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1.
Summary The pelagic summer distribution of Antarctic seabirds, seals and whales was studied in the marginal ice zone of the northwestern Weddell Sea from November 1988 to January 1989. In order to relate top predators to other components of the ecosystem studied simultaneously, their distribution is mainly described in terms of energy flow. Bird, seal, and probably also whale requirements were highest in ice-covered areas. There was no evidence of higher numbers of top predators along the ice edge: densities generally increased further into the ice. In the pack ice, combined energy requirements of top predators often amounted to about 200.000 kJ/day/km 2, or about 45 kg fresh food, indicating high abundance and availability of prey under the ice. There was a lack of conformity between top predator abundance on the ice and abundance of other life in the water column below. In open water, bird requirements were generally less than 25.000 kJ/day/km 2, seals were virtually absent and whales were distributed unevenly. Tubenosed birds concentrated along the outer ice edge in early summer but they moved north to open water during December, leaving the area of maximum phytoplankton biomass associated with the retreating ice edge. This pattern matched northward movements of krill swarms that may be related to changes in quality rather than quantity of phytoplankton stocks.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation 相似文献
2.
Summary The activity of the respiratory electron transport system (ETS) of the microplankton (<240 m size) was measured in the Northern Weddell Sea during EPOS 1, in the Close Pack Ice (CPI), and in the ice edge (Outer and Inner Marginal Zones, OMIZ and IMIZ). During early spring the activity increased with time and in the pack ice-open water direction. The temporal trend was more obvious than the spatial one. ETS activity ranged from 0.01 to 1.25 ml O 2 m –3 h –1 under the ice and from 0.1 to 1.6 ml O 2 m –3 h –1 in the open water at the ice edge. Depth-integrated ETS activity in the upper 300 m ranged from 13 to 130 ml O 2 m –2h –1. 60% to 80% of the activity took place above 100 m in the OMIZ in the prebloom conditions at the end of the cruise. ETS/Chl a ratios showed the importance of microheterotrophs under the ice, versus a greater phytoplankton dominance in the ice edge-open water zone. The carbon-specific activity reached a maximum (0.43 day –1) in the innermost zone of the CPI where bacteria dominated. Respiratory activity under the ice is important in producing the oxygen deficit observed, due to the negative balance between photosynthesis and respiration. The ETS activity was at the lower range of that found in the region in summer and is comparable to that measured in other oligotrophic, stratified systems in oceanic areas.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation 相似文献
3.
We compared six biochemical measures of nutritional condition: citrate synthase activity (CS), malate and lactate dehydrogenase activity (MDH and LDH), RNA:DNA ratio, and percent body protein and lipid. Adult females of five species of calanoid copepod ( Calanoides acutus, Calanus propinquus, Metridia gerlachei, Rhincalanus gigas and Paraeuchaeta antarctica) were collected in the marginal ice zone of the northwestern Weddell Sea at the time of the annual phytoplankton bloom that occurs in association with the receding ice edge during austral spring. Three zones within the marginal ice zone were sampled: heavy-ice-cover pre-bloom, ice-edge bloom and low-ice-cover post-bloom. Lipid generally increased greatly from ice-covered to open water zones, and its importance in the life of polar copepods cannot be overstated. Increases in protein from ice-covered to open water were also observed, but were of less significance. Each species exhibited significant changes in at least one enzyme activity level. Citrate synthase activity in C. acutus, C. propinquus and R. gigas, all herbivores, increased between pre- and post-bloom stations. C. propinquus and M. gerlachei, which feed during winter, had large increases in LDH activity between pre- and post-bloom stations. Rhincalanus gigas and P. antarctica, the two largest species studied, showed variations in MDH activity, with peak enzyme activity occurring in post-bloom stations. RNA:DNA ratio did not change in any species. The effects of size, shipboard handling and freezer storage were easily corrected statistically, and did not alter any conclusions. The patterns observed in copepod nutrition at the Antarctic ice edge were consistent with existing models of life history for each species. The observations reported here, in conjunction with previously reported data, suggested that measurement of metabolic enzyme activity, especially in concert with lipid, enables estimation of nutritional condition in adult copepods. Additional studies comparing metabolic activity and ecology of common species should yield more information on the ecology of rarer species. 相似文献
4.
