Salinity Adaptations and Bathymetric Distribution of Bivalve Mollusks Portlandia arcticaand Nuculana pernula in the White Sea

We examined changes in the oxygen consumption rate, the number of active animals, rate of losses of salts, and the level of cell hydration under conditions of decreased salinity in the mollusks Portlandia arctica(Gray) and Nuculana pernula(O.F. Müller), inhabiting the White Sea in the deepest depths under high salinity (about 30) and negative temperatures of –1.3 to –1.4°C throughout the year. It has been shown that the mollusks demonstrate a relatively great tolerance of desalination at the organism level and a capability to regulate cell volume under decreased salinity of the environment. We concluded that the depletion of fauna of the White Sea in the deepest depths is not connected with the tolerance level of deep-sea animals to salinity fluctuations, but rather is due to environmental conditions (liquid silts and negative temperatures).     

Salinity-stress-induced changes in the resistance of embryos of the White Sea herringClupea pallasi marisalbi to freshwater

The short-term effects of extremely low salinity (3‰) on the resistance of White Sea herring to freshwater were studied. An increasing resistance of the embryos against a sudden drop in salinity, and a decreasing resistance against gradual changes in salinity (to 0‰) was revealed.     

Evaluating impacts of shellfish and baitworm digging on bird populations: short-term negative effects on the availability of the mudsnail Hydrobia ulvae to shorebirds

Many shorebird populations show evidence of declines. To identify the causes is a key issue in developing comprehensive shorebird conservation plans. In coastal areas, shorebirds are vulnerable to effects of shellfish and baitworm digging, including reduction of the food supply. The mudsnail Hydrobia ulvae is often reported to be the dominant inhabitant of intertidal mudflats, and is common in the diet of migrating and wintering shorebirds. This prosobranch mollusc lives at or just below the surface of intertidal mudflats, so it might be directly damaged and killed or buried within the mud by hand diggers. We studied the short-term effects of digging by hand on the availability of mudsnail to shorebirds. Twenty centimetres deep core samples were collected from undisturbed and recently disturbed intertidal mud. The total mudsnail density and biomass per core sample was similar in disturbed and undisturbed mud. However, mudsnail density and biomass were significantly lower in disturbed mud than in undisturbed mud when only the upper five centimetres of the mud were compared. If only the mudsnails found in this surface layer are potentially available for shorebirds, the available mudsnail density and biomass fraction for shorebirds had decreased by 62.6? ?±? 11.4% and 75.7? ?±? 7.2% in disturbed mud, respectively. The potential impact of this decreasing mudsnail fraction on shorebirds is addressed.     

Variability of morphological characteristics in <Emphasis Type="Italic">Oithona similis</Emphasis> (Copepoda: Cyclopoida) in the White Sea

The spatial variability of the body size and morphological structures of the planktonic copepod Oithona similis in the White Sea was studied. From north to south, there was a tendency for the male cephalothorax length to decrease. In moving from the central to the northern part of the sea and from the eastern to the western part, the relative antennule length in both sexes increased. The average body size of copepods was positively and the absolute (and relative) lengths of the antennules were negatively correlated with water salinity. The morphological variations have adaptive significance and are determined by environmental factors.     

Long-Term Changes in Shallow-Water Fouling Communities of the White Sea

The replacement of an ascidian (Styela rustica L.) fouling community by a blue mussel (Mytilus edulis L.) community was described for the White Sea. The alternation of populations of these two species takes place in fouling communities developing in the upper 3- to 5-m layer of water. The life span of each type of fouling probably depends on interannual climate fluctuations.     

Growth and Longevity of the Gastropod Nucella heyseana in Vostok Bay,Sea of Japan

Features of the morphology, longevity, and growth of the gastropod mollusk Nucella heyseana collected in different seasons in 2000–2001 in Vostok Bay (Sea of Japan) were investigated. Shell surface features such as grooves and spurs of the axial sculpture have proven to be unhelpful in the estimation of individual age and growth rate of this species. Concentric rings on the outside of the operculum formed yearly in the cold season are useful for these purposes. The longevity of N. heyseana in southern Primorye is 10 years; this value is similar to the life span of mollusks from the southern Kuril Islands. Local differences in longevity, growth allometry, and age changes in the body size and mass of N. heyseana in relation to habitat conditions are discussed.     

