Primary production and environmental factors in an oligotrophic biome in the Aegean Sea

The rate of the primary production of the phytoplankton community in the Petalion Gulf, Aegean Sea, was studied from January 1970 to May 1971, at a station situated at approximately Latitude 37°54N; Longitude 24°11E. A variety of physical and chemical parameters such as chlorophyll, primary nutrients (N,P,Si), temperature, salinity, oxygen and light penetration were also studied simultaneously. The rate of the gross primary production varied from 40 to 200 mg C m^-2 day^-1, with a mean value of 90 mg C m^-2 day^-1. The annual gross primary production was calculated to be 33 g C m^-2, which is the minimum known value in the Aegean and Mediterranean Seas. Maximum production was found at the depth of 20 m on the average, mainly due to high light intensities. Petalion Gulf supports a small photosynthetic biomass, as indicated by the low seasonal values of chlorophyll a (0.01 to 0.18 mg m^-2), the highest values being found in the summer. The low production rate noted may have been due to the low nutrient concentrations found: N, 0.04 to 0.32 g-at/1; P, 0.00 to 0.15 g-at/1; Si, 0.45 to 2.25 g-at/1. It is suggested that inorganic phosphorus and nitrogen may alternate in limiting primary production rates in these oligotrophic waters. The temperate waters of the Petalion Gulf are stratified in summer (15.5° to 24.7°C) and well-mixed in winter (12.9° to 15.0°C); they are oxygen-saturated throughout the year, and of high transparency, with 86 m depth for the euphotic zone on the average yearly. The Petalion Gulf is therefore characterized as a typical oligotrophic biome in the Aegean and Eastern Mediterranean Seas.     

Respiration and excretion by the ctenophore Mnepiopsis leidyi

Respiration (dissolved oxygen and carbon dioxide) and excretion (dissolved organic carbon, inorganic and organic nitrogen and phosphorus) rates were measured for a variety of sizes of Mnemiopsis leidyi over a temperature range of 10.3° to 24.5°C. Both respiration and excretion rates were a direct linear function of animal weight and very temperature sensitive (Q₁₀4). Oxygen uptake ranged from 155 to 489 g at O/(g dry weight) day^-1 and carbon dioxide release from 43 to 166 M. Organic carbon made up about 38% of the total carbon released. Inorganic nitrogen excretion, exclusively in the form of ammonium, comprised 54% of the total nitrogen release and ranged from 10 to 36 M NH₄/(g dry weight) day^-1. Average release of dissolved primary amines (expressed as glycine equivalents) equaled 43% of the organic nitrogen fraction. Inorganic phosphorus release ranged from 2.0 to 4.9 M/(g dry weight) day^-1 and made up about 72% of the total phosphorus loss. The turnover of elements in the body was calculated as 5 to 19% per day for carbon and nitrogen, depending on the temperature, and an even higher 20 to 48% per day for phosphorus. These values are comparable to rates observed for small, active zooplankton.     

Nitrogen assimilation by phytoplankton and other microorganisms in the surface waters of the central North Pacific Ocean

Assimilation rates of ¹⁵N-labelled ammonium, urea, and nitrate by plankton in the upper euphotic zone were measured in 2 summer, 2 winter, and 1 spring cruise in the central North Pacific Ocean. Average rates of ammonium plus urea assimilation could not be determined precisely, but were estimated to be 7 to 25 g-at. N m^-3 day^-1. Indirect evidence suggested that non-photosynthetic microorganisms contributed to these rates. Nitrate assimilation was negligible in the upper waters considered in this report (above the chlorophyll maximum and the nutricline). Potential, nitrate-saturated rates were in the range 1 to 8 g-at. N m^-3 day^-1. Seasonal comparison showed lowest rates of both carbon and nitrogen assimilation rates per chlorophyll a in winter.     