Northern lakes are ice-covered for considerable portions of the year, where carbon dioxide (CO 2) can accumulate below ice, subsequently leading to high CO 2 emissions at ice-melt. Current knowledge on the regional control and variability of below ice partial pressure of carbon dioxide ( pCO 2) is lacking, creating a gap in our understanding of how ice cover dynamics affect the CO 2 accumulation below ice and therefore CO 2 emissions from inland waters during the ice-melt period. To narrow this gap, we identified the drivers of below ice pCO 2 variation across 506 Swedish and Finnish lakes using water chemistry, lake morphometry, catchment characteristics, lake position, and climate variables. We found that lake depth and trophic status were the most important variables explaining variations in below ice pCO 2 across the 506 lakes . Together, lake morphometry and water chemistry explained 53% of the site-to-site variation in below ice pCO 2. Regional climate (including ice cover duration) and latitude only explained 7% of the variation in below ice pCO 2. Thus, our results suggest that on a regional scale a shortening of the ice cover period on lakes may not directly affect the accumulation of CO 2 below ice but rather indirectly through increased mobility of nutrients and carbon loading to lakes. Thus, given that climate-induced changes are most evident in northern ecosystems, adequately predicting the consequences of a changing climate on future CO 2 emission estimates from northern lakes involves monitoring changes not only to ice cover but also to changes in the trophic status of lakes. 相似文献
5.
Autonomous, in situ sensors for the partial pressure of CO 2( pCO 2) and dissolved oxygen (DO) were deployedin a freshwater lake during the winters of 1997 and 1998 to evaluate magnitudeand sources of variability during ice-covered periods. Gas variability ondiel or shorter time scales was small or undetectable during most of thedeployment periods, only becoming significant prior to ice-out whenrunoff and light penetration increased, promoting convective currents andbiological production. A surprising 7.6 d period oscillation,apparently driven by a baroclinic seiche, dominated the short-termvariability during the first year. The gas trends associated with the seicheoscillations and periodic profile measurements revealed that ice formation ledto gas gradients directly under the ice. Long-term variability wascharacterized by increasing CO 2 and decreasing DO as a consequenceofbiological oxidation of organic matter. The results suggest that both spatialand temporal variability can be significant over intervals which would not beresolved by traditional sampling-based studies. 相似文献
6.
The respiratory behaviour and partitioning of O 2 uptake between air and water were investigated in Polypterus genegalus using continuous-flow and two-phase respirometers and lung gas replacement techniques P. senegalus rarely resorts to aerial respiration under normal conditions. Partitioning of O 2 consumption depends on the activity and age of fish and the availability of aquatic oxygen. Immature fish (12–22 g) cannot utilize aerial O 2 but older fish exhibit age-dependent reliance on aerial respiration in hypoxic and hypercarbic waters. Pulmonary respiration accounts for 50% of the total requirement at aquatic O 2 concentrations of about 3.5 mg · l –1 (or CO 2 of about 5%) and fish rely exclusively on aerial respiration at O 2 concentrations of less than 2.5 mg · l –1. Branchial respiration is initially stimulated by hypercarbia (CO 2: 0.5–0.8%) but increased hypercarbia (CO 2 – 1%) greatly depresses (by over 90%) brancial respiration and initiates (CO 2: 0.5%) and sustains pulmonary respiration. 相似文献
7.
Through use of a recently developed technique that can measure CO 2 exchange by individual attached roots, the influences of soil O 2 and CO 2 concentrations on root respiration were determined for two species of shallow-rooted cacti that typically occur in porous,
well-drained soils. Although soil O 2 concentrations in the rooting zone in the field were indistinguishable from that in the ambient air (21% by volume), the
CO 2 concentrations 10 cm below the soil surface averaged 540 μLL −1 for the barrel cactus Ferocactus acanthodes under dry conditions and 2400 μLL −1 under wet conditions in a loamy sand. For the widely cultivated platyopuntia Opuntia ficus-indica in a sandy clay loam, the CO 2 concentration at 10 cm averaged 1080 μLL −1 under dry conditions and 4170 μLL −1 under wet conditions. For both species, the respiration rate in the laboratory was zero at 0% O 2 and increased to its maximum value at 5% O 2 for rain roots (roots induced by watering) and 16% O 2 for established roots. Established roots of O. ficus-indica were slightly more tolerant of elevated CO 2 than were those of F. acanthodes, 5000 μLL −1 inhibiting respiration by 35% and 46%, respectively. For both species, root respiration was reduced to zero at 20,000 μLL −1 (2%) CO 2. In contrast to the reversible effects of 0% O 2, inhibition by 2% CO 2 was irreversible and led to the death of cortical cells in established roots in 6 h. Although the restriction of various
cacti and other CAM plants to porous soils has generally been attributed to their requirement for high O 2 concentrations, the present results indicate that susceptibility of root respiration to elevated soil CO 2 concentrations may be more important. 相似文献
8.
