Sublethal effects of zinc and municipal effluents on larvae of the red abalone Haliotis rufescens

Experiments were conducted to develop a sensitive sublethal toxicity test protocol to determine the toxicity of municipal wastewater effluents to larvae of the red abalone Haliotis rufescens. In multiple tests, fertilized abalone embryos were exposed for 48 h to dilutions of a reference toxicant, zinc sulfate, and to dilutions of primary-and secondary-treated effluents. The resulting veliger larvae were examined microscopically for larval shell abnormalities. In a longer flowthrough experiment, abalone were exposed for the entire larval phase, from the two-cell stage through metamorphosis, to compare zinc effects on metamorphosis with zinc effects on short-term larval shell development. Dissolved oxygen, pH, salinity and temperature were measured daily in test solutions, and zinc concentrations were verified by chemical analysis. No observed effect concentrations (NOECs) for zinc were 39±2.1 g l^-1 in three 48 h exposures, and 19 g l^-1 for the 9 d exposure through metamorphosis. Median effect concentrations (EC₅₀s) were 68±6.9 g l^-1 in 48 h tests and 50 g l^-1 in the 9 d test. Abalone larvae were affected at lower concentrations of primary than of secondary effluent.     

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.     

Grazing and ingestion rates of nauplii,copepodids and adults of the marine planktonic copepod Calanus helgolandicus

The average grazing and ingestion rates of all stages of the marine planktonic copepod Calanus helgolandicus (Calanoida) from nauplius stage IV to adults were measured experimentally at 15°C in agitated cultures. The chain-forming diatom Lauderia borealis and the unarmoured dinoflagellate Gymnodinium splendens were offered as food. The food concentrations were close to natural conditions and ranged from 36 to 101 g of organic carbon per liter. The medium body weights expressed in g of organic carbon of almost all larval stages raised at 49 g C/1 were identical with the weight of the same stages caught in the Pacific Ocean off La Jolla, California, USA. In a log-log system, grazing and ingestion rates increased almost linearly with increasing body weight. Grazing rates ranged from 4 to 21 ml/day/nauplius stage IV to 286 ml to 773 ml/day/female. Ingestion rates increased from 0.2 g to 0.8 g C/day/nauplius stage IV to 18 g to 69 g C/day/female. Grazing and ingestion rates per unit body weight decreased gradually with increasing body weight. The daily ingested amount of food decreased from 292 to 481% of the body weight (g C) of nauplius stage V to 28–85% of the body weight of adult females. Grazing and ingestion performances of all stages increased with increasing particle size. Grazing rates decreased and ingestion rates increased with increasing food concentrations. The published data on food intake of the different age groups of C. helgolandicus show that the young stages of herbivorous planktonic copepods can play a major part in the consumption of phytoplankton in the sea due to their high grazing and ingestion rates.     

Ultrastructure of the gonad and gametogenesis in the eastern oyster,Crassostrea virginica. II. Testis and spermatogenesis

The pelagic harpacticoid copepod, Macrosetella gracilis (A. Scott), is found in association with colonies of the nitrogen-fixing (diazotrophic), bloomforming cyanobacterium Trichodesmium spp. in tropical and subtropical waters. M. gracilis is one of the few direct grazers of these often toxic cyanobacteria. Experiments investigating NH ₊ ⁴ regeneration by M. gracilis were conducted in the Caribbean in September 1992 and the Coral Sea, Australia in November 1994. Rates of M. gracilis ingestion of Trichodesmium thiebautii labelled with ¹⁵N₂ measured in the eastern Caribbean indicated that M. gracilis could consume 33 to 45% of total T. thiebautii colony N d^-1 and >100% of new N fixed d^-1. We also measured the release of NH ₊ ⁴ by M. gracilis feeding on T. thiebautii, as well as by non-feeding copepods, using ¹⁵N isotope dilution methods. In non-feeding copepods, rates of NH ₊ ⁴ release increased as numbers of copepods were increased as both copepod numbers and food availability increased. In the presence of T. thiebautii colonies, M. gracilis had an average rate of NH ₊ ⁴ regeneration of 7.7±1.5 nmol N copepod^-1 h^-1 (±SE), which was significantly higher than when food was absent (1.9±0.7 nmol N copepod^-1 h^-1). Rates of M. gracilis excretion were relatively high based on excretion: ingestion ratios, which could be due to having a high-N food source readily available, to sloppy-feeding effects, or as a response to toxins in the cyanobacterium. Incubations of M. gracilis with and without T. erythraeum resulted in significant increases in [NH ₊ ⁴ ] as a function of copepod density only. Ammonium leakage from the cyanobacterium and/or microheterotroph associates was relatively low. M. gracilis, through excretion and possible mechanical breakage of cells while grazing, appears to provide a direct link between atmospherically derived new nitrogen and regenerated NH ₊ ⁴ in the oligotrophic systems where Trichodesmium spp. are abundant.     