Life cycle and production of Hydrobia acuta Drap. (Gastropoda: Prosobranchia) in a hypersaline coastal lagoon

The life cycle and annual production of Hydrobia acuta was studied in a hypersaline lagoon (s = 39 in summer), forming a part of solar salt works. Quantitative random samples were taken at regular intervals over a period of 15 months using a corer, and snails collected were counted and measured. Weight and biomass was calculated from a length-weight relationship and from measurements of ash content. H. acuta was a strictly annual species in the study lagoon. Recruitment takes place over a brief period in May and June, after which the breeding population dies. Growth of the new generation was slow during summer, probably due to the unfavourably high salinity. A period of rapid growth took place in autumn coinciding with a drop in salinity caused by rainfall. In winter Hydrobia hibernated by burrowing deeply into the sediment. Growth recommenced in spring when the lagoon was reflooded, but by this time the number of survivors was low.The maximum density of snails was 6 000 m^–2 and maximum biomass 500 mg organic dry wt · m^–2. Annual cohort production was estimated as 786 mg organic dry wt · m^–2 · a^–1. These figures are low compared to other studies on hydrobiid snails, and for production in inland waters, but the value for annual P/B = 4.5 is typical for a univoltine species. The relevance of the results to foraging by wading birds (the main consumers), is discussed.     

Salinity tolerance of the copepod Apocyclops dengizicus (Lepeschkin, 1900), a key food chain organism in the Salton Sea,California

The copepod Apocyclops dengizicus is a key item in the food chain of the Salton Sea where the salinity is currently 45 g 1^–1. The salinity of the Salton Sea may reach 90 g 1 ^–1 within the next 20 years. This study examined the salinity tolerance of this copepod.Large copepodite and adult A. dengizicus were introduced into various salinities with and without acclimation. The 96 h LC₅₀ without acclimation was 101 g 1^–1. Mortality (at 96 h) without acclimation was low at salinities of 90 g 1 ^–1 or less.Copepod cultures were maintained, with successful reproduction of at least one new generation, at salinities of from 0.5 to 68 g 1 ^–1 for at least 120 days. Copepods maintained at higher salinities, up to 79 g 1 ^–1, remained alive up to 90 days, but a new generation was not produced. In laboratory studies of larval production and survivorship, few nauplii were released at salinities of 68 g 1 ^–1 or higher, and none survived to the copepodite stage.     

Modulating role of lipids and their fatty acids in adaptation of the White Sea mussels <Emphasis Type="Italic">Mytilus edulis</Emphasis> L. to environmental salinity change

Role of lipids and fatty acids (FA) in littoral and sublittoral White Sea mussels Mytilus edulis L. was studied at various stages of reproductive cycle in the phenotypic adaptation (acclimation) to changes of the sea water salinity. The obtained data indicate differences in the mussel lipid and fatty acid spectra, which are connected both with their location (littoral or sublittoral) and with the spawning period stage (3b—release of gametes or 3c—resorption of residual sex products). Lipids and FA of both mussel groups respond to the salinity changes to the greater degree at the 3b than at the 3c stage. In the littoral mussels at the 3b and 3c stages there were revealed differently directed changes in the content of membrane lipid—cholesterol—and in the cholesterol: phospholipids ratio. In the sublittoral mussels that are less adapted to extreme action of abiotic factors, more significant changes were found in the lipid and FA compositions.     

Succession of Fouling Communities on an Artificial Substrate of a Mussel Culture in the White Sea

The pattern of development of a fouling community, based on research data on their formation in the mussel culture in the White Sea is presented. The succession may come to an end either by the mussel community or by the community of Styela rustica, which is analogous to the natural epitbenthic biocenosis of Laminaria saccharina. It also might develop with the deletion of some stages. The presence of the mussel phase is not necessary in the development of fouling. The final stage of the fouling development is determined, apparently, by hydrological conditions.     

