Climate change with increasing temperature and ocean acidification (OA) poses risks for marine ecosystems. According to Pörtner and Farrell [1], synergistic effects of elevated temperature and CO2-induced OA on energy metabolism will narrow the thermal tolerance window of marine ectothermal animals. To test this hypothesis, we investigated the effect of an acute temperature rise on energy metabolism of the oyster, Crassostrea gigas chronically exposed to elevated CO2 levels (partial pressure of CO2 in the seawater ~0.15 kPa, seawater pH ~ 7.7). Within one month of incubation at elevated Pco2 and 15 °C hemolymph pH fell (pHe = 7.1 ± 0.2 (CO2-group) vs. 7.6 ± 0.1 (control)) and Peco2 values in hemolymph increased (0.5 ± 0.2 kPa (CO2-group) vs. 0.2 ± 0.04 kPa (control)). Slightly but significantly elevated bicarbonate concentrations in the hemolymph of CO2-incubated oysters ([HCO− 3]e = 1.8 ± 0.3 mM (CO2-group) vs. 1.3 ± 0.1 mM (control)) indicate only minimal regulation of extracellular acid-base status. At the acclimation temperature of 15 °C the OA-induced decrease in pHe did not lead to metabolic depression in oysters as standard metabolism rates (SMR) of CO2-exposed oysters were similar to controls. Upon acute warming SMR rose in both groups, but displayed a stronger increase in the CO2-incubated group. Investigation in isolated gill cells revealed a similar temperaturedependence of respiration between groups. Furthermore, the fraction of cellular energy demand for ion regulation via Na+/K+-ATPase was not affected by chronic hypercapnia or temperature. Metabolic profiling using 1H-NMR spectroscopy revealed substantial changes in some tissues following OA exposure at 15 °C. In mantle tissue alanine and ATP levels decreased significantly whereas an increase in succinate levels was observed in gill tissue. These findings suggest shifts in metabolic pathways following OA-exposure. Our study confirms that OA affects energy metabolism in oysters and suggests that climate change may affect populations of sessile coastal invertebrates such as mollusks.

Kurochkin IO, Ivanina AV, Eilers S, Downs CA, May LA, Sokolova IM. Cadmium affects metabolic responses to prolonged anoxia and reoxygenation in eastern oysters (Crassostrea virginica). Am J Physiol Regul Integr Comp Physiol 297: R1262-R1272, 2009. First published September 2, 2009 doi:10.1152/ajpregu.00324.2009.-Benthic marine organisms such as mollusks are often exposed to periodic oxygen deficiency (due to the tidal exposure and/or seasonal expansion of the oxygen-deficient dead zones) and pollution by metals [e.g., cadmium, (Cd)]. These stressors can strongly affect mollusks' survival; however, physiological mechanisms of their combined effects are not fully understood. We studied the effects of Cd exposure on metabolic responses to prolonged anoxia and subsequent recovery in anoxia-tolerant intertidal mollusks Crassostrea virginica (eastern oysters). Anoxia led to an onset of anaerobiosis indicated by accumulation of L-alanine, acetate, and succinate. Prolonged anoxia (for 6 days) caused a decline in the maximum activity of electron transport chain and ADP-stimulated (state 3) oxygen uptake by mitochondria (MO 2), but no change in the resting (state 4) MO 2 of oyster mitochondria, along with a slight but significant reduction of mitochondrial respiratory control ratio. During reoxygenation, there was a significant overshoot of mitochondrial MO 2 (by up to 70% above the normoxic steady-state values) in control oysters. Mild mitochondrial uncoupling during prolonged shutdown in anoxic tissues and a subsequent strong stimulation of mitochondrial flux during recovery may help to rapidly restore redox status and protect against elevated reactive oxygen species formation in oysters. Exposure to Cd inhibits anaerobic metabolism, abolishes reoxygenation-induced stimulation of mitochondrial MO 2, and leads to oxidative stress (indicated by accumulation of DNA lesions) and a loss of mitochondrial capacity during postanoxic recovery. This may result in increased sensitivity to intermittent hypoxia and anoxia in Cd-exposed mollusks and will have implications for their survival in polluted estuaries and coastal zones. air exposure; recovery; mitochondrial function; oxidative damage; mollusks PERIODICAL OXYGEN DEFICIENCY is an important environmental stressor in intertidal and coastal habitats. Short-term intermittent hypoxia/anoxia (from several hours to several days, depending on the state of the tides) often occurs in intertidal invertebrates during the low tide, and may also occur in tidal pools and shallow lagoons with limited water exchange (8,36,49). Furthermore, long-term severe hypoxia and anoxia triggered by anthropogenic release of nutrients has become a serious issue in many estuaries and coastal zones rivaling the climate change (18,22). In the coastal dead zones, benthic invertebrates including mollusks can be exposed to severe hypoxia or anoxia for prolonged periods (from weeks to up to several months) (10,22,34,46). Long-term oxygen deficiency often leads to the massive die-offs in species with limited or...

Knowledge about species habitat requirements is important when designing conservation strategies as well as for predicting species distributions. For herbivorous insects, insights in oviposition preferences can provide important information on their habitat requirements. The oviposition preferences of Oberthür's Grizzled Skipper butterfly Pyrgus armoricanus Oberthür at its northern range boundary in southern Sweden were studied and it was also tested to what extent oviposition preferences can predict variation in population size among monitored sites. Oviposition behaviour was observed and analysed using a two‐step approach. First the characteristics of host plant ramets that female butterflies inspected for oviposition (including both ramets that were rejected and ramets used for oviposition) were compared with with control ramets. Second, ramets on which female butterflies oviposited were compared with ramets that butterflies inspected but rejected. The preferred plant species for oviposition was Filipendula vulgaris Moench. Filipendula vulgaris ramets inspected for oviposition by P. armoricanus females were situated in warm microclimates, primarily on south facing slopes, surrounded by lower vegetation and a higher percentage cover of bare ground compared with random control ramets. Among the inspected ramets, females chose to oviposit those situated in the warmest micro‐climates and those surrounded by the largest percentage cover of bare ground. Together with habitat patch area, oviposition preferences explained 65% of the variation in butterfly population size. These results reveal the importance of a microclimate as a component of habitat quality for insect populations at the margins of their geographical range.