High turnover of inorganic carbon in kelp habitats as a cause of δ13C variability in marine food webs

In a study to assess qualitatively the importance of organic matter derived from kelp production in the Aleutian Islands of subarctic Alaka, replicated samples of autotrophic sources and primary and secondary consumer organisms were sampled for ¹³C among sources, sites, (treatment) islands, and years. Unanticipated variation in the ¹³C of kelps occurred among overtly similar sites at different islands. Variation in the ¹³C of the surface canopy-forming kelp Alaria fistulosa was particularly extreme, ranging from-15.5 to-28.0 compared to the understory kelps, Laminaria spp. A. fistulosa ¹³C varied by as much as 6 to 7 among similar sites at a given island within years, and by as much as 3 to 4 between years at the same sampling site. In serveral cases, ¹³C variation was weakly tracked by some consumer organisms, suggesting that even detritus pathways through the food web can be localized and tightly coupled. Dynamic cycles in the concentration and ¹³C of dissolved inorganic carbon (DIC) and aqueous CO₂ concentration ([CO₂]_aq) were measured at three sites on one island. The ¹³C or organic carbon fixed by A. fistulosa, calculated from diurnal DIC concentration and ¹³C measurements, varied by 15 and varied inversely with [CO₂]_aq concentrations. Local DIC variability, probably resulting from high productivity and decreased turbulence in dense kelp habitats, provides a possible mechanism of variation in kelp ¹³C. The short-term variability in the ¹³C of organic carbon fixed by kelps indicates that sampling methodology and design must assess this potential variation in marine macrophyte ¹³C before making assumptions about the transfer of ¹³C-invariate organic matter to higher trophic levels. On the positive side, a predictable relationship between [CO₂]_aq concentration and kelp ¹³C offers a potentially robust means to assess productivity effects on CO₂ limination in kelps and other complex aquatic macrophyte habitats.     

The respiratory metabolism of Tilapia mossambica (Teleostei)

Tilapia mossambica (Teleostei) weighing 5 to 80 g were acclimated at 30°C to salinities of 0.4 (tap water), 12.5 (50% sea water) and 30.5 (100% sea water). Their respiration was measured at routine activity and the partial pressure of ambient oxygen gradually reduced from 250 to 50 mm Hg. Respiration is salinity-dependent; the proportionate ability to use oxygen in any one salinity is — above the critical pO₂ —the same in all experimental groups. This ability is a function of temperature and increases from 15° to 30°C, becoming temperature independent from 30° to 40°C as long as the pO₂ remains above 150 mm Hg. At 50 mm Hg pO₂, the limiting effect of oxygen causes a decrease in metabolic rate. This limiting effect is minimal in 80 g fish kept in an isotonic medium (12.5 S), allowing greater scope for activity and a higher rate of oxygen uptake.     

