Annual cycle of nanophytoplankton in coastal waters of the Barents Sea

The seasonal dynamics of biomass and size structure of nanophytoplankton in Central Murman (off the southern coast of the Barents Sea) are described according to the results of six-year continuous observations. The pattern of the annual successional cycle indicates that the nanophytoplankton community as a structural unit of coastal pelagic algocenoses is a specific integrated ecological group of primary producers. The issue of a major contribution of nanoalgae to the total biomass and production of the autotrophic component of coastal ecosystems in Arctic seas is discussed.     

Production of planktonic crustaceans in the White Sea

This paper analyzes different methods for assessment of the production of marine organisms. The estimated values of annual production and ration of planktonic copepods of the White Sea are 5.0 × 10¹² and 2.2 × 10¹³ kcal, respectively. Comparison of the planktonic copepod ration with phytoplankton production shows that the energy demands of the copepod community are met by consumption of phytoplankton and, probably, also bacterioplankton and detritus.     

Annual survey of planktonic dinoflagellates and related cysts in the Gulf of Trieste (Northern Adriatic Sea)

Abstract

A survey of planktonic dinoflagellates and related cysts was carried out in the Gulf of Trieste throughout one year from April 1992 to March 1993. 113 taxa were recovered by the analysis of phytoplankton net samples. The most represented genera were Protoperidinium (34 species), Ceratium (24 species), Dinophysis (15 species), Gonyaulax (11 species) and Prorocentrum (8 species). A particular attention was given to potentially toxic species belonging to the genera Dinophysis, Alexandrium and Prorocentrum. The highest number of species (67 species) was recorded in July, and the lowest one (18 species) in February.

33 cyst morphotypes were recorded by the analysis of sediment samples. The most represented genera were Protoperidinium (8 morphotypes), Scrippsiella (3 morphotypes), Gonyaulax (3 morphotypes) and Alexandrium (2 morphotypes); the cysts most frequently found were those of Conyaulax polyedra and Alexandrium pseudogonyaulax.     

Distribution of the under-ice mesozooplankton in the Kara Sea in February 2002

Mesozooplankton distribution was investigated under the sea ice in the Kara Sea at five stations in February of 2002 by Juday net hauls. Copepods dominated the mesozooplankton community, accounting for 46–88% of the total abundance and 68–99% of the biomass. Oithona similis was the most abundant species in Yenisei Bay, being present with all age stages (including egg-carrying females). For the first time, Oithona atlantica (CIII–CV copepodites, females and males) were found in the southeastern Kara Sea. In the southern part, Copepoda nauplii prevailed in terms of total abundance while the mesozooplankton in the northwestern part was entirely dominated by older stages of Pseudocalanus minutus. The mesozooplankton structure appears to be determined by available food resources and increased water temperature due to a strong influence of warm Atlantic waters.     

Annotated list of fish-like vertebrates and fish of the Kara Sea

Based on literature and new actual data from 2007–2012, a revised list of fish species inhabiting the Kara Sea is given. The modern ichthyofauna of the Kara Sea comprises 77 species of marine, anadromous, and freshwater fish from 24 families of 14 orders. For the first time, 12 fish species are indicated for this region.     

Spatial patterns of planktonic microcrustaceans in a small shallow lake

The horizontal distribution of planktonic microcrustaceans was studied at two different spatial scales in a small shallow lake (Créteil Lake, Paris suburb, France) during the summer.At all scales of sampling, the distribution was patchy. However, the variations between sampling units were smallest when considering the smallest sampling grid (30 sampling units in a 0.5 ha area). Positive correlations between densities of most taxa were observed at this scale, indicating that a common set of factors could influence zooplankton patchiness.Physical factors, such as wind-induced currents, strongly influenced the lakewide distribution of zooplankton (43 sampling units in a 42 ha area). The horizontal pattern of each taxon appeared to be linked to its ability to form vertical aggregations. Moreover, offshore-nearshore differences in fecundity of several taxa suggest the action of biotic factors in the horizontal distribution of zooplankton. A higher predation risk in the littoral neighbourhood seems to be the more probable proximate - or ultimate - factor which could explain this pattern.In this small and shallow lake, most factors that can affect distribution of zooplankton are temporally variable and unpredictable. In the absence of automatic and efficient measuring techniques, the realisation of a small number of integrated samples at the level of the whole ecosystem could be a simple and suitable solution to obtain statistically reliable data on zooplankton demography.     

Species composition of ichthyofauna of Baidaratskaya Bay of the Kara Sea

An inventory of the fish species composition of the community from Baidaratskaya Bay in the Kara Sea was performed. On the basis of published data and the results of our own studies, the dynamics of changes in the species composition of marine ichthyocenosis of Baidaratskaya Bay from 1932 to 2007 was analyzed. Differences in qualitative (occurrence) and quantitative (proportion in catches) characteristics are shown.     