Abstract Oxygen effects on apparent photosynthetic and dark respiratory O 2 exchange rates of detached leaves of Elodea canadensis Michx. (Hydrocharitaceae) were determined over a range of conditions which the submersed plant is likely to experience in shallow water. Apparent photosynthesis is inhibited by O 2 under all the experimental regimes of light, temperature, CO 2 concentration and pH. This inhibition is not caused solely by an accelerated rate of dark respiration, and the observed variations in O 2 inhibition are comparable to O 2 effects on photosynthesis and photorespiration of terrestrial C 3 plants. Percentage inhibition of apparent photosynthesis is enhanced by high O 2 and also by low CO 2. These results indicate that high O 2, high pH and low CO 2 conditions could cause major losses in photosynthetic activity under field conditions. This may account for some of the losses in biomass that are observed under still water conditions. 相似文献
9.
Microbial biomass and activity were determined in cambisol incubated under ambient and increased (up to 2.23 mmol/L) CO 2 concentrations. An immediate negative response of the soil microbial community to [CO] 2 increase was observed during the first day with respect to microbial biomass, soil respiration and specific respiration activity
(both expressed as CO 2 evolution). In contrast, O 2 consumption was not affected but anabolic utilization of available substrate increased. These phenomena were observed under
conditions of increased CO 2 tension but without any change in O 2 concentration. 相似文献
10.
Leaf photosynthesis of the sensitive plant Mimosa pudica displays a transient knockout in response to electrical signals induced by heat stimulation. This study aims at clarifying the underlying mechanisms, in particular, the involvement of respiration. To this end, leaf gas exchange and light reactions of photosynthesis were assessed under atmospheric conditions largely eliminating photorespiration by either elevated atmospheric CO 2 or lowered O 2 concentration (i.e. 2000 μmol mol ?1 or 1%, respectively). In addition, leaf gas exchange was studied in the absence of light. Under darkness, heat stimulation caused a transient increase of respiratory CO 2 release simultaneously with stomatal opening, hence reflecting direct involvement of respiratory stimulation in the drop of the net CO 2 uptake rate. However, persistence of the transient decline in net CO 2 uptake rate under illumination and elevated CO 2 or 1% O 2 makes it unlikely that photorespiration is the metabolic origin of the respiratory CO 2 release. In conclusion, the transient knockout of net CO 2 uptake is at least partially attributed to an increased CO 2 release through mitochondrial respiration as stimulated by electrical signals. Putative CO 2 limitation of Rubisco due to decreased activity of carbonic anhydrase was ruled out as the photosynthesis effect was not prevented by elevated CO 2. 相似文献
11.
Summary Zooplankton biomass and respiratory ETS activity were studied along a transect at 49°W, running from open Scotia Sea water (57°S) into the Weddell Sea pack ice (62°S) in November–December 1988. Zooplankton biomass and respiratory activity were relatively high in the ice edge region and in the frontal zone separating the Scotia Sea from waters in the south; low biomasses and activities were encountered under the pack ice. The higher activities in the frontal zone were mainly attributed to locally higher water temperatures, while in the ice edge region they were probably related to changes of the Zooplankton population into more active developmental stages. This development in life stages is possibly a response to ice edge generated phytoplankton blooms. A comparison of the most abundant Zooplankton taxa indicated that amphipods and euphausiids had relatively the highest weight specific ETS activities. The developmental stages of Euphausia superba, from juvenile to sexually mature adults, showed a large variability in ETS activity; only the most inactive stages were found under the pack ice. The difference in respiration between the most active and inactive stages was at least a factor of 6 and is of importance to the overwintering of the species in the under ice habitat.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation 相似文献
12.