Environmental and behavioural factors affecting activity in the intertidal gastropod Hydrobia ulvae

Laboratory microcosms were used to investigate the mud snail Hydrobia ulvae (Pennant) bioturbation activities and behavioural changes in response to snail density, algal food, sediment moisture content, light regime and water cover conditions. Density-dependent kinetics of bioturbated muddy areas were described by von Bertalanffy equations, which provided reliable estimates of mud surface covering rates by snail tracks (m² h⁻¹ snail⁻¹). Snails need a wet habitat to be active either covered by seawater or by moving in fluid layers for low-tide conditions. Light and microphytobenthic biomass, which are less potent to affect snail activity, are positively interrelated to increase covering rates in the tested chl a concentrations within the range of 1-15 μg g⁻¹. Experimental results suggested us the relevance of microphytobenthos migration processes in affecting crawling activities of H. ulvae that appeared to adjust their foraging efforts in response to benthic algal biomass. Behavioural processes of H. ulvae, in terms of floating, crawling, burrowing and inactive snails, were described using a Markov model. Finally, an empirical model based on von Bertalanffy equations was proposed to describe kinetics of sediment covering by snail tracks under the influences of snail density, sediment moisture content, chl a concentrations and the four combinations of presence/absence of light and seawater. This model should provide a base for further development of a hydrosedimentary model to simulate the effects of H. ulvae bioturbation activities on the resuspension of the intertidal cohesive sediment-water interface for various in situ conditions.     

Changes in Resistance to Salinity and Temperature in Some Species of Polychaetes from the White Sea in Early Ontogenesis

We studied the effects of different salinities on plankton larvae of some polychaetes in the White Sea. It has been found that the salinity resistance of Alitta virens (Nereidae) increases during ontogenesis. Successful fertilization and further larval development in this species occur at the salinity of 22 to 34; embryos taken into the experiment at the stage of 32 blastomeres, trochophores, and early nektochaetes could survive and normally develop at the salinity of 16–32, 14–45, and 12–45 respectively. The rate of settling and metamorphosis in late nektochaetes of A. virens at normal or lowered (down to 14) salinity is dependent on temperature in the range of 5 to 23°C. It is found that the larvae of Harmothoe imbricata (Polynoidae) show the greatest salinity resistance at the stage of nektochaeta, whose lower limit of salinity is 14. Later larval stages of these species can survive in a wide range of salinity due to the development of a provisory nephridial system. The eurybionty of larvae of Spirorbis spirorbis ready for metamorphosis was higher than that in the larvae of Circeus spirillum (Spirorbidae). Under salinity reduced down to 10 the larvae of S. spirorbis die in 8–14 days, whereas more stenohaline larvae of C. spirillum die by the 3-rd day of the experiment. At water temperatures under 5°C the survival of S. spirorbis was the highest at three examined values of salinity, whereas C. spirillum showed the highest survival only under normal salinity.     

Subtidal Underwater Rock Communities of the White Sea: Structure and Interaction with Bottom Flow

The taxonomic composition and quantitative characteristics of typical subtidal rock communities of the White Sea (biocenosis of Laminaria and biocenosis of Lithothamnion and the sponges Polymastia arctica) were studied. The hydrodynamic activity of the near-bottom water layer within and beyond the communities was estimated using the plaster structures technique. A comparative analysis of our results and the literature data revealed three main types of interactions between the benthic community and the water flow: turbulation of the water flow (mussel banks), smoothing of turbulent pulsations (Laminaria community), and an insignificant effect on the water flow (community of Lithothamnion and sponges).     

