Hydrostatic pressure-induced apoptosis on nauplii of Calanus sinicus

The effect of hydrostatic pressure on embryonic development of the calanoid copepod Calanus sinicus was studied. Differences of pressure effect among blastomere stages, 1-cell, 2-cell, 4-cell, 8-cell, 16-cell, blastula and limb-bud stage, were examined under two pressurizing conditions, abruptly (10 atm/min) and gradually (0.1 atm/min) increasing. Egg hatching success, deformity frequency and apoptotic cell degradation of hatched nauplii were examined. Egg hatching success rate was not significantly different between blastomere stages, and also between pressurizing conditions. Deformity frequencies of hatched nauplii were low in the early 1-cell and 2-cell stages, and high in the later blastula and limb-bud stages, in both abrupt and gradual pressurizing conditions. On the other hand, in regard to difference in pressurizing conditions, deformity frequency in gradual pressurizing was significantly higher than that in abrupt pressurizing rate. Gradual pressure increase seems to be more harmful to C. sinicus eggs than abrupt pressure change. Apoptosis induced in nauplii by hydrostatic pressure was detected for the first time in marine zooplankton. The embryos of C. sinicus are sensitive to pressure variations, that is, these embryos are supposed to sink to deeper waters, incurring greater risk of having deformities. In the field, C. sinicus ascend to the surface and spawn at night. By looking from this upward behavior, eggs are spawned at lower pressure and warmer temperature. Probably, the harmless low pressure and warm temperature lead eggs to hatch early and to recruit successfully.     

Influence of hydrostatic pressure on l-glutamate dehydrogenase from the Antarctic fish Chaenocephalus aceratus

The influence of hydrostatic pressure on the stability and activity of glutamate dehydrogenase (GDH) from the liver of the Antarctic fish Chaenocephalus aceratus (Notothenioidei: Channichthyidae) has been investigated using the homologous bovine enzyme for comparison. At gradually increasing pressure, the fish GDH retains all activity up to 140 MPa, whereas in the same pressure range the bovine enzyme is slightly inactivated. The kinetics of pressure-induced inactivation of Antarctic GDH displays an exponentially decreasing residual activity as a function of the incubation time, whereas the bovine enzyme shows a complex pattern of behaviour in the first 20 min of incubation, attributable to the transient formation of aggregates. The coenzyme NAD increases the stability of both enzymes. The activation volume calculated for the reaction catalysed under pressure by fish GDH is higher than that of the bovine enzyme. These results indicate that the molecular properties of fish and bovine GDH are affected differently by hydrostatic pressure. A common mode of inactivation under extreme conditions of pressure and temperature of the cold-adapted Antarctic fish and mesophilic bovine GDH is deduced and discussed. Received: 20 October 1998 / Accepted: 7 May 1999     

Possible strategy for the survival of marine bacteria under starvation conditions

A population of a psychrophilic marine vibrio (Ant-300) suspended at a low cell density in natural seawater (SW) or artificial seawater (ASW) showed an initial 200-fold increase in cell numbers. Ant-300 suspended in ASW at various densities showed a magnified initial increase in numbers as well as increased longevity as the population density decreased. The magnitude of the initial increase and the viability of the cells after 7 weeks continued incubation were the same whether the cells were suspended in SW, ASW amended with amino acids, or organic-free ASW. Continued incubation (long-term starvation) of a culture of Ant-300 at low cell densities in ASW showed that after 70 weeks over 15 times the orginal number of cells were still viable. When compared to the starvation survival of other bacceria, Ant-300 exceeds the longest reported starvation survival by at least 2.5 times. Our data indicate that Ant-300 is especially adapted for survival at low nutrient concentrations and low population densities due to a sustained increase in cell numbers that may represent a species survival mechanism for marine bacteria.Technical Paper No. 4493, Oregon Agricultural Experiment Station.     

