Biokinetics of plutonium,americium and californium in the marine isopod Cirolana borealis,with observations on its feeding and molting behavior

In a series of laboratory experiments carried out during 1982, the biokinetics of ²³⁷Pu (IV), ²³⁷Pu (V), ²⁴¹Am (III), and ²⁵²Cf (III) were studied in the benthic marine isopod Cirolana borealis Lilljeb. Following a 3 wk exposure to labelled seawater, isopods reached non-equilibrium concentration factors of 52±15, 54±12, 176±14, and 185±53 for Pu (IV), Pu (V), Am and Cf, respectively. Uptake of these radionuclides occurred to a great extent by surface adsorption, with the major fraction of the accumulated radionuclides being associated with exoskeleton and lesser percentages located in gut, digestive gland, muscle and haemolymph. The pattern of radiotracer depuration was in all cases biphasic, with the long-lived retention compartment retaining the largest fraction of whole-body radioactivity. Biological half-lives for radionuclide turnover in the long-lived compartment were 60±3 d, 87±5 d, 261±12 d and 288±60 d for Pu (IV), Pu (V), Am and Cf, respectively. Examination of radionuclide distribution among tissues following longterm depuration showed that the radionuclides were eliminated from internal tissues more rapidly than from the exoskeleton. Uptake and depuration studies indicated that the biokinetics of americium and californium were similar to each other, but that they differed significantly from those of oxidized and reduced plutonium. In general, these experimental results support previous reports that americium and californium are more bioavailable than plutonium in the marine waters. The fraction americium and californium assimilated into tissue from food was very low and did not exceed 5%. Unassimilated labelled food was often retained in the gut for more than 2 mo and released only infrequently in a loosely bound condition. In the event of contamination, this particular feeding-digestion strategy in highly mobile, scavenging isopods could act as a potential biological mechanism for the widespread dispersion of radioactive wastes.     

Plutonium and Americium: Uptake from contaminated sediments by the polychaete Nereis diversicolor

The polychaete Nereis diversicolor O.F. Müller was exposed to marine sediments which had been contaminated with plutonium and americium either through the testing of nuclear devices or by the release of liquid waste effluent from a nuclear fuel reprocessing plant. The uptake of both plutonium and americium was small, about 0.5% of the concentration of these transuranics in the sediments. The degree of relative uptake of plutonium from both sediments was comparable; relative uptake of americium from sediments contaminated by waste effluent was greater than that from nuclear sediment and those previously determined from water-uptake experiments to environmentally determined plutonium concentrations in sediments and overlying waters leads to the tentative conclusion that water may be the predominant pathway for plutonium accumulation by deposit-feeding worms like N. diversicolor.     

237Pu experiments with the thornback ray Raja clavata

Some experiments have been made on the metabolism of ²³⁷Pu — a high specific activity, gamma-emitting isotope of plutonium — by the thornback ray Raja clavata L. Unlike previous experiments with the plaice (Pleuronectes platessa L.) it was found that the thornback ray absorbed plutonium across the gut wall, as readily observed by analysis of the liver. The liver accumulated up to 0.2% of the ²³⁷Pu given in a single labelled meal after a period of 12 days. Direct injection of the isotope into the muscle of thornback rays resulted in extremely slow rates of elimination from the fish, the highest internal concentrations being attained by the spleen. The largest fractions of the whole-body burden, however, were those of liver and skeleton.     

Kinetics of zinc uptake from solution,accumulation and excretion by the decapod crustacean<Emphasis Type="Italic"> Penaeus indicus</Emphasis>