Dependence of consumers on macroalgal (Laminaria solidungula) carbon in an arctic kelp community: δ13C evidence

Stable carbon isotope measurements (¹³C) were used to assess the importance of kelp carbon (-13.6 to-16.5) versus phytoplankton carbon (-25.5 to-26.5) to resident fauna of an isolated kelp bed community on Alaska's north arctic coast from 1979 to 1983. The predominant kelp, Laminaria solidungula, showed some seasonal variation in ¹³C which was correlated with changes in the carbon content of the tissue. Animals that showed the greatest assimilation of kelp carbon (>=50%) included macroalgal herbivores (gastropods and chitons,-16.9 to-18.2), a nonselective suspension feeder (an ascidian,-19.0) and a predatory gastropod (-17.6). Animals that showed the least incorporation of kelp carbon into body tissues (<=7%) included selective suspension-feeders (hydroids, soft corals and bryozoans,-22.8 to-25.1). Sponges, and polychaete, gastropod and crustacean omnivores exhibited an intermediate dependence on kelp carbon (15 to 40%). Within some taxonomic groups, species exhibited a broad range in isotopic composition which was related to differences in feeding strategies. In the polychaete group alone, ¹³C values identified four major feeding habits: deposit-feeders (-18.0), omnivores (-20.4), predators (-22.2) and microalgal herbivores (-23.0). Distinct seasonal changes in the ¹³C values of several animals indicated an increased dependence on kelp carbon during the dark winter period when phytoplankton were absent. Up to 50% of the body carbon of mysid crustaceans, which are key prey species for birds, fishes and marine mammals, was composed of carbon derived from kelp detritus during the ice-covered period.     

Changes in blood lead and water lead in Edinburgh. An eight year follow-up to the Edinburgh lead study

This study aimed to measure changes in household water lead and blood lead in young people living in Edinburgh over a period of 8 years. Two hundred and twenty-three families were eligible and 207 (93%) agreed to participate. A half-hour stagnation sample of kitchen cold water was taken from each household, and 171 young people (aged 14–17 years) provided a blood sample for lead analysis. Information on plumbing changes, exposure to other sources of lead and factors which might influence blood lead was collected by questionnaire. Edinburgh is supplied with water treated in one of two treatment plants. There was a different programme of water treatment in each plant. In one (A) lime and orthophosphate was introduced in the interval between the original and follow-up studies. In the other (F) lime treatment began before the original study and orthophosphate was introduced subsequently. In water from treatment plant A, mean water lead levels fell from 34 to 4.3 gL-1 (87%). In water supplied from treatment plant F the corresponding values were 9.3 to 3.6 gL-1 (61%). These reductions were due to both water treatment and removal of lead plumbing. Houses with no lead plumbing have water lead levels 89% lower than houses with lead tanks, and 47% lower than houses with lead pipes. About one-third of households with lead tanks are predicted to have water lead levels above the current EC limit of 50 gL- 1, though only 3% or less of the remaining households would exceed this limit. If the proposed 10 gL-1 limit were introduced, 34% of households supplied from plant A and 25% from plant F would breach the limit. Blood lead levels fell from an average of 11.0 gdL-1 to 4.0 gdL-1. Males had higher values than females and the main factors influencing levels were water lead and age of house. Our results show substantial reductions in household water lead and blood lead in our sample over a period of 8 years and represent an important achievement in public health. However, more progress will be required if the proposed new limit of 10 gL-1 for water lead is to be met. There is a need for the continuing surveillance of household water lead and blood lead levels in representative samples of the population.     

Effects of Hg2+ and Cu2+ on the cytosolic Ca2+ level in molluscan blood cells evaluated by confocal microscopy and spectrofluorimetry

In the present work the effect of Hg²⁺ and Cu²⁺ on the level of cytosolic Ca²⁺ in mussel (Mytilus edulis L.) haemolymph cells were investigated by confocal microscopy and spectrofluorimetry utilizing the fluorescent dye Fluo3. In the blood cells of marine molluscs, exposure to Cu²⁺ and Hg²⁺ in the nanomolar and micromolar range causes a time-and concentration-dependent increase in the cytosolic Ca²⁺ level. Both the presence of a low-calcium containing medium and pretreatment of the cells with the channel blocker Verapamil greatly reduced the effects of higher (50 M) Hg²⁺ concentrations, this indicating that Hg²⁺ enhances the influx of extracellular Ca²⁺ partly through activation of voltage-dependent Ca²⁺ channels. Low concentrations of Hg²⁺ (1 M) and also of Cu²⁺ (0.5 M), an essential element, were able to induce a sustained increase in cytosolic Ca²⁺, which was not affected either by Verapamil pretreatment or by lowering the extracellular calcium concentration. These data indicate that in mussel haemocytes heavy metal cations impair Ca²⁺ homeostasis not only by affecting Ca²⁺ channels, but also by interfering with other mechanisms of calcium transport across cellular membranes, such as the Ca²⁺-ATPases. The resulting increase in cytosolic Ca²⁺ could activate Ca-dependent processes which may be involved in many of the biochemical and physiological alterations observed in the cells of metal-exposed mussels. Specimens used in these experiments were collected from the river Linker near Plymouth, U.K. in June 1991.     

