Thallium in marine plankton

Concentrations of thallium in phytoplankton (0.02 to 0.8 g g^–1), zooplankton (0.03 to 0.5 g g^–1) and ichthyoplankton (0.1 g g^–1) from the central Pacific were comparable , as were the atomic ratios of thallium to calcium (3x10^–6) and to potassium (1x10^–6) in those organisms. These relatively constant ratios, plus the biounlimited ocean profile of thallium, indicate that it is rapidly cycled through plankton in the same manner as potassium, its principal biogeochemical analogue. The higher atomic ratios of thallium to potassium in pelagic clays (6x10^–6) and ferromanganese nodules (4x10^–3) suggest that both biological transport processes and abiotic transport processes influence this trace element's oceanic cycle.     

Evidence for the remobilisation of transuranic elements in the terrestrial environment

The transuranium elements, Np, Pu and Am discharged from the BNFL fuel reprocessing plant at Sellafield have accumulated in the local environment. The processes responsible for their dispersal rely both on physical transportation and their chemical reactivity. The transuranics have a complex chemistry, with multiple oxidation states and a strongly polarising character. In the environment, the particle active III/IV and more mobile VNI oxidation state groups are important and govern their geochemical behaviour and subsequent dispersal. Studies of the behaviour of the transuranics, particularly Pu, in the Irish Sea, have shown that the majority of the radionuclides in the liquid effluent discharged from Sellafield, quickly becomes associated with the marine sediments. Their dispersal and distribution in the environment is then governed primarily by the movement of particulate material and for some sites it has been suggested that sediment profiles preserve the historical record of discharges from the plant. In tidally inundated soils, radionuclide levels are greatly enhanced. These soils are water-logged for long periods of the year, are strongly anoxic and accretion rate are very low. The distribution of Np, Pu and Am in the soil suggests that simple sedimentary accumulation mechanism cannot provide an adequate explanation for the profiles observed. From preliminary studies of soil pore water composition and detailed analysis of the variation of isotopic ratios in the soil cores, it is apparent that a small but significant component of the radionuclide inventory is mobile. In addition, it is clear that the mechanisms responsible for this mobility allows differentiation between the transuranium nuclides.     

Some experiments on phosphate assimilation by coastal marine plankton

A study of phosphate assimilation by coastal marine plankton revealed that both phytoplankton and microheterotrophs incorporated radioactive phosphorus (³³P). Size fractionation of the particulate matter (using 1 m pore diameter Nucleopore^® membrane filters), antibiotic treatment (using garamycin), and independent estimaties of photoautotrophic (¹⁴CO₂ uptake) and heterotrophic (³H-glucose uptake) activities were employed to separate phyto- and bacterioplankton phosphate uptake. Results indicated that phytoplankton ³³P-uptake was best estimated by the fraction of particulate matter retained on the 1 m membrane filters. Usually, less than 10% of the phytoplankton (based on chlorophyll a measurements) passed the 1 m pore-diameter filters, whereas about 90% of the heterotrophic activity passed. At least 50% of the ³³P-uptake was associated with the <1 m fraction. It may be possible to resolve the phytoplankton and bacterial contributions to ³³P-uptake by comparing the percent of total ³³P-uptake with the percent of total ³H-glucose uptake associated with the >1 m fraction.     

Spring phenological responses of marine and freshwater plankton to changing temperature and light conditions

Shifts in the timing and magnitude of the spring plankton bloom in response to climate change have been observed across a wide range of aquatic systems. We used meta-analysis to investigate phenological responses of marine and freshwater plankton communities in mesocosms subjected to experimental manipulations of temperature and light intensity. Systems differed with respect to the dominant mesozooplankton (copepods in seawater and daphnids in freshwater). Higher water temperatures advanced the bloom timing of most functional plankton groups in both marine and freshwater systems. In contrast to timing, responses of bloom magnitudes were more variable among taxa and systems and were influenced by light intensity and trophic interactions. Increased light levels increased the magnitude of the spring peaks of most phytoplankton taxa and of total phytoplankton biomass. Intensified size-selective grazing of copepods in warming scenarios affected phytoplankton size structure and lowered intermediate (20–200?μm)-sized phytoplankton in marine systems. In contrast, plankton peak magnitudes in freshwater systems were unaffected by temperature, but decreased at lower light intensities, suggesting that filter feeding daphnids are sensitive to changes in algal carrying capacity as mediated by light supply. Our analysis confirms the general shift toward earlier blooms at increased temperature in both marine and freshwater systems and supports predictions that effects of climate change on plankton production will vary among sites, depending on resource limitation and species composition.     