Juveniles of the dendrobranchiate decapod Penaeus indicus take up radiolabelled zinc from solution at all exposure concentrations studied from 5.6 to 100 g l^–1, with an uptake rate constant of 0.045 l g^–1 day^–1 at 15 salinity and 25°C. Over the first 10 days of zinc exposure, the new zinc taken up is added to the existing zinc content of the prawn with no significant excretion; over this period the rate of accumulation of radiolabelled zinc is a measure of the absolute zinc uptake rate from solution. Over the next 10 days of zinc exposure to 10 g Zn l^–1, however, zinc is excreted at about half the rate of uptake resulting in a raised body concentration of zinc. Moulting had no significant effect on the accumulation of zinc. Newly accumulated zinc is distributed to all organs with the highest proportions of body content being found in the exoskeleton, followed by the muscle, the hepatopancreas and the antennal organs. Radiolabelled zinc is subsequently lost from all organs. Unlike caridean shrimps or prawns (pleocyemate decapods), therefore, penaeids (dendrobranchiate decapods) do not show regulation of zinc body concentrations to a constant level over a range of dissolved zinc bioavailabilities by matching zinc excretion to zinc uptake. Nevertheless, unlike amphipod crustaceans, P. indicus does excrete some of the zinc newly accumulated from solution after a time delay. Unlike their caridean counterparts, penaeid prawns inhabiting anthropogenically contaminated coastal waters with raised zinc bioavailabilities can be expected to contain raised body concentrations of zinc.Communicated by J.P. Thorpe, Port Erin     

Donax trunculus and Venus verrucosa as bioindicators of trace metal concentrations in Mauritanian coastal waters

Trace-metal concentrations (Cd, Cu, Fe, Mn and Zn) were investigated in two species of abundant filter-feeding molluscs from Mauritania, the wedge shell Donax trunculus L. and the clam Venus verrucosa L. D. trunculus were collected on the beach of Nouakchott at low tide and V. verrucosa were sampled at the Banc d'Arguin at depths varying from 10 to 20 m, in mid-February 1987. D. trunculus contains significantly higher Fe and Zn concentrations than the clam. Total trace-metal content per individual (Y) in D. trunculus could be related to body weight (W) as the power function Y=aW ^b . The subsequent regression coefficient b was >1 for Cu, Fe, Mn and Zn and >1 for Cd. Metal concentrations in both species decreased in the order: Fe>Zn>Mn>Cu>Cd. Comparison of trace-metal concentrations in the small D. trunculus and the large V. verrucosa revealed lower contents in V. verrucosa, except for Cd. The trace-metal distribution in the various organs of V. verrucosa indicates that gills seem to concentrate metals, except Cu, to a greater degree than the other organs (visceral mass and remainder). The relatively elevated content of Fe in D. trunculus and of Cd, Fe and Zn in the gills of V. verrucosa seem to be of natural origin. In view of the scarcity of Mytilus sp. along the Mauritania coast, the molluscs D. trunculus and V. verrucosa are proposed as useful bioindicators of trace-metal concentrations.     

Further 237Pu experiments with the plaice Pleuronectes platessa: Subcellular distribution of plutonium in the liver

The subcellular distribution of ²³⁷Pu in the livers of the plaice Pleuronectes platessa has been studied by differential and isopycnic gradient centrifugation. It has been shown that the ²³⁷Pu is particularly accumulated in pellets sedimenting out at 3000 and 6000 g which, by deduction from marker enzyme tests, contain a mixture of mitochondria and lysosomes. Separation of lysosomes from mitochondria was achieved by using a non-lytic detergent injected into the fish 3 d prior to removal of the livers; it was found that ²³⁷Pu was associated with the lysosomal fraction. In this respect, the metabolism of plutonium of the plaice resembles that of the rat.     

Factors affecting the flux of arsenic through the mussel Mytilus galloprovincialis

Radiotracer experiments were designed to study the effects of certain environmental and biological factors on arsenic accumulation and elimination processes in the Mediterranean mussel Mytilus galloprovincialis. Arsenic (as arsenate) uptake increased with increasing arsenic concentration in the water; however, the response was not proportional, indicating that accumulation was partially suppressed at higher external arsenic concentrations. In general, approximately 80% of the ⁷⁴As taken up was associated with the soft parts, with small mussels concentrating ⁷⁴As to a greater degree than larger individuals. The highest ⁷⁴As concentrations were recorded in the byssus and the digestive gland. Increased temperature enhanced both arsenic uptake and loss. Mussels in sea water at 19 S accumulated approximately three times more ⁷⁴As than those held at 38 S. Arsenic loss was much less affected by salinity, with only a tendency for greater arsenic retention noted at lower salinities. Studies carried out in the laboratory and in situ revealed that arsenic turnover was significantly more rapid in actively growing individuals living under natural conditions. Arsenic-74 loss from the in situ group was essentially biphasic, with biological half-times of approximately 3 and 32 days for the fast and slow compartments, respectively. The active secretion of arsenic in the byssal threads contributed to the total elimination of the element from the mussels.     