Reproduction of the colonial hydroid Obelia geniculata (L., 1758) (Cnidaria,Hydrozoa) in the White Sea

Populations of the colonial hydroid Obelia geniculata in the White Sea reproduce asexually by frustule formation. Young medusae appear in the plankton during July and August. The number of medusae rarely exceeds 36 per m³, and the average number varies every year from 0.4 to 10 per m³. The size of medusae is smaller than reported from other regions. The umbrella of the largest recorded medusa was only 0.57 mm in diameter and the specimen had just 35 tentacles. Only a few mature medusae were found during the study. The colonies in the White Sea are epiphytic and grow only on laminarian thalli. At the beginning of July there are no colonies on thalli from the upper subtidal zone. By the end of August, colonies of O.␣geniculata had increased in density to 30 per m². Hydroid recruitment was attributed to active frustule production by colonies living below that zone. The frustules detach from the stems of the hydroids and are found in plankton. Production of frustules on branches occurs continuously during colony growth until water temperatures climb above 0 °C. We found that water temperature in this Arctic environment is generally too low for medusa maturation and planula development in the species. Propagation by frustule formation is the principal means of reproduction in Obelia geniculata within the White Sea, and this phenomenon accounts for the species being a dominant epiphyte on laminarian thalli there.     

Abiotic factors influencing cyanobacterial bloom development in the Gulf of Finland (Baltic Sea)

Blooms of cyanobacteria are a recurrent phenomenon in the Baltic Sea, including the Gulf of Finland. The spatial extension, duration, intensity and species composition of these blooms varies widely between years. Alg@line data collected regularly from ferries as well as weather service and marine monitoring data from 1997 to 2005 are analysed to determine the main abiotic factors influencing the intensity and species composition of cyanobacterial blooms in the Gulf of Finland. It is demonstrated that the development of the Nodularia spumigena Mertens bloom is highly dependent on weather conditions such as photosynthetically active radiation and water temperature. Nutrient conditions, especially the surplus of phosphorus (according to Redfield ratio) related to the pre-bloom upwelling events in the Gulf, affect the intensity of Aphanizomenon sp. (L.) Ralfs blooms. Differences in bloom timing and duration indicate that, if the preconditions (like nutrient ratio/concentration and weather conditions) for bloom formation are favourable, then the Aphanizomenon bloom starts earlier, the overall bloom period is longer and the Nodularia peak might appear in a wider time window. Handling editor: K. Martens     

大豆SbPRP3基因表达及转基因烟草非生物胁迫鉴定

为研究大豆(Glycine max L.)细胞壁脯氨酸富集蛋白基因(SbPRP3)在逆境胁迫中的作用,利用实时荧光定量PCR,对SbPRP3在高盐、干旱和低温处理下的表达情况进行检测。结果显示,SbPRP3在高盐处理下表达量升高,在干旱和低温处理下表达量先升高后降低。将SbPRP3构建到植物表达载体pRI101-AN上并转化烟草,获得阳性转基因烟草3株。对转基因烟草植株进行高盐、干旱和低温胁迫处理。结果表明,与对照相比,高盐和低温处理下转基因烟草脯氨酸积累量增加,而丙二醛产生量降低。但干旱处理后转基因烟草脯氨酸和丙二醛的含量与对照相比没有显著差异。由此推测SbPRP3可以提高转基因烟草的耐盐性和耐寒性。     

油菜种子发育和萌发过程中脱水耐性相关基因的cDNA-AFLP分析

选取甘蓝型油菜种子发育和萌发过程中与脱水耐性相关的不同时间点,采用cDNA-AFLP技术通过128对引物组合分析,共获得394条特异转录衍生片段(TDFs)。经BLAST序列比对,发现其中189条与GenBank数据库中已知功能基因同源,按其功能可分为转录因子、基础代谢、抗逆胁迫、信号转导等相关蛋白。RT-PCR技术对差异显著性片段验证结果显示,泛素蛋白、油体蛋白、热激蛋白和一些转录因子片段均受到种子脱水诱导表达。研究结果表明,发生在种子发育和萌发过程中的脱水耐性反应非常复杂,涉及植物生命活动的诸多领域。     

Life history characteristics of the clam<Emphasis Type="Italic"> Mya arenaria</Emphasis> in the White Sea

