Spring distribution of larger (>64 μm) protozoans in the Atlantic sector of the Southern Ocean

Distribution of larger protozoans (armoured dinoflagellates, tintinnids, heliozoans, radiolarians and foraminiferans >64 μm) is presented for three major water masses of the Southern Ocean: the Polar Front region (PFr), the southern Antarctic Circumpolar Current (southern ACC) and the northern Weddell Gyre. Sampling took place during the SO-JGOFS cruise ANT X/6 of R/V Polarstern (October–November 1992) along a meridional transect at 6°W between 48°00′S and 59°30′S. Multinet samples (64 μm mesh size) were taken at six stations from the surface down to 500 m depth at five different depth intervals. In the upper 100 m of the water column abundances of larger protozoans varied between 94 and 10,930 ind. m^–3, with highest abundances in the PFr, where phytoplankton blooms occurred, and lowest values in the Antarctic Circumpolar Current–Weddell Gyre Boundary (AWB). Foraminiferans and polycystine and smaller (<300 μm) phaeodarian radiolarians dominated larger protozoan assemblages in the PFr. In open water of the southern ACC, tintinnids, armoured dinoflagellates, foraminiferans and smaller (<300 μm) phaeodarian radiolarians were equally important. The heliozoans Sticholonche spp. and nassellarian radiolarians dominated assemblages in the Weddell Gyre and AWB. Larger protozoan biomasses ranged between 2 and 674 μg C m⁻³ and were always dominated by larger (>300 μm) phaeodarians. Highest biomasses were found in the AWB between 200 and 500 m depth. Standing stocks of larger protozoans constituted a negligible fraction of zooplankton biomass in the upper 200 m of the water column. In deeper layers of the ice-covered Weddell Gyre and AWB their biomasses, dominated by larger (>300 μm) phaeodarians, was significant contributing up to 45% to total larger protozoan and metazoan biomass. Analysis of correlation between distribution patterns and environmental conditions at the stations sampled indicate that spring distribution patterns of heterotrophic armoured dinoflagellates, polycystine radiolarians and foraminiferans follow productivity in the water column. Of the protozoan groups studied the smaller (<300 μm) phaeodarian radiolarians also showed a significant correlation with productivity during spring, however, results from previous studies do not suggest a consistent pattern. Spring distribution patterns of other larger protozoans were not related to differences in productivity in the water column, and effects such as ice-cover, grazing or silica limitation might be determining. Dead radiolarian skeletons constituted on average 27, 8 and 11% of the population of nassellarians, spumellarians and smaller (<300 μm) phaeodarians, respectively. The contribution of dead radiolarian skeletons to total radiolarian stocks varied with depth and water mass. Differences between live and skeleton assemblages composition were observed. These differences should be taken into consideration when interpreting the geological record.     

Activity of the turbidite levees of the Celtic–Armorican margin (Bay of Biscay) during the last 30,000 years: Imprints of the last European deglaciation and Heinrich events