Variability in dry weight and vertical distributions of decapod larvae in the Irish Sea and North Sea during the spring

Accumulation of waterborne cadmium in Littorina littorea, Mytilus edulis and Carcinus maenas (collected in 1988 and 1989 around the island of Funen, Denmark) was investigated in a matrix of salinities (10 to 30) and calcium concentrations (2.9 to 8.9 mM Ca⁺⁺). Cadmium accumulation rates in soft parts of L. littorina, soft parts and shells of M. edulis and whole bodies and exoskeletons of C. maenas decreased with increasing salinity. Changes in the calcium concentrations accounted for 72% of the salinity effect on cadmium accumulation rates in L. littorina, whereas calcium concentrations had little or no effect on cadmium accumulation in M. edulis. Cadmium accumulation in the whole body of C. maenas was affected equally by calcium concentrations and total salinity, whereas accumulation in the exoskeleton was mainly affected by changes in total salinity. Individual variability in cadmium accumulation in the organs of C. maenas was greater than the variation attributable either to changes in ambient calcium concentrations or total salinity. An appreciable amount of the inter-individual variability in the cadmium accumulation in all three species was correlated with wet:dry weight ratios of the tissues and size of the organisms.     

Copepod grazing during a declining spring phytoplankton bloom in the Northern North Sea

Grazing rates of larger (Calanus finmarchicus) and smaller (Acartia clausii Pseudocalanus elongatus etc.) copepods on naturally occurring phytoplankton populations were measured during a declining spring phytoplankton bloom. During the initial period, dominated by Chaetoceros spp. diatoms, constant ingestion rates were observed in Calanus finmarchicus at suspended particulate concentrations above 300 g carbon l^-1. Average daily intake during this time amounted to 35 to 40% of body carbon and reached a maximum of 50%. The feeding response of the smaller copepods was not so well defined, although a maximum daily intake of 56% body carbon was recorded. In both groups, feeding thresholds were at particulate concentrations around 50 g C l^-1. The feeding response of C. finmarchicus was correlated with both a change in their own population and in the food cell type. Linear regressions describing the concentration-dependent feeding response were: ingestion rate (IR)=1.16 total particulate volume (TPV)-36.15 during the initial part of the period compared with IR=0.41 TPV-12.18 for the latter period. C. finmarchicus filtered out slightly larger (x 1.2 diameter) particles than the small copepods and, in both groups, some filtering adjustment was made to accomodate to modal changes in the phytoplankton population from 20–30 m to 10 m diameter cells. Particle production during feeding was frequently evident in the smallest size ranges of particles and the ratio of particle production to ingestion rate was greater at low feeding rates.     

237Pu experiments with the plaice Pleuronectes platessa

Some experiments have been made on the metabolism of ²³⁷Pu — a high specific activity, gamma-emitting isotope of plutonium — by the plaice Pleuronectes platessa L. Very little of the isotope was incorporated into fish after 2 months exposure to labelled water. The oral retention from a variety of labelled foods was also very poor, and apart from the gut itself no incorporation of the isotope could, in fact, be demonstrated. Injected ²³⁷Pu was eliminated very slowly, and some evidence was obtained for an inverse relationship between the rate of ²³⁷Pu loss and the rate of growth of the fish. Growing fish incorporated a relatively larger fraction of the ²³⁷Pu body burden into skeletal material, and this was attained at the expense of the isotopic content of the liver. Very little ²³⁷Pu was incorporated into muscle.     

Population dynamics and production of euphausiids

Seasonal changes in abundance, size and aspects of the population structure of Meganyctiphanes norvegica (M. Sars) and Nyctiphanes couchi (Bell) are described from samples taken with the Continuous Plankton Recorder at 10 m depth over a 2 yr period (1966 and 1967) in the North Atlantic Ocean and the North Sea. M. norvegica lived for a maximum of just over 2 yr, and adults of both year-classes spawned during a limited breeding season in the spring or summer. N. couchi spawned over a prolonged breeding season, giving rise to a complex of cohorts with overlapping size ranges. It was concluded that 3 or 4 cohorts were spawned in each year and that the maximum life span was probably greater than 1 yr, although maturity may be attained in less than a year. Estimated annual production at 10 m depth for M. norvegica ranged from 0.80 to 18.74 mg m^-3yr^-1 and for N. couchi from 0.67 to 8.23 mg m^-3yr^-1. P:B ratios ranged from 1.3:1 to 6.3:1 for M. norvegica and 4.0:1 to 5.5:1 for N. couchi.     

