Cardiovascular physiology of the edible crab Cancer pagurus under Ocean Warming and Acidification

Rising atmospheric CO2 levels have caused warming of the atmosphere and oceans and reduced the seawater pH. Thermal tolerance of marine ectotherms was shown to be reduced in high-CO2 waters, limiting chances for survival under the combined effects of warming and acidification. An enhanced temperature sensitivity in a high-CO2 ocean has been confirmed by reduced O2 levels in the body fluids of large marine crustacea. The haemolymph O2 level is a function of oxygen supply and demand and largely influenced by the activities of ventilatory and circulatory systems. The present work highlights the impact of combined CO2 and temperature effects on the ventilatory and cardiovascular performance of the edible crab Cancer pagurus. It adds to previous mechanistic studies on the general synergistic effects of both drivers, revealing limitations in ventilatory performance and cardiac work. The relevance of these results is underlined by the non-invasive measurements on truly resting animals

Cardiovascular physiology of the edible crab Cancer pagurus under Ocean Warming and Acidification

Rising atmospheric CO2 levels have caused warming of the atmosphere and oceans and reduced the seawater pH. Thermal tolerance of marine ectotherms was