Effect of inhibitors of carbonic anhydrase activity on photosynthesis in the red alga Soliera filiformis (Gigartinales: Rhodophyta)

The effect of light intensity, pH and carbonic anhydrase (CA) inhibitors on photosynthesis of the red marine macroalgae Solieria filiformis (Kützing) Gabrielson, collected from Taliarte (Gran Canaria, Canary Islands) in 1991, has been investigated. Plants taken from the sea (wild phenotype) developed spherical morphology (ball phenotype) after 2 mo culture in aerated tanks. The photosynthetic oxygen evolution in the wild phenotype was saturated at 100 mol photons m^-2s^-1, while the ball phenotype displayed saturation at 200 mol photons m^-2s^-1. The inhibitors of total CA activity (6-ethoxizolamide) and extracellular CA activity (dextran-bound sulfonamide) inhibited photosynthesis at pH 8.2, to 90 and 50% respectively, in both phenotypes. No inhibition of the photosynthetic oxygen evolution was detected at pH 6.5. CA activity was associated with both supernatant and pellet fractions of crude extracts of S. filiformis. The rate of alkalization of the medium by the algae was dependent on light intensity. We suggest that carbon dioxide is the general form of inorganic carbon transported across the plasmamembrane in S. filiformis. HCO₃ transport into the cell takes place simultaneously by an indirect mechanism (dehydration to CO₂ catalyzed by CAext) and by direct uptake. Extracellular (CAext) and intracellular (CAint) CAs are involved in the mechanisms of inorganic carbon assimilation by S. filiformis.     

Aqua regia extractable trace elements in surface soils of venezuela

Surface soils (0–15 cm) were sampled at 10–20 km intervals along two transects in Venezuela. One (1162 km, 70 samples) ran west to east parallel with the Caribbean coastline, the other (920 km, 92 samples) ran south to north from the frontier with Brazil to the Caribbean shore. Sampling took place in both a wet and a dry season. Trace metals were extracted from dried, sieved (<2 mm) soil with boiling aqua regia followed by analysis by ICP or flame AAS. Metal values did not differ significantly between the two seasons and dates were averaged. Geometric mean values for the west–east transect were: Cr=41.5, Cu 17.9, Cs 3.6, Li=13.9, Mn=294, Ni=21.3, Pb=17.4, Sr=39.4, V=60.4 and Zn = 83.7g g^–1, respectively. Similarly, for the south–north transect Cr=21.3, Cu=4.3, Cs=1.1, Li=2.0, Mn=55.7, Ni=4.4, Pb=6.1, Sr=13.3, V=28.2 and Zn=16.7g g^–1, respectively. A classification of samples by lithology showed surface soil composition to be related to rock composition. Metal values were low in the soils in the south of the country, in the Guyana highlands (Gran Sabana). Low Zn contents were prevalent. Lead contents were affected by roadside fallout from vehicles using leaded petrol except that high Pb contents of soils in the Gran Sabana were of more complex origin.     

Effects of nitrogen and phosphorus enrichement on in vivo symbiotic zooxanthellae of Pocillopora damicornis

The reef coral Pocillopora damicornis (Linnaeus) was grown for 8 wk in four nutrient treatments: control, consisting of ambient, unfiltered Kaneohe Bay seawater [dissolved inorganic nitrogen (DIN, 1.0 M) and dissolved inorganic phosphate (DIP, 0.3 M)]; nitrogen enrichment (15 M DIN as ammonium); phosphorus enrichment (1.2 M DIP as inorganic phosphate); and 15 M DIN+1.2 M DIP. Analyses of zooxanthellae for C, N, P and chlorophyll a after the 8 wk experiment indicated that DIN enrichment increased the cellular chlorophyll a and excess nitrogen fraction of the algae, but did not affect C cell^-1. DIP enrichment decreased both C and P cell^-1, but the decrease was proportionally less for C cell^-1. the response of cellular P to both DIN and DIP enrichment appeared to be in the same direction and could not be explained as a primary effect of external nutrient enrichment. The observed response of cellular P might be a consequence of in situ CO₂ limitation. DIN enrichment could increase the CO₂ (aq) demand by increasing the net production per unit area. DIP enrichment could slow down calcification, thus decreasing the availability of CO₂ (aq) in the coral tissue.Hawaii Institute of Marine Biology Contribution No. 920     