High-resolution sedimentological and micropaleontological studies of several deep-sea cores retrieved from the levees of the Celtic and Armorican turbidite systems (Bay of Biscay — North Atlantic Ocean) allow the detection of the major oscillations of the British–Irish Ice Sheet (BIIS) and ‘Fleuve Manche’ palaeoriver discharges over the last 30,000 years, which were mainly triggered by climate changes.Between 30 and 20 cal ka, the turbiditic activity on the Celtic–Armorican margin was weak, contrasting with previous stratigraphic models which predicted a substantial increase of sediment supply during low sea-level stands. This low turbidite deposit frequency was most likely the result of a weak activity of the ‘Fleuve Manche’ palaeoriver and/or of a reduced seaward transfer of sediments from the shelf to the margin. However, two episodes of turbiditic activity increase were detected in the Celtic–Armorican margin, during Heinrich events (HE) 3 and 2. This strengthening of the turbiditic activity was triggered by the meltwater releases from European ice sheets and glaciers favouring the seaward transfer of subglacial material, at least via ‘Fleuve Manche’ palaeoriver.At around 20 cal ka, a significant increase of turbidite deposit frequency occurred as a response to the onset of the last deglaciation. The retreat of the European ice sheets and glaciers induced a substantial increase of the ‘Fleuve Manche’ palaeoriver discharges and seaward transfer of continentally-derived material into the Armorican turbidite system. The intensification of the turbiditic activity on the Celtic system was directly sustained by the widespread transport of subglacial sediments from the British–Irish Ice Sheet (BIIS) to the Celtic Sea via the Irish Sea Basin. A sudden reduction of turbiditic activity in the Armorican system, between ca. 19 and 18.3 cal ka, could have been triggered by the first well known abrupt sea-level rise (‘meltwater pulse’, at around 19 cal ka) favouring the trapping of sediment in the ‘Fleuve Manche’ palaeoriver valleys and the decrease of the seaward transfer of continentally-derived material.The maximum of turbiditic activity strengthening in the Celtic–Armorican margin, between ca. 18.3 and 17 cal ka, was induced by the decay of European ice sheets and glaciers producing the most extreme episode of the ‘Fleuve Manche’ palaeoriver runoff and a great seaward transfer of subglacial material into the Bay of Biscay. Between ca. 17.5 and 16 cal ka, the turbiditic activity significantly decreased in both Celtic and Armorican turbidite systems in response to a global re-advance of glaciers and ice sheets in Europe. The last episode of ice sheet retreat, between ca. 16 and 14 cal ka, is well expressed in the Celtic system by a new increase of the turbiditic activity. The major episode of sea-level rise at around 14 cal ka (‘Meltwater Pulse 1A’), precluding the seaward transfer of sediments, induced the end of turbiditic activity in both the Celtic and the Armorican system.Although two main phases of global sea-level rise seem to have had an effect on the Celtic–Armorican margin, this work proposes the BIIS retreat and associated riverine discharges as the main trigger mechanisms of the turbiditic activity in this region during the last 30,000 years.     

Characteristics of the Japanese sea cucumber <Emphasis Type="Italic">Apostichopus japonicus’s</Emphasis> population in the Sea of Japan (Kievka Bay)

In Kievka Bay of the Sea of Japan, the population of the Japanese sea cucumber Apostichopus japonicus inhabits the areas of coarse sediments and complex bottom topography. These distributional patterns are closely related to the species’ ecology, i.e., to the demand for protection against the wave turbulence. The aggregationing coverage of the sea cucumber population is about 80 hectares, where ∼200 thousand animals were accounted for in the last years. The aggregation’s area varies during the year, which is closely related to the species’ biological peculiarities, such as their behavioral patterns and the redistribution of their food resources. A significant increase of the juvenile population occurred after the farm-reared sea cucumber spat were released in 2003.     

Reply to the comment of Talwani et al. (2017) on the Sibuet et al. (2016) paper entitled “Thinned continental crust intruded by volcanics beneath the northern Bay of Bengal”

The northern Bay of Bengal velocity-depth profiles do not follow the velocity-depth curve for the North Atlantic volcanic margins, and only partially the Kerguelen plume velocity-depth curves. Compared with the South China Sea northern margin proxy, we still suggest that the Bay of Bengal crust is thinned continental crust intruded by post-rifting volcanics, as also shown by the interpretation of the numerous high-quality deep multichannel seismic profiles we collected there. What was supposed to be underplating might be sills intruded through the lower thinned continental crust.     

Influence of the Bottom Sediment Characteristics on the Bivalve Mollusk <Emphasis Type="Italic">Anadara kagoshimensis</Emphasis> Histopathology’s Variability in the Northeastern Coast of the Black Sea

With increasing anthropogenic impact on the environment, investigations of organism’s response to the contamination of natural habitats, are especially relevant. In the present study, we sought to identify the correlation between the bottom sediments and local variability in histopathology of Anadara kagoshimensis (Bivalvia) in four sites of the north-eastern coast of the Black Sea. Bottom sediment grain size, redox potential of pore water, heavy metals, benzo-α-pyrene and DDT concentrations have been used as characteristics of bottom sediments. Analysis of the data revealed differences in the geochemical background of the studied sites and the histopathological state of the molluscs from these areas. Among the 10 studied elements as well as benzo-α-pyrene and DDT, only Ni has shown an exceedance of statutory limits of concentration in bottom sediments. The study reveals a relationship between Ni concentration in the bottom sediments and frequency of heavy histopathologies in the molluscs. In addition to causes directly related to pollution, mild pathology may be influenced by “natural” causes; in particular, the high content of brown cells in the connective tissue of the digestive gland may be due to the age of molluscs.     

