The structure and long-term dynamics of the communities of Arctica islandica (Bivalavia) in Rugozerskaya Guba of the White Sea

The age structure of a dense settlement of Arctica islandica (Bivalvia) near Vysokii Island (Rugozerskaya Guba (bay)) of the White Sea is described. The data collected by trawling in 2003, 2006–2007 and grab sampling in 2009–2011 are summarized. The A. islandica community in the Rugozerskaya Guba was first described in 1953–1959, but to date, no reliable quantitative estimates have been obtained and the community’s size structure was not studied. The size structure of this community was stable over the last eight years; the main part of the community was represented by individuals with a body weight of 3–10 g. It was revealed that the distribution of different A. islandica classes depends on the depth. The majority of the largest individuals were found in the shallowest parts of the study area (9–11 m); middle-size individuals were registered at depths of 9–14 m; and the smallest ones, at depths of 12–17 m.     

Vertical distributions of zooplankton across the Almeria-Oran frontal zone (Mediterranean Sea)

The vertical distribution of zooplankton in the upper 700 mof the water column was investigated across the Almeria–Oranfront (Alboran Sea) during winter 1997/98 (Almofront 2 cruise).Eight sites corresponding to three hydrodynamic structures (theAtlantic jet, an anticyclonic gyre and the surrounding Mediterraneanwaters) were explored, by day and at night, using multiple-netsampling. Results are presented for the major species of copepods(>500 µm), macroplankton and microplankton. Speciesinhabiting the surface layer or occupying it at night extendeddeeper in the gyre. On the other hand, mesopelagic species (e.g.Pleuromamma borealis, Pleuromamma abdominalis, Euphausia krohniand Cyclothone braueri) were found to live deeper, at leastby day for the migrants, in the Mediterranean waters comparedwith the two other structures. These changes in preferentialdepths across the front are discussed in relation to environmentalfeatures, such as light level, abundance of food and mixed layerdepth. This study also documented the vertical distributionof some overwintering copepod species (Calanus helgolandicus,Eucalanus hyalinus and Eucalanus monachus).     

Spatial Distribution of Picophytoplankton in the White Sea in the Beginning of Summer

Biomass of photosynthetic picoplankton (B_pic), its contribution to the total phytoplankton biomass (B_pic%), chlorophyll a concentration (Chl), and associated hydrophysical characteristics of the water masses in the White Sea were estimated in June 2015 at 47 stations located in the open parts and in the inlets of the Onega and Kandalaksha Bays and in the western part of the Basin. Spatial variability of mean values of B_pic in the photic layer (0.01–1.91 mg C/m³) was preconditioned by sub- and mesoscale heterogeneity of the hydrological conditions. The values of B_pic were higher near the frontal zones than those in the water masses characterized by quasi-homogeneous distribution of the thermohaline characteristics. The relative contribution of B_pic did not exceed 1% at half of the stations and varied from 1 to 8% for the rest of the studied water area. The value of B_pic% reached 40.5% in the Basin and did not exceed 2% during the phytoplankton bloom in Knyazhaya Inlet (Chl > 3 mg/m³) accompanied by the dominance of Skeletonema costatum sensu lato.     

On the spatial distribution of larval White Sea herring (Clupea pallasii marisalbi) in estuaries of Kandalaksha Bay of the White Sea

According to results of layer-by-layer fishings performed in June 2006 in the Knyazhaya and Kolvitsa estuaries, data on the spatial distribution of larval White Sea herring Clupea pallasi marisalbi during the tidal cycle are provided. In these estuaries, the presence of a system of counter-currents that form a two-layer circulation was revealed. The surface current that is directed to the bay is traced to a depth of 2–4 m; below this, a current directed to the tail part of estuaries was recorded. It was established that larval herrings perform vertical migrations, as a result of which they can be freely drifted from inlets with a surface current and penetrate back from the adjoining water areas with a counter-current, which promotes a decrease in their drift in the open part of Kandalaksha Bay beyond shallow zones of juvenile feeding.     