Arsenic tissue concentration of immature mice one hour after oral exposure to gold mine tailings

A potentially high bioavailability of arsenic in gold mine tailings from a site in northern California has been suggested by solubility studies. To help address this issue, an in vivo dosing study was conducted using 12dayold Swiss Webster mouse pups (n=8/group). A sample of sizefractionated mine tailings from the site (<20m particle size, 691g g^–1 arsenic) was prepared as an aqueous suspension and administered by gavage in a volume that provided 4mg As/kg body weight. The control group received the same volume of a commercial soil (1g g^–1 As) of similar particle size (<60m). No mortality or toxic signs were noted in either group. Tissue samples were collected 1h after gavage, freezedried, microwavedigested and analysed for arsenic by ICP/MS (detection limit 2ng As g^–1 dry weight). Arsenic concentrations (ng As g^–1 dry weight) in tissues from the pups who received mine tailings were significantly higher than in control tissues. The mean elevation in arsenic concentration was highest in the liver (3364% of control, p<0.0001), followed by blood (818 of control, p<0.0001), skin (207% of control, p=0.07), and brain (143% of control, p<0.0001). The carcass arsenic concentration (excluding the GI tract, liver, brain and skin) was 138 of control (p=0.02). The data indicate uptake of arsenic from weathered mine tailings by the immature mouse pups after oral exposure.     

Elemental composition (C,N,H) in larval and crab-1 stages of Pagurus bernhardus (Decapoda,Paguridae) and Carcinus maenas (Decapoda,Portunidae)

Analyses of individual content of carbon (C), nitrogen (N), and hydrogen (H) were carried out for all larval stages of Pagurus bernhardus and Carcinus maenas, and for newly metamorphosed crabs. Maximum range in total larval development is 12.8 to 165.8 g C, 3.2 to 35.1 g N, and 1.9 to 24.9 g H in P. bernhardus and 3.1 to 43.2 g C, 0.7 to 10.1 g N, and 0.4 to 6.3 g H in C. maenas. From these data energy equivalents were calculated. Maximum range in total larval life is 0.43 to 6.38 J ind. ^-1 in P. bernhardus and 0.1 to 1.49 J ind. ^-1 in C. maenas. There is a 32.4% mean loss of energy in P. bernhardus megalopa development; this seems to describe the normal developmental pattern in this stage. Biomass was determined as fresh and dry weight respectively. Individual dry weight is about 3.6 to 5.6 times higher in P. bernhardus (44 to 340 g) than in C. maenas (12 to 93 g) larvae.Contribution to research project Experimentelle marine Ökosystemanalyse sponsored by Bundesministerium für Forschung und Technologie, Bonn (Grant No. MFU-0328/1)     

Bacteriastrum solitarium Mangin,a stage in the life history of the centric diatom Bacteriastrum hyalinum

The initial cell of Bacteriastrum hyalinum Lauder, which is the result of lateral auxospore formation, is identical with the solitary species B. solitarium Mangin. This evidence was obtained in laboratory cultures on B. hyalinum.     

Carbon-isotope ratio gradients in western arctic zooplankton

Zooplankton from 87 stations in the Bering, Chukchi and Beaufort Seas sampled in 1985, 1986 and 1987 showed a geographic gradient in stable carbon-isotope ratios (¹³C). The zooplankton most depleted in ¹³C were found in the central and eastern Beaufort Sea and those most enriched were from the Bering and Chukchi Seas. Average ¹³C values ranged from-20.9 to-26.7 for copepods and from-19.4 to-25.1 for euphausiids. Euphausiids show a minimum of 1.0 enrichment relative to copepods throughout the study area. Relative biomasses of the major zooplankton taxa varied significantly across the Alaskan Beaufort Sea in October 1986, with euphausiids dominating in the west and copepods in the east. These differences in taxonomic composition affected the weighted ¹³C values for total zooplankton and may produce an even more pronounced geographic gradient in zooplankton ¹³C than that found within a single taxon. The bowhead whale Balaena mysticetus migrates between wintering areas in the Bering Sea and summering areas in the Beaufort Sea and feeds over this geographic range. The zooplankton ¹³C gradient is the probable source of ¹³C oscillations found along the baleen plates of this planktivore.     