Summary During a cruise in the Weddell-Scotia Confluence area (EPOS Leg 2: November–January 1988/1989) nanophytoplankton composition was determined by employing taxon-specific pigment measurements with HPLC. The biomass of the most important components was estimated by using specific pigment ratios measured in cultures of two cryptomonads and a prasinophyte. Highest cryptophyte biomass was found along the retreating ice-edge; the contribution of cryptophytes to total phytoplankton crop increased with time, reaching monospecific bloom conditions at the end of the cruise. Chlorophyll b-containing organisms and Prymnesiophyceae were present everywhere and dominated in the ice-covered part of the survey area. Cryptophyte-specific pigment measurements were in reasonable agreement with cryptophyte cell numbers. Prasinophyte cell counts, however, did not match with measured chlorophyll b concentrations. The quantitative importance of the nanophytoplankton groups reported here underlines the diversity of the plankton in the Southern Ocean's marginal ice zone system which may have implications for food chain dynamics.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation 相似文献
13.
Carbon exchange rates (CER) and whole-plant carbon balances of beech ( Fagus grandifolia) and sugar maple ( Acer saccharum) were compared for seedlings grown under low irradiance to determine the effects of atmospheric CO 2 enrichment on shade-tolerant seedlings of co-dominant species. Under contemporary atmospheric CO 2, photosynthetic rate per unit mass of beech was lower than for sugar maple, and atmospheric CO 2 enrich ment enhanced photosynthesis for beech only. Aboveground respiration per unit mass decreased with CO 2 enrichment for both species while root respiration per unitmass decreased for sugar maple only. Under contemporary atmoapheric CO 2, beech had lower C uptake per plant than sugar maple, while C losses per plant to nocturnal aboveground and root respiration were similar for both species. Under elevated CO 2, C uptake per plant was similar for both species, indicating a significant relative increase in whole-seedling CER with CO 2 enrich ment for beech but not for sugar maple. Total C loss per plant to aboveground respiration was decreased for beech only because increase in sugar maple leaf mass counterbalanced a reduction in respiration rates. Carbon loss to root respiration per plant was not changed by CO 2 enrichment for either species. However, changes in maintenance respiration cost and nitrogen level suggest changes in tissue composition with elevated CO 2. Beech had a greater net daily C gain with CO 2 enrichment than did sugar maple in contrast to a lower one under contemporary CO 2. Elevated CO 2 preferentially enhances the net C balance of beech by increasing photosynthesis and reducing respiration cost. In all cases, the greatest C lost was by roots, indicating the importance of belowground biomass in net C gain. Relative growth rate estimated from biomass accumulation was not affected by CO 2 enrichment for either species possibly because of slow growth under low light. This study indicates the importance of direct effects of CO 2 enrichment when predicting potential change in species distribution with global climate change. 相似文献
14.
Nitrogen-fixing nodules of soybean [ Glycine max (L.) Merr. cv. Maple Arrow inoculated with Bradyrhizobium japonicum USDA 16] were studied before and after excision from the root to determine the role the O 2 regulation plays in the inhibition of nodule activity and the potential for using excised nodules nodules in studies of nodule metabolism. Relative nitrogenase (EC 1.7.99.2) activity (H 2 evolution in N 2:O 2) and nodule respiration (CO 2 evolution) were monitored first in intact nodulated roots and then in freshly excised nodules of the same plant to determine the time course of the decline in nodule metabolism. Folowing excision, nitrogenase activity and respiration declined rapidly in the first minute and then more gradually. After 40 min the rate of H 2 evolution was only 14–28% of that in the intact plant. In some nodules activity declined steadily, and in others there was a partial recovery in activity ca 10 min after detachment. Infected cell O 2 concentration (O i), measured by a spectro-photometric technique, also declined after nodule detachment with a time course similar to the declines in nitrogenase activity and respiration. Following excision, O i levels declined rapidly from ca 21 nM in attached nodules to 8–12 nM at 4–10 min after excision and then more gradually to 2–3 nM O 2 at 30–40 min after excision. These results show that the nodules' permeability to gas diffusion continued to be regulated for up to 40 min after detachement. At 40 min after detachment, when excised nodules displayed steady-state rates of gas exchange, linear increases in pO 2 from 20 to 100% at 4% min ?1 resulted in recoveries of H 2 and CO 2 evolution, indicating that O i limited nitrogenase activity durig this period, and that energy reserves were greatly in excess of the O 2 available for respiration. When detached nodules were equilibrated for 12 h at 20, 30 and 50% O 2, O i values measured at supra-ambient pO 2 were greater than those at 20% O 2 and were linked with a more rapid decline in nitrogenase activity. Also, increases in external pO 2 (O c) failed to stimulate nodule metabolism, suggesting that the nodules' energy reserves were no longer greatly in excess of their respiratory demands. It was concluded that soybean nodules could provide useful material for steady-state studies of nodule metabolism between 40 and 240 min after detachment, but to attain metabolic rates equivalent to in vivo rates the nodules must be exposed to above-ambient pO 2. 相似文献
15.