Concentrations of Mn,Fe, Cu,Zn and Cd in the mesopelagic decapod Systellaspis debilis from the East Atlantic Ocean

Specimens of the oceanic decapod Systellaspis debilis were collected from six sites in the East Atlantic Ocean between 1970 and 1984, and were analysed for Mn, Fe, Cu, Zn and Cd. The data confirm that there are small but significant differences in mean metal concentrations from some sites which showed no obvious pattern in relation to geographic location of the samples. As a result, ranges of site means are quoted as baseline levels for each metal (g g^-1 dry wt): 2.3 to 2.9 g Mn g^-1, 31.2 to 77.8 g Fe g^-1, 25.9 to 83.4 g Cu g^-1, 41.9 to 92.9 gZn g^-1, 11.1 to 31.8 g Cd g^-1. The concentration of cadmium in S. debilis from all sites was raised relative to cadmium concentrations reported for coastal decapods, perhaps as a result of dietary enrichment. Metal accumulation may provide useful information for understanding the complex feeding behaviour of many oceanic animals.     

Effect of heavy metals (Zn,Hg, Cu,Cd, Pb,Ni) on the length growth of Mytilus edulis

The shortterm (10–22 d) effect of Zn, Hg, Cu, Cd, Pb, and Ni on the length growth of Mytilus edulis is studied. Significant reductions of growth rate was found at 0.3 g Hgl^-1, 3 g Cul^-1, 10 g Znl^-1, and 10 g Cdl^-1 added to the local sea water, while concentrations of up to 200 gl^-1 of Pb and Ni had no effect on the growth. With exposure to Cu and Zn, there was a linear reduction in growth rate with increasing metal concentration up to about 6 g Cul^-1 and 100 g Znl^-1. Above these levels, growth stopped with Cu, while with Zn it was stabilized at about 20% of control growth. When Hg and Cd were added, a curvilinear relationship between growth and metal concentration is indicated. With Hg, growth rate is nearly zero above 3–4 g Hgl^-1, while the growth rate was 50% of control after 10 d of exposure to 100 g Cdl^-1. At 2 g Cdl^-1 there was a significant stimulation of length increase. Observed EC₅₀-values for growth were 0.3–0.4 g Hgl^-1, 3–4 g Cul^-1, 60 g Znl^-1, and 100 g Cdl^-1.     

Calcification in the maerl coralline alga Phymatolithon calcareum: Effects of salinity and temperature

The coralline alga Phymatolithon calcareum was dredged from 13 m in the Kattegatt, Baltic Sea, in December, 1980, and its rate of calcification was measured by ⁴⁵Ca⁺⁺-uptake methods. Light-saturated calcification rates at 5°C ranged from 15.8 g CaCO₃ g^-1 dry wt h^-1 for the basal parts of the plants to 38.7 g CaCO₃ g^-1 dry wt h^-1 for the tips. These age gradients were not apparent when calcification rates were expressed on the basis of surface area. Experiments with salinity (10, 20, 30) and temperature (0°, 5°, 10°, 20°C) indicated that optimum conditions for calcification were at 30 S and at temperatures above 10°C. Salinity had a greater influence on calcification rate than did temperature, and there was a positive relationship between salinity and calcification rate at all temperatures. In 6 mo old cultures, salinity was again the important factor, with all plants remaining healthy at 30 except those at the highest temperature (20°C). These trends, and the low calcification rates at 10S (4.6 g CaCO₃ g^-1 dry wt h^-1 at 5°C to 8.6 g CaCO₃g^-1 dry wt h^-1 at 20°C) suggest that low salinity may be the explanation for the general absence of P. calcareum from the brackish waters of the Baltic Sea. Short-term experiments in which salinity was kept constant while Ca⁺⁺ concentration was altered, and experiments in which salinity was varied and Ca⁺⁺ concentration kept constant, suggest that it is the calcium ion concentration and not salinity per se which affects calcification rates.     