Dynamics of Mya arenaria beds in two bights of the Chupa Inlet (Kandalaksha Bay, White Sea) were studied on a long-term basis. Observations were carried out at 1– to 3-year intervals from 1979 up to 1999. The studied soft-shell clam beds were characterised by a substantial instability of age structure. Since 1988, only one year-class has dominated in the beds while other generations have been scarce and recruitment was not observed. This pattern of Mya bed dynamics was related neither to interannual environmental changes nor to differential reproduction success or predation effects in the benthic assemblages. Favourable conditions for spat formation in 1988 (low abundance of other M. arenaria generations), as well as for juvenile survival during the following winter, resulted in high abundance of juveniles in both investigated locations in 1989. The mortality rate (μ) in this 1988 generation varied throughout the period of investigation and was related to age. The mortality level decreased for the first 2–4 years of the life cycle, then stabilised for the next 3–4 years, and eventually increased in subsequent years. Overall μ values ranged from 0 to 1.68 year^–1. The oldest specimens observed were 17 years old and had a maximum shell length of 79 mm. Significant differences in average growth rates were observed between molluscs of different locations. Communicated by H.-D. Franke     

Phytoplankton composition of the Kandalaksha Gulf, Russian White Sea: Dinophysis and lipophilic toxins in the blue mussel (Mytilus edulis)

Dinophysis acuminata and D. norvegica were observed in plankton net samples during the summer of 2002 from the Kandalaksha Gulf in the White Sea (North European Russia). Prorocentrum lima was found as an epiphyte on subtidal macroalgae in August, but not observed in plankton net samples. Protein phosphatase 2A (PP2A) inhibition measured 127.8 ng OA-equivalent/g of mussel (Mytilus edulis) hepatopancreas from samples collected a few days after when Dinophysis was recorded at a density of 1550 cells L⁻¹. Liquid chromatography–mass spectrometry confirmed presence of several classes of lipophilic shellfish toxins associated with Dinophysis spp. in the mussels including okadaic acid, dinophysistoxin-1, pectenotoxins and yessotoxins. No azaspiracid was detected. This represents the first identification of phycotoxicity in the White Sea.     

Time-Series Evolution of Toxic Organisms and Related Environmental Factors in a Brackish Ecosystem of the Mediterranean Sea

In the framework of the EU Project STRATEGY, a short-term study was carried out in the Marinello ecosystem, a small brackish area located on the Tyrrhenian coast of Sicily (Italy). The investigation was aimed at understanding the dynamics of phytoplankton toxic blooms in relation to other planktonic species and environmental conditions. The study started on 10 March 2003, in coincidence with the first detection of Alexandrium minutum, a dinoflagellate known as a producer of Paralyzing Shellfish Toxins (PST) and lasted until 4 June 2003, when the bloom collapsed. The specific identity of A. minutum was confirmed on field mixed samples, through the use of species-specific PCR-primers targeting the 5.8S rDNA-ITS regions. Water samples and phytoplankton net hauls were taken approximately at 10 days intervals in the Verde Pond, one of the five basins of the Marinello ecosystem, in order to evaluate the incidence of toxic and non-toxic dinoflagellate species over the whole planktonic community. The evolution of the main environmental and trophic parameters (temperature, salinity, dissolved oxygen, POC, C/N, DIN, PO₄–P) was simultaneously investigated. Alexandrium blooms were mostly characterized by A. minutum (max. 6 × 10⁵ cells l⁻¹ on April 11) and Alexandrium tamarense as an associated species (max. 2.5 × 10⁴ cells l⁻¹ on March 25). During the bloom, dinoflagellates or small flagellates dominated over the other taxa, with a minimum incidence of diatoms. The load of dissolved inorganic nitrogen was maximum in the pre-bloom phase (29 μM on March 19), after which it decreased sharply. An oxygen supersaturation event was registered in coincidence with the A. minutum bloom. The amounts of POC ranged between 266 and 658 μg l⁻¹ showing a discontinuous temporal trend. A recent introduction of A. minutum into the Verde Pond is suggested on the basis of the absence of this species in past years.