The measurement of respiratory electron-transport-system activity in marine zooplankton

A modification of the tetrazolium reduction method (Packard, 1971) for measurement of respiratory electron transport system activity in marine zooplankton is described. A major modification is the addition of Triton X-100 to the reaction mixture to solubilize formazan produced, thus eliminating an organic extraction step and increasing the sensitivity and versatility of the method. The kinetic parameters of the assay are presented and the apparent effects of Triton X-100 are discussed. The correlation between electron-transport-system (ETS) activity and in vivo respiration (ETS/R) for Calanus pacificus has been found to be 2.02±0.29 (standard deviation). The method is presented as providing a reliable estimate of the zooplankton component of oxygen consumption in the sea.     

Correlation between oxygen utilization and electron transport activity in marine phytoplankton

Measurement of a respiratory control ratio is deemed very useful in determination of energy balance in respiration. We have defined and computed a control ratio as the ratio of the rate of oxygen consumption in vivo to the calculated maximum rate of oxygen consumption in vitro as measured by enzymatic electron transport rates. In order for a control ratio to serve a useful purpose in calculating in situ oxygen consumption in a water parcel, the ratio must be fairly constant. Our results indicated that this is precisely so in healthy cultures of the 9 species of phytoplankton studied. The data presented in this communication further point towards the potential for making reasonable estimates of phytoplankton oxygen consumption in an ocean water parcel by directly utilizing in vitro electron transport activity measurements.     

Cadmium accumulation,LC50 and oxygen consumption in the tropical marine amphipod Elasmopus rapax

Adult Elasmopus rapax, collected from the eastern coast of Venezuela in 1990, were exposed to seawater containing various CdCl₂ concentrations ranging from 0.25 to 5.5 mol l^-1. The 48-h and 96-h LC₅₀ values obtained were 4.0 and 1.6 mol Cd l^-1, respectively. In amphipods exposed to 1 mol Cd l^-1 for up to 240 h, the apparent rate of cadmium uptake was higher in dead animals (most of which had molted during the preceding 24 to 48 h) than in those which survived throughout the treatments without molting. Thus, whole-body cadmium content reached 1.74 mol g^-1 dry weight (dw) in the former and only 0.85 mol g^-1 dw in the latter; the higher body Cd-load may have caused the increased mortality observed in molters. On exposure to cadmium levels above 0.5 mol l^-1 the oxygen consumption rate of non-molters decreased from 2.2 to about 1.5 ml O₂ g^-1 dw h^-1 over the first 24 h, remaining unchanged thereafter. The results place E. rapax among the most sensitive marine organisms yet studied concerning cadmium toxicity, and emphasize the usefulness of the Amphipoda as bioindicators and research tools for bioassays.     

Effects of pressure,temperature and oxygen on the oxygen consumption rate of the Midwater copepod Gaussia princeps

In this study we assessed the amount of lead accumulated in the body of a grazing mollusc by transfer from its algal food in laboratory experiments, and compared these results with the amounts found in naturally occurring molluscs and seaweed. Near La Jolla, California (USA), where the concentration of lead in seawater is probably less than 0.08 g l^-1, most of the naturally occurring Egregia laevigata contains less than 0.4 g Pb g^-1 wet weight. The total body masses, without shells, of juvenile Haliotis rufescens fed on this seaweed for 3 to 6 months showed similar concentrations. When, however, E. laevigata is placed for 1 to 6 days in seawater to which lead has been added (0.1 or 1.0 mg l^-1) both the seaweed and the abalone subsequently fed with it accumulate proportionally larger amounts of lead. After 6 months, young abalone fed on E. laevigata pretreated with 1.0 mg Pb l^-1 accumulated up to 21 g Pb g^-1 wet weight. This amount of lead had no apparent consequences on the growth or activity of the molluscs. Analyses of 6 different organs from adult abalone showed that the lead was selectively concentrated in the digestive gland. In the foot (muscle tissue), which is the part normally consumed by humans, only negligible amounts were found.     

