Method for indirectly defining optimum temperatures of inhabitancy for marine cold-blooded animals

Investigations on the influence of pressure on the activity of alkaline phosphatase of some marine invertebrates from the Baltic Sea were carried out at temperatures between 5° and 55°C. The results obtained indicate that the influence of pressure on alkaline phosphatase activity is modified by temperature. At low temperatures, pressure has a decreasing effect on enzyme activity, while it has an increasing effect at higher temperatures. The gill homogenates of the relatively pressure-resistent bivalves Cyprina islandica and Mytilus edulis show a lower decrease of activity under pressure at low temperatures than the gill-homogenate of Carcinus maenas and a purified enzyme preparation of a homoiothermal animal.     

Effects of seawater pCO2 and temperature on shell growth, shell stability, condition and cellular stress of Western Baltic Sea Mytilus edulis (L.) and Arctica islandica (L.)

Acidification of the World’s oceans may directly impact reproduction, performance and shell formation of marine calcifying organisms. In addition, since shell production is costly and stress in general draws on an organism’s energy budget, shell growth and stability of bivalves should indirectly be affected by environmental stress. The aim of this study was to investigate whether a combination of warming and acidification leads to increased physiological stress (lipofuscin accumulation and mortality) and affects the performance [shell growth, shell breaking force, condition index (C_i)] of young Mytilus edulis and Arctica islandica from the Baltic Sea. We cultured the bivalves in a fully-crossed 2-factorial experimental setup (seawater (sw) pCO₂ levels “low”, “medium” and “high” for both species, temperature levels 7.5, 10, 16, 20 and 25 °C for M. edulis and 7.5, 10 and 16 °C for A. islandica) for 13 weeks in summer. Mytilus edulis and A. islandica appeared to tolerate wide ranges of sw temperature and pCO₂. Lipofuscin accumulation of M. edulis increased with temperature while the C_i decreased, but shell growth of the mussels only sharply decreased while its mortality increased between 20 and 25 °C. In A. islandica, lipofuscin accumulation increased with temperature, whereas the C_i, shell growth and shell breaking force decreased. The pCO₂ treatment had only marginal effects on the measured parameters of both bivalve species. Shell growth of both bivalve species was not impaired by under-saturation of the sea water with respect to aragonite and calcite. Furthermore, independently of water temperatures shell breaking force of both species and shell growth of A. islandica remained unaffected by the applied elevated sw pCO₂ for several months. Only at the highest temperature (25 °C), growth arrest of M. edulis was recorded at the high sw pCO₂ treatment and the C_i of M. edulis was slightly higher at the medium sw pCO₂ treatment than at the low and high sw pCO₂ treatments. The only effect of elevated sw pCO₂ on A. islandica was an increase in lipofuscin accumulation at the high sw pCO₂ treatment compared to the medium sw pCO₂ treatment. Our results show that, despite this robustness, growth of both M. edulis and A. islandica can be reduced if sw temperatures remain high for several weeks in summer. As large body size constitutes an escape from crab and sea star predation, this can make bivalves presumably more vulnerable to predation—with possible negative consequences on population growth. In M. edulis, but not in A. islandica, this effect is amplified by elevated sw pCO₂. We follow that combined effects of elevated sw pCO₂ and ocean warming might cause shifts in future Western Baltic Sea community structures and ecosystem services; however, only if predators or other interacting species do not suffer as strong from these stressors.     

Gas-exchange studies with the staghorn coral Acropora acuminata and its zooxanthellae

Compensation point and light-saturation values were determined from oxygen-exchange experiments with branches and isolated zooxanthellae from the staghorn coral Acropora acuminata. Branches and dense suspensions of zooxanthellae showed similar lightresponse curves for oxygen exchange, with light saturation at about 23 Klux (300 W. m^-2) and compensation point occurring between 4 and 6 Klux (60–80 W. m^-2). Zooxanthellae appear to be mutually shaded in dense suspensions and coral tissues. The effects of metabolic inhibitors, including photosynthetic and respiratory inhibitiors, on oxygen exchange in coral branches and isolated zooxanthellae are presented. Bubbles formed on coral tissues and on several macroalgae under conditions of high illumination contained large amounts of oxygen, suggesting that a high oxygen tension may occur in coral tissues during the day. Photorespiration and dissolved organic carbon production by suspensions of zooxanthellae are discussed in relation to a high oxygen tension which probably occurs in coral tissues during daylight.     