Summary Evolution of CO 2 into CO 2-free air was measured in the light and in the dark over a range of temperatures from 15 to 50°. Photosynthetic rates were measured in air and O 2-free air over the same range of temperatures. Respiration in the light had a different sensitivity to temperature compared with respiration in the dark. At the lower temperatures the rate of respiration in the light was higher than respiration in the dark, whereas at temperatures above 40° the reverse was observed. For any one species the maximum rates of photosynthesis and photorespiration occur at about the same temperature. The maximum rate for dark respiration generally is found at a temperature about 10° higher. Zea mays and Atriplex nummularia showed no enhancement of photosynthesis in O 2-free air nor any evolution of CO 2 in CO 2-free air at any of the temperatures. 相似文献
16.
Root respiration associated with symbiotic fixation in soybean ( Glycine max [L.] Merr.) was estimated by four methods. Averaged over the life of the plant, the root respires 5.8 milligrams C per milligram N accumulated from fixation. When nitrogenase (C2H2) activity and root respiration were decreased by treating roots briefly with 1.0 atmosphere O2, the respiration associated with nitrogenase was estimated as 2.10 micromoles CO2 per micromole C2H4. When nitrogenase activity and respiration were decreased by addition of nitrate, the respiration associated with fixation was calculated as 2.90 micromoles CO2 per micromole C2H4. Removing nodules from roots decreased fixation and root respiration, and the ratio was 4.08 micromoles CO2 per micromole C2H4. When soybean plants were kept in prolonged darkness, then returned to light, the associated drop and recovery of respiration and nitrogenase activity had a ratio of 4.36 micromoles CO2 per micromole C2H2. 相似文献
17.
A comparison was made of energy metabolism of nodulated N 2 fixing plants and non-nodulated NO 3-fed plants of Lupinus albus L. Growth, N-increment, root respiration (O 2 uptake and CO 2 production) and the contribution of a SHAM-sensitive oxidative pathway (the alternative pathway) in root respiration were measured. Both growth rate and the rate of N-increment were the same in both series of plants. The rate of root respiration, both O 2 uptake and CO 2 production, and the activity of the SHAM-sensitive pathway were higher in NO 3-fed plants than in N 2 fixing plants. The rate of ATP production in oxidative phosphorylation was computed also to be higher in NO 3-fed plants. It is concluded that both carbohydrate costings and ATP costings for synthesis + maintenance of root material were lower in N 2 fixing than in NO 3-fed plants. The respiratory quotient of root respiration was 1.6 in N 2-fixing plants and 1.4 in NO 3-fed plants. These values were slightly higher than the values calculated on the basis of CO 2 output due to N-assimilation and the experimental values of O 2 uptake, but showed the same trend: highest in N 2 fixing plants. Root respiration of NO 3-fed plants showed a diurnal pattern (both O 2 uptake, CO 2 production and the activity of the SHAM-sensitive pathway), whilst no diurnal variation in root respiration was found in N 2 fixing plants. However, C 2H 2 reduction did show a diurnal rhythm, which is suggested to be related to the diurnal variation in transpiration. Addition of NO 3 to N 2 fixing plants increased the rate of root respiration and the activity of the alternative pathway. This treatment did not decrease C 2H 2 reduction and H 2 evolution within 4 days. Withdrawal of NO 3-supply from NO 3-fed plants decreased the rate of root respiration but had no effect on the relative activity of the alternative pathway. It is suggested that the higher rate of root respiration and the higher activity of the SHAM-sensitive pathway in NO 3-fed plants is due to a larger supply of carbohydrates to the roots, partly due to a better photosynthetic performance of the shoots and partly due to a higher capacity of the roots to attract carbohydrates. 相似文献
18.
