Distribution of zooplankton in the estuary of Keretskaya Guba (White Sea)

The horizontal heterogeneity of common zooplankton species in the Keretskaya Guba tidal estuary in the White Sea was studied. Based on an analysis of a series of simultaneously taken samples and the dispersion index, I _w = σ²/[`(m)]\bar{m} (where σ<sup>2</sup> is dispersion and [`(m)]\bar{m} is average population number), the existence of two and more levels of aggregation in most of the studied zooplankton species was found. The formation of patches of 1–20 m was most likely determined by biological causes, while patches some hundreds of meters long were formed due to the hydrodynamic conditions of the area.     

The Mitochondrial Genome of Arctica islandica; Phylogeny and Variation

Arctica islandica is known as the longest-lived non-colonial metazoan species on earth and is therefore increasingly being investigated as a new model in aging research. As the mitochondrial genome is associated with the process of aging in many species and bivalves are known to possess a peculiar mechanism of mitochondrial genome inheritance including doubly uniparental inheritance (DUI), we aimed to assess the genomic variability of the A. islandica mitochondrial DNA (mtDNA). We sequenced the complete mitochondrial genomes of A. islandica specimens from three different sites in the Western Palaearctic (Iceland, North Sea, Baltic Sea). We found the A. islandica mtDNA to fall within the normal size range (18 kb) and exhibit similar coding capacity as other animal mtDNAs. The concatenated protein sequences of all currently known Veneroidea mtDNAs were used to robustly place A. islandica in a phylogenetic framework. Analysis of the observed single nucleotide polymorphism (SNP) patterns on further specimen revealed two prevailing haplotypes. Populations in the Baltic and the North Sea are very homogenous, whereas the Icelandic population, from which exceptionally old individuals have been collected, is the most diverse one. Homogeneity in Baltic and North Sea populations point to either stronger environmental constraints or more recent colonization of the habitat. Our analysis lays the foundation for further studies on A. islandica population structures, age research with this organism, and for phylogenetic studies. Accessions for the mitochondrial genome sequences: KC197241 Iceland; KF363951 Baltic Sea; KF363952 North Sea; KF465708 to KF465758 individual amplified regions from different speciemen     

Imperceptible senescence: ageing in the ocean quahog Arctica islandica

The ocean quahog Arctica islandica is the longest-lived of all bivalve and molluscan species on earth. Animals close to 400 years are common and reported maximum live span around Iceland is close to 400 years. High and stable antioxidant capacities are a possible strategy to slow senescence and extend lifespan and this study has investigated several antioxidant parameters and a mitochondrial marker enzyme in a lifetime range spanning from 4-200 years in the Iceland quahog. In gill and mantle tissues of 4-192 year old A. islandica, catalase, citrate synthase activity and glutathione concentration declined rapidly within the first 25 years, covering the transitional phase of rapid somatic growth and sexual maturation to the outgrown mature stages (approximately 32 years). Thereafter all three parameters kept rather stable levels for > 150 years. In contrast, superoxide dismutase activities maintained high levels throughout life time. These findings support the 'Free Radical-Rate of Living theory', antioxidant capacities of A. islandica are extraordinarily high and thus may explain the species long life span.     

Mathematical Investigations into the Longevity of the Ocean Quahog Arctica islandica (Mollusca: Bivalvia)

Annual internal growth banding of Arctica islandica has shown that the species has a surprising longevity of up to 149 years as stated by THOMPSON , JONES and DREIBELBIS (1980). The authors have compiled 100 values of valve height against age as reproduced in Figure 1. Visually gained growth curves have been added for single specimens that leave some doubt as to the existence of an inflexion point. In this paper a cross-sectional evaluation of growth behaviour is carried out with nine funtions using nonlinear regressions. Five growth functions yield almost equally good results with a final valve height just below 100 mm. An inflexion point is either present in early youth or lacking altogether, depending on the growth function used.     

Amino acid composition of aragonitic concholin in the shell of Arctica islandica

Haugen, J. E. & Sejrup, H. P. 1990 04 15: Amino acid composition of aragonitic conchiolin in the shell of Arctica islandica. Lethaia , Vol. 23, pp. 133–141. Oslo. ISSN 0024–1164.
The distribution of amino acids within the two aragonitic shell layers of modern specimens of the mollusc Arctica islandica (Linné) has been studied in detail. The mean total hydrolyzed amino acid content was 19 nmol*mg in the inner layer and 15 nmol/mg in the outer layer. No significant difference in amino acid composition could be found between the two layers. The layers contained minor amounts of free amino acids which made up 0.3–0.7% of the total hydrolyzed amino acid content. The composition of the free amino acid fraction was very similar in each of the two layers, but differed somewhat from the total hydrolyzed fraction. The total hydrolyzed fraction was dominated by aspartic acid, glycine. alanine and glutamic acid, which together made up 62% of the total amount of amino acids, whereas the free fraction was dominated by Asp. Ser, Gly and Tyr. Amino acid content and composition within a single layer showed little variation from umbo to the ventral margin. The amino acid composition is in accordance with previously reported data on similar mineral structures which support the theory of structure specific rather than species specific amino acid composition. * Arctica islandica. amino acids. shell structure .     