About New Findings of the Greenland Shark Somniosus microcephalus in the Kara Sea

Journal of Ichthyology - Visual observation data of the Greenland shark Somniosus microcephalus in August–September 2017 in the Kara Sea specifying the species range in this Arctic region are...     

The seasonal periodicity of planktonic diatoms in a shallow eutrophic lake

The seasonal periodicity of four species of planktonic diatoms in a small eutrophic lake in the Shropshire-Cheshire Plain, England, is examined. Diatoms typically dominate the spring increase; a second period of growth follows in the summer months. The growth phases are considered in relation to environmental factors in the mere. Of these, light levels appear to be critical in determining the onset of growth and the size of the population maxima, whilst stratification and turbulence play a leading role in the vertical distribution of the algae, and hence, of the growth conditions to which they are exposed. The thermocline is believed to provide a reservoir of diatoms in summer, maintaining them in a position where they are able to gain maximum advantage from increased wind-induced turbulence. Relative specific differences in growth requirements and in behaviour under varying physical conditions are important in determining which species dominate. Dominance may be modified by the effect of attacks by fungal parasites. It is also shown that, generally, nutrients are present in relative abundance, and only rarely does their availability become a limiting factor. Tt is concluded that diatom growth in this lake is typically subject to physical rather than chemical control.     

Distribution of membrane lipids of planktonic Crenarchaeota in the Arabian Sea

Intact core tetraether membrane lipids of marine planktonic Crenarchaeota were quantified in water column-suspended particulate matter obtained from four depth intervals ( approximately 70, 500, 1,000 and 1,500 m) at seven stations in the northwestern Arabian Sea to investigate the distribution of the organisms at various depths. Maximum concentrations generally occurred at 500 m, near the top of the oxygen minimum zone, and the concentrations at this depth were, in most cases, slightly higher than those in surface waters. In contrast, lipids derived from eukaryotes (cholesterol) and from eukaryotes and bacteria (fatty acids) were at their highest concentrations in surface waters. This indicates that these crenarchaeotes are not restricted to the photic zone of the ocean, which is consistent with the results of recent molecular biological studies. Since the Arabian Sea has a strong oxygen minimum zone between 100 and 1,000 m, with minimum oxygen levels of <1 microM, the abundance of crenarchaeotal membrane lipids at 500 m suggests that planktonic Crenarchaeota are probably facultative anaerobes. The cell numbers we calculated from the concentrations of membrane lipids are similar to those reported for the Central Pacific Ocean, supporting the recent estimation of M. B. Karner, E. F. DeLong, and D. M. Karl ( Nature 409:507-510, 2001) that the world's oceans contain ca. 10(28) cells of planktonic Crenarchaeota.     

Pelagic larvae of bivalve mollusks and polychaetes in winter plankton of the Kara Sea

Quantitative zooplankton samples were obtained by vertical tows with a Juday plankton net, in the southern Kara Sea, from November 28 to December 11, 2005 (by an expedition of the Murmansk Marine Biological Institute KSC RAS aboard the nuclear ice-breaker “Soviet Union”). The most abundant meroplankton forms were juveniles of Bivalvia and larvae of Polychaeta (the maximum abundances were 106.2 ind/m³ and 7.5 ind/m³, respectively). The results are discussed in relation to changes in the thermal regime of the Arctic Ocean observed during the recent decades.     

Extraordinary prolongation of the life cycle in a freshwater planktonic copepod

The limnetic copepod Cyclops scutifer Sars shows an extraordinarily prolonged life cycle in a temperate lake near Oslo, Norway. Developmental sequences become one, two, and three years old, and there are circumstantial evidence of a four year old fraction. Prolongation of the cycle is mainly caused by two consecutive periods of diapause, the first as small copepodids during the second winter, the other as large copepodids during the third winter. There is a marked concentration of diapausing individuals in a small area of the bottom at the deepest part of the lake. There is evidence that this concentration is caused by a horizontal migration to areas with optimal oxygen conditions. The adaptive value of a prolongation of the life cycle is assumed to be an increase in the reproductive potential caused by a spreading out of the reproductive period by three year classes succeeding each other throughout the summer.     