Silicon and the ecology of marine plankton diatoms. II. Silicate-uptake kinetics in five diatom species

The variation of the rate of silicate uptake with varying silicate concentration in the medium was investigated in short-term experiments with the following marine diatom species:Skeletonema costatum, Thalassiosira pseudonana, T. decipiens, Ditylum brightwellii, andLicmophora sp. The uptake conformed to Michaelis-Menten kinetics only after a correction had been made for reactive silicate that apparently could not be utilized by the diatoms. The magnitude of this correction was in the range of 0.3 to 1.3 g-at Si/l. Mean values of the half-saturation constant of silicate uptake were calculated for the different species. The lowest value was found inS. costatum (0.80 g-at Si/l) and the highest inT. decipiens (3.37 g-at Si/l). Growth limitation by low silicate concentrations could be a cause of species succession in marine plankton-diatom blooms.     

Interactions between two species of marine diatoms: Effects on their individual copper tolerance

The purpose of this study was to examine the effect of the interaction of two species of marine diatoms,Skeletonema costatum (Cleve) Greville andNitzschia thermalis (Ehrenberg) Auerswald, on their individual copper tolerances. The two species, obtained from stock cultures in 1989, were grown together at three copper concentrations (1, 4 and 5 × 10^–7 M added total copper). In the unialgal cultures that were used as controls, the two species grew as predicted from their tolerance tests. However, in mixed cultures,N. thermalis was the only species that exhibited growth, regardless of the copper concentration in the medium. Growth retardation ofS. costatum in the presence ofN. thermalis was attributed to an inhibitory exudate. The effect of the exudate appeared to have been temporary, as demonstrated by the extended lag phase and subsequent satisfactory exponential growth rate ofS. costatum. It is suggested that the exudate degraded within a period of 5 d (=lag phase) because exponential growth rate was resumed. It thus appears that the interaction between the two diatom species is more important in determining the survival ofS. costatum than its individual copper tolerance. This is not the case forN. thermalis. Such interactions would be unaccounted for in single-species toxicity tests. On the other hand, if they are known, prediction of how a community that includes these two species would respond to copper additions becomes possible.     

Ecological aspects of plankton production

The study was carried out in the neritic and estuarine waters of Porto Novo, Coromandel Coast, Bay of Bengal, India during the period January, 1960 to December, 1967. The average displacement volume of plankton usually varied between 2 and 4 c²/m². During summer, with a season of high plankton productivity, the average plankton displacement volume rose to 8 c²/m³. Generally speaking, the average zooplankton density (standing crop) was usually between 80,000 and 100,000 organisms/m³, of which copepods alone comprised usually between 70,000 and 90,000 organisms/m³. The average copepod density per sample varied from 30,000 to 50,000 organisms/m³. However, in the summer months, the copepod density was usually not less than 100,000 organisms/m³; in some years this was even higher (from 125,000 to 170,000 organisms/m³). Copepods comprised between 80 and 95% of the zooplankton population. The maximum non-copepod population in the zooplankton seldom reached 30%, was ofter below 25%, and usually less than 20%. During the period March to October (in some years as early as February, and in some years up to November), either an increasing or a steady trend of plankton production was evident. It would appear that salinity and rainfall determine the occurrence and distribution of plankton in Porto Novo.Contribution No. 189 from the Centre of Advanced Study in Marine Biology, Marine Biological Station of Annamalai University, Porto Novo, Tamilnadu, India.     