Effects of environmental factors and body size on rates of oxygen consumption in Archaeomysis grebnitzkii and Neomysis awatschensis (Crustacea: Mysidae)

The rates of oxygen consumption in relation to oxygen tension, temperature, salinity and body size were determined for Archaeomysis grebnitzkii Czerniavsky and Neomysis awatschensis (Brandt). Oxygen uptake was regulated by both species down to an oxygen tension of about 50 mm Hg (30% of saturation value); below this level, it was related to the oxygen tension in the medium. Oxygen tension below 20 mm Hg was lethal. A statistically significant interaction was noted for the effects of species, temperature, and salinity. In general, oxygen-uptake rate decreased with decreasing salinity in both species. The effect of size is expressed as a power function of body weight. The regression coefficients of oxygen consumption on body weight, 0.70 for A. grebnitzkii and 0.62 for N. awatschensis, were found to be significantly different from each other.Contribution No. 726 from the Department of Oceanography, University of Washington, Seattle, USA.     

Synergistic physiological effects of low copper and various oxygen concentrations on Macoma balthica

The negative effects of copper on Macoma balthica are significantly increased when this bivalve is simultaneously exposed to low oxygen concentrations. This might be explained by the fact that low oxygen concentrations (oxygen deficiency) are combined with a slightly lower pH and thus with a different copper speciation, resulting in a higher bio-availability of copper and, consequently, in a higher copper uptake by M. balthica. Symptomatic for the increased negative effects of copper on M. balthica at low oxygen concentrations is an increased oxygen demand, which in turn reflects an increased consumption of energy. Consequently, at low oxygen levels, low copper concentrations (8–15 μg dm^-3) greatly affect the glycogen content of the tissues, and finally (at 15 μg Cu dm^-3) result in a heavy loss of dry weight and a drastic reduction of the adenylate energy charge (AEC). Generally, it might be concluded that dry weight, glycogen content and AEC are more affected by a combination of oxygen deficiency and a low copper concentration (2.5 cm³ O₂ dm^-3, 15 μg Cu dm^-3) than by higher copper concentrations (up to 86 μg dm^-3) at high oxygen levels (5.0 cm³ dm^-3).     

Gender- and oxygen-related irrigation behaviour of the decapod Nephrops norvegicus

The Norway lobster Nephrops norvegicus (L.) inhabits burrows in muddy clay sediments (e.g. on the Swedish west coast), where an autumnal oxygen deficiency in the bottom water can occur. Our experiments investigated whether the irrigation of the burrows would reflect a behavioural adaptation to hypoxia, and whether any gender differences of such behaviour exist. Irrigation is performed by the pleopods which may compensate for a decreasing oxygen tension. Pleopod activity (total number of strokes per sampling time), associated with oxygen concentration and gender, was studied in N. norvegicus kept in artificial burrows resembling their natural habitat. Male and female lobsters were separately exposed to either normoxia (70% oxygen saturation) or hypoxia (30% oxygen saturation). A sexual difference in behaviour was found, where females irrigated the burrow less than males during normoxia. Females showed a significant increase of pleopod activity in hypoxia compared with normoxic conditions, which was not displayed by the males probably due to the degree of individual variation found. However, when only males were studied during progressive hypoxia (from 60 to 5% oxygen saturation), following any changes of irrigational behaviour, a significant increase of accumulated pleopod activity occurred. A major increase of pleopod activity appeared between 60 and 50% oxygen saturation, below which the activity remained high until a critical point (<10% saturation, 11 °C, 33 psu) where irrigation dropped to a level close to that of normoxic values. Activity sessions during hypoxia were longer and had a higher stroke rate than during normoxia. Received: 22 October 1997 / Accepted: 26 February 1998     

Calorimetric studies on the energy metabolism of an infaunal bivalve,Abra tenuis,under normoxia,hypoxia and anoxia