Settling fluxes of diatoms to the interior of the Antarctic circumpolar current along 170 °W

An array of four sediment trap moorings recorded the particulate flux across the Antarctic Circumpolar Current (ACC) at 170 °W, between November 1996 and January 1998, as part of the US JGOFS-Antarctic Environment and Southern Ocean Process Study (AESOPS) program. The trap locations represent sampling within the Polar Frontal Zone, the Antarctic Polar Front, the Antarctic Zone and the Southern Antarctic Zone. Here we report observations from 1000 m below the sea-surface compared to seafloor and surface water distributions. Sub-sample splits from each trap were obtained and total diatom flux and species composition were determined. The diatom fluxes were quantified using both a dilution and a ‘spike’ method to allow for the rapid repeatability of measurements. Diatom flux was found to be highly seasonal across the ACC particularly at higher latitudes. Marine snow aggregates of intact diatom cells and chains were the major components of the biogenic flux. Siliceous particle size was noted to decrease with increasing latitude, which could be aligned with a shift of the diatom assemblage to small-size species/sea-ice affiliated species. A ‘double-structured’ diatom flux was recorded at the location of the Antarctic Polar Front trap, with a shift in the diatom assemblage from larger to smaller diatoms in the second flux episode. The sediment trap assemblage shows deviations from the surface water assemblage, while surface sediment samples indicate that significant dissolution occurs after 1000 m and at the sediment–water interface. Estimation of diatom biovolumes across the ACC shows that large diatoms have the potential to greatly impact biogenic fluxes to the ocean interior despite their low fluxes. Small species of the genus Fragilariopsis could potentially export as much C_org as Fragilariopsis kerguelensis near the retreating ice edge. However, their low abundance in the surface sediments also suggests that these diatoms are a shallow export species.     

Facies architecture and heterogeneity of the fluvial–aeolian reservoirs of the Sergi formation (Upper Jurassic), Recôncavo Basin,NE Brazil

The Sergi Formation (Upper Jurassic) represents the main hydrocarbon reservoir of the Recôncavo Basin, Brazil. The basal vertical facies succession of the Sergi Formation comprises reservoirs formed by a complex fluvio–aeolian–lacustrine interaction. Facies architecture and detailed petrophysical analysis of these reservoirs have enhanced the understanding of heterogeneity at a variety of scales and has allowed the development of predictive models that describes the range of styles of mixed fluvial–aeolian reservoirs. At megascopic scale, the reservoirs are predominantly composed of sand bodies deposited by fluvial channel and aeolian facies associations. Regional flooding surfaces and sequence boundaries are their main flow barriers. The regional flooding surfaces are composed of fine-grained sediments deposited by lacustrine facies associations and the sequence boundaries act as flow barriers due to mechanically infiltrated clays. Based on its geometrical relations, reservoirs linked to fluvial–aeolian–lacustrine interaction formed two types of reservoirs at macroscopic scale: (i) with good lateral continuity of aeolian packages and relatively simple stratigraphic correlation and (ii) of highly compartmentalized aeolian packages with complex stratigraphic correlation and truncation by fluvial deposits. Mesoscopic heterogeneity reflects lithofacies, sedimentary structures, and lamina-scale variability within aeolian and fluvial facies associations.     