Silicon and the ecology of marine plankton diatoms. I. Thalassiosira pseudonana (Cyclotella nana) grown in a chemostat with silicate as limiting nutrient

The small marine plankton diatom Thalassiosira pseudonana Hasle and Heimdal (Guillard's clone 3H) was grown in chemostats with silicate as the limiting nutrient. The calculated maximum growth rates were comparable to those previously reported for this species. The silica content of the diatom shells varied with the growth rate. As the growth rate approached zero, there were still measurable quantities of residual reactive silicate in the medium. In one of the two chemostats used, silicate assimilation by the cells was inefficient due to some unknown internal or external factor. In the other chemostat, statistically calculated half-saturation constants of growth were in the range of 0.5 to 0.8 g—at Si/l, depending on which kind of correction was made for residual silicate. Half-saturation constants of steady-state mean silicate uptake per cell and hour, calculated in a similar fashion, were in the range of 1.4 to 2.6 g—at Si/l. These results indicate that the silicate concentrations causing a reduced silicate uptake by this species in nature do not necessarily result in a correspondingly reduced growth rate. Growth in coastal waters is likely to become seriously limited by a shortage of silicate only when most of the silicate originally present has been removed in the course of a diatom bloom.     

Simple and reliable methods for the fixation,mounting and staining of small and delicate marine plankton for light microscopic identification

The fixation capacity of mixtures of acrolein, glutaraldehyde, and tannic acid, was investigated to arrive at a fixative for small and delicate marine plankton that is more universal than the current selective fixatives. A mixture containing 4% acrolein, 4% glutaraldehyde and 2% tannic acid added 1:1 to the cell suspension proved to be satisfactory. Mounting of the material in euparal before staining is recommended. Of several dyes tried, fuchsin acid proved suitable for observation of flagella and cell shapes. Delafield haematoxylin staining gave the best results for internal details. Fuchsin base staining, requiring a complex procedure, is recommended when it is necessary to search for flagellar hairs as found in Ochromonas spp. Schedules for the fixation, mounting and staining are given.     

Ecotoxicological effects of Trichloroethene upon plankton

A case study in an experimental pond was performed to evaluate the ecotoxic effects of Trichloroethene (TRI) upon the population density and productivity of phyto‐ and zooplankton. TRI was continuously released into two pond enclosures over 11 weeks (mean concentrations 1.5 and 7.5 mg/l). The chronic chemical treatment showed distinctive toxic influences upon the biota. Following the high TRI concentration, the phytoplankton density slightly increased; the productivity per single cells, however, was significantly reduced compared to the controls and the low TRI concentration. Cryptophyceae were the most sensitive algae taxa. The density and reproductivity of Daphniae and Phyllopodae decreased by the high TRI concentration. Most of the Rotatoriae were not negatively influenced. With increasing TRI concentrations two different bacteria forms showed a mass development. Small amounts of Trichloroacetic acid were detected in both enclosures as a conversion product of TRI (～3 μg/l after 80 days treatment).     

Interactions between nutritional status and long-term responses to ultraviolet-B radiation stress in a marine diatom

Influences of nutritional status on the photoinhibitory effects of ultraviolet-B radiation (UVBR: 290 to 320 nm) on the specific growth rates (_obs) and biomass of Phaeodactylum tricornutum were determined using nutrient-replete batch cultures and nutrient-limited continuous cultures. P. tricornutum cultures were exposed to UVBR doses representative of current mid-latitude and ozone-depletion intensities. Specific growth rates and biomass were inhibited from 2 to 16% by UVBR during nutrient-replete growth. However, no effect of UVBR on _obs or biomass was detectable when nutrient limitation exceeded the potential for limitation by UVBR. Thus, a competitive interaction appears to occur between macronutrient stress and UVBR stress, such that _obs and biomass will be determined by the most limiting factor. Our results suggest that measurable decreases in phytoplankton _obs and biomass from UVBR are most likely in nutrient-rich areas of the ocean, while these parameters may not be appropriate for measuring UVBR stress in regions of nutrient limitation.     