Larvae of Barnacles (Cirripedia: Thoracica) in the White Sea Plankton

The barnacle fauna of the White Sea is briefly described. The morphology of barnacle larvae in this water body is comparatively analyzed. The characters important for the larvae identification are given particular attention. A classification key for the naupliar and cyprid larvae of White Sea barnacles is proposed.     

Basin scale distribution of zooplankton in the Ligurian Sea (north-western Mediterranean) in late autumn

Mesozooplankton biomass and abundance were evaluated in epipelagic waters at 59 stations covering the Italian sector of the Ligurian Sea (north-western Mediterranean) in December 1990. This region is characterised by a cyclonic circulation which encloses a central divergence zone and is associated with a main thermohaline front offshore the western Ligurian coast. At the end of autumn, mesozooplankton biomass (range: 0.80–4.24 mg DW m⁻³) and the abundance (range: 83.8–932 ind. m⁻³) were lower in the divergence zone. On the contrary, in the Ligurian frontal zone at the periphery of the divergence and on the eastern continental shelf the greatest values of biomass and abundance were recorded. Copepods and appendicularians dominated the mesozooplankton community, the main taxa being the copepods Clausocalanus spp. (46% of total zooplankton) and Oithona spp. (15%) and the appendicularian Fritillaria spp. (12%). Three hydrological sub-regions, i.e. the divergence, the eastern continental shelf and the periphery of the divergence, were characterised by different zooplankton communities and characteristic species. Environmental differences between the three zones were mainly related to changes in bottom topography, sea surface temperatures and quantity of particulate organic matter. Vertical mesozooplankton abundance and taxa distribution from the surface to 1,900 m depth were also examined in one station. The results showed that the bulk of the community was concentrated in the upper 200 m, small copepods being dominant particularly in the upper 50 m. The copepod community was more diversified in sub-superficial waters, with a maximum observed in the 200–400 m layer. The distributions of main zooplankton taxa described in epipelagic waters in the eastern Ligurian Sea in autumn were compared with their distribution at surface in the north-western Mediterranean obtained by sampling performed with the Continuous Plankton Recorder in 1997–1999. The analysis of the zooplankton community in CPR samples confirms the dominance of small copepods (Paracalanus spp., Clausocalanus spp., Oithona spp.) and appendicularians in the north-western Mediterranean in late autumn-winter and shows that their distribution is mainly related to the main mesoscale hydrographic features characterising this basin. Guest editors: S. Souissi & G. A. Boxshall Copepoda in the Mediterranean: Papers from the 9th International Conference on Copepoda, Hammamet, Tunisia     

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.     

Aspects of Scotia Sea zooplankton

Information on small scale distributions of three species of Antarctic zooplankton is reviewed. Aggregations of the euphausiid Euphausia superba , the tunicate Salpa thompsoni , and the amphipod Parathemisto gaudichaudii are compared, and the manner in which such aggregations mav arise is discussed. A possible relationship between swarming and feeding activity in E. superba is suggested in which krill are thought to be dispersed whilst feeding but that on repletion they swarm. It is thought that this may account for this species' irregular spatial distribution as recorded bv previous expeditions. A further consequence of this theory is that during the Winter swarming will be minimal.     

Interannual fluctuations of zooplankton in the Kola Section (Barents Sea) in relation to environmental factors

An analysis of interannual variations of zooplankton composition and biomass in the Kola Section (Barents Sea) in summer was conducted based on the data of 2003–2010. Maximum values of the mean water temperature and temperature anomaly were found in 2006 and in 2007. Variations in the zooplankton composition and relative biomass of common species were studied in relation to climatic factors. It is discussed which parameters may be used as indicators of climatic changes in the southern Barents Sea.     