Determination of <Emphasis Type="Italic">Rapana venosa</Emphasis> individuals’ ages based on the δ<Superscript>18</Superscript>O dynamics of the shell carbonates

The results of the analysis of the stable oxygen isotopes content in shell carbonates for the purpose of the individual age determination of the Rapana venosa gastropod (Valenciennes 1846) are presented. The data acquired via this method agreed with the number of spawning marks on the shell surface. Additionally, the duration of the seasonal extrema can indicate the velocity of the shell’s growth throughout the mollusk life, and the relative δ¹⁸O value in the shell’s near-apex increments, the season when a young shell comes out of its cocoon. It has been shown that the common method of growth rings counting at the operculum is unreliable for a shell’s age determination. The distinguishing of modal classes is ineffective as well, since the corridor of the variations in size for coeval individuals is very broad. Apparently, such variable characteristics as the growth rate, the wall’s thickness, and the relative weight are greatly dependent on the alimentary conditions, which are unequal even in the same biotope.     

Structure of plankton phytocoenoses in the shelf waters of the northeastern Black Sea during the <Emphasis Type="Italic">Emiliania huxleyi</Emphasis> bloom in 2002–2005

It is shown that, in 2002–2005, the mass development of the coccolithofore Emiliania huxleyi on the Gelendzhik shelf occurred annually and in May–June its abundance reached 1.5 × 10⁶ cells/l. In 2004–2005, the bloom of E. huxleyi was accompanied by a mass development of the diatom alga Chaetoceros subtilis var. abnormis f. simplex (0.6–0.9 × 10⁶ cells/l); for the first time, it was registered as a dominating form of the Black Sea phytoplankton. Small flagellates and picoplankton algae played a noticeable role in the phytoplankton throughout the entire period of the studies. Meanwhile, in the early summer period, the bulk of the biomass consisted of coccolithophores (50–60%), while, in the late summer period, diatomaceous algae dominated (50–70%). Among the ecological factors that favor the coccolithophore development one may note the microstratification of the upper mixed layer at a high illumination level and high temperature in the surface waters (18–21°C). The terrigenous runoff during the rainy period had a negative effect on the E. huxleyi development, while storms dispersed the population over the upper mixed layer. The wind-induced near-shore upwelling stimulated the development of diatoms.     

Numerical analysis of the sea (lake) breeze dynamics and initialization of the model

In this paper, analysed are the effects of synoptic wind, earth-rotation inertia and land surface roughness on sea (lake) breeze process, on the basis of the calculated results of a 2-D primitive equation model with turbulent energy closure. The results show that a moderate background wind field acts as a trigger for sea (lake) breeze onset, and presents prominent effect on the breeze intensity, inland advance rate and structure feature. The effects of Coriolis force not only make the breeze veering round, but also damp the development of the breeze component normal to shore.The paper also discussed the dynamic method of wind field initialization based on one-site radiosonde. Three approaches of initialization have been tested. In comparison, it was found that the approach of one-dimensional dynamic initialization with nudging term was preferable to the others.     

Multidisciplinary Program of Field Studies of the Ecosystem in the Atlantic Sector of the Southern Ocean (December 2019–March 2020)

Oceanology - The research program of the dynamics and ecosystem of the Drake Passage and Scotia Sea is scientifically substantiated. Measurements will be carried out by the interdepartmental...     

Studies on the egg, larval and juvenile development of Bostrichthys sinensis (Lacépède)

Artificial hatching and fry culture of Bostrichthys sinensis (Lacépède) has been successful under conditions of enclosed seawater circulation system in the Aquarium Lab, South China Sea Fish. Res. Inst, on the 13th of April, 1984. The development of each stage of the eggs, larvae and juveniles are described, and colour photographs of every development stage were taken. According to their physiological characteristics in each stage, necessary ecological conditions for the developments are preliminarily discussed.     

Notes on the presence of the brown mudfish (Neochanna apoda günther) on the west coast of the south Island of New Zealand

Two visits to the West Coast revealed that Neochanna apoda Giinther is present in six clearly defined types of habitat examined between Oparara and Whataroa.

The location of habitats varied from heavily forested country to open pakihi bog, between sea level and 200 m. A Neochanna apoda habitat was generally uninhabited by any other species of fish; occasionally short‐finned eels (Anguilla australis) and, once, banded kokopu (Galaxias fasciatus) were present. An association with freshwater crayfish (Paranephrops planifrons) was often noted.

Neochanna apoda was found in all stages of development from fry to adults over 150 mm in length, and all size ranges were present in some places.     