Grazing of Acartia hudsonica (A. clausi) on Skeletonema costatum in Narragansett Bay (USA): Influence of food concentration and temperature

Grazing experiments were performed with temperatureacclimated Acartia hudsonica fed the diatom Skeletonema costatum in concentrations ranging from 50 to 3×10⁴ cell ml^-1 at 5°, 10° and 15°C. The ingestion data were best fit by an Ivlev equation. Feeding threshold values of 39 and 59 cells ml^-1 were not significantly different from zero; however, filtration rates were depressed at low food concentrations. Maximum filtration rates increased exponentially with temperature, reaching a maximum with copepods collected at 14°–15°C, and then declining. Both the increase in ingestion rate with increasing food concentration and the maximum ingestion rate were significantly greater as experimental temperature was increased. Maximum ingestion rates were reached at concentrations greater than 6×10³ cells ml^-1. Percent of body carbon ingested per day at 5 g C L^-1 increased from 1.5% at 5°C to 6.7% at 15°C. At 500 g C L^-1, the ingestion increased from 84% (5°C) to 660% (15°C). Percent of body nitrogen at 0.5 g N L^-1 increased from 0.6% per day at 5°C to 2.5% per day at 15°C. At 50 g N L^-1, the ingestion was 42% body nitrogen at 5°C and 250% at 15°C. The influence of grazing by A. hudsonica on phytoplankton in Narragansett Bay, USA was estimated for 1972–1977. The percent of standing stock removed by grazing rarely exceeded 5% per day except during the late spring when S. costatum growth becomes nutrient limited and higher temperatures favor the rapid population growth of A. hudsonica.     

Growth,nutrient uptake capacities and tissue constituents of the macroalgae Cladophora vagabunda and Gracilaria tikvahiae related to site-specific nitrogen loading rates

Cladophora vagabunda (L.) van den Hoek and Gracilaria tikvahiae (McLachlan) have become dominant components of the macroalgal assemblage in Waquoit Bay, a Massachusetts embayment, possibly due to nitrogen (N) enrichment from anthropogenic inputs transported via groundwater. During 1989–1993, we measured site-related growth, ammonium uptake rates and tissue constituents of these macroalgae from areas subject to high N loading rates (Childs River) and lower N loadings rates (Sage Lot Pond). We also conducted in situ and microcosm enrichment experiments to determine what limited algal growth throughout the year. Our results indicated that these species are strongly affected by and have a strong impact on the N environment of this embayment. For example, C. vagabunda and G. tikvahiae from Childs River had higher light-harvesting pigments and tissue-N concentrations than Sage Lot Pond populations. Additionally, both Childs River populations showed greater site-specific growth and N uptake rates, particularly during the summer period of peak growth. In fact, maximum uptake rates of 90 and over 140 mol dry wt g^-1 h^-1 for Childs River C. vagabunda and G. tikvahiae, respectively, suggest that these species can remove substanital quantities of N from overlying waters, and may be responsible for low (often (<1 M) water-column nutrient concentrations during summer. In situ and tank enrichment experiments indicated that growth rates were limited by available N during summer, while P may be limiting during a brief period toward the end of the annual growth cycle (autumn). Under experimental enrichment, growth rates of Sage Lot Pond algae were similar to values measured at the site receiving higher N inputs, and generally, G. tikvahiae showed growth enhancement (up to 0.2 doublings d^-1) under light-saturating conditions (0.5 m) while C. vagabunda showed nutrient-enhanced growth at 2.5 m. The effects of available nutrients on algal growth were strongly influenced by irradiance and temperature, resulting in a complex seasonal interaction that emphasized the dynamic nature of species response to N loading. Dominance by these two macroalgae in Waquoit Bay, as in other areas undergoing eutrophication, is likely related to physiological strategies that enable these species to tolerate large environmental variations, to take advantage of greater N availability and to survive indirect effects of N loading (e.g. reduced irradiance, anoxia).     