Plasticity in echolocation signals of European pipistrelle bats in search flight: implications for habitat use and prey detection

We studied the echolocation and hunting behavior of three aerial insectivorous species of bats (Vespertilionidae: Pipistrellus) in the field in order to characterize the signals used by the bats and to determine how call structure varies in relation to habitat structure (uncluttered versus cluttered space). We documented free-flying, naturally foraging wild pipistrelles in various habitats using multiflash stereophotography combined with simultaneous sound recordings. Then we reconstructed the bat's flight position in three-dimensional space and correlated it with the corresponding echolocation sequences. In all three species of pipistrelles, signal structure varied substantially. In echolocation sequences of the search phase we found a consistent association of signal types with habitat types. In uncluttered habitats (obstacles more than 5 m from the bat) pipistrelles emitted almost exclusively narrowband signals with bandwidths less than 15 kHz. In cluttered habitats (obstacles less than 5 m from the bat) they switched to signals with bandwidths of more than 15 kHz. Wideband signals were also used when the bats were turning in cluttered and uncluttered spaces and for an instant after turning away from obstacles. Prey detection occured only when the outgoing signal did not overlap with the returning echo from potential prey. The bats also avoided overlap of echoes from potential prey and obstacles. Based on the results of this study, we propose an overlap-free window within which pipistrelles may detect potential prey and which allows predictions of minimum distances to prey and clutter-producing objects. Correspondence to: E.K.V. Kalko     

Physiological ecology of picoplankton in the North Sea

The distribution of cyanobacteria in the surface waters of the North Sea was measured during July 1987. Numbers of cyanobacteria ranged from 2.5x10⁶ to 1.7x10⁸ cells 1^-1. In the majority of stations, cyanobacterial numbers were highest in the near-surface water and a subsurface maximum was found at only one station. The distribution of ¹⁴C among the end-products of photosynthesis was determined for picoplankton (<1 m) and other phytoplankton >1 m throughout the North Sea. The majority of label was found in the protein fraction of both picoplankton and >1 m phytoplankton; incorporation into lipids and polysaccharides plus nucleic acids was much lower. We interpret the large incorporation into protein to be a consequence of nutrient limitation of these natural assemblages. Photosynthetic parameters of the two size fractions were also determined. Assimilation number (P _m ^B ) and initial slope were greater for the picoplankton fraction than for phytoplankton >1 m but there was no evidence of significant photoinhibition of either fraction at irradiances up to 1 000 E m^-2 s^-1.     

Primary production in Dumbell Bay in the Arctic Ocean

Photosynthesis, chlorophyll, inorganic nutrients, and related factors were measured throughout a productive season in a small coastal inlet of the Arctic Ocean. Significant production was confined to 5 m for a very limited time period beacause of both light and nutrient limitations. Maximum chlorophyll was 8.2 mg Chl a m^-3 and maximum gross and net photosynthesis rates were 830 and 550 mg C m^-2 d^-1. Annual gross and net photosynthesis is estimated at about 12 and 9 g C m^-2 respectively. The effect of light stimulation on assimilation is described, sources of coastal zone nutrient enrichment are considered, and discrepancies between gross and net photosynthesis are discussed with reference to the growth characteristics of the phytoplankton population.Bigelow Laboratory for Ocean Sciences. Contribution No. 76008     