Behavioral response to hydrostatic pressure in larvae of two species of xanthid crabs

Responses of pelagic larvae of two species of xanthid crabs to manipulations of hydrostatic pressure were examined and compared. One species, Rhithropanopeus harrisii (Gould), is a temperate estuarine species, while the other, Leptodius floridanus (Gibbes), inhabits shallow water and reefs in tropical and subtropical regions. All zoeal stages of R. harrisii detected pressure stimuli presented in increments as small as 0.025 atm. Both Stage I and II zoeae of L. floridanus responded to pressure stimuli presented in increments of 0.1 atm. Stage I responded when pressure was changed by the smallest increment tested, 0.025 atm, but Stage II did not. L. floridanus zoeal Stages III and IV, however, did not change vertical position relative to control larvae when subjected to pressure stimuli. The capacity of R. harrisii zoeae to respond to changes in hydrostatic pressure may be related to their retention in the estuarine environment. In L. floridanus, a non-estuarine species, the pressure response is important only in the first zoeal stage and may function promarily in dispersal.     

Microbial transformations in deep-sea sediments: free-vehicle studies

Radiotracer techniques can be used to assess eitherin-situ metabolic activities of natural microbial populations or potential turnover rates of specific substrates under the givenin-situ conditions. The second approach has been used in deep-sea sediment studies where steady-state conditions are unlikely to occur because of the heterogeneous distribution of nutrients as a result of a patchy input by depositing particulates. Recent sediment trap studies have shown that particulate matter reaching the deep sea does contain simple organic compounds. Therefore, the present experiments dealt with the measurement of carbon incorporation and respiration of¹⁴C-labeled acetate, glucose, glutamate and trimethylamine in deepsea sediments. Free vehicles, i.e. aluminum framed tripods that descend untethered to the deep sea floor and return automatically, were used for thein-situ injection and incubation of cores at depths of 2600 to 5330 m. The data were compared to those obtained from (1) parallel samples incubated at 1 atm andin-situ temperature and (2) a shallow-water station (Buzzards Bay, 12 m). Rates measuredin situ generally decrease with water depth as well as with depth in the upper 9 cm of top sediment. In most experiments, rates measured in the 1 atm controls were higher than those observedin situ. This fact supports the general notion that natural populations of deep-sea sediment contain barotolerant and barophilic microorganisms in varying proportions.     

Hydrostatic pressure-induced apoptosis on nauplii of Calanus sinicus

The effect of hydrostatic pressure on embryonic development of the calanoid copepod Calanus sinicus was studied. Differences of pressure effect among blastomere stages, 1-cell, 2-cell, 4-cell, 8-cell, 16-cell, blastula and limb-bud stage, were examined under two pressurizing conditions, abruptly (10 atm/min) and gradually (0.1 atm/min) increasing. Egg hatching success, deformity frequency and apoptotic cell degradation of hatched nauplii were examined. Egg hatching success rate was not significantly different between blastomere stages, and also between pressurizing conditions. Deformity frequencies of hatched nauplii were low in the early 1-cell and 2-cell stages, and high in the later blastula and limb-bud stages, in both abrupt and gradual pressurizing conditions. On the other hand, in regard to difference in pressurizing conditions, deformity frequency in gradual pressurizing was significantly higher than that in abrupt pressurizing rate. Gradual pressure increase seems to be more harmful to C. sinicus eggs than abrupt pressure change. Apoptosis induced in nauplii by hydrostatic pressure was detected for the first time in marine zooplankton. The embryos of C. sinicus are sensitive to pressure variations, that is, these embryos are supposed to sink to deeper waters, incurring greater risk of having deformities. In the field, C. sinicus ascend to the surface and spawn at night. By looking from this upward behavior, eggs are spawned at lower pressure and warmer temperature. Probably, the harmless low pressure and warm temperature lead eggs to hatch early and to recruit successfully.     