The biogeochemical cycle of methane in the coastal zone and littoral of the Kandalaksha Bay of the White Sea

Microbiological and biogeochemical investigations of the processes of methane production (MP) and methane oxidation (MO) in the coastal waters and littoral of the Kandalaksha Bay of the White Sea were carried out. The studies were conducted in the coastal zones and in the water areas of the Kandalaksha Preserve, Moscow University White Sea Biological Station, and Zoological Institute (RAS) Biological Station in August, 1999, 2000, and 2001 and in March, 2001. The rate of CO2 assimilation in the shallow and littoral sediments was 35-27800 microg C/(dm3 day) in summer and 32.8-88.9 microg C/(dm3 day) in winter. The maximal rates of MP were observed in the littoral sediments in the zone of macrophyte decomposition, in local depressions, and in the estuary of a freshwater creak (up to 113 microl/(dm3 day)). The maximal level of MO was observed in the shallow estuarine sediments (up to 2450 microl/(dm3 day)). During the winter season, at the temperature of -0.5 to 0.5 degrees C, the MP rate in the littoral sediments was 0.02-0.3 microl/(dm3 day), while MO rate was 0.06-0.7 microl/(dm3 day). The isotopic data obtained indicate that the C(org) of the mats and of the upper sediment layers is enriched with the heavy 13C isotope by 1-4 per thousand as compared to the C(org) of the suspension, comprised on 33.5-34.3% of phytoplankton. A striking difference was found between the levels of methane emission by the typical littoral microlanscapes. In fine sediments, the average emission was 675 microl CH4/(m2 day), in the stormy discharge stretch sediments it was 1670 microl CH4/(m2 day), and under the stones and in silted pits, 1370 microl CH4/(m2 day). The calculation performed with consideration of the microlandscape areas with a high production allowed the CH4 production of 1 km2 of the littoral to be estimated as 192-300 1 CH4/(km2 day).     

Phosphorus kinetics of planktonic and benthic assemblages in a shallow subtropical lake

1. Phosphate uptake kinetics and uptake rates were calculated for planktonic (phytoplankton and bacterioplankton) and benthic (epiphyton and epipelon) assemblages in a large, shallow, subtropical lake. Samples were taken bimonthly over the period of 1 year at three different sites to examine spatial and temporal variability in these processes. 2. Two of the sites, located at the edge of the littoral zone next to the open water (ecotone sites), had low irradiance at the sediment surface and high total phosphorus (TP) concentration (annual mean TP = 112 μg L^–1). The third site, located in the littoral marsh zone, had high irradiance at the sediment surface and low TP concentration (annual mean TP = 7 μg L^–1). 3. Based on ³²P-PO₄ turnover time, P availability varied temporally and spatially. At the two high TP ecotone sites, P concentration was lowest in July and August. At the low TP marsh site, P limited algal production throughout the year. 4. The quotient of maximum uptake rate to half saturation constant (V_m/K_s) in the plankton increased by over two orders of magnitude during the P-limited (summer) period at the two ecotone sites, suggesting that plankton used the scarce phosphorus more efficiently. The specific uptake rate of plankton was significantly greater than that of periphyton at all sites, suggesting that the plankton were more efficient than periphyton at taking up phosphate. 5. Periphyton biomass, as well as absolute and percentage P uptake rate, was greater at the marsh site than at the ecotone sites, despite the lower P concentrations in the marsh. This was probably a result of rapid nutrient cycling, combined with high light availability in the marsh.     

The Quantitative Features of the Phytoplankton Community in the Southwestern Kara Sea in the Summer of 2015

This paper presents results from a study of phytoplankton communities that was performed in 2015 at 213 stations in the southwestern part of the Kara Sea. The values of primary production at most stations exceeded the estimates obtained in 1993 by several times. A continued increase in productivity indices and no outbreaks of phytoplankton were consistent with long-term satellite monitoring data. At the same time, grouping of stations showed a highly mosaic structure of the spatial distribution of phytoplankton and a significant range of variation of most of the studied parameters.     

Distribution of recent planktonic foraminifera in surface sediments of the Mediterranean Sea

The Mediterranean Sea is a partillay isolated ocean where excess evaporation over precipitation results in large east to west gradients in temperature and salinity. Recent planktonic foraminiferal distributions have been examined in 66 surface sediment samples from the Mediterranean Sea. In addition to mapping the frequency distribution of 16 species, the faunal data has been subjected to cluster analysis, factor analysis and species diversity analysis. The clustering of species yields assemblages that are clearly temperature related. A warm assemblage contains both tropical and subtropical elements, while the cool assemblage can be subdivided into cool-subtropical, transitional and polar-subpolar groupings. Factor analysis is used to delineate the geographic distribution of four faunal assemblages. Factor 1 is a tropical-subtropical assemblage dominated by Globigerinoiden ruber. It has its highest values in the warmer eastern basin. Transitional species (Globorotalia inflata and Globigerina bulloides) dominate factor 2 with highest values occurring in the cooler western basin. Factor 3 reflects the distribution of Neogloboquadrina dutertrei and is considered to be salinity dependent. Subpolar species dominate factor 4 (Neoglobuquadrina pachyderma and G. bulloides), with highest values occurring in the northern part of the western basin where cold bottom water is presently being formed. The Shannon-Weiner index of species diversity shows that high diversity exists over much of the western basin and immediately east of the Strait of Sicily. This region is marked by equitable environmental conditions and relatively even distribution of individuals among the species. Conversely, in areas where temperature and salinity values are more extreme, diversity values are lower and the assemblages are dominated by one or two species.