Environmental information stored in otoliths: insights from stable isotopes

The present study compares the stable oxygen-and carbon-isotope ratios (¹⁸0:¹⁶O;¹³C:¹²C) in the otoliths of Atlantic cod,Gadus morhua, with those expected at equilibrium with seawater. Otoliths from juveniles reared for a 3 mo period under controlled conditions indicate that otoliths are formed in isotopic disequilibrium with seawater. This is probably due to positive metabolic fractionating of the heavier isotopes. This vital effect remains constant over the temperature range studied here (9 to 16°C) but may differ among other species. Our data indicate that the concentration of¹⁸O in calcium carbonate is inversely related to temperature and is described as ¹⁸O_a – _w – 3.79 – 0.200(T°C). The¹³C:¹²C ratios of otoliths and body tissues are related to the carbon ratio in the food source, although we found that the¹³C concentration is considerably higher in the otoliths relative te, the body tissues and the diet.     

A Preliminary Study on Soil–Gas Radon Geochemistry According to Different Bedrock Geology in Korea

Three study areas of Kwanak campus (Seoul National University), Boeun (Choongbuk) and Gapyung (Kyonggi) were selected and classified according to their bedrock types in order to investigate soil–gas radon concentrations. The mean values of radon concentrations decreased in the order of Gapyung (40BqL^–1) > Kwanak campus (30BqL^–1) > Boeun (22BqL^–1), and decreased in the order of granite gneiss > banded gneiss > granite > black slate–shale > mica schist > shale–limestone > phyllite schist according to bed rock types. Variation in radon emanation with water content in soils and with soil grain size was assessed by the modified Morse (1976) 3min method. Soil–gas radon concentrations increased with increasing water content in the range of less than about 6–16wt.%, but decreased above 6–16wt.%. Radon concentrations also increased with decreasing soil grain size. Radioactivity analysis of radionuclides of ²³⁸U series in some soil samples indicated their possible radioactive disequilibrium between ²²⁶Ra and ²³⁸U due to the differing geochemical behaviour of intermediate radionuclides. Thus, a radioactive isotope geochemical approach should be necessary for soil–gas radon study.     

Does displacement of spawning time occur in the sibling species Cerastoderma edule and C. lamarcki?

The spawning cycles of the sibling species Cerastoderma edule (L.) and C. lamarcki (Reeve) were studied in allopatric and sympatric Danish populations from 1978–1980. The results do not support earlier findings of reproductive character displacement in sympatric populations of the two species. New records of hybrid formation and intermediate forms are presented and discussed.     

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.     

Temporal variation and distribution of trace metals in freshwater and fish from Calabar River, S.E. Nigeria

An investigation on the abundance and distribution of trace metals (Fe, Cu, Zn, Mn, Cr, Cd and Pb) in water, and nine species of fish samples from Calabar river was carried out in 1992. The concentrations of iron (6000–7240gl^–1), zinc (4910–7230gl^–1), and cadmium (3–7gl^–1) showed moderate pollution while those of copper (420–630gl^–1), manganese (23–48gl^–1), chromium (<10–20gl^–1) and lead (<1–10gl^–1) in water were well below WHO permissible levels. Significant seasonal changes (0.001p0.25) were obtained for iron, copper, zinc, manganese and cadmium in water. Furthermore, iron, zinc and cadmium showed statistically significant spatial changes (0.005p0.10). Of the nine fish species studied, no statistically significant relationship between body weight and the concentrations of the metals was observed. The concentrations of the metals per mean total body weight apparently decreases in the order Fe>Zn>Cu>Mn>Pb>Cd=Cr and were within the limits that were safe for consumption.     

Grazing of the mixotrophic dinoflagellate Gymnodinium sanguineum on ciliate populations of Chesapeake Bay

In situ grazing rates for the mixotrophic dinoflagellate Gymnodinium sanguineum Hirasaka feeding on nanociliate populations of Chesapeake Bay were determined in June and October of 1990 using a gut clearance/gut fullness approach. Recently ingested prey were digested beyond the point of recognition at a rate of 23% h^-1. Estimates of in situ ingestion and clearance ranged from 0 to 0.06 prey dinoflagellate^-1 h^-1 and 0 to 5.8 l dinoflagellate^-1 h^-1, respectively, with daily removal of ciliate biomass representing 6 to 67% of the 20-m oligotrich standing stock. Daily consumption of ciliate biomass by G. sanguineum averaged 2.5% of body carbon and 4.0% of body nitrogen with maximal values of 11.6 and 18.5%, respectively. Ingestion of ciliates may help balance nitrogen requirements for G. sanguineum and give this species an advantage over purely photosynthetic dinoflagellates in nitrogen limited environments. By preying on ciliates, these dinoflagellates reverse the normal flow of material from primary producer to consumer and thereby influence trophodynamics of the microbial food web in Chesapeake Bay.     