Long-term dynamics of common species of polychaetes in fouling communities of the White Sea

Based on the data from long-term observations on the development of fouling communities of mussel culture farms in the White Sea, an analysis of dynamics of population density of common polychaete species was carried out. The expansion of the polychaete Lepidonotus squamatus for the past 9 years was recorded. Cyclic variations of population density were revealed practically in all studied species. The duration of the period of these cycles varied from 7–8 years (L. squamatus and Amphitrite cirrata), 11–14 years (Nereis pelagica, Harmothoe imbricata, Eulalia viridis, Neoamphitrite figulus) and even about 20 years (Nereimyra punctata and Capitella capitata). Observable periodic variations in the abundance of polychaetes apparently were not related to long-term fluctuations of water temperature.     

The extreme longevity of Arctica islandica is associated with increased peroxidation resistance in mitochondrial membranes

The deleterious reactive carbonyls released upon oxidation of polyunsaturated fatty acids in biological membranes are believed to foster cellular aging. Comparative studies in mammals and birds have shown that the susceptibility to peroxidation of membrane lipids peroxidation index (PI) is negatively correlated with longevity. Long‐living marine molluscs are increasingly studied as longevity models, and the presence of different types of lipids in the membranes of these organisms raises questions on the existence of a PI–longevity relationship. We address this question by comparing the longest living metazoan species, the mud clam Arctica islandica (maximum reported longevity = 507 year) to four other sympatric bivalve molluscs greatly differing in longevity (28, 37, 92, and 106 year). We contrasted the acyl and alkenyl chain composition of phospholipids from the mitochondrial membranes of these species. The analysis was reproduced in parallel for a mix of other cell membranes to investigate whether a different PI–longevity relationship would be found. The mitochondrial membrane PI was found to have an exponential decrease with increasing longevity among species and is significantly lower for A. islandica. The PI of other cell membranes showed a linear decrease with increasing longevity among species and was also significantly lower for A. islandica. These results clearly demonstrate that the PI also decreases with increasing longevity in marine bivalves and that it decreases faster in the mitochondrial membrane than in other membranes in general. Furthermore, the particularly low PI values for A. islandica can partly explain this species’ extreme longevity.     

Metabolic and physiological responses in tissues of the long-lived bivalve Arctica islandica to oxygen deficiency

In Arctica islandica, a long lifespan is associated with low metabolic activity, and with a pronounced tolerance to low environmental oxygen. In order to study metabolic and physiological responses to low oxygen conditions vs. no oxygen in mantle, gill, adductor muscle and hemocytes of the ocean quahog, specimens from the German Bight were maintained for 3.5 days under normoxia (21 kPa=controls), hypoxia (2 kPa) or anoxia (0 kPa). Tissue levels of anaerobic metabolites octopine, lactate and succinate as well as specific activities of octopine dehydrogenase (ODH) and lactate dehydrogenase (LDH) were unaffected by hypoxic incubation, suggesting that the metabolism of A. islandica remains fully aerobic down to environmental oxygen levels of 2 kPa. PO(2)-dependent respiration rates of isolated gills indicated the onset of metabolic rate depression (MRD) below 5 kPa in A. islandica, while anaerobiosis was switched on in bivalve tissues only at anoxia. Tissue-specific levels of glutathione (GSH), a scavenger of reactive oxygen species (ROS), indicate no anticipatory antioxidant response takes place under experimental hypoxia and anoxia exposure. Highest specific ODH activity and a mean ODH/LDH ratio of 95 in the adductor muscle contrasted with maximal specific LDH activity and a mean ODH/LDH ratio of 0.3 in hemocytes. These differences in anaerobic enzyme activity patterns indicate that LDH and ODH play specific roles in different tissues of A. islandica which are likely to economize metabolism during anoxia and reoxygenation.     

Regular and irregular events in fouling communities in the White Sea

Patterns of long-term changes in fouling communities developing on artificial substrates in the White Sea are reviewed. The most significant shifts occurring in these communities are caused by biological successions that can last for several decades. Terminal stages of succession are the communities of a mussel Mytilus edulis or a solitary ascidian Styela rustica which can periodically replace one another within a narrow range of depths: from 1–1.5 to 5 m. Sporadic local invasion of a sponge Halichondria panicea can transiently modify the composition and performance of fouling communities. Sudden invasion of species that are not a typical component of fouling communities (infaunal polychaetes and molluscs, crabs) is not rare phenomenon but these organisms do not play a significant role there. Representatives of the associated polychaete fauna in fouling communities show long-term cyclic fluctuations in their abundances. Duration of these cycles is 7–8, 11–14, or 20 years.     