Compositional topography of melon and spermaceti organ lipids in the pygmy sperm whale Kogia breviceps: Implications for echolocation

The forehead of the pygmy sperm whale Kogia breviceps contains a large melon of fatty tissue in front of a small, fat-filled, cornucopia-shaped spermaceti organ. This unique anatomical structure may possibly play an acoustical role in the whale's echolocation system, similar to the fatty melon sound lens postulated for dolphins. To better understand its function, we have studied the compositional topography of the K. breviceps melon and spermaceti organ lipids. The fatty head tissues of an adult K. breviceps were serially sectioned into 9 transverse slices. Appropriate tissue samples were cut from every other slice, and analyzed for % lipid and lipid class composition. Wax esters and triglycerides were the only major lipids present; their average carbon number in each sample was determined by gas-liquid chromatography (GLC). Our topographical analyses of K. breviceps melon indicate 3 regions of distinctive lipid composition: a fat-poor melon exterior, an outer melon of medium fat content having % triglyceride>% wax ester, and a fat-rich inner melon having % wax ester>% triclyceride. The spermaceti organ contains a fat-rich core of very high wax-ester content (84 to 99%), surrounded by a fat-poor case. Average carbon numbers of both wax esters and triglycerides were lowest in the inner melon and the spermaceti organ. At the rear of the spermaceti organ lies the museau de singe, an apparent sound generator. The lipid topography data plus anatomical and acoustical considerations suggest that the K. breviceps melon/spermaceti organ system may function as an acoustical transducer, directing and refracting sound waves from this source for the purpose of echolocation.     

Osmotic and ionic regulation in the fiddler crab Uca rapax acclimated to dilute and hypersaline seawater

Adult male Uca rapax, collected from the central coast of Venezuela in early 1994 were gradually acclimated to salinities ranging from 1.7 to 139S. The hemolymph osmolality (791±15 mOsmol in crabs from 26S) changed less than three-fold over the entire range of concentrations tested. The urine was isosmotic with the hemolymph in crabs exposed to dilutions <26S, and significantly hyperosmotic in those exposed to media >34.8S. The hemolymph levels of Na⁺, Cl^–, K⁺, Ca²⁺ and Mg²⁺ (320±13, 405±17, 7.8±0.7, 7.2±0.1 and 31±2.2 mmol l^–1, respectively, in crabs acclimated to 26S) were maintained fairly constant over the range from 8.7 to 99S, decreasing by 15% in the more dilute media or increasing sharply to about twice those values in crabs from 139S. The excretory organs contributed to the osmoionic regulation of the hemolymph in crabs exposed to <3.5 or to >34.8S, by means of the partial reabsorption or excretion, respectively, of salts from or into the urine. The results described place U. rapax among the most powerful hypo/hyper-regulating crustaceans known.     

The ammonium/methylammonium uptake system of Symbiodinium microadriaticum

The substrate analogue [¹⁴C]-methylammonium was used to study ammonium/methylammonium uptake by Symbiodinium microadriaticum (zooxanthellae). The value of the Michaelis constant (K _m) for the uptake system was approximately 35 M with methylammonium as substrate; ammonium was a competitive inhibitor of methylammonium uptake, and the K _m for ammonium uptake (determined as the inhibition constant, K _i, for methylammonium) was 6.6 M. Methylammonium uptake by zooxanthellae was light-dependent. Methylammonium uptake rates of zooxanthellae which had been freshly isolated from the hermatypic coral Acropora formosa (0.85±0.05x10^-10 mol min^-1 cell^-1) were lower than those of axenic cultures of the zooxanthellae from Montipora verrucosa (Acroporidae) grown under various nitrogen regimes (1.6 to 12x10^-10 mol min^-1 cell^-1). Maximum uptake rates were found for ammonium-starved cultured M. verrucosa zooxanthellae (10.2 to 12x10^-10 mol min^-1 cell^-1); M. verrucosa zooxanthellae growing with ammonium as nitrogen source and zooxanthellae which had been freshly isolated from A. formosa gave similar and considerably lower uptake rates (0.85 to 1.6x10^-1 mol min^-1 cell^-1). These results suggest that either coral tissue contains sufficient ammonium to repress synthesis of the uptake system of the algal symbionts or, alternatively, there are additional barriers to ammonium transport for zooxanthellae in vivo.     