Direct calorimetry was employed to measure the energy metabolism of infaunal bivalves, Abra tenuis, collected from a tidal lagoon in the Fleet, southern England, in June 1989, at various oxygen partial pressures. A significant anaerobic component (i.e., 20% of total metabolic rate) was detected under normoxia, presumably brought about by the intermittent ventilatory activity of this bivalve under these conditions. Under hypoxia (2.3 to 10 kPa, or 11 to 48% of full air saturation), however, the energy metabolism was maintained fully aerobic; the measured heat equivalent of oxygen uptake was not significantly different from the theoretical ranges for fully aerobic catabolism. Under anoxia, the rate of heat dissipation was reduced to 5–6% of the normoxic rate of heat dissipation. This conserves energy expenditure and would thus increase resistance of A. tenuis to anoxia or emersion. Physiological compensation by A. tenuis under conditions of declining oxygen tension involved a marked increase in ventilation rate. Comparison between fed and starved individuals indicated that costly physiological processes, such as digestion, absorption and growth declined at 10 and 5 kPa and were arrested at P_{O 2} (oxygen partial pressure) levels below 2.3 kPa. The present study provides evidence that there are no major differences between the metabolic responses of epifaunal suspension-feeding (eg. Mytilus edulis) and infaunal deposit-feeding (eg. A. tenuis) bivalves when exposed to environmental hypoxic stress.     

Cell turnover in tissues of the long-lived ocean quahog Arctica islandica and the short-lived scallop Aequipecten opercularis

Cell proliferation and apoptosis were investigated in tissues of two bivalve species, Arctica islandica from the German Bight (age of bivalves: 33–98 years) and Iceland (7–148 years) and Aequipecten opercularis from the English Channel (2–4 years). High proliferation rates (10% nuclei dividing) and apoptosis in tissues of A. opercularis were in line with high-energy throughput and reduced investment into antioxidant defence mechanisms in the scallop. In contrast, cell turnover was slow (<1% nuclei dividing) in A. islandica and similar in mantle, gill and adductor muscle between young and old individuals. In the heart, cell turnover rates decreased with age, which indicates less-efficient removal of damaged cells in ageing A. islandica. Cell turnover rates, mass specific respiration and antioxidant enzyme activities were similar in German Bight and Iceland ocean quahog. Variable maximum life expectancies in geographically separated A. islandica populations are determined by extrinsic factors rather than by fundamental physiological differences.     

Behavioural response to gradually declining oxygen concentration by Baltic Sea macrobenthic crustaceans

Behavioural responses to decreasing oxygen concentrations were studied in the amphipods Monoporeia affinis (Lindström) and Pontoporeia femorata Krøyer and the isopod Saduria entomon (L.), all benthic macrofauna species from the Baltic Sea. Infrared time-lapse video recording was used. Seven oxygen concentrations were studied, starting near saturation (about 90%), followed by about 65, 49, 33, 16, 8 and 5% oxygen saturation, with each oxygen level maintained for 24?h. M. affinis was more active than P. femorata. The duration of swimming activity of M. affinis was shorter at ≤33% oxygen saturation compared with at the two highest levels. The duration of swimming by P. femorata was longest at 90, 65 and 5% oxygen saturation. For both amphipods the frequency of swimming activity was highest at 5% oxygen saturation. Above 7% oxygen saturation, S. entomon spent most of its time in the sediment, whereas at levels ≤7% it was most often found on the sediment surface. Both amphipods were predominantly night active (nocturnal), whereas no diurnal variation in behaviour was detected for S. entomon. It is suggested that the amphipods minimise the costs associated with obtaining oxygen as well as their risk of predation by moving little on or above the sediment until a lower critical oxygen level is reached. Below this level, they show an oxygen-seeking behaviour. S. entomon also hid in the sediment for as long as possible, suddenly coming to the surface once the oxygen concentration became intolerably low. Its behaviour is also indicative of a trade-off between predation risk and obtaining sufficient oxygen. It is suggested that the change in behaviour shown at about 33% oxygen saturation could lead to a long-term alteration in community structure in the deeper parts of the northern Baltic proper, whereas the change at about 8% oxygen saturation reflects a more acute, short-term response.     