The cycle of mussels: long-term dynamics of mussel beds on intertidal soft bottoms at the White Sea

Dense blue mussel assemblages are unstable, their structure changing from year to year. Three types of models can be used to describe this instability: (1) “exogenous” model based on regional temperature fluctuations, (2) “endogenous” deterministic model associated with negative impact of adult mussels on juveniles and (3) “density-linked stochasticity” model based on positive feedbacks resulting in overcrowding and destabilizing the settlement. We compared predictions deduced from these models with a time series based on the results of long-term (18 years) monitoring of abundance and demographic structure of three mussel beds at the White Sea. Most of our findings agreed well with the predictions deduced from the endogenous model. In particular, (1) long-term changes in mussel abundance and demographic structure were strictly cyclic, with non-matching periods (5–9 years) at different sites; (2) stages with the dominance of old mussels alternated with those where juveniles dominated and (3) some signals of delayed density dependence were revealed. However, the time series also contained elements of long-term trends, which may testify to the involvement of some exogenous factors (probably long-term climate changes).     

The dynamics of the abundance, age, and sex structure of the Solovetsky reproductive gathering of the Beluga whale Delphinapterus leucas (Onega Bay, White Sea)

Based on the data from long-term research in 1999?C2009 we studied the population dynamics of Beluga whales in the Solovetsky reproductive gathering (RG) in the White Sea. This aggregation of Beluga whales is formed each year in the second half of May after the break-up of fast ice and persists to September inclusive. The aggregation numbers about 100 individuals from visual observations, with long-term variations of 20?C30 individuals. The percentage of whales of different age groups also varied in the gathering depending on year, but typically one half was formed by mature animals and the other half consisted of immature whales and yearlings. There are two pronounced peaks in numbers for the summer season in the Solovetsky Beluga RG. The number of Belugas increased with the appearance of males and females that were ready to breed and females that were ready to bear calves. The daily dynamics of Belugas in the gathering largely depended on the time of day and tidal regime. In the summer season, the state of the sea and human impacts were key factors in number fluctuations of the Belugas of the Solovetsky RG. The revealed negative correlation of the long-term population of Belugas in the gathering on air temperature is considered as a special instance of general laws of the migration activities of Beluga whales in the White Sea.     

亚热带山地森林珍稀植物群落的结构与动态

为探讨亚热带山地常绿落叶阔叶混交林中珍稀植物群落的性质和特征,调查了长江三峡大老岭地区６类珍稀树种占优势的森林群落,分析它们植物区系与物种多样性、群落结构、种间关系及其空间格局、珍稀树种的种群结构。结果表明：①这些珍稀植物群落的区系构成中,东亚、东亚－北美和中国特有成份的比例更高;②群落内物种非常丰富,乔木层和草本层多样性尤高;③各珍稀植物群落的生活型谱相似,却与亚热带常绿阔叶林和退化次生的混交林     

Sea ice microbial communities (SIMCO)

Summary Sea ice microbial communities (SIMCO) grow luxuriantly within several microhabitats of sea ice, indicating that the microorganisms comprising these communities are well adapted to the physicochemical gradients which characterize sea ice. We used SIMCO obtained from the bottom of congelation ice in McMurdo Sound, Antarctica, to test the hypothesis that low temperature limits microbial productivity in polar oceans and also to investigate the effect of salinity on rates of autotrophic and heterotrophic metablism. Substantial rates of carbon fixation, incorporation of thymidine, and uptake of glutamate occurred at the in situ temperatures of-1.9°C, with maximum rates at temperatures considerably warmer but below 15°C. Microalgae and bacteria of SIMCO are thus indicated to be psychrophiles. The relative rates of autotrophic and heterotrophic microbial growth (based on rates of fixation of ¹⁴CO₂ by microalgae and incorporation of ³H-thymidine by bacteria, respectively) were similar and overlapped from 4° and 7°C. These data suggest that a recent hypothesis proposing the uncoupling of primary production and bacterial production in cold water, due to differential growth of phytoplankton and bacterioplankton at low temperatures, is refuted with respect to SIMCO. Maximum rates of carbon fixation by autotrophs of SIMCO occurred at salinities which characterized the ice from which the SIMCO were collected. In contrast, heterotrophs of SIMCO exhibited a more stenohaline response to variable salinity, with maximum incorporation of thymidine and uridine from 20 to 30. Adaptations by autotrophs and heterotrophs of SIMCO that permit substantial metabolism and growth at very low temperatures and variable salinities are significant when considering production and trophodynamics in polar oceans. Actively growing microorganisms in these unique communities contribute to overall production in polar oceans, provide carbon for food webs associated with sea ice, and upon release from melting ice may contribute to microbial blooms in marginal ice edge zones, which in turn support cryopelagic food webs.     