Carbonate system of the Razdolnaya River estuary (Amur Bay, Sea of Japan)

Two methods, the total alkalinity measurement by Bruevich [4] and pH measurement in a cell without liquid junction [11], were suggested for study of the carbonate system of estuaries. Based on new measurements, the empirical equations were obtained for the first and second seawater concentration constants of carbonic acid for the ranges of salinity 0–40 and temperatures 0–30°C. Applying the constants and above methods, we studied the carbonate system of the Razdolnaya River-Amur Bay estuary in two expeditions of July 2001, the first in a period of average water level and the second after a flood. In the latter survey, extremely low values (60 µatm) of pCO₂ (carbon dioxide partial pressure) were recorded in the seaward part of the estuary and extremely high ( 13 300 µatm) were noted in the river. High pCO₂ in the surface water was caused by intense bacterial activity, and low levels were caused by phytoplankton bloom. The nonconservative behavior of the total alkalinity and dissolved inorganic carbon was revealed in the estuary. Based on the data of the carbonate system, the production/destruction of organic matter was assessed.Original Russian Text Copyright © 2005 by Biologiya Morya, Tishchenko, Wong, Volkova, Gramm-Osipov, Johnson, Dudarev, Zvalinskii, Nedashkovskii, Pavlova, Chichkin, Sagalaev, Shevtsova, Shkirnikova.     

The zooplankton community in bays of Toulon area (northwest Mediterranean Sea,France)

The abundance and the diversity of the zooplankton community were studied during an annual cycle in three shallow bays differently affected by anthropogenic inputs of Toulon area in the northwest Mediterranean Sea (France). Environmental variables of water quality were also considered. Our results discriminated Little Bay from the La Garonne and Niel Bay. Little Bay, heavely perturbed by anthropogenic inputs, had high chlorophyll a levels, abundant zooplankton, a low diversity index, a high dominance Index and a single dominant species (Oithona nana). La Garonne Bay and Niel Bay, much less polluted, had low chlorophyll a levels, low zooplankton abundance, low dominance Index and high diversity index and eveness. In addition, O. nana occurred rarely in the latter bays. Zooplankton successions were also different between Little Bay and the two other bays.     

Ecological zonation of the hyperhaline estuary of the Casamance River (Senegal): Foraminifera,zooplankton and abiotic variables

Due to a long-lasting drought afflicting the Sahel, the Casamance River has been transformed into a hyperhaline estuary, with salinities up to 170% at a distance of 210 km from the sea. Foraminifera and zooplankton populations both show a marked decrease in the number of species in increasingly confined water, the distribution of species being closely related to the evolution of abiotic variables. Our three-prong study allowed us to identify six zones, upwards from the sea. The uppermost ones are characterized by drastic conditions which considerably reduce the number of species. Therefore, the populations of Foraminifera, zooplankton and even fish become oligo or mono specific. The Casamance River appears to fit quite well into the general rules concerning hyperhaline environments. However, it shows some peculiar features which are: the large dimensions of the hyperhaline estuary (over 230 km long and over 5 km wide in the lower course); peak salinities among the highest known for a permanently open estuary (up to 170%); and water remaining trapped inside the river for several years.     

Long-term dynamics of zooplankton in the southeastern Baltic Sea

Long-term research in the Baltic Sea revealed the basic trends of zooplankton community variations depending on oceanographic processes. Alternation of the periods of increase and decrease in salinity of the Baltic Sea against the background of climate changes (temperature increase) and eutrophication affect the state of the entire Baltic ecosystem, including zooplankton. For these periods, the dynamics of zooplankton in the Baltic Sea were analyzed based on literature data and results of regular research in the southeastern Baltic Sea during 1998–2007. The changes in the hydrological situation were accompanied by significant changes in the zooplankton community. In the 1990s–2000s, the abundance and biomass of brackish-water and thermophilous species primarily of Cladocera and Copepoda increased markedly. The role of the previously dominant marine copepod Pseudocalanus elongatus decreased due to salinity reduction in the deep-water part of the Baltic Sea. Maximum development of zooplankton occurred in years of the greatest warming-up of the water (2001, 2005–2007) against the background of a general positive trend of zooplankton abundance in the last decade.