Exposure assessment for mercury from consumption of marine fish in Iran

Seven species of marine fish in the Persian Gulf and three species of marine fish in the Caspian Sea were collected from the local wholesale market in Mashhad, Iran. The mercury (Hg) concentration in muscle samples was determined by atomic absorption spectrophotometry. High total Hg concentration was found in Anchovy sprat (2.04 ± 1.23 µg g^?1) and Whitecheek shark (1.26 ± 1.85 µg g^?1) and the lowest content was detected in common carp (0.24 ± 0.24 µg g^?1) and Caspian salmon (0.25 ± 0.08 µg g^?1). The mean Hg content in all samples was 0.91 ± 1.07 µg g^?1. All samples of Persian Gulf and one sample of Caspian Sea had mean Hg concentration above 0.5 µg g^?1, the level established by joint FAO/WHO on Food Additives. Results showed that the estimated weekly intake of total Hg by a 60 kg adult is below the provisional tolerable weekly intakes recommended by joint FAO/WHO on Food Additives. For prevention of health risks, populations in Iran need to consume fish in moderate amounts.     

Nitrate-reductase activity and in vivo nitrate-reduction rate in Ulva rigida illuminated by blue light

In the marine green alga Ulva rigida C. Agardh, nitrate reductase (NR) is synergetically induced by blue light and nitrate. The present study examines the effect of blue light and a large NO ₃ ^– pulse (0.3 mM) on relevant variables of NO ₃ ^– -assimilation such as NO ₃ ^– -uptake, intracellular NO ₃ ^– -storage, NR activity, in vivo NO ₃ ^– -reduction rate and NO ₂ ^– and NH ₄ ⁺ -accumulation. Nitrate uptake started immediately upon addition of NO ₃ ^– , suggesting the presence of a constitutive carrier, however in the first 1.5 to 2 h, periods of net NO ₃ ^– efflux were frequent. After this time, NO ₃ ^– -uptake and intracellular NO ₃ ^– -accumulation proceeded linearly with time, suggesting the existence of a different NO ₃ ^– -uptake mechanism, which seems to be inducible. Our results indicate that in vivo NO ₃ ^– -reduction is not exclusively dependent on the potential NR activity. In U. rigida, during the first 2 h after a NO ₃ ^– pulse (300 M) there were clear indications that the induction state of the NO ₃ ^– -carrier limits the reduction rate of NO ₃ ^– . Once the induction of the NO ₃ ^– -transporter had been completed (1.5 to 2 h), the NO ₃ ^– -assimilation pathway reached a steady state, NO ₃ ^– -uptake rate, NO ₃ ^– -reduction rate and NO ₂ ^– and NH ₄ ⁺ -accumulation being linear with time. Since the reduction of NO ₃ ^– leads mainly to the accumulation of NH ₄ ⁺ , we conclude that, after the NO ₃ ^– -reduction itself, NH ₄ ⁺ -fixation into carbon skeletons is the limiting step in the assimilation of NO ₃ ^– by U. rigida under blue light.     

Diel fluctuation in zooplankton grazing rate as determined from the downward vertical flux of pheopigments

The diel grazing activity of zooplankton was measured at a single study site in a temperate fjord, Dabob Bay, Washington, USA at several periods during spring, summer and fall of 1979–1981. Pheopigments were used as an indicator of herbivorous zooplankton activity. The downward vertical flux of pheopigment-containing fecal pellets was measured with sediment traps deployed over repetitive 4 h periods. Experiments were run for 24 to 36 h. A maximum in the flux of pheopigments was consistently noted within the euphotic zone during hours of darkness. Diel fluctuations in pheopigment flux showed amplitudes up to 29-fold. Nightly grazing activity accounted for 41 to 82% of the daily (24 h) grazing and was indirectly related to seasonal changes in daylength.Contribution No. 1405 from the School of Oceanography, University of Washington     

Influence of activity and salinity on the weight-dependent oxygen consumption of the rainbow trout Salmo gairdneri

Two types of secretory cell have been found in the cement glands of the cypris larva of Balanus balanoides (L.). Histochemical tests show the presence of proteins, phenols and the enzyme polyphenol oxidase in both the glands and secreted cement. It is proposed that cyprid cement is composed of tanned protein, all the components of which are derived from the cement glands.     

