diatom species to document climate change at the seasonal scale. Here we present the relative abundances of four diatom species and species groups (Fragilariopsis curta group as a proxy for yearly sea ice cover, F. kerguelensis as a proxy for summer sea-surface temperature, Chaetoceros Hyalochaete resting spores as a proxy for spring sea ice melting and the Thalassiosira antarctica group as a proxy for autumn sea ice formation) in core MD03-2601 retrieved off Adélie Land on the Antarctic continental shelf. These abundances were compared to surface temperatures and sea ice cover modelled over the last 9000 years. Both the marine records and the simulated climate demonstrated a cooler Early Holocene (9000–7700 years BP), a warmer Mid-Holocene (7700–4000 years BP) and a colder Late Holocene (4000–1000 years BP). Yearly sea ice cover followed an inverse pattern to temperatures with less sea ice during the Mid-Holocene Hypsithermal than during the Late Holocene Neoglacial. However, diatom census counts and model output indicate that sea ice spring melting happened earlier in the season, as expected, but that autumn sea ice formation also occurred earlier in the season during the Hypsithermal than during the colder Neoglacial, thereby following seasonal changes in local insolation.     

The First Finding of the Actinia Synandwakia hozawai in the Sea of Okhotsk

The finding of the actinia Synandwakia hozawai in the coastal waters of northern Sakhalin (Sea of Okhotsk) suggests a wider range of this species, which was previously only known to inhabit the coastal waters of eastern Japan. Data are presented on the morphology of the S. hozawai specimen from the Sea of Okhotsk and the types of its nematocysts.     

Stable carbon isotope variability associated with taxonomic composition of lotic benthic algae

We examined the relationship between the δ¹³C and taxonomic composition of benthic algae collected from a riffle (fast current habitat) of a non‐shaded mountain stream, which is a tributary of the Kiso River, Japan. The benthic algal δ¹³C ranged from ?20.6 to ?14.2‰ and tended to be ¹³C‐depleted with increasing relative abundance of upright filamentous cyanobacteria and ¹³C‐enriched with increasing relative abundance of prostrate filamentous cyanobacteria. Using isotopic mass balance equations, the relative abundance of the dominant taxa, upright and prostrate filamentous cyanobacteria, small diatoms and others, explained 74% of δ¹³C variability. This study shows a case where the difference in taxonomic composition is a possible source of the isotopic variability of benthic algae, which is a mixture of taxa with distinct isotopic signatures.     

Seasonal variation in marine phytoplankton and ice algae at a shallow antarctic coastal site

The phytoplankton population near Davis, Vestfold Hills, Antarctica was monitored throughout 1982. Chlorophyll-a determinations and counts of living cells in both the water column and sea ice demonstrated a marked seasonality in phytoplankton abundane and species composition. From April to October nanoplanktonic organisms contributed most of the chlorophyll-a in both the sea ice and water column. Blooms of diatoms occurred in May, November and December in the bottom of the sea-ice and in January and February in the water column. Phaeocystis pouchetii was dominant during December in the water column. Large numbers of dead diatoms were found in winter. The concentrations of nitrate, dissolved inorganic phosphate and dissolved silicate increased throughout the year until December, when the concentrations of nitrate and silicate fell sharply, followed a month later by a reduction in phosphate concentration. The diversity of phytoplankton was greatest during the summer months.     

Toxic HAB species from the Sea of Okhotsk detected by a metagenetic approach,seasonality and environmental drivers

During recent decades, the distribution of harmful algal bloom (HAB) species has expanded worldwide together with the increase of blooms and toxicity events. In this study, the presence of toxic HAB species in the Sea of Okhotsk was investigated based on metagenetic data collected during 6 years of weekly monitoring. Operational taxonomic units (OTUs) associated with the toxic HAB species were detected based on amplifying 18S V7-V9 and 28S D1 rRNA gene regions. In total, 43 unique OTUs associated with toxic HAB species were revealed, with 26 of those previously not reported from the Sea of Okhotsk. More OTUs belonging to dinoflagellates were detected by 18S, whereas a similar number of OTUs associated with dinoflagellates and diatoms were detected by targeting the 28S region. Species belonging to genera Alexandrium, Karenia and Karlodinium were mainly associated with OTUs under Dinophyceae, whereas Bacillariophyceae was represented by the species belonging to genus Pseudo-nitzschia. From the detected OTUs, 22 showed a clear seasonal pattern with the majority of those appearing during summer-autumn. For Alexandrium pacificum, Aureococcus anophagefferens, and Pseudo-nitzschia pungens, the seasonal pattern was detected based on both rRNA regions. Additionally, 14 OTUs were detected during all seasons and two OTUs appeared sporadically. OTUs associated with the toxic species had low relative read abundances, which together with other factors such as similar and variable morphology as well as usage of fixatives, may explain why those species have previously not been detected by light microscopy. Environmental parameters, especially water temperature, significantly (<0.05) influenced the variability in OTU relative abundances and displayed significant (<0.05) correlations with the unique OTUs. The results of this study demonstrate the usefulness of the metagenetic approach for phytoplankton monitoring, which is especially relevant for detecting toxic HAB species.     