A mathematical model of PCB bioaccumulation in plankton

In batch experiments exposing individual plankton constituents to Aroclor 1254 PCB, the rate at which the organism approaches partitioning equilibrium appears to be partly size-dependent while the extent of PCB accumulation is species-specific. The sorptive desorptive kinetics of PCB in these experiments can be described mathematically by a first-order expression. Employing this expression in a model plankton food web permits examination of the role of feeding and sorptive processes in determining PCB body burden under various environmental conditions. When ingestion rates exceed desorption and excretion rates, a consuming organism accumulates PCB above levels predicted by equilibrium partitioning relationships. Feeding-induced oscillations in PCB body burden could thus obscure the reduction of soluble PCB concentration which determine a “baseline” PCB body burden. Unless referenced to a specific set of biological and environmental conditions, the importance of direct partitioning from water vs. food uptake appears to be a moot topic.     

The structure of plankton communities of the Indian Ocean

Species diversity and trophic structure of plankton communities have been considered as most important biological features. The Fisher () and Simpson () indices and the information index H=- pi log₂ pi (Margalef) were used for evaluation of species diversity. The indices have been calculated within the group of filter feeders by numbers ( and H) and biomass ( and H) of the species; the best results were obtained in the latter case. The index H=- pi log₂ pi is proposed for the quantitative evaluation of trophic structure, where a portion of an individual trophic group is taken as pi. The plankton material was collected by the R.V. Vityaz in the northern Indian Ocean in January through February, 1960. Analysis of characteristics of zooplankton distribution, species and trophic diversity in connection with characteristics of the water regime resulted in the definition of 3 types of the plankton communities: (a) those in intensive divergence zones; (b) those in poor divergence zones; (c) those in regions with stable water stratification or with feebly marked convergence, distiguished by different values of biomass, species diversity, and trophic group ratios.     

Parasites in larvae of the herring (Clupea harengus L.) fed with wild plankton

In winter 1965/66 larvae of Downsherring were reared in aquaria at the Marine Station of the Biologische Anstalt Helgoland. They were fed with wild plankton caught on Helgoland Roads. About 10% of the actively feeding larvae were lost due to two endo-parasites and two ecto-parasites. The endoparasites are: a nematode (Contracoecum sp.) which is taken in by the larvae with the food and enters the host's body cavity from the gut, and a cestode (Scolex pleuronectis) which is found in the posterior part of the gut. The ecto-parasites are: a copepodite stage of a lernaeocerid, which attaches itself preferably close to the anus area of the herring larvae, and the copepode Caligus rapax. The nematode and copepodite were observed when the larvae had reached a total length of 9 to 13 mm. The cestode was found for the first time in larvae of 15 to 18 mm, and Caligus rapax in larvae of 20 to 25 mm total length.     

Assimilation efficiencies and turnover rates of trace elements in marine bivalves: a comparison of oysters, clams and mussels

Assimilation efficiencies (AEs) and physiological turnover-rate constants (k) of six trace elements (Ag, Am, Cd, Co, Se, Zn) in four marine bivalves (Crassostrea virginica Gmelin, Macoma balthica Linnaeus, Mercenaria mercenaria Linnaeus, and Mytilus edulis Linnaeus) were measured in radiotracer-depuration experiments. Egestion rates of unassimilated elements were highest during the first 24 h of depuration and declined thereafter. Significant egestion of unassimilated Co, however, continued for up to 5 d in Macoma balthica, Mercenaria mercenaria and Mytilus edulis. With the exception of the extremely low values for ^110 mAg, ¹⁰⁹Cd, and ⁶⁵Zn in C. virginica, physiological turnover-rate constants (k) showed no general pattern of variation among elements, bivalve species or food types, and were relatively invariant. Values from  ≤0.001 to 0.1 d⁻¹ were observed, but excluding those for Co, most values were  ≤0.04 d⁻¹. In all four species, the AEs of Ag, Am, and Co were generally lower than those of Cd, Se, and Zn. The AEs of Ag, Cd, Se, and Zn in these bivalves are directly related to the proportion of each element in the cytoplasmic fraction of ingested phytoplankton, indicating that >80% of elements in a prey alga's cytoplasm was assimilated. C. virginica, Macoma balthica, and Mercenaria mercenaria assimilated ∼36% of the Ag and Cd associated with the non-cytoplasmic (membrane/organelle) fraction of ingested cells in addition to the cytoplasmic fraction. The ratio of AE:k, which is proportional to the consumer–prey trace-element bioaccumulation factor (concentration in consumer:concentration in prey) was generally greater for Cd, Se, and Zn than for Ag, Am, and Co. This ratio was lowest in Mytilus edulis, suggesting that this bivalve, the most widely employed organism in global biomonitoring, is relatively inefficient at accumulating important elements such as Ag, Cd, and Zn from ingested phytoplankton. Received: 7 February 1997 / Accepted: 24 February 1997     