Effects of tetrahydrofuran on dissolved oxygen,pH, culturable aerobic microbes and enzyme activity in wastewater

Tetrahydrofuran (THF) is easy to volatilize and hard to biodegrade. Little is known about the influence and fate of tetrahydrofuran in the environment. The effects of THF were examined on dissolved oxygen, pH, culturable aerobic microbes (bacteria, actinomycetes, and fungi) and four selected enzymes (protease, phosphatase, amylase, and lipase) in wastewater. The wastewater containing some activated sludge was taken from the aeration basin in Sibao sewage plant in Hangzhou, China. THF at lower concentrations of enhanced aerobic respiration and higher concentrations decreased utilization of oxygen in wastewater. The short-term influence of THF on pH was not obvious, but the long-term effect was apparent. Inhibition of THF on culturable aerobic microbes rose with increasing THF concentrations but decreased with prolongation of incubation time. No effect of THF on the activity of protease, phosphatase, amylase, and lipase was found. Data indicate that lower concentrations of THF exert no marked influence on wastewater in an urban sewage plant.     

Carbon conversion and metabolic rate in two marine sponges

The carbon metabolism of two marine sponges, Haliclona oculata and Dysidea avara, has been studied using a ¹³C isotope pulse-chase approach. The sponges were fed ¹³C-labeled diatoms (Skeletonema costatum) for 8 h and they took up between 75 and 85%. At different times, sponges were sampled for total ¹³C enrichment, and fatty acid (FA) composition and ¹³C enrichment. Algal biomarkers present in the sponges were highly labeled after feeding but their labeling levels decreased until none was left 10 days after enrichment. The sponge-specific FAs incorporated ¹³C label already during the first day and the amount of ¹³C label inside these FAs kept increasing until 3 weeks after labeling. The algal-derived carbon captured by the sponges during the 8-h feeding period was thus partly respired and partly metabolized during the weeks following. Apparently, sponges are able to capture enough food during short periods to sustain longer-term metabolism. The change of carbon metabolic rate of fatty acid synthesis due to mechanical damage of sponge tissue was studied by feeding sponges with ¹³C isotope–labeled diatom (Pheaodactylum tricornutum) either after or before damaging and tracing back the ¹³C content in the damaged and healthy tissue. The filtration and respiration in both sponges responded quickly to damage. The rate of respiration in H. oculata reduced immediately after damage, but returned to its initial level after 6 h. The ¹³C data revealed that H. oculata has a higher metabolic rate in the tips where growth occurs compared to the rest of the tissue and that the metabolic rate is increased after damage of the tissue. For D. avara, no differences were found between damaged and non-damaged tissue. However, the filtration rate decreased directly after damage.     

Comparison between the carbon-14 and oxygen consumption method for the determination of the activity of heterotrophic bacterial populations

The activity of the heterotrophic microbial population in the saline Lake Grevelingen (The Netherlands) and the Mediterranean Etang Salses Leucate (France) was determined by measuring the oxygen consumption rate, and the uptake of ¹⁴C-labelled glycollate, pyruvate and an amino acid mixture. The maximum uptake rate of the applied organic compounds in Lake Grevelingen was generally less than 10% of the carbon mineralization rate calculated from the oxygen consumption experiments. Only for pyruvate and glycollate higher values were found of about 30 to 40% with one exceptionally high value for pyruvate of 149%. However, these higher percentages were found in winter, when the activity of the heterotrophic microbial population was very low. In Etang Salses Leucate higher maximum uptake rates of the ¹⁴C-labelled compounds were found, relating this uptake to the oxygen consumption rate. Yet the maximum uptake rate is still always lower than 35% of the carbon mineralization calculated from the oxygen uptake rate. Taking into account that maximum uptake rates were considered, the results demonstrate that the uptake of ¹⁴C-labelled organic compounds represents a serious underestimation of the activity of the bacterial population in situ. The extent of the underestimation depends on the water type. It was concluded that the determination of the heterotrophic activity by measuring oxygen consumption rates offers a better insight into the carbon mineralization process in natural waters than the uptake experiments with ¹⁴C-labelled substrates.Communication no. 228 of the Delta Institute for Hydrobiological Research, Yerseke, The Netherlands     