Relationship between phytoplankton cell size and the rate of orthophosphate uptake: in situ observations of an estuarine population

Orthophosphate uptake by a natural estuarine phytoplankton population was estimated using two methods: (1) ³²P uptake experiments in which filters of different pore sizes were used to separate plankton size-fractions; (2) ³³P autoradiography of phytoplankton cells. Results of the first method showed that plankton cells larger than 5 m were responsible for 2% of the total orthophosphate uptake rate. 98% of the total uptake rate occurred in plankton composed mostly of bacteria, which passed the 5 m screen and were retained by the 0.45 m pore-size filter. There was no orthophosphate absorption by particulates in a biologically inhibited control containing iodoacetic acid. Orthophosphate uptake rates of individual phytoplankton species were obtained using ³³P autoradiography. The sum of these individual rates was very close to the estimated rate of uptake by particulates larger than 5 m in the ³²P labelling experiment. Generally, smaller cells were found to have a faster uptake rate per m³ biomass than larger cells. Although the nannoplankton constituted only about 21% of the total algal biomass, the rate of phosphate uptake by the nannoplankton was 75% of the total phytoplankton uptake rate. Results of the plankton autoradiography showed that the phosphate uptake rate per unit biomass is a power function of the surface: volume ratio of a cell; the relationship is expressed by the equation Y=2x10^-11 X ^1.7, where Y is gP m^-3 h^-1 and X is the surface: volume ratio. These results lend support to the hypothesis that smaller cells have a competitive advantage by having faster nutrient uptake rates.     

β-glucanase activity in the seastar Pisaster ochraceus

Specimens of Pisaster ochraceus, an intertidal carnivorous seastar, were collected in northern Puget Sound at Post Point, near Bellingham, Washington, USA, in November 1993, and used in experimentation through September 1994. Ammonium sulfate fractions (60% precipitates) from excised pyloric caeca (digestive glands) possessed -glucanase activity directed toward such -linked substrates as carboxymethylcellulose (CMC), partially-digested cellulose (cellodextrins) and the synthetic substrate p-nitrophenyl--D-glucoside (PNDG). pH-activity and pH-stability maxima were at pH 6 and 5, respectively. No hydrolytic activity was detectable on native cellulose, native chitin or on cationic-modified celluloses such as DEAE-cellulose. Gel filtration (Sephadex G-100) of this 60% precipitate followed by DEAE-Sephadex column chromatography revealed heterogeneity of -glucanase activity, with an indication of up to 11 distinct fractions with variable activity directed toward the substrates indicated above (CMC, cellodextrins and PNDG). These fractions displayed differing ratios of hydrolytic activity on these substrates. None of the isolated fractions displayed activity toward either native cellulose or native chitin. Gut extracts from the edible mussel (Mytilus edulis), a common prey species of P. ochraceus, were shown to possess partially digested cellulose (cellodextrins). These cellodextrins were further degraded by seastar -glucanases in vitro. The digestion of the gut contents of ingested prey provides a possible adaptive explanation for the presence of -glucanase activity in a carnivore.     