Seston composition of the bottom waters of Great Lameshur Bay,St. John,US Virgin Islands

Seston composition [particulate organic carbon (POC), particulate nitrogen (PN), phyto- and microzooplankton numbers and biomass] was investigated in the bottom waters of Great Lameshur Bay, St. John, Virgin Islands (USA), in October, 1970 during Tektite II Mission 17–50. Mean values of 67.4 g POC · I^-1 and 7.2 g PN · I^-1 were determined. A mean phytoplankton carbon content of 42.2 g · I^-1 and zooplankton carbon content of 5.5 g · I^-1 were calculated from counts. The phytoplankton consisted mainly of dinoflagellates 71.2% phytoplankton carbon. Copepods were the dominant zooplankters (61.8% zooplankton carbon), followed by larvaceans (30.9% zooplankton carbon). Organic carbon content of counted zooplankton faecal pellets ranged between 0.4 and 1.6 g · I^-1, and amounted probably to about 15% of the total zooplankton carbon value. Plankton and detritus components as possible food for coral-reef animals are discussed. The ratio carbon: nitrogen of suspended particles is compared to that of sedimented matter.     

Planktonic ciliates in Southampton Water: abundance,biomass, production,and role in pelagic carbon flow

The abundance and biomass of marine planktonic ciliates were determined at monthly intervals at two stations in Southampton Water between June 1986 and June 1987. The two stations, an outer one at Calshot and an inner one at N. W. Netley, were subject to differing marine and terrestrial influences. The potential ciliate production at cach station on each visit was estimated from these data. Enumeration of ciliates and measurements of biovolume were performed on Lugol's iodinepreserved samples and potential production was calculated using a predictive relationship based on temperature and cell volume. Heterotrophic ciliate abundance and biomass were greatest at both stations during spring and summer months, with respective maxima of 16x10³ organisms 1^-1 and 219 g Cl^-1 recorded at N. W. Netley. Estimates of the potential production of the ciliate community ranged from <1 to 18 g Cl^-1 d^-1 at Calshot and <1 to 141 g Cl^-1 at N. W. Netley, with annual values of 2 and 9 mg Cl^-1 yr^-1, respectively. Abundances, biomass and potential production estimates were generally greater at N. W. Netley than at Calshot. Carbon flow through the ciliate community was assessed using annual production values from both this study and the literature. The annual ciliate carbon requirement was equivalent to 9 and 11% of annual primary production at Calshot and N. W. Netley, and potential annual ciliate production was equivalent to 34% and >100% of the energy requirements of metazoan zooplankton at these locations, although comprising only 8 and 10% of their available food.     

Primary productivity and sizes of pools of organic carbon in the mixed layer of the ocean

We estimated primary productivity and distributions of carbon in the phytoplankton, micro-zooplankton, and suspended and dissolved matter in various areas of the World Ocean to increase our information about the organic carbon cycle in the surface layer of the sea. Primary productivity ranged from about 0.1 gC m^–2 day^–1 in the Gulf of Mexico to 9 gC m^–2 day^–1 in nutrient-rich water off Peru. Phytoplankton carbon ranged from less than 10 g/l in the former to 750 g/l in the latter and in nutrient-rich water off southwest Africa. Micro-zooplankton carbon usually was less than 50 g/l in all waters, and was dominated by ciliates, copepodids, and copepod nauplii in all areas. Concentrations of particulate carbon ranged from 12 g/l off the east coast of South America to 850 g/l off southwest Africa. Concentrations of dissolved organic carbon varied between 0.5 and 1.5 mg/l in all areas except off Peru, where maximum values of 4.5 mg/l were observed. Turnover rates of carbon by small standing crops of micro-flagellates (1 to 5 longest dimension) and dinoflagellates in nutrient-poor waters were lower than those by large standing crops of diatoms and micro-flagellates in nutrient-rich waters. Concentrations of phytoplankton usually accounted for 20 to 55% and micro-zooplankton for 2 to 30% of the particulate carbon in the surface layer of the sea. Concentrations of dissolved organic carbon were not related to concentrations of particulate carbon in most waters except off Peru, where they appear to be directly related.     

