Posts Tagged 'crustaceans'

Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios (update)

Coastal hypoxia is a problem that is predicted to increase rapidly in the future. At the same time, we are facing rising atmospheric CO2 concentrations, which are increasing the pCO2 and acidity of coastal waters. These two drivers are well studied in isolation; however, the coupling of low O2 and pH is likely to provide a more significant respiratory challenge for slow moving and sessile invertebrates than is currently predicted. The Gullmar Fjord in Sweden is home to a range of habitats, such as sand and mud flats, seagrass beds, exposed and protected shorelines and rocky bottoms. Moreover, it has a history of both natural and anthropogenically enhanced hypoxia as well as North Sea upwelling, where salty water reaches the surface towards the end of summer and early autumn. A total of 11 species (Crustacean, Chordate, Echinoderm and Mollusc) of these ecosystems were exposed to four different treatments (high or low oxygen and low or high CO2; varying pCO2 of 450 and 1300 µatm and O2 concentrations of 2–3.5 and 9–10 mg L−1) and respiration measured after 3 and 6 days, respectively. This allowed us to evaluate respiration responses of species of contrasting habitats to single and multiple stressors. Results show that respiratory responses were highly species specific as we observed both synergetic as well as antagonistic responses, and neither phylum nor habitat explained trends in respiratory responses. Management plans should avoid the generalized assumption that combined stressors will result in multiplicative effects and focus attention on alleviating hypoxia in the region.

Continue reading ‘Variable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenarios (update)’

Effects of high pCO2 on the northern krill Thysanoessa inermis in relation to carbonate chemistry of its collection area, Rijpfjorden

Polar oceans are predicted to be the first marine environments affected by ocean acidification (OA). Thysanoessa inermis is one of the most abundant krill species in northern waters of the Atlantic and a key species in the food web of this ecosystem. Yet, we know very little about potential OA effects on this species. We studied the effects of elevated pCO2 on T. inermis in a laboratory experiment by exposing individuals for 11 weeks to low and high pCO2 (450 and 1200 µatm, respectively, n = 12 per pCO2 treatment). Survival, growth, and moulting frequency was monitored during the experiment, and feeding and oxygen consumption rates (n = 3–5 per pCO2 treatment) were measured at the end of the experiment. No significant effects of high pCO2 on survival, growth, moulting, oxygen consumption, and feeding rate were observed, indicating that T. inermis is tolerant to predicted high OA levels. We also explored physical and chemical properties of waters near the collection area of krill, Rijpfjorden (Svalbard 80° North) during the polar summer (July–August). In situ measurements showed large temperature and salinity gradients from surface to bottom and pCO2 and pH ranged, respectively, 161–417 µatm and 7.99–8.37. Even though substantial spatial variability in pCO2 could be observed, krill in this area is not confronted yet with the investigated high pCO2 levels.

Continue reading ‘Effects of high pCO2 on the northern krill Thysanoessa inermis in relation to carbonate chemistry of its collection area, Rijpfjorden’

Effect of carbon dioxide-induced water acidification and seasonality on the physiology of the sea-bob shrimp Xiphopenaeus kroyeri (Decapoda, Penaeidae)

Climate changes are altering the chemistry of the oceans, and knowing their effects on the biology of animals is urgent. Since the physiological responses of crustaceans may be different given the seasons of the year, this work evaluated the synergistic effect of ocean acidification and seasonality on the physiology of the sea-bob shrimp, Xiphopenaeus kroyeri. Experimental groups were exposed for 5 days to two levels of pH, representing present-day mean ambient conditions (pH 8.0) and distant-future conditions (pH 7.3) during the summer and winter. Metabolism, nitrogen excretion, energy type and storage were determined, respectively, by oxygen consumption, ammonia excretion, atomic ratio O/N and hepatosomatic index. The reduction of pH resulted in a decrease of about 30% in the X. kroyeri metabolism during the summer and winter. Nitrogen excretion (reduction of 40%) and hepatosomatic index (increase of 120%) showed to be altered in animals exposed to reduced pH only throughout summer. Regardless of pH and seasons of the year, animals use mainly proteins as energy substrate and they do not show mortality. The increase of the hepatosomatic index, indicator of the accumulation of energy reserves, associated with metabolism reduction, suggests the suppression of activities that demand energy expenditure. The consequences of the physiological alterations observed may include decreases in growth and reproduction rate and displacement of populations to more appropriate conditions. The results might be associated with a set of factors resulting from the exposure to reduced pH, the synergy between pH and temperature, but also with a pattern of different physiological responses that may occur according to seasonality.

Continue reading ‘Effect of carbon dioxide-induced water acidification and seasonality on the physiology of the sea-bob shrimp Xiphopenaeus kroyeri (Decapoda, Penaeidae)’

Effects of ocean acidification and salinity variations on the physiology of osmoregulating and osmoconforming crustaceans

Survival, osmoregulatory pattern, oxygen consumption, energy spent on metabolism, ammonia excretion, type of oxidized energy substrate, and hepatosomatic index were evaluated in decapods (an osmoregulating crab, Callinectes danae, and an osmoconforming seabob shrimp, Xiphopenaeus kroyeri) exposed to carbon dioxide-induced water acidification (pH 7.3, control pH 8.0) and different salinities (20, 25, 30, 35, and 40‰) for 3 days. Compared to the animals kept at controlled pH, exposure to reduced pH resulted in the loss of osmoregulatory capacity in C. danae at all salinities, except for some hyporegulation at 40‰, and reduced oxygen consumption and ammonia excretion at 20 and 40‰. Xiphopenaeus kroyeri remained an osmoconformer in all evaluated conditions, except for some hyporegulation at 40‰, and when exposed to the reduced pH, it presented changes in oxygen consumption at all salinities and reductions in ammonia excretion at 20 and 35‰ compared to the control animals. Both species use protein as the main energy substrate and decrease the hepatosomatic index when exposed to reduced pH relative to the control. The observed changes may be associated with changes in the activity of enzymes related to osmoregulation, the use of amino acids as osmotic effectors of cell volume control and recovery, and the Bohr effect, and, because the gills are multifunctional organs related to osmoregulation, the changes may be related to acid–base control, nitrogen excretion, and respiration, with a change in one of these functions bringing about changes in the others.