Pattern of distribution of selected trace elements in the marine brown alga,Sargassum filipendula Ag. from Sri Lanka

Baseline concentrations together with biological variations of 29 trace elements (Ag, As, Au, Ba, Br, Cd, Ce, Co, Cr, Cs, Eu, Fe, Hf, I, Mn, Mo, Ni, Pb, Rb, Sb, Sc, Se, Sm, Sr, Tb, Th, Yb, Zn and Zr) were investigated in the brown alga, Sargassum filipendula collected from the western coast of Sri Lanka. Several elements (Co, Cr, Fe, Hf, Ni, Sc, Se, Th, Zr and the rare earth elements) were found to be enriched in S. filipendula compared to NIES No. 9 Sargasso reference material. Concentration of strontium in S. filipendula was highest at all sites. Chemical abundance of the rare earth elements decreased approximately linearly with increasing atomic numbers. The pattern of elemental distribution appears to be due to the fact that S. filipendula seems capable of concentrating high levels of trace elements under conditions of their very low availability in sea water. Concentration factors for elements in S. filipendula lie in a higher range compared with those reported in the literaure for brown algae.     

The heterotrophic phase of plankton succession in the Japan Sea

The vertical structure, composition and productivity of a plankton community was studied in the Japan Sea in June, 1972 during a period of thermocline formation; the parameters measured were: phytoplankton production and biomass; number, biomass, and production of planktonic bacteria; biomass of phagotrophic flagellates, ciliates and remaining microzooplankton. The concentration of micro- and mesozooplankton attained a basic maximum in a layer near the upper part of the thermocline. The biomass and calculated production of the heterotrophic part of the community exceeded considerably the amount of primary production. The heterotrophic phase of the seasonal succession of a plankton community in a temperate sea is described, when heterotrophic metabolism and production predominate. Heterotrophs at this stage use mostly energy from organic matter accumulated during the previous spring phytoplankton bloom.     

On the near-surface plankton of the eastern South Pacific Ocean

A study has been made of the plankton of the near-surface water layer (0 to 30 cm) of the eastern South Pacific Ocean in the region lying to the east of the meridian 90°W, between latitudes 5°N and 35°S. This region is influenced by the Peru Current: the current brings water from high latitudes, which results in a decrease in the number of species of the local fauna of copepods of the family Pontellidae, typical of tropical near-surface plankton. Some of the widely tropical and one bicentral species are absent or rare. Least affected by the Peru Current are the waters of equatorial structure in the northern part of the region. Here, 7 species of pontellids were recorded: the widely tropical Labidocera detruncata, Pontella tenuiremis, Pontellopsis regalis, the distant-neritic Pontella danae and Labidocera acuta, the bicentral Labidocera acutifrons, and the neritic Pontellopsis lubbockii. The dominant species among these are L. detruncata and L. acuta. To the west of the convergence, in the southern part of the region, live the southern central species Pontella valida and P. whiteleggei, with Pontellopsis regalis occurring occasionally. In these regions the copepod fauna is frequently dominated by pontellids. To the south of the boundary of the waters of equatorial structure, between the coast of South America and the line of convergence, lies a region most subjected to the effect of waters from high latitudes and of upwellings. It is inhabited by 2 pontellids only: Pontellopsis regalis and Labidocera acutifrons, but they too disappear close to the coast. In this particular region the copepods Calanus australis and Centropages brachiatus are common; they are found in a thicker water layer (0 to 200 m), and are often more abundant than the pontellids.