Scale dependency of dynamic relative permeability–satuartion curves in relation with fluid viscosity and dynamic capillary pressure effect

Capillary pressure–saturation-relative permeability relationships (P_c–S_w–K_r) are functions of importance in modeling and simulations of the hydrodynamics of two-phase flow in porous media. These relationships are found to be affected by porous medium and fluid properties but the manner in which they are affected is a topic of intense discussion. For example, reported trends in fluid viscosity and boundary conditions effects have been found to be contrary to each other in different studies. In this work, we determine the dependency of dynamic K_r–S_w relationships (averaged data) on domain scale in addition to investigating the effects of fluid viscosity and boundary pressure using silicone oil (i.e. 200 and 1000 cSt) and water as the respective non-wetting and wetting fluids with a view to eliminating some of the uncertainties reported in the literature. Water relative permeability, K_rw, was found to increase with increasing wetting phase saturation but decreases with the increase in viscosity ratio. On the other hand, the oil relative permeability, K_rnw, was found to increase with the increasing non-wetting phase saturation in addition to the increase in viscosity ratio. Also, it was found that with the increasing boundary pressure K_rw decreases while K_rnw increases. The influence of scale on relative permeability was slightly indicated in the non-wetting phase with K_rnw decreasing as domain size increases. Effect of measurement location on dynamic relative permeability was explored which is rarely found in the literature. Comparison was also made between K_r–S_w relationships obtained under static and dynamic condition. Finally, mobility ratio (m) and dynamic coefficient (τ) were plotted as a function of water saturation (S_w), which showed that m decreases as τ increases at a given saturation, or vice versa.     

Vergleichende ökologisch-physiologische Untersuchungen zur zellulären Kälteresistenz mariner Evertebraten

Cellular freezing and chilling resistances of different marine bivalve species have been measured comparatively, using isolated pieces of gill tissues. The species-specific resistance values correspond to the ecological behaviour and the geographical distribution of the species. Among marine animals from subarctic and boreal regions, cellular freezing resistance is significantly higher in species living, during the whole year, in the upper littoral than in bottom dwellers or sublittoral forms. Tissues of tropical littoral bivalves are very sensitive to freezing. Similar responses are obtained in deepwater species of the temperate zone. Studies on geographically separated populations of species from both sides of the Atlantic Ocean demonstrate small differences in cellular freezing resistance; no genetically fixed distinctions could be recognized. Among species within the same littoral habitat, those suffering from mass mortalities in extremely severe winters also exhibit comparatively lower cellular chilling and freezing resistances. In littoral bivalves from normal sea water, considerable seasonal variations of cellular freezing resistance occur; such variations are very small in specimens from brackisk waters. Maximum freezing resistance results from adaptation to low temperature combined with high salivity. The adaptation time required for reaching the final level of resistance depends on temperature and salinity. Also, the considerable increases in cellular freezing resistance caused by exposure to air, or to oxygen-deficient water, or by different organic compounds, are modified by temperature and salinity conditions during pretreatment. The subtropical-tropical species Chione cancellata, exhibits “meaningful” adaptation of cellular chilling resistance when the adaptation temperature is changed from 10° to 23.5°C; however, no comprehensible change in cellular freezing resistance occurs at the same time. Increased calcium contents of the external medium affect cellular chilling and freezing resistances of marine bivalves differently. Quick effluxes of aldolase (from cytoplasm) and of acid phosphatase (from lysosomes) after freezing and thawing of isolated gills indicate damage to membranes before cellular injuries are recognized by microscopical observations. Partial inactivation of acid phosphatase by exposure to freezing and thawing is only found after “death” of the tissue.     

Studies on the resistance of marine bottom invertebrates to oxygen-deficiency and hydrogen sulphide

Oxygen-deficient and H₂S-containing marine areas are characterized by a decline in the number of species. In laboratory experiments with bottom invertebrates from various biotopes of the North Sea and the Baltic, comparative measurements of the resistance to oxygen-deficiency alone, and to the simultaneous presence of H₂S, were carried out. The resistance values obtained show relations to the substratum on which the species naturally occur. The resistance to H₂S is greater in those macrofauna species which show higher survival rates under oxygen-deficiency. Further experiments with isolated tissues demonstrate that the species specific differences in resistance occurring in whole animals are already based on the cell metabolism. In general, oxygen-deficiency and simultaneous presence of H₂S were endured better in cold than in warmth, and at somewhat reduced pH-values (around 7). The dependence of this resistance on the salinity was only minimal in euryhaline species.     