Physicochemical modeling of the behavior of microelements under the mixing of acid riverine water (the Yur’ev River) with seawater

By means of physicochemical modeling with the Selektor software package, models were created and calculated for acid riverine water (pH = 2.19), for seawater, and for the mixing of these types of waters. The Yur’ev River-Sea of Okhotsk system was assessed as an example. The physicochemical migration forms of microelements (aluminum, zinc, lead, iron, manganese, and silicon) and their behavior in the water-mixing zone were established. The formation of solid hydrogenous phases under the mixing of acid riverine waters with seawater was shown. By means of the MINTEQA2/PRODEFA2 software package, the influence of the sorption processes on the behavior of the elements considered in the mixing zone was revealed.     

Petrogeochemistry and Ore Mineralization of Sericite–Quartz Schists of the Southern Slope of the Kashevarov Bank (Sea of Okhotsk)

Oceanology - Data on the structure and chemical and mineral composition of sericite–quartz schists of the southern slope of the Kashevarov Bank of the Sea of Okhotsk are presented. The...     

Algorithm of the <Emphasis Type="Italic">k</Emphasis>–ω Turbulence Equations Solution for the Ocean General Circulation Model

The algorithm for splitting k–ω turbulence equations is used to parameterize viscosity and diffusion coefficients in the ocean general circulation model. The k–ω equations are split into stages describing the transport-diffusion and generation-dissipation of the turbulent kinetic energy and frequency function ω. At the generation-dissipation stage, the equations are solved analytically. Calculations of circulation in the North Atlantic–Arctic Ocean for 1948–2009 have been carried out. The experiments demonstrate an adequate reproduction of hydrophysical characteristics and high efficiency of the algorithm. It is shown that considering the climatic annual mean buoyancy frequency in the turbulence equations at the generation-dissipation stage is an important factor in improving the accuracy of simulated fields.     

Are the smallest fishing vessels the most sustainable?—trade-off analysis of sustainability attributes

This article discusses application of systems engineering principles and trade-off analysis of sustainability in the fishing fleet. Sustainability in the fishing fleet may be characterized by seven attributes measured by performance indicators. Evaluations show that the energy consumption is higher for the Norwegian ocean going fleet than the coastal fleet, whereas the opposite is the case for the number of fatalities. An important part of the systems engineering process is analysis and optimization of system alternatives. Thus, the main objective of the article is to investigate ranking of the sustainability attributes, which implies use of multi-attribute decision-making methods. The analytic hierarchy process was used to interview stakeholders to the fishing fleet about their preferences. The article concludes that if “accident risk” is weighted as the most important attribute, the smallest fishing vessels are not as sustainable as often claimed.     

Age and growth of filefish, <Emphasis Type="Italic">Thamnaconus modestus</Emphasis> (Günther, 1877) off the Jeju Island of Korea

The age and growth of filefish, Thamnaconus modestus (Günther 1877) in the southern waters of Korea were investigated. Samples were collected with commercial trawl catches during the period from May 2009 to December 2011. Of the 2,626 specimens collected, the sex ratio was not significantly different from 1:1 (P > 0.05). The total length ranged from 11.3 to 42.1 cm. The gonadosomatic index for both sexes was the highest in May to June, indicating that May to June is the main spawning period. The length of females at sexual maturity was 25.92 cm. The length-weight relationship of the filefish was TW = 0.0121TL^3.0536 (n = 1,692, r² = 0.9034, P < 0.001). The age of the sampled individuals was estimated by counting growth rings recorded on the 5^th vertebrae; ages ranged from 0 to 9 years. The filefish of the same age displayed a high individual variation in total length. Length-at-age data were fitted by using the Von Bertalanffy growth model. The estimated Von Bertalanffy growth parameters were L_∞ = 42.04 cm, k = 0.21 year^?1 and t₀ = ?1.56 for females, L_∞ = 41.20 cm, k = 0.18 year^?1 and t₀ = ?2.36 for males, and L_∞ = 43.16 cm, k = 0.17 year^?1 and t₀ = ?2.18 for the combination of both male and female. These data can be used as useful biological information for the future fishery management of filefish resources in Korean waters.