Zooplankton communities in the Southern Weddell Sea (Antartica)

Summary Standardized abundances of 40 frequently occurring macrozooplankton taxa collected by double-oblique bongo net hauls between the surface and 200 m depth were submitted to an agglomerative hierarchical cluster analysis, to characterize surface zooplankton communities in the southern and eastern Weddell Sea. The sensitivity of the analysis concerning reduction of the number of considered taxa (especially stages of species) was tested. Dominant taxa in the entire area over the whole period were copepods Metridia gerlachei and Calanoides acutus. Calanus propinquus, Appendicularia spp. and calyptopis-1 larvae of krill, Euphausia superba were abundant at 73°S/19°W. Euphausia crystallorophias and larval fish Pleuragramma antarcticum dominated at 77°S/40°W on the southern shelf. The cluster analysis revealed marked similarities between the southern shelf community and the January community further to the northeast. E. crystallorophias, and larval Pleuragramma antarcticum are thought to be transported in surface layers of the coastal current to the southwest. Oceanic species such as Thysanoessa sp. and E. superba are probably not transported in the same way. Possible mechanisms for the maintenance of the community structures are discussed. A simplified method of characterizing communities, based on analysis of euphausiids, is presented.     

Elevated CO2 Levels do not Affect the Shell Structure of the Bivalve Arctica islandica from the Western Baltic

Shells of the bivalve Arctica islandica are used to reconstruct paleo-environmental conditions (e.g. temperature) via biogeochemical proxies, i.e. biogenic components that are related closely to environmental parameters at the time of shell formation. Several studies have shown that proxies like element and isotope-ratios can be affected by shell growth and microstructure. Thus it is essential to evaluate the impact of changing environmental parameters such as high pCO₂ and consequent changes in carbonate chemistry on shell properties to validate these biogeochemical proxies for a wider range of environmental conditions. Growth experiments with Arctica islandica from the Western Baltic Sea kept under different pCO₂ levels (from 380 to 1120 µatm) indicate no affect of elevated pCO₂ on shell growth or crystal microstructure, indicating that A. islandica shows an adaptation to a wider range of pCO₂ levels than reported for other species. Accordingly, proxy information derived from A. islandica shells of this region contains no pCO₂ related bias.     

Long-term dynamics of the abundance of several intertidal polychaetes in two inlets of Kandalaksha Bay (White Sea)

Based on eigenvector filtering and phase surface methods, the correlation between abundance dynamics and water temperature was studied in seven species of White Sea littoral polychaetes. Cyclic fluctuations in abundance with periods of approximately 5 and 12 years were revealed. Some instances of the 5-year cycles of abundance can be explained by climatic changes in the Arctic.     

Seasonal and long-term dynamics of sand-dwelling dinoflagellates (Dinoflagellata) in Peter the Great Bay,Sea of Japan

The seasonal and long-term dynamics of the species composition and abundance of dinoflagellates that live in subtidal sands in Russian waters of the Sea of Japan was studied for the first time. The overall species composition of sand-dwelling dinoflagellates in Peter the Great Bay was represented by 67 taxa that belong to 25 genera. Among them, 17 species were recorded for the first time from the seas of Russia, and 8 species were found from the Pacific coast of Russia for the first time. The greatest number of species belonged to the genera Amphidinium, Amphidiniopsis, and Thecadinium. A list of the species composition, including the distribution of taxa throughout the localities and seasons, is presented. Most species of the microalgae are illustrated by light and scanning electron micrographs. The species richness varied from 18 to 44 during the year. In the winter, at a water temperature less than 0°C, the species richness of sand-dwelling dinoflagellates (24–26 taxa) roughly coincided with that found in summer (20–44 taxa). The average density of dinoflagellates ranged from 16 to 1121 cells/cm³ across localities and throughout the year. During the annual cycle, the highest cell density (595 and 2576 cells/cm³) were recorded in the winter–spring period and a slight increase in abundance was observed in fall. This was due to the high cell densities of the dominant species Amphidiniopsis uroensis Toriumi, Yoshimatsu et Dodge, and Thecadinium kofoidii (E.C. Herdman) Larsen. Sand-dwelling dinoflagellates contributed 58 to 80% to the total annual density of the subtidal microphytobenthos in different localities of Peter the Great Bay.