Daily ration and specific daily ration of the chaetognath Sagitta enflata

Digestion times, obtained directly from laboratory feeding, were used in conjunction with a day/night series of field samples to estimate the daily ration and specific daily ration of Sagitta enflata Grassi, the most abundant chaetognath in the Gulf Stream near Miami, Florida (USA), during winter and early spring. Feeding was independent of time of day and increased with increasing chaetognath size from 1.7 prey day^-1 for the 11.5 mm size class to 2.9 prey day^-1 for the 21.5 mm class. The diet of s. enflata consisted of 94.8% copepods having a mean weight of 21.8 g, and 5.2% prey chaetognaths estimated to be two-thirds the length of the predators. The daily ration of S. enflata from 12.5 to 20.5 mm in length increased from 48.3 to 143.3 g of prey dry weight and from 18.5 to 48.1 g of prey carbon. The specific daily ration declined from 0.12 to 0.08 dry weight basis, and from 0.26 to 0.14, carbon basis, over the same size range. Prey chaetognaths contributed as much as 51% of the ration on a carbon basis.     

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.     

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.     

Particulate organic carbon and nitrogen in the adjacent seas of the Pacific Ocean

Particulate organic carbon (POC) and nitrogen in sea water were measured in samples collected in the adjacent seas of the Pacific Ocean during the cruises of T. S. Oshoro-Maru (1969, 1970) and the R. V. Hakuho-Maru (KH-70-4, KH-72-1). High values were obtained in the northern North Pacific and the Bering Sea, the concentration of particulate carbon in the upper 50-m layer ranged from 35 to 550 g Cl^-1. In the deep waters of these area, values above 50 g Cl^-1 were frequently observed. The lowest values in the surface layer and deeper layers were obtained in the Japan Sea (23 gCl^-1) and in the South China Sea (7 g Cl^-1) respectively. A consistent minimum was located in the intermediate waters (100–400 m) throughout the entire region studied. Variation with depth was generally irregular with marked peak values in different layers. The POC distribution consited of these peak values and a relatively uniform background concentration. These background values slightly decreased with increasing depth and were different locally. Correlation analysis between carbon concentration and apparent oxygen utilization (AOU) of ambient water for the samples in the Japan Sea and the Sulu Sea showed that there was no systematic decrease of particulate carbon with increasing AOU. In these areas, the carbon concentration scattered in the higher AOU domain ranged from 10–100 g Cl^-1. These observations support the conception that downward transport of particulate matter from the overlying surface layer in the adjacent seas of the Pacific Ocean may be fairly rapid.     

Rates of primary productivity and growth in<Emphasis Type="Italic"> Ecklonia radiata</Emphasis> measured at different depths,over an annual cycle,at West Island,South Australia

The pattern of growth (biomass accumulation) in Ecklonia radiata throughout the year and across a depth profile was investigated using the traditional hole-punch method, and the information presented in context with concurrently measured in situ net productivity rates. The rate of net daily productivity showed a lack of consistent seasonal variability, remaining constant throughout the year at two of the four depths measured (3 m and 12 m), and becoming higher during winter at another (5 m). Throughout the year, rates of net daily productivity differed significantly across the depth profile. Net daily productivity rates averaged 0.017 g C g^–1 dwt day^–1 and 0.005 g C g^–1 dwt day^–1 at a depth of 3 m (1,394 mol O₂ g^–1 dwt day^–1) and 10 m (382 mol O₂ g^–1 dwt day^–1) respectively. In contrast, the biomass accumulation rate of E. radiata was highly seasonal, with low rates of growth occurring in autumn (0.002 g dwt g^–1 dwt day^–1 at both 3 and 10 m) and summer (0.007 and 0.004 g dwt g^–1 dwt day^–1 at 3 and 10 m respectively) and higher rates in spring (0.016 and 0.007 g dwt g^–1 dwt day^–1 at 3 and 10 m respectively) and winter (0.015 and 0.008 g dwt g^–1 dwt day^–1 at 3 and 10 m respectively). The proportion of assimilated carbon used for biomass accumulation varied throughout the year, between 5% and 41% at 3 m and between 28% and 128% at 10 m. The rates of biomass accumulation at all depths represented only a small proportion of the amount of carbon assimilated annually.Communicated by P.W. Sammarco, Chauvin     