The effect of male calling on female locomotor activity of Teleogryllus commodus

Summary The calling song of the -cricket, Teleogryllus commodus, attracts for mating. Both calling and -locomotor activity are under circadian control and the behaviors occur approximately at the same time. Daily playback of calling songs for 3–12 h in constant light failed to entrain -running. Instead, calling acts as an external stimulus which can release -locomotion at any time of the 24-h period, while the clock-induced activity continues to run freely. The stimulatory effect of the calling song causes flexible extension of -locomotor activity, but a subsequent restorative period is necessary. The ecological consequences of acoustical stimulation are discussed.     

Dynamics of the TIT FOR TAT strategy during predator inspection in the guppy (Poecilia reticulata)

Summary One well-known solution to the iterated Prisoner's Dilemma is the TIT FOR TAT strategy. This strategy has three characteristics associated with it. TIT FOR TAT is nice (cooperates on the first move of a game), retaliatory (plays defect against an individual that defected on the prior move), and forgiving (cooperates with an individual which has defected in the past but cooperates in the present). Predator inspection behavior in guppies (Poecilia reticulata) was examined in order to determine whether guppies displayed these three characteristics. Results indicate that while it can be quite difficult to translate the abstract concepts of niceness, retaliation, and forgiveness into measurable behaviors, the data support the hypothesis that guppies display the three characteristics associated with the TIT FOR TAT strategy.The selfish herd and dilution effect are discussed as possible alternative explanations for the observed behavior. These hypotheses alone were insufficient to explain the results.     

Male bird song attracts females — a field experiment

Summary The initial stage of pair formation of the pied and the collared flycatcher (Ficedula hypoleuca and F. albicollis) was simulated in a field experiment. Male dummies positioned near nest boxes and singing by means of tape-recorded song from loudspeakers offered prospecting females a nest box combined with an automatic trap. An unequivocal demonstration of female arrival at the male's territory was obtained by the trapping of the female. Control nest-box traps were provided with silent dummies. Factors other than male song causing female attraction were controlled by a daily switch of the position of singing and silent dummies. Nine out of ten females were caught in nest-box traps with singing dummies (one-tailed binomial test, P=0.011). The result supports the hypothesis that male song functions in mate attraction. This hypothesis has never previously been tested in field experiments although circumstantial evidence for it has been available.     

Copper effects on reproductive stages of Baltic Sea Fucus vesiculosus

Copper is an active ingredient in many antifouling products, and pleasure boats are estimated to be the major single source of copper pollution in Swedish coastal waters. For this reason, the effects of copper were studied on egg volume, fertilization, germination and development of apical hairs of Baltic Sea Fucus vesiculosus L. Germination was the most sensitive stage and was studied at different concentrations of copper, different salinities and different ages of zygotes. Low concentrations of copper, 2.5 g Cu l^-1, added to natural brackish water before fertilization, adversely affected germination at the ambient, suboptimal salinity of 6, suggesting that as little as a doubling of the copper levels in the studied area will severely affect the germination frequency of F. vesiculosus. The addition of 20 g Cu l^-1 caused about 70 to 80% decline in germination at 6S but also at 20S which is higher than optimum. At a salinity close to optimum (14S) no negative effect was noticed on germination when 20 g Cu l^-1 was added. The results suggest that the degree of salinity stress acting upon the zygotes is a more important factor for the response to copper than the influence of salinity on metal availability. When 2.5 to 60 g Cu l^-1 was added to the medium 24 h after fertilization, the zygotes were more resistant, resembling the response of adult marine fucoid tissue.