Mechanisms of production and fate of organic phosphorus in the northern Adriatic Sea

In the period from 1980 to 1984 organic phosphorus, nutrients, primary production rates (¹⁴C), chlorophyll a (chl a) standing crops, and basic oceanographic parameters were measured during 23 cruises at six stations in the open waters of the northern Adriatic Sea. These waters are significantly influenced by polluted Po River discharge. Organic phosphorus was correlated with several parameters which characterize phytoplankton activity and organic matter decomposition processes. In the late winter-spring period, organic phosphorus is produced during phytoplankton blooms. It is hypothesized that microzooplankton grazing is the main factor increasing the organic phosphorus concentrations in summer (up to 1.1 mol 1^-1). Fall and winter had much lower values (below 0.3 mol 1^-1) due to remineralization processes and an increased water mass exchange between the northern and central Adriatic regions. The direct contribution of organic phosphorus by freshwater discharge was not found to be significant. The higher organic phosphorus concentrations that can occur in low salinity waters are most likely due to their increased capability to support primary production.     

Elemental composition of the hydrothermal vent clam Calyptogena magnifica from the East Pacific Rise

Specimens of the hydrothermal vent clam Calyptogena magnifica were collected at a depth of 2 600 m from 21° N on the East Pacific Rise in spring, 1982. The elemental composition was determined for the total soft tissues, individual organs, and the shell. The soft parts contained high concentrations of a number of trace metals. Iron, copper, and zinc, at 760, 148 and 2 152 g g^-1 dry weight, respectively, were present at the highest concentrations. Silver and antimony exhibited the greatest enrichments when their concentrations in C. magnifica were compared with those measured in a shallow-water marine mussel, Mytilus edulis. In contrast to the soft parts, the shell was not a site of metal accumulation or deposition. Within the soft parts; gills, kidney, pericardium, and mantle were involved in the concentration of various metals; the degree of concentration varied depending on the particular metal under consideration. C. magnifica possesses metal body burdens which are ordinarily considered to be very high and potentially toxic in other species.     

Branchial Na+−K+-ATPase activity during osmotic adjustments in two freshwater euryhaline teleosts,tilapia (Sarotherodon mossambicus) and orange chromid (Etroplus maculatus)

Effects of osmotic stress on the branchial Na⁺–K⁺-ATPase activity in two freshwater euryhaline teleosts (the tilapia Sarotherodon mossambicus Peters and the orange chromid Etroplus maculatus Bleeker) were studied. Direct transfer from fresh water to salt water with a salinity of 35 S caused extensive mortality in tilapia. Of the remaining four saltwater concentrations (4.375, 8.75, 17.5, and 26.25 S), the higher two increased the enzyme activity significantly in the first week without affecting it further during the remaining seven weeks of acclimation. The lower two concentrations failed to elicit any significant change. In the case of orange chromid, all three salt-water concentrations (4.375, 8.75, and 17.5 S) which the fish survived produced a more significant and extensive change in the enzyme activity, which continued to rise during the entire acclimation period. Employing a procedure of gradual transfer, tilapia and orange chromid were successfully adapted to saltwater concentrations of up to 61.25 and 35 S, respectively. In this experiment, almost each successive increase in salinity elevated the enzyme activity further, but the total change in both species was considerably less extensive than might be expected from the direct transfer study. When the freshwater fish were transferred to identical concentrations of pure NaCl or whole ocean salt, the former produced a relatively greater change in the enzyme activity in tilapia. No such difference was seen in orange chromid. During reacclimation of the saltwater-adapted fish to fresh water, the enzyme activity began to decrease immediately in both species, but remained above the freshwater control levels at the end of eight weeks.     

Kinetic sodium analyses in the crab Carcinus mediterraneus

Kinetic analyses were made of the stable sodium and radioactive sodium (²²Na) in some tissues of the crab Carcinus mediterraneus CSRN. Fast ²²Na outflux constant is increased in gills, hepatopancreas, hemolymph, digestive tract and muscles. In the reproductive organs the values of the sodium outflux constant are lower. The values of the fast outflux rates (t=20°C) of sodium amount, in the whole animal, to 22.5 M Na/g/h, in the hemolymph, to 69.3 M Na/g/h; the slow outflux rates have much lower values (0.02 to 0.13 M Na/g/h). Moulting crabs show a rate of sodium outflux 6 times greater than that of intermoulting individuals.     