Bacteria as food for marine harpacticoid copepods

Feeding experiments were carried out on the harpacticoid copepods Tisbe holothuriae and Paramphiascella vararensis, using various species of marine and brackish water bacteria as food. Short-term experiments with ³H-labelled bacteria are described, as well as experiments covering longer periods of time using non-labelled, dried bacteria. Results show that for both T. holothuriae and P. vararensis, the amount of dry bacteria consumed ranged from 2.06 to 7.07 g copepod^-1 day^-1, indicating a carbon requirement of 1 to 3.5 g copepod^-1 day^-1. The food value of the bacteria strains tested is given in terms of the generation time of the copepods raised on these bacteria.     

The development of a natural plankton population in an outdoor tank with nutrient-poor sea water. I. Phytoplankton succession

Due to complex hydrodynamic and biological inhomogeneities, the phytoplankton species succession cannot be satisfactorily observed, apart from the seasonal blooms which occur in temperate waters. Large flexible plastic tanks have proved to be useful for such observations. In 1972, for 28 days, a phytoplankton succession in nutrient-poor water in the outer harbor of Helgoland was observed in a flexible plastic tank (3 m³). During this period, 3 phytoplankton biomass maxima were formed with many significant correlations. In the first 7 days the ammonia concentration decreased from over 6 to 2 mol 1^-1 for 14 days. The nitrate concentration remained in the range of 3–6 mol 1^-1 and then fell abruptly to 0–2 mol 1^-1. The phosphate concentration was about 0.1 mol 1^-1. Lauderia borealis dominated the first period, and its increase was significantly correlated with the decrease in ammonia. The diatom was succeeded by two dinoflagellates, Dinophysis acuminata and Prorocentrum micans. The last period of the experiment was characterized by a stronger development of Rhizosolenia species. The rapid recovery of the crop in the nutrient-poor water points to intensive remineralization processes. The irregular occurrence of ammonia near the surface was correlated with the appearance of Noctiluca miliaris at this depth. It is expected that repetitions of this type of experiment will permit further explanations of statistical correlations which are not yet clear. As a first step, in order to test hypotheses, a correlation analysis was employed to eliminate the statistically non-significant correlations.This work was supported by the Sonderforschungsbereich 94, Hamburg, of the Deutsche Forschungsgemeinschaft.     

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.     

Effect of pentachlorophenol (PCP) on meiobenthic communities established in an experimental system

Aquaria containing clean sand received a continuous supply of seawater from Santa Rosa Sound, Florida, USA, mixed with known concentrations (7, 76 and 622 g l^-1) of pentachlorophenol (PCP). After 9 weeks, nematodes accounted for 87% of the total meiofauna. Nematode biomass and densities were greatest in aquaria exposed to 76 g PCP l^-1 and were least in aquaria exposed to 622 g PCP l^-1. Epistrate feeders were abundant in control aquaria and aquaria exposed to 7 and 76 g PCP l^-1, but not in aquaria exposed to 622 g PCP l^-1. Selective deposit feeders were not abundant in the control aquaria and aquaria exposed to 7 g PCP l^-1, but comprised 19% of the nematodes in aquaria exposed to 76 g PCP l^-1 and 61% in aquaria exposed to 622 g PCP l^-1.     