Activité biologique en domaine profond: transformations biochimiquesin situ de composés organiques marqués au carbone-14 à l'interface eau-sédiment par 2000 m de profondeur dans le golfe de Gascogne

In June 1983,in situ water-sediment interface experiments were conducted with the submersible Cyana at 2 000 m depth in the Bay of Biscay. Dissolved or particulate¹⁴C-labelled organic compound was injected into a compartment of a box-corer specifically adapted for use with the submersible. After incubation, the biochemical reactions were stopped by addition of Formalin. In the laboratory, the pathways of the labelled molecules in the various extracts were followed by means of chemical and granulometric fractionation and isolation of meiofauna. Various experiments run at 1 atm and atin situ pressures, for incubation times of between 3 and 144 h, revealedin situ biochemical transformation. After recovery of the samples, activity at 1 atm was low, with only 4% of the radioactivity being recovered in the macromolecules against 84% for thein situ experiments. These results comprise new evidence of the existence of a rapid biochemical transformation at great depth in the ocean and therefore of the activity of the microflora, microfauna and meiofauna which are living in the superficial sediment.

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Contribution No. 49 de l'IFREMER     

Aerobic nitrogenase activity measured as acetylene reduction in the marine non-heterocystous cyanobacterium Trichodesmium spp. grown under artificial conditions

Aerobic nitrogenase activity in the marine non-heterocystous cyanobacterium Trichodesmium spp. NIBB 1067, isolated off the Izu Peninsula, Japan in 1983 and grown under artificial conditions, was assayed by the acetylene reduction method. This strain exhibited acetylene reduction activity under aerobic conditions when cells had been grown in the medium free of combined nitrogen. Activity was markedly enhanced by light, and dependent on the growth phase being higher during the exponential growth phase and lower during the late linear and stationary growth phases. Since typical colony formation occurred during the last growth phase, the present results contradict the idea that N₂-fixation depends on colony formation. The photosynthesis inhibitor DCMU at 10^-6 M inhibited light-dependent acetylene reduction completely. Acetylene reduction by Trichodesmium spp. was tolerant of O₂ as strongly as that in the heterocystous cyanobacteria. Even at a partial pressure of oxygen (p_{O 2}) of 3 atm, the activity still remained as high as half of the maximum. It was almost under anaerobic conditions. Maximum activity was obtained at pO₂ of ca. 0.1 atm.     

Assessing the Leakage Rates from Punctured Submerged Vessels

The leakage of fluid leaving a puncture in a pressurized vessel immersed in a quiescent, miscible medium is studied under steady flow conditions. This problem has engineering applications in submerged pipelines and hazardous gas lines. The leakage rate for the puncture is characterized as functions of various hydrodynamic and geometric conditions. Dimensional analysis shows that the leakage percent, Q*, is a function of the Reynolds number, the pressure ratio between the center of the tube and the external hydrostatic pressure, P^*, and the hole-to-main tube diameter ratio, D^*. The effect of puncture shape is also examined, rectangular and circular. A 3-D finite volume computational model is constructed for laminar flow of a Newtonian fluid under steady conditions and validated with supporting experiments. The results show that the fractional leakage rate Q* increases with P^* and approaches a constant value at high P^* for a fixed Reynolds number. In addition, it is found that the leakage rate increases with decreasing Reynolds number at a fixed pressure ratio. The geometric effect of the diameter ratio is shown to have a more pronounced effect near a pressure ratio of two with more fluid exiting the puncture for larger diameter ratios. The results of the shape analysis show that the circular puncture has the largest fractional leakage when compared to a rectangle with an equivalent cross-sectional area.     

铜锈环棱螺室内实验条件优化

铜锈环棱螺作为一种新兴的潜在生态毒理学模式生物,适宜实验条件是开展其室内毒理学研究的基础。在人为控制条件下,初步探讨了饵料、水深、底质、密度和钙离子浓度养殖条件对铜锈环棱螺成体生长的影响,并进一步对麻醉条件进行了筛选(Mg Cl2·2H2O、乙醇、丁香酚、盐酸普鲁卡因和MS-222)。结果表明:当投喂冰鲜小球藻、密度6个·L-1水体积、水深10~15cm、泥土底质并且水中钙离子浓度30 mg·L-1时,铜锈环棱螺的体重增长最为明显。麻醉效果表明,Mg Cl2·2H2O对成螺的麻醉时间短并且伤害小,可作为实验用麻醉剂首选。以上研究结果为发展以铜锈环棱螺为模式生物开展环境(生态)毒理学研究奠定了基础。     