Chlorophyll a fluorescence,an alternative method for estimating primary production

The in vivo chlorophyll a fluorescence index (F_+DCMU-F_-DCMU/F_+DCMU) of natural waters was compared to the ¹⁴C-determined primary production, and the fluorescence intensity in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (F_+DCMU) was studied as a function of extracted and spectrophotometrically determined chlorophyll concentrations. Samples were taken every second week from May through October, 1979, at the station Systrarna situated in a coastal area of the Bottnian Sea. In addition, samples from the Archipelago Sea of the Baltic were collected on board the Finnish research vessel R/S Aranda during the September cruise 1979. The correlations between the fluorescence index and the ¹⁴C-determined primary production and between F_+DCMU and total chlorophyll concentration were good when samples taken over short time intervals were compared. The shortcomings of both the fluorescence and the ¹⁴C methods are discussed. It is concluded that the fluorescence method is useful if it is desirable to follow with high time resolution any changes in the potential for photosynthesis (or primary production) in a water mass over relatively short time periods; e.g. during an algal bloom. The fluorescence method can furthermore be technically developed for automatic monitoring with a high time resolution. Efforts are being made in our laboratory to develop the method further to give information about the in situ rates of photosynthesis rather than the potential for photosynthesis in a photoplankton population.     

Photosynthesis-irradiance responses and photosynthetic periodicity in the sea anemone Aiptasia pulchella and its zooxanthellae

Sea anemones (Aiptasia pulchella) containing zooxanthellae (Symbiodinium microadriaticum) were maintained in a long-term laboratory culture on a 12 h light (100 E m^-2 s^-1):12 h dark cycle. Photosynthetic oxygen production was measured for the symbiotic association and for freshlyisolated zooxanthellae. Light utilization efficiencies () were similar for both sets of zooxanthellae, suggesting negligible shading of zooxanthellae by animal tissue in this association. Whereas freshly-isolated zooxanthellae were photoinhibited at high irradiances (800 to 1 800 E m^-2 s^-1), zooxanthellae in the host continued to function at photosynthetic capacity. Time of day may influence photosynthetic measurements in symbiotic organisms, as it was found that photosynthesis in A. pulchella followed a diel periodicity at both light-saturating (1 200 E m^-2 s^-1) and subsaturating (150 E m^-2 s^-1) irradiances. There was a peak period of photosynthesis between 12.00 and 14.00 hrs. Light stimulated dark respiration rates of A. pulchella. Dark respiration of sea anemones increased somewhat towards the end of the light cycle and was always greater after exposure to high irradiances.     

Nutrition studies in the nauplius larva of Calanus pacificus (Copepoda: Calanoida)

Nauplii of Calanus pacificus were raised on a mixture of algae. Details of the mouth-parts, such as denticles, labial palps and lobes, setations and structure of the masticatory teeth were examined by scanning electron microscopy (SEM). Under the experimental conditions (15°C and 300 gC l^-1), exponential growth coefficients for the period Nauplii II–VI were 0.179 for carbon and 0.228 for nitrogen. C:N ratios dropping from 5.1 to 4.7. Growth was isochronous, each stage lasting 1.5 days. Respiratory losses were 15 to 19.6% of body carbon daily. Nauplii raised on a given alga showed higher rates of ingestion in the presence of this food, compared to nauplii switched to other algae. Minimal threshold concentrations for feeding were found, depending on the size of the food offered and ranging from 5.8 gC I^-1 for Lauderia borealis (28.7 m spherical diameter) to 47.1 gC 1^-1 for Chlamydomonas sp. (11.0 m). Unlike the Copepodite I stage, Nauplii II–VI larvae were not able to ingest small cells such as Isochrysis galbana (4.3 m), or very large ones such as Ditylum brightwellii (47.5 m) at more than maintenance rations. Below the critical concentration for maximal feeding, ingestion was clearly dependent on size of the cells offered, but the size-dependent relationship was different for diatoms and non-diatoms. Filtering rates increased from a threshold concentration to a maximal rate at about 50 gC 1^-1, and decreased at higher concentrations. Critical concentrations ranged from 125 gC 1^-1 for L. borealis to 1000 gC 1^-1 for Chlamydomonas sp. Maximal daily rations ranged between 100 and 150% of body carbon.