Carotenoids in the tiger prawn Penaeus esculentus during ovarian maturation

Female Penaeus esculentus Haswell were collected by 15 to 20 min duration trawls during 1990. Carotenoids were analysed in the digestive gland, abdominal muscle, the remainder of the body (hereafter called integument) and ovary of prawns in Stage 2 through Stage 4 (fully mature) of maturation. The only oxycarotenoids (xanthophylls) identified were astaxanthins or astaxanthin esters; occasionally low levels of -carotene were detected in the digestive gland. The concentrations of astaxanthin monoesters (AM) and diesters (AD) were highest, with only minor amounts of free astaxanthins (Ast), except in the maturing ovaries, where free astaxanthins predominated (up to 80% of the total carotenoid). Of the total carotenoid, 82 to 94% was in the integument, but at maturity the digestive gland contained 10.7±3.4% and the ovary 5.6±0.9% of the total carotenoid. Only the ovary increased in mass during maturation, reaching up to 5.2% of total prawn mass. During this period, digestive gland concentrations of AM, AD and Ast all increased (tota 20 to 120 g g^-1); levels in the muscle and integument varied little throughout maturation (total 0.4 and 100 g g^-1, respectively); ovary AM levels remained low throughout (1.5 to 1.2 g g^-1), AD increased from only 2 to 5 g g^-1, but Ast increased from 2 to 34 g g^-1. Apart from the ovary, AM concentrations were the most variable. In common with other decapod Crustacea, the maturing ovary of P. esculentus contained high levels of carotenoids, indicating that these may have an important role in early development. The natural diet of P. esculentus includes a variety of carotenoids, but except for a little -carotene, the digestive gland, where absorption occurs, contained astaxanthins, with only an occasional trace of -carotene. This suggests that the conversion of dietary carotenoids to astaxanthin occurs soon after ingestion.     

Environmental Geochemistry of Soils and Waters of Susaki Area, Korinthos, Greece

Soil and water samples were collected from the Susaki area of Korinthos and analysed for heavy metals in order to evaluate their environmental impact. The geology of the studied area includes ultrabasic rocks and Neogene and Quaternary deposits whereas magnesite veins are found within the ultrabasic rocks. In the north part of the studied area post volcanic emissions of H₂S, CO₂ and H₂O vapor continue to the present day. All the samples were analysed for heavy metals by the ICP method. The element ranges (in g g^–1) for soil samples are: Cu 11–63, Pb 5–256, Zn 21–604, Ni 183–2665, Co 12–124, Mn 456–1434, As 5–104, Sr 44–730, V 21–84, Cr 163–2346, Ba 48–218, Zr 3–41, Y 3–13. The metals Pb, Zn, Ni, Co, Cr, Fe, Cu, Mn, As and Sr are enriched in the Susaki soils. The element ranges for water samples are: Cu 65–103ppb, Pb<10ppb, Zn<5ppb, Ni 21–163ppb, Co 2–12ppb, As<30ppb, Cr<20ppb, Ba 36–785ppb, Sb<10ppb, W<10ppb, Bi<30ppb, Mn 0.0–0.9 g g^–1, Fe 0.01–0.22 g g^–1, Na 843–3076 g g^–1, K 98–278 g g^–1, Si 39–65 g g^–1, P 0.1–0.2 g g^–1. There is a natural pollution of soils with elevated concentrations of Ni, Co, Mn, Fe and Cr due to the presence of ultrabasic rocks. Another natural case of As pollution of soils is due to the volcanic activity and the geothermal field in the area. The geochemical data of ground waters and also the ¹⁸, D data showed a mixing in different proportions between sea water and meteoric water.     

Problems in the assessment of the package effect in five small phytoplankters

The magnitude of the package effect in five small phytoplankters [Thalassiosira sp., Clone 2601 (an unidentified eucaryote), Nannochloris atomus, Synechococcus Syn and Synechococcus WH 7803] was assessed by comparison of the absorption spectra of intact and disrupted cells. The package effect was considerably reduced with reductions in cell size and this was broadly in agreement with theoretical predictions based on Mie theory. However, the quantitative assessment of the package effect is confounded by an inability to assign attenuation (apparent absorption) measurements at =750 nm to either scattering or absorption. The magnitude of the apparent absorption at =750 nm was greatest with the smallest picoplankton species examined, and was reduced, but not eliminated, after cell disruption. Whilst the apparent absorption at =750 nm is commonly thought to be due to residual scattering losses, the available evidence does not exclude the possibility that this may be due in part to absorption by cells or cell constituents and this requires further examination. Although these difficulties are particularly evident with the small picoplankton species, there is no reason to expect that they will not complicate the assessment of the package effect in larger phytoplankton cells.