大亚湾海产中重金属的健康风险与海产消费建议

为了解大亚湾常见野生海产品中重金属的含量及其摄食的健康风险,本文分析了大亚湾10种野生海产品可食用部分中7种重金属(As、Cd、Cr、Cu、Pb、Ni、Zn)含量,并采用单因子污染指数(P_i)、综合污染指数(P_c)方法评价其污染程度,进一步采用美国环保署推荐的健康风险评估模型评估其摄食的健康风险.结果表明,7种重金属含量分别为4.28×10~(-2)—1.31×10~(-1)、8.58×10~(-5)—2.19×10~(-2)、2.69×10~(-3)—9.54×10~(-3)、1.92×10~(-2)—3.05×10~(-1)、ND—2.14×10~(-2)、8.40×10~(-4)—2.75×10~(-1)、1.92×10~(-1)—6.13×10~(-1) mg·kg~(-1)(湿重).与国内外其它地区相比,处于相对较低水平;与历史数据相比,呈现降低趋势.P_i及P_c结果表明,金钱鱼、平鲷、口虾蛄和棒锥螺中As处于轻度污染水平,其余重金属均处于无污染水平.风险评估结果表明,大亚湾海产品可食用部分中总砷的摄食致癌风险较高,儿童/青少年的致癌风险高于成人1.5倍.金钱鱼、口虾蛄、杜氏枪乌贼、近缘新对虾、蟹和棒锥螺的日均消费量(成人57.4 g·d~(-1),儿童/青少年42.4 g·d~(-1))均高于消费建议中给出的相应安全阈值,建议消费者适当控制这些海产品的日食用量和月食用餐数.As在海产品中较高的检出,需予以进一步关注.     

Heavy metals uptake from aqueous solutions using marine algae (Colpomenia sinuosa): kinetics and isotherms

The adsorption of copper, zinc, cobalt, lead and cadmium ions onto Colpomenia sinuosa was studied as a function of contact time, initial metal ion concentration and initial pH. In addition, desorption studies were performed. Characterisation of this adsorbent was also confirmed by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analysis. Batch adsorption experimental data were analysed using Langmuir, Freundlich and Dubinin–Raduschkevich (D–R) adsorption isotherms. The results indicated that the biosorption equilibrium was well described by both the Freudlich and D–R isotherms. Moreover, sorption kinetics was performed and it was observed that equilibrium was reached in<60 min, which could be described by the pseudo-second-order kinetic model for all heavy metals. The sorption of heavy metals onto the biomass was largely dependent on the initial solution pH. The elution efficiency for heavy metal ions desorption from C. sinuosa was determined for 0.1 M HCl, 1.0 M HCl and 1.0 M HNO₃. Desorption efficiency and also adsorption capacity were highest for Pb(II). The results indicate that C. sinuosa has great potential for the removal of heavy metals in an ecofriendly process.     

Stable isotope and biochemical fractionation in the marine pelagic food chain: the jellyfish Pelagia noctiluca and net zooplankton

In our field study we analyzed the C and H isotopic and biochemical (C, N, P, protein, lipid, carbohydrate) composition of the jellyfish Pelagia noctiluca (collected from the Gulf of Trieste in 1985 to 1986) and its presumed diet-net zooplankton. The mean ¹³C (-18.8) and D (-58.4) ratios of P. noctiluca showed enrichment in heavy isotopes relative to net zooplankton (2 for carbon and 30 for hydrogen). Both the jellyfish and net zooplankton were characterized by a linear correlation between ¹³C and D. C. N, P, protein, lipid, and carbohydrate contents of P. noctiluca were low on a dry weight basis as compared to net zooplankton. Significantly lower C:N and C:P ratios were found in jellyfish indicating a greater loss of carbon relative to nitrogen and phosphorus along the passage to a higher trophic level. Isotopic and biochemical evidence indicate that, though collected in nearshore waters, P. noctiluca depended on autochthonous marine organic matter.     

Effects of oxygen,mannitol and ammonium concentrations on nitrogenase [C2H2] activity in a marine skeletal carbonate sand