In the present open‐top chamber experiment, two silver birch clones ( Betula pendula Roth, clone 4 and clone 80) were exposed to elevated levels of carbon dioxide (CO 2) and ozone (O 3), singly and in combination, and soil CO 2 efflux was measured 14 times during three consecutive growing seasons (1999–2001). In the beginning of the experiment, all experimental trees were 7 years old and during the experiment the trees were growing in sandy field soil and fertilized regularly. In general, elevated O 3 caused soil CO 2 efflux stimulation during most measurement days and this stimulation enhanced towards the end of the experiment. The overall soil respiration response to CO 2 was dependent on the genotype, as the soil CO 2 efflux below clone 80 trees was enhanced and below clone 4 trees was decreased under elevated CO 2 treatments. Like the O 3 impact, this clonal difference in soil respiration response to CO 2 increased as the experiment progressed. Although the O 3 impact did not differ significantly between clones, a significant time × clone × CO 2× O 3 interaction revealed that the O 3‐induced stimulation of soil respiration was counteracted by elevated CO 2 in clone 4 on most measurement days, whereas in clone 80, the effect of elevated CO 2 and O 3 in combination was almost constantly additive during the 3‐year experiment. Altogether, the root or above‐ground biomass results were only partly parallel with the observed soil CO 2 efflux responses. In conclusion, our data show that O 3 impacts may appear first in the below‐ground processes and that relatively long‐term O 3 exposure had a cumulative effect on soil CO 2 efflux. Although the soil respiration response to elevated CO 2 depended on the tree genotype as a result of which the O 3 stress response might vary considerably within a single tree species under elevated CO 2, the present experiment nonetheless indicates that O 3 stress is a significant factor affecting the carbon cycling in northern forest ecosystems. 相似文献
19.
The dependence of alfalfa ( Medicago sativa L.) root and nodule nonphotosynthetic CO 2 fixation on the supply of currently produced photosynthate and nodule nitrogenase activity was examined at various times after phloem-girdling and exposure of nodules to Ar:O 2. Phloemgirdling was effected 20 hours and exposure to Ar:O 2 was effected 2 to 3 hours before initiation of experiments. Nodule and root CO 2 fixation rates of phloem-girdled plants were reduced to 38 and 50%, respectively, of those of control plants. Exposure to Ar:O 2 decreased nodule CO 2 fixation rates to 45%, respiration rates to 55%, and nitrogenase activities to 51% of those of the controls. The products of nodule CO 2 fixation were exported through the xylem to the shoot mainly as amino acids within 30 to 60 minutes after exposure to 14CO 2. In contrast to nodules, roots exported very little radioactivity, and most of the 14C was exported as organic acids. The nonphotosynthetic CO 2 fixation rate of roots and nodules averaged 26% of the gross respiration rate, i.e. the sum of net respiration and nonphotosynthetic CO 2 assimilation. Nodules fixed CO 2 at a rate 5.6 times that of roots, but since nodules comprised a small portion of root system mass, roots accounted for 76% of the nodulated root system CO 2 fixation. The results of this study showed that exposure of nodules to Ar:O 2 reduced nodule-specific respiration and nitrogenase activity by similar amounts, and that phloem-girdling significantly reduced nodule CO 2 fixation, nitrogenase activity, nodule-specific respiration, and transport of 14C photoassimilate to nodules. These results indicate that nodule CO 2 fixation in alfalfa is associated with N assimilation. 相似文献
20.
- 1.1. Salt exchange characteristics (permeability, half-time for salinity adaptation and net salt flux after a change in salinity) of adult shore crabs were studied in relation to experimentally increased external CO2 (TCO2 = carbon dioxide, carbonic acid, bicarbonate and carbonate) concentrations.
- 2.2. Up to about 15mM TCO2/1, elevated external TCO2 concentrations induce an increase in the salt permeability of shore crabs, resulting in higher passive salt fluxes across the body wall. The effect is most pronounced in larger animals (body weight > 25 g).
- 3.3. When external TCO2 concentrations exceed internal TCO2 concentrations, then permeability and salt exchange drop to low values, comparable to those observed in control animals. The results clarify a connection between blood gas transport and salt transport.
- 4.4. Elevated CO2 levels are unfavourable by inhibiting the chloride/bicarbanate pump (thus disturbing the removal of metabolically produced CO2 and the salt uptake in a hypotonic environment). High TCO2 levels, up to about 20 mmol TCO2/1, cause stress but Carcinus maenas can survive, at least temporarily, at the expense of metabolic energy.
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