Saving by freezing? Metabolic rates of<Emphasis Type="Italic"> Adamussium colbecki</Emphasis> in a latitudinal context

Standard metabolic rates of the endemic Antarctic scallop, Adamussium colbecki (Smith, 1902), were measured in austral summer and under simulated winter conditions. Average mass-specific metabolic rates were significantly different between "summer" (151.17±45.06 µl O ₂ g ^-1 h ^-1) and "winter" (106.52±39.65 µl O ₂ g ^-1 h ^-1) animals. The overall metabolic rates of A. colbecki are comparable to those of other Antarctic bivalve species, but well below those of temperate scallop species. Data for 24 scallop populations (13 species) from different latitudes give no evidence for elevated metabolic rates in A. colbecki as suggested by the concept of "metabolic cold adaptation". A world-wide comparison of metabolic rate and overall growth performance of scallops indicates that in the Antarctic scallop the energetic advantage of low basal metabolism does not counterbalance the disadvantage of the prolonged seasonal period of food shortage.     

Developmental physiology of Antarctic asteroids with different life-history modes

Rates of respiration and protein synthesis were measured during embryonic and larval development of Antarctic asteroids with different life-history modes (non-feeding and feeding larvae: Acodontaster hodgsoni, Porania antarctica, Odontaster meridionalis). Patterns of respiration for these species all show an increase during embryogenesis, with subsequent maintenance of routine respiration (“starvation resistance”), even in the absence of food for ~4 months (O. meridionalis). Fractional rates of protein synthesis (i.e., rate per unit mass of whole-body protein content) in the Antarctic larvae are essentially identical to those of temperate species. Larvae of O. meridionalis had an average fractional synthesis rate of 0.52% ± 0.05 h⁻¹ at −1.0°C, which is comparable to the temperate asteroid Asterina miniata at 0.53% ± 0.14 h⁻¹ at 15°C. For embryos of the asteroids A. hodgsoni and P. antarctica, fractional rates of protein synthesis (~0.2% h⁻¹) also are comparable to those reported for embryos of temperate echinoderm species. While rates of synthesis are high, rates of protein deposition are relatively low (percent of protein synthesized that is retained for growth). During a ~4 month growth period for larvae of O. meridionalis, the average protein depositional efficiency was 5.2%. This contrasts with higher rates of depositional efficiency reported for similar developmental stages of temperate echinoderm species. The biological significance of maintaining high rates of macromolecular synthesis for species with low rates of cell division and low protein depositional efficiencies is intriguing in the context of understanding the mechanistic bases of extended life spans and dispersal potential in response to changing Antarctic environments.     

Larval viability and heterozygote deficiency in populations of marine bivalves: evidence from pair matings of mussels

Using a pressurized temperature gradient, which rapidly equilibrates bacteria to a wide range of temperature and pressures, temperature ranges for growth and survival of Vibrio harveyi (strain B 392) were found to narrow with increasing pressures. Both temperature and pressure ranges were greater in an enriched seawater medium than in unenriched seawater. Using a kinetics apparatus, V. harveyi was also exposed to gradual changes in temperature and pressure, simulating a particle sinking at approximately 200 m d^-1 from surface waters (17 °C; 1 bar pressure) to 3 400 m (4°C; 340 bars pressure). With gradual temperature changes, cells were able to grow and survive at lower temperatures than they had in rapid equilibration experiments. Gradual pressurization, however, did not increase pressure tolerance. Under all experimental conditions, the combined effects of low temperatures and high pressures were lethal for V. harveyi. It is hypothesized that temperature and pressure stratify the ocean into regions of growth, survival, and death for V. harveyi, and perhaps other bacteria.     