Following a lag of 3 to 18 h, acetylene reduction in mannitol-amended sand systems proceeded at approximately constant and high rates for periods up to 4 days. Carbon dioxide production and O₂ consumption were low in these systems in comparison to similar systems additionally amended with ammonium, indicating N-limitation of growth in the former. Thus, long-term acetylene assays of mannitol-amended sand and suspensions from the sand incubated at various partial pressures of oxygen could be used to characterize the O₂-sensitivity of the N₂-fixing bacterial population as a whole, in batch-type systems with a minimal degree of enrichment or change in pO₂ during the course of the assays. Results of various studies suggested that aerobic or microaerophilic N₂-fixing bacteria were absent or scarce in the sand, and that nitrogenase activity occurring in aerobically incubated systems occurred in anaerobic microenvironments. Hydrogen stimulated acetylene-reducing activity, but the time course differed from that of mannitol-supported activity, and proceeded with shorter lags in systems incubated at 0.2 and 0.05 atm O₂ than in systems incubated anaerobically. Efficiency of N₂ fixation [C₂H₂] increased with decreasing initial mannitol concentration. For sand washed with seawater to remove native combined inorganic nitrogen, and amended with 0.015% mannitol, 374 μmoles added NH₄-N/kg wet sand caused almost complete repression of nitrogenase activity, while concentrations as low as 12 μmoles added NH₄-N/kg wet sand appeared to cause at least partial repression of nitrogenase activity. Some implications of these results for the existence of anaerobic microenvironments in the cavities of skeletal carbonates, and for N₂-fixation in the seagrass rhizosphere are discussed.     

Comparative studies on the metabolism of shallow-water and deep-sea marine fishes. V. Effects of temperature and hydrostatic pressure on oxygen consumption in the mesopelagic zoarcid Melanostigma pammelas

Measurements have been made of routine oxygen consumption rates ( ) of the mesopelagic deep-sea zoarcid fish Melanostigma pammelas. Determinations were made over ecologically relevant ranges of 3 variables; temperature (3° to 10°C), hydrostatic pressure (1 to 170 atm), and oxygen partial pressure (1 to 160 mm Hg). Weight-specific s were uniformly low. Of the 3 test variables, only temperature had significant metabolic effects within the ranges studied. Q₁₀'s were 6.75 between 3° and 5°C. 1.47 between 5° and 7°C, and 17.4 between 7° and 10°C. These Q₁₀'s were constant over the hydrostatic pressure range studied. Between 3° and 7°C the fish regulated their rates of oxygen consumption down to PO₂'s comparable to those occurring in their natural environments (6 to 12 mm Hg). The showed no capacity to tolerate anoxic conditions. The physiological and ecological significance of these results is discussed, particularly with reference to thermal effects and to the basis of survival of this fish in the oxygen minimum layers of the eastern Pacific Ocean. Since it is possible to maintain M. pammelas in the laboratory for extended periods of time (over 12 months) it could serve as the basis for many interesting studies of deep-sea fish biology.     

Use of biomarkers in zooplankton for assessment of the 'health status' of marine and brackish environments: a short overview

The biomarker approach has been used for 25 years to study the environmental quality of marine, brackish and freshwater ecosystems. Biomarkers may indicate health status and can be applied to organisms of all zoological phyla by destructive or non destructive methods. For 5 years we have been using this approach in zooplankton to detect ecotoxicological alterations at low levels of the food chain due to contaminants. Here we review our approach to validate and apply biomarker techniques in zooplankton. We discuss advantages, limitations, some results and future research. We indicate that biomarkers in zooplankton can be used as new indices of trophic status and ecological integrity of Italian marine coastal and lagoon environments, to be included among the tools specified by Italian law D.Lgs. 152/2006.     

Changes in oxygen consumption and heart rate of the blue swimming crab, Portunus pelagicus (Linnaeus, 1766) following exposure to sublethal concentrations of copper

Weight specific oxygen consumption and heart rates were investigated in blue swimming crab, Portunus pelagicus to indicate the stress in response to increasing salinities (50, 75, 100 and 125%SW) and increasing copper concentration (0, 0.75, 1.5, 3 and 6 ppm copper) at temperature 25 degrees C. Oxygen consumption (micromol.g(-1).h(-1) was measured using closed system respirometer (Strathkelvin Instruments oxygen meter model 781). Heart rates (beat.min(-1)) were recorded using impedance techniques. It has been found that oxygen consumption and heart rate increased with decreasing salinities and increasing copper concentration. The statistic showed weight specific oxygen consumption of P. pelagicus after 96 hr exposure to 6 ppm copper in all salinities were significantly different (P < 0.05) from 0 ppm copper. Mean heart rate of P. pelagicus in 50%SW after 96 hr exposure to 6 ppm copper were significantly different (P < 0.05) from 0 ppm copper.