Über den Einfluß der Adaptationstemperatur und des Salzgehaltes auf die Hitze-und Gefrierresistenz von Enchytraeus albidus (Oligochaeta)

This paper investigates the combined effects of temperature and salinity on resistance-adaptation to temperature in the oligochaete Enchytraeus albidus Henle. This worm shows reasonable resistance-adaptation to both cold (-13.2°C) and heat (35.8 °C). Acclimation to high salinity increases the degree of resistance to temperature extremes. The effect of salinity on heat-resistance, and especially on cold-resistance, decreases with rising adaptation-temperature. While a general effect of cations (Na, K, Ca, Mg) on temperature resistance does not exist, the influence of special ions depends upon ion concentration and adaptation-temperature; addition of Na, K, Ca and Mg reduces cold-resistance in cold-acclimated (5 °C) individuals, while, in warm-acclimated (23 °C) specimens, cold tolerance increases after addition of K and Ca. Heat-resistance decreases in warm-acclimated worms after addition of Mg and Ca. Higher proportions of cations reduce thermal resistance in all cases. Over the salinity range which allows homeo-osmotic conditions (2 to 15‰), E. albidus does not exhibit a constant resistance level (at least not to heat). The cryoprotective agent dimethylsulphoxide is highly effective both in cold and warm acclimated worms.     

The effect of copper and zinc on the metabolism of the mussel Mytilus edulis

The effects of copper and zinc on the metabolism of the mussel Mytilus edulis (L.) and its component tissues were studied. 500 ppm copper sodium citrate inhibited oxygen consumption of the whole animal and gill tissue, but no similar effect was observed on digestive gland tissue. 500 ppm zinc sodium citrate exerted no effect upon gill or digestive gland respiration, and neither metal salt affected the respiration of homogenates of gill, digestive gland or gonad. Direct observation of gill tissues during exposure to the metals revealed that 500 ppm copper sodium citrate caused inhibition of ciliary activity; exposure of tissues to 2 ppm Cu for 24 h resulted in only partial inhibition of the cilía. It is suggested that metabolic suppression noted in whole animals and gill tissues is due to the inhibition of an energy-consuming process such as ciliary activity rather than interference with respiratory enzyme systems.     

Influence of size on primary production in the reef coral Pocillopora damicornis and the macroalga Acanthophora spicifera

Size influences the photosynthesis-irradiance (P-I) relationship in colonies of the branched reef-coral Pocillopora damicornis and in intact plants of the branched redmacroalga Acanthophora spicifera. The light saturation constant is proportional to size. Maximum net rate of oxygen production (net photosynthesis) per colony and nocturnal dark oxygen-uptake rate per colony (respiration) increase with increasing size, but the latter increases at a much lower rate. Therefore, the photosynthesis to respiration ratio increases with increasing canopy size. Large increases in chlorophyll per unit reef area also accompany increase in size. The initial slope (alpha) of the chlorophyll-specific P-I curve and assimilation number are inversely related to size. Integrated daytime oxygen production increases with size more rapidly than nighttime oxygen consumption. Consequently, net primary production of an entire colony or plant (or rate per unit area of reef) increases with increasing size of the canopy. Production efficiency also increases with size. The coral is rigid, symmetrical and highly organized. Chlorophyll distribution is more stratified in comparison to the macroalga. The coral shows higher photosynthetic efficiency, as would be expected according to the stratified production model of Odum et al. (1958). This research was conducted on specimens from Kaneohe Bay, Oahu, Hawaii, USA in 1981.     

Effets de l'ablation de l'organe axial sur l'activité respiratoire chez Asterina gibbosa (échinodermes,astérides)

The removal of the axial organ from the sea-star Asterina gibbosa Penn is followed by disturbances in respiratory activity. Decrease in oxygen uptake occurs from 1/2 to 2 h after which continues from 4 h to 2–3 days. Oxygen uptake then decreases and the test individuals die. These results are compared with those obtained with certain echinids. Since survival after removal of the axial organ is observed in certain other animals, it is concluded that, although the axial organ may partake in respiratory mechanisms, it is nevertheless not indispensable.     