Effect of unfavorable trophic scenarios on amylase and protease activity of <Emphasis Type="Italic">Nephrops norvegicus</Emphasis> (L.) larvae during their first vertical migration: a laboratory approach

In Portuguese waters, Nephrops norvegicus larvae hatch at 400–800 m depth and need to perform a vertical migration to food-rich shallower waters to find suitable prey. The effect of suboptimal feeding on digestive enzymes activity of N. norvegicus larvae during this early period of their larval life remains unknown. Protease and amylase activities were investigated ex situ using flurometry in laboratory-hatched larvae exposed to different feeding and/or starving scenarios in the 24 h following hatching, the period during which they typically accomplish their upward vertical migration. Amylase activity was very low in comparison with protease activity, indicating that carbohydrates are not a primary energy reserve. Larvae starved for 12 h and subsequently fed displayed no increase in amylase activity, which suggests that feeding may be required before 12 h post-hatch to trigger amylase activity. Protease activity was high under all feeding conditions, and the increase in protease activity under sustained starvation indicated the catabolism of protein reserves. The ability of first-stage N. norvegicus larvae to metabolize protein reserves may play a decisive role for their survival during their first vertical migration, as it enables them to overcome the deleterious effects of short-term starvation and/or suboptimal feeding.     

Isotopic composition (C & N) of the suspended particles and N uptake by phytoplankton in a shallow tropical coastal lagoon

The spatial distribution of the C/N ratios and variations in δ¹³C and δ¹⁵N of suspended particulate matter were used to characterise their source in Asia’s largest brackish water lagoon, Chilika, India. In addition, the significance of re-mineralised nutrients in the primary productivity of the shallow lagoon was also determined through quantification of the subsurface nitrogen uptake conditions at two relatively stable locations in the lagoon. The results indicated that the influence of terrestrial organic matter was the maximum in the northern sector and was relatively limited at the central and southern part of the lagoon. In situ ¹⁵N uptake experiments (daytime) under biogeochemically stable conditions revealed that the N uptake by phytoplankton ranged between 0.24 and 1.01?mM?m^?3?h^?1 during pre-monsoon and post-monsoon seasons. New production and regenerated production in the shallow lagoon was also estimated by calculating f-ratios (ratio of nitrate assimilation by phytoplankton to total nitrogenous nutrient assimilation, have been estimated), which varied from 0.52 in the post-monsoon to 0.38 in the pre-monsoon. Lowering of the f-ratio from post- to pre-monsoon indicated a dominance of mineralisation over the new production.     

210Pb as a dietary indicator in the Antarctic pelagic community

The naturally occurring radionuclide ²¹⁰Po is useful as a tracer of diets of marine organisms. Data for ²¹⁰Pb, the grandparent of ²¹⁰Po, are less abundant: we therefore report here ²¹⁰Pb concentrations in a substantial collection of marine biota obtained from the Antarctic Ocean during the SIBEX II cruise in 1985. The general levels of ²¹⁰Pb are within the range of previously published data but, as in the case of ²¹⁰Po, there are differences which can be associated with variations in the diet of the organism. The levels of ²¹⁰Pb in the krill Euphausia superba show seasonal changes which can be interpreted in terms of changing diet. In a simple classification of the pelagic food chain, the levels of ²¹⁰Pb tend to increase from omnivores to filter-feeders to predators.     

Deep-sea caging of the mussel Mytilus galloprovincialis: Potential application in ecotoxicological studies

We experimented with caging the Mediterranean mussel (Mytilus galloprovincialis) at various depths for 69 d to measure basic physiological parameters, histological response and bio-accumulation of contaminants in a deep-sea contaminated area. In preliminary experiments, we demonstrated, under artificial pressure conditions, the ability of mussels Mytilus galloprovincialis to tolerate rapid immersion (at a speed of up to 120 m min^?1). In situ experiments were performed using submerged lines enabling mussels to be maintained at depths ranging of 40–1550 m with survival rates ranging from 80 to 38%, respectively. No significant differences in condition indexes were observed between treated and control specimens. However, histological observations demonstrated a clear reduction in thickness of the digestive epithelium with increasing depth exposure. By determining the contaminants in caged mussels, we found the following values for chromium accumulation: 27.4 μg g^?1 dry weight at 580 m depth and 9.8 μg g^?1 dry weight at 1550 m. Selected stations were located downstream of an industrial effluent at 420 m. The biological and environmental consequences of deep-sea contamination demonstrate the suitability of caged mussels for monitoring contaminant accumulation.     