Comparative immunological characterization of various photosynthetic cytochromes c from pro- and eukaryotic algae

Photosynthetic c-type cytochromes isolated from various pro- and eukaryotic algae have been compared by an immunochemical method. Thereby the extent of cross-reactivity of several cytochromes with antisera to cytochrome c from Spirulina platensis, Bumilleriopsis filiformis, and Scenedesmus acutus was quantitatively determined by antigen-binding tests. When immunological relationship is taken as a measure of structural relationship, the following conclusions can be drawn: (1) c-type cytochromes from Anabaena variabilis, Nostoc muscorum, Calothrix membranacea, and Spirulina platensis show large differences in cross-reactivity. (2) The acidic Spirulina cytochrome c is fairly closely related to the two eukaryotic cytochromes assayed here.Abbreviations SAUG Sammlung von Algenkulturen am Pflanzenphysiologischen Institut der Universität Göttingen, FRG - PCC Pasteur Culture Collection     

Contribution of sea ice microbial production to Antarctic benthic communities is driven by sea ice dynamics and composition of functional guilds

Organic matter produced by the sea ice microbial community (SIMCo) is an important link between sea ice dynamics and secondary production in near‐shore food webs of Antarctica. Sea ice conditions in McMurdo Sound were quantified from time series of MODIS satellite images for Sept. 1 through Feb. 28 of 2007–2015. A predictable sea ice persistence gradient along the length of the Sound and evidence for a distinct change in sea ice dynamics in 2011 were observed. We used stable isotope analysis (δ¹³C and δ¹⁵N) of SIMCo, suspended particulate organic matter (SPOM) and shallow water (10–20 m) macroinvertebrates to reveal patterns in trophic structure of, and incorporation of organic matter from SIMCo into, benthic communities at eight sites distributed along the sea ice persistence gradient. Mass‐balance analysis revealed distinct trophic architecture among communities and large fluxes of SIMCo into the near‐shore food web, with the estimates ranging from 2 to 84% of organic matter derived from SIMCo for individual species. Analysis of patterns in density, and biomass of macroinvertebrate communities among sites allowed us to model net incorporation of organic matter from SIMCo, in terms of biomass per unit area (g/m²), into benthic communities. Here, organic matter derived from SIMCo supported 39 to 71 per cent of total biomass. Furthermore, for six species, we observed declines in contribution of SIMCo between years with persistent sea ice (2008–2009) and years with extensive sea ice breakout (2012–2015). Our data demonstrate the vital role of SIMCo in ecosystem function in Antarctica and strong linkages between sea ice dynamics and near‐shore secondary productivity. These results have important implications for our understanding of how benthic communities will respond to changes in sea ice dynamics associated with climate change and highlight the important role of shallow water macroinvertebrate communities as sentinels of change for the Antarctic marine ecosystem.     

Denitrification activity and oxygen dynamics in Arctic sea ice

Denitrification and oxygen dynamics were investigated in the sea ice of Franklin Bay (70°N), Canada. These investigations were complemented with measurements of denitrification rates in sea ice from different parts of the Arctic (69°N–85°N). Potential for bacterial denitrification activity (5–194 μmol N m⁻² day⁻¹) and anammox activity (3–5 μmol N m⁻² day⁻¹) in melt water from both first-year and multi-year sea ice was found. These values correspond to 27 and 7%, respectively, of the benthic denitrification and anammox activities in Arctic sediments. Although we report only potential denitrification and anammox rates, we present several indications that active denitrification in sea ice may occur in Franklin Bay (and elsewhere): (1) despite sea ice-algal primary production in the lower sea ice layers, heterotrophic activity resulted in net oxygen consumption in the sea ice of 1–3 μmol l⁻¹ sea ice per day at in situ light conditions, suggesting that O₂ depletion may occur prior to the spring bloom. (2) The ample organic carbon (DOC) and NO₃ ⁻ present in sea ice may support an active denitrification population. (3) Measurements of O₂ conditions in melted sea ice cores showed very low bulk concentrations, and in some cases anoxic conditions prevailed. (4) Laboratory studies using planar optodes for measuring the high-resolution two-dimensional O₂ distributions in sea ice confirmed the very dynamic and heterogeneous O₂ distribution in sea ice, displaying a mosaic of microsites of high and low O₂ concentrations. Brine enclosures and channels were strongly O₂ depleted in actively melting sea ice, and anoxic conditions in parts of the brine system would favour anaerobic processes.