Myosin ATPase activity in an estuarine decapod crustacean,Scylla serrata,as a function of salinity adaptation

The myosin ATPase activity of the flexor muscle of an estuarine crab, Scylla serrata, was studied in relation to salinity adaptation. The enzyme is activated more by calcium than by magnesium; it exhibits maximum activity at pH 9.0, and substrate inhibition above 0.5 mM ATP. The enzyme activity increases in crabs adapted to higher salinities. The enzyme from normal (70% sea water) crabs shows two pH optima; one at pH 7.0, the other at pH 9.0. The neutral optimum shifts to pH 6.0 upon adaptation to full strength sea water, but disappears upon adaptation to 25% sea water. The enzyme from normal crabs shows an optimum at 30 °C; adaptation to full strength sea water raises this optimum to 38 °C, whereas adaptation to 25% sea water decreases it to 24 °C. These changes are discussed in relation to estuarine conditions.     

High pressure effects on marine invertebrates and fishes

A survey of literature and of new information from the author's laboratory is presented concerning the comparative pressure physiology of marine invertebrates and fishes. Short term experiments on littoral marine animals have revealed that the taxonomic groups exhibiting the greatest resistance to high pressures are those with the greatest vertical distributions in the deep sea, namely, echinoderms, molluscs, amphipods, isopods and polychaetes. Shallow water species which possess high thermal and osmotic resistance also show an exceptionally high degree of pressure resistance. The relative differences in genetic pressure resistance of lower marine invertebrates are the same in whole, intact animals and in isolated, surviving tissue pieces. Adaptation of nonregulating euryoecous invertebrates to higher temperatures, higher osmotic concentrations and higher calcium contents of the tissues results in increased pressure resistance. Under pressure, the optimum cellular pH shifts downward to a lower pH range.Lecture presented on October 23, 1967 at Duke University, Marine Laboratory, Beaufort (USA); on November 6, 1967 at the Instituto di Biologia Marinha of the University of São Paulo (Brasil); and on November 8, 1967 at the Institute of Marine Science of the University of Miami (USA).     

Respiratory metabolism of crabs from marine and estuarine habitats: an interspecific comparison

The gill-surface area and R-T (metabolic rate-temperature) response during aquatic and aerial respiration of three different species of crabs, the subtidal Scylla serrata, the intertidal Sesarma quadratum, and the supratidal Ocypoda platytarsis, were compared. Scylla serrata has the highest, Sesarma quadratum the second highest, and O.platytarsis the lowest gill-surface area. Oxygen-consumption values in water under different ambient partial pressures of oxygen indicate that all three species display equally efficient aquatic respiration despite variation in gill area and number. There is no coherent R-T response either inter- or intra-specifically. However, the ability to extract oxygen from the surrounding medium (respiratory efficiency) conditions the R-T response in the different species. The R-T trends in aquatic respiration of Scylla serrata and aerial respiration of O.platytarsis reveal a normal response to temperature. The proportion of aquaticoxygen uptake to total respiration in all sizes in both Scylla serrata and Sesarma quadratum remains more or less constant (between 88 and 92%), whereas in the supratidal O.platytarsis, this proportion decreases with increasing weight (from 88 to 64 %), indicating a progressive loss of gill respiration to total respiration. All three species are metabolically equally efficient; what one lacks in respiratory surface it compensates by respiratory efficiency.     

Behavioural and physiological responses of the Norway lobster,<Emphasis Type="Italic"> Nephrops norvegicus</Emphasis> (Crustacea: Decapoda), to sulphide exposure

The Norway lobster, Nephrops norvegicus, is moderately tolerant of sulphide [the lethal time to 50% mortality (LT₅₀) was 22.5 h when exposed to 500 M sulphide] but, whenever possible, it attempts to avoid the presence of sulphide in its immediate vicinity. Any sulphide entering the animal is oxidized to thiosulphate, which accumulates in the haemolymph and in the tissues. During exposure to low concentrations of sulphide, the rate of oxygen consumption is maintained or even enhanced even though the lobsters become quiescent. The apparent increase in oxygen consumption is probably due to the oxidation of sulphide to thiosulphate. At higher concentrations, oxygen consumption decreases, perhaps because of the inhibitory effect of sulphide on electron transport, and N. norvegicus resorts to anaerobic metabolism as indicated by the accumulation of lactate in the haemolymph and in the tissues.Communicated by L. Hagerman, Helsingør