Seasonal photosynthetic characteristics of Ascoseira mirabilis (Ascoseirales,Phaeophyceae) from King George Island,Antarctica

Monthly variation in photosynthesis, dark respiration, chlorophyll a content and carbon: nitrogen (C:N) ratios in different lamina sections of adult plants of Ascoseira mirabilis Skottsberg from King George Island, Antarctica, was investigated between September 1993 and February 1994. Light saturated net photosynthesis (P _max) showed maximum values in September (12 to 25 mol O₂ g^-1 fr wt h^-1), and decreased towards the summer to values ranging between 2.0 and 5.0 mol O₂ g^-1. In the distal section, however, a second optimum occurred in December (25 mol O₂ g^-1 fr wt h^-1). Dark respiration rates were also highest in October and November and decreased strongly in December to February (6.0 and 1.0 mol O₂ g^-1 fr wt h^-1, respectively). Gross photosynthesis exhibited high values between September and December. Concomitant with the seasonal decrease of photosynthetic efficiency () from mean values of 1.2 mol O₂ g^-1 fr wt h^-1 (mol photons cm^-2 s^-1)^-1 in September to 0.3 mol O₂ g^-1 fr wt h^-1 (mol photons cm^-2 s^-1)^-1 in January, the initial light saturating point (I _k) gradually increased from 19 to 60 mol photons m^-2 s^-1. Likewise C:N ratios were low in spring (12 to 13) and increased in summer (20). In general, the photosynthetic parameters P _max, gross photosynthesis, and Chl a concentrations were significantly higher in the distal section of the thallus. In contrast, C:N ratios were lower in the distal section of the lamina. The results show that photosynthesis obviously strongly supports growth of the alga in late winter to spring, as it does in some morphologically related brown algae from temperate and polar regions. The question whether growth is additionally powered     

Fractionated phytoplankton primary production,exudate release and bacterial production in a Baltic eutrophication gradient

The distribution of phytoplankton primary production into four size fractions (>10 m, 10-3 m, 3-0.2 m and <0.2 m), the utilization of algal exudates by bacteria and the bacterial production were studied in a eutrophication gradient in the northern Baltic proper. The polluted area exhibits substantially increased nutrient, especially nitrogen, levels while only minor differences occur in salinity and temperature regimes. Total primary production was 160 g C · m^-2 · yr^-1 at the control station and about 275 g C · m^-2 · yr^-1 at the eutrophicated stations. The estimated total exudate release was 16% of the totally fixed ¹⁴CO₂ in the control area and 12% in the eutrophicated area (including the estimated bacterial uptake of exudates). The difference in¹⁴CO₂ uptake rates between incubation of previously filtered water (<3, <2, <1 m) and unfiltered water was used to estimate bacterial uptake of phytoplankton exudates which were found to contribute about half of the estimated bacterial carbon requirement in both areas. Bacterial production was estimated by the frequency of dividing cells (FDC) method as being 38 g C · m^-2 · yr^-1 at the control station and 50 g C · m^-2 · yr^-1 at the eutrophicated stations. To estimate the mean in situ bacterial cell volume a correlation between FDC and cell volume was used. The increased annual primary production in the eutrophicated area was due mainly to higher production during spring and autumn, largely by phytoplankton cells (mainly diatoms) retained by a 10 m filter. Primary production duringsummer was similarin the two areas, as was the distribution on different size fractions. This could possibly explain the similar bacterial production in the trophic layers at all stations since the bulk of bacterial production occurs during summer. It was demonstrated that selective filtration does not quantitatively separate photoautotrophs and bacteria. A substantial fraction of the primary production occurs in the size fraction <3 m. The primary production encountered in the 3-0.2 m fraction was due to abundant picoplankton (0.5 to 8 · 10⁷ ind · l^-1), easily passing a 3 m filter. The picoplankton was estimated to constitute up to 25% of the total phytoplankton biomass in the control area and up to 10% in the eutrophicated area.     