Effects of UV-B irradiation on growth and survival of Antarctic marine diatoms

Growth rate, survival, and stimulation of the production of UV-B (280 to 320 nm) absorbing compounds were investigated in cultures of five commonly occurring Antarctic marine diatoms exposed to a range of UV-B irradiances. Experimental UV-B exposures ranged from 20 to 650% of the measured peak surface irradiance at an Antarctic coastal site (0.533 J m^-2 s^-1). The five diatom species (Nitzschia lecointei, Proboscia alata, P. inermis, Thalassiosira tumida and Stellarima microtrias) appear capable of surviving two to four times this irradiance. In contrast to Phaeocystis cf. pouchetii, another major component of the Antarctic phytoplankton, the concentrations of pigments with discrete UV absorption peaks in diatoms were low and did not change significantly under increasing UV-B irradiance. Absorbance of UV-B by cells from which pigments had been extracted commonly greatly exceeded that of the pigments themselves. Most of this absorbance was due to oxidisable cell contents, with the frustule providing the remainder. Survival of diatoms did not correlate with absorption by either pigments, frustules or oxidisable cell contents, indicating that their survival under elevated UV-B irradiances results from processes other than screening mechanisms.     

Über den einfluß des hydrostatischen druckes auf die ultrastrukturen von zellen und geweben. III. Untersuchungen an filament-und mikrotubulisystemen verschiedener gewebe mariner muscheln und Branchiostoma lanceolatum

Employing the technique of pressure fixation, the effect of high hydrostatic pressure (1 to 800 atm) at 5°C has been investigated on cilia of the gill epithelium in Modiolus modiolus, Mytilus edulis (Baltic and North Seas), and on the skin and muscle cells of Branchiostoma lanceolatum (Pallas). With increasing pressure, the filaments and tubuli are increasingly disorganized to an electron-dense material, which seems to be a conglomeration of the globular structure units. Minimum pressure causing disintegration of filaments and tubules is 300 atm; 600 atm is critical, especially for filaments in skin cells of B. lanceolatum. Whereas the filaments do not show any intermediate stages of damage at any one pressure, microtubules show different stages of disorganization. There seems to be a direct relation between motility and structural organization of cilia. Probably the mechanisms of disintegration of filaments and microtubules are related to the enzymatic activities and the protein-protein-interactions of the subunits. The difference between di-and monomer enzymatic systems in the structures may be important for pressure resistance of the organelles.     

Nitrogen fixation (acetylene reduction) associated with macroalgae in a coral-reef community in the Bahamas

N₂ fixation (C₂H₂ reduction) was associated with several species of macroalgae on a coral reef near Grand Bahama Island. The highest rates were associated with Microdictyon sp. (Chlorophyceae) and Dictyota sp. (Phaeophyceae). Extensive mats of filamentous blue-green algae, not heterotrophic bacteria, were the N₂ fixing agents: in experiments with samples of Microdictyon sp., the activity was lightdependent and not stimulated by organic compounds under either aerobic or anaerobic conditions. Assays in situ, at 20 m depth, and on shipboard, gave similar rates of N₂ fixation; the cyanophytes presumably have pigment adaptations to function in blue light. The maximum rate of N₂ fixation, associated with Microdictyon sp., was 3.8 g N fixed g dry weight^-1 h^-1. Coral-reef communities flourish in nutrientimpoverished waters, and therefore any input of nitrogen is probably important in stabilizing such ecosystems.