Continue reading ‘Effects of ocean acidification and salinity variations on the physiology of osmoregulating and osmoconforming crustaceans’

Water bicarbonate modulates the response of the shore crab Carcinus maenas to ocean acidification

Ocean acidification causes an accumulation of CO2 in marine organisms and leads to shifts in acid–base parameters. Acid–base regulation in gill breathers involves a net increase of internal bicarbonate levels through transmembrane ion exchange with the surrounding water. Successful maintenance of body fluid pH depends on the functional capacity of ion-exchange mechanisms and associated energy budget. For a detailed understanding of the dependence of acid–base regulation on water parameters, we investigated the physiological responses of the shore crab Carcinus maenas to 4 weeks of ocean acidification [OA, P(CO2)w = 1800 µatm], at variable water bicarbonate levels, paralleled by changes in water pH. Cardiovascular performance was determined together with extra-(pHe) and intracellular pH (pHi), oxygen consumption, haemolymph CO2 parameters, and ion composition. High water P(CO2) caused haemolymph P(CO2) to rise, but pHe and pHi remained constant due to increased haemolymph and cellular [HCO3]. This process was effective even under reduced seawater pH and bicarbonate concentrations. While extracellular cation concentrations increased throughout, anion levels remained constant or decreased. Despite similar levels of haemolymph pH and ion concentrations under OA, metabolic rates, and haemolymph flow were significantly depressed by 40 and 30%, respectively, when OA was combined with reduced seawater [HCO3] and pH. Our findings suggest an influence of water bicarbonate levels on metabolic rates as well as on correlations between blood flow and pHe. This previously unknown phenomenon should direct attention to pathways of acid–base regulation and their potential feedback on whole-animal energy demand, in relation with changing seawater carbonate parameters.

Continue reading ‘Water bicarbonate modulates the response of the shore crab Carcinus maenas to ocean acidification’

Composition and spatial distribution of the meiofauna in the Wagner and Consag basins, Gulf of California, Mexico

In this study, we analyse the horizontal and vertical distribution of the meiofauna in the Wagner and Consag basins. Samples were collected at soft bottom sites on board of the R/V “El Puma” (WAGNER-02 Expedition) during July- August 2010 with a Smith McIntyre grab and 10 cm cores. At each station physical and chemical variables were measured including depth, salinity, pore water temperature and pH. Twelve higher taxa of meiofauna were recorded in both basins. Meiofauna was dominated by Nematoda (73.1%) followed by Copepoda Harpacticoida (11.28%), Polychaeta (8.41%) and Kinorhyncha (4.71%). Density of meiofauna in these two basins ranked from 19.12 to 742.20 ind.10 cm-2 and were mainly concentrated in the first four centimeters of the sediment (78.6%) and decreased with sediment depth; PERMANOVA analysis show significant differences among sediment depth layers. However, PERMANOVA analysis did not show significant differences of the abundances of meiofauna between basins. Multivariate Correspondence Canonica l Analysis (MCCA) was performed but the assemblages identified had no spatial gradient. This only confirms the patchy distribution already reported for the meiofauna. This analysis reported two faunal groups: Nematoda -Polychaeta and Copepoda – Kinorhyncha. In the present study, we report for the first time the horizontal and vertical distribution of the meiofauna in a natural CO2 venting area in the Gulf of California. There is still so much that we do not know about meiofauna processes, more studies are needed specially down to species level in order to have a clearer view of how environmental factors affect each species spatial distribution.

Continue reading ‘Composition and spatial distribution of the meiofauna in the Wagner and Consag basins, Gulf of California, Mexico’

Decreased growth and increased shell disease in early benthic phase Homarus americanus in response to elevated CO2

Marine calcifiers, especially those in larval and juvenile stages, are thought to be most vulnerable to ocean acidification (OA) due to the effects of carbon dioxide (CO2) on growth and calcification. However, recent evidence in lobsters is contradictory. We monitored molting activity, length, and weight in early benthic phase Homarus americanus (Milne-Edwards 1837) over 90 to 120 d under 3 targeted CO2 partial pressures ( pCO2; 400, 1000, and 2000 µatm) to determine how elevated CO2 affects growth at this life stage. Lobsters exposed to higher pCO2 over that 90 to 120 d period exhibited altered intermolt period length and decreased growth increments (length and weight). Lobsters in the elevated CO2 treatments were also more susceptible to shell disease. These results suggest juvenile lobsters may remain smaller, and thus more susceptible to predation, for a longer period of time and may be more susceptible to disease in a high CO2 ocean.

Continue reading ‘Decreased growth and increased shell disease in early benthic phase Homarus americanus in response to elevated CO2’


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Ocean acidification in the IPCC AR5 WG II

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