Amino acid uptake and respiration by marine heterotrophs

The concentration and turnover of dissolved free amino acids were measured in samples from 25 and 100 m on three occasions at a station 6 miles off the California (USA) coast. Individual amino acid concentrations varied from undetectable (<0.05 g/l) to 3 g/l, the total amino acid concentration from 1.8 to 8.5 g/l. The greater concentration of total amino acids was always found at 25 m. The predominant amino acids were serine, lysine, aspartate, glutamate and alanine; reliable analyses could not be made for glycine because of a high blank. For the 10 individual amino acids studied, the rate of heterotrophic turnover ranged from undetectable to 1.2 g/l day^-1; serine, aspartate, alanine and glutamate showed the highest rates. In samples from 25 m, the rates were 15 to 20 times higher than those taken from 100 m. The total calculated flux of the amino acids studied varied from 0.015 to 3.2 g/l day^-1 and amounted to 1–10% of photosynthetic carbon dioxide fixation.     

Diurnal gut pigment rhythm and metabolic rate of<Emphasis Type="Italic"> Calanus euxinus</Emphasis> in the Black Sea

The vertical distribution, diel gut pigment content and oxygen consumption of Calanus euxinus were studied in April and September 1995 in the Black Sea. Gut pigment content of C. euxinus females was associated with diel vertical migration of the individuals, and it varied with depth and time. Highest gut pigment content was observed during the nighttime, when females were in the chlorophyll a (chl a) rich surface waters, but significant feeding also occurred in the deep layer. Gut pigment content throughout the water column varied from 0.8 to 22.0 ng pigment female^–1 in April and from 0.2 to 21 ng pigment female^–1 in September 1995. From the diel vertical migration pattern, it was estimated that female C. euxinus spend 7.5 h day^–1 in April and 10.5 h day^–1 in September in the chl a rich surface waters. Daily consumption by female C. euxinus in chl a rich surface waters was estimated by taking into account the feeding duration and gut pigment concentrations. Daily carbon rations of female C. euxinus, derived from herbivorous feeding in the euphotic zone, ranged from 6% to 11% of their body carbon weight in April and from 15% to 35% in September. Oxygen consumption rates of female and copepodite stage V (CV) C. euxinus were measured at different temperatures and at different oxygen concentrations. Oxygen consumption rates at oxygen-saturated concentration ranged from an average of 0.67 g O₂ mg^–1 dry weight (DW) h^–1 at 5°C to 2.1 g O₂ mg^–1 DW h^–1 at 23°C for females, and ranged from 0.48 g O₂ mg^–1 DW h^–1 at 5°C to 1.5 g O₂ mg^–1 DW h^–1 at 23°C for CVs. The rate of oxygen consumption at 16°C varied from 0.62 g O₂ mg^–1 DW h^–1 at 0.65 mg O₂ l^–1 to 1.57 g O₂ mg^–1 DW h^–1 at 4.35 mg O₂ l^–1 for CVs, and from 0.74 g O₂ mg^–1 DW h^–1 at 0.57 mg O₂ l^–1 to 2.24 g O₂ mg^–1 DW h^–1 at 4.37 mg O₂ l^–1 for females. From the oxygen consumption rates, daily requirements for the routine metabolism of females were estimated, and our results indicate that the herbivorous daily ration was sufficient to meet the routine metabolic requirements of female C. euxinus in April and September in the Black Sea.Communicated by O. Kinne, Oldendorf/Luhe     

Relationship between lead concentrations in seawater and in the mussel Mytilus edulis: a water-quality criterion

Regression analysis on data collected from Port Phillip Bay and Western Port, Australia in 1979 shows that there is a significant equilibrium relationship between total recoverable lead in seawater and its concentrations in the mussel Mytilus edulis (P<0.001). The concentration of lead in seawater should not exceed 1.27 g l^-1 if the mussel is not to reach a lead concentration of 2.5 mg kg^-1 wet weight, a value frequently used as a food standard for human consumption. When a lead value of 2.5 mg kg^-1 wet weight is reached, the concentration factor by mussels for lead from seawater is 1969. The critical value of 1.27 g l^-1 could be used as a marine water-quality criterion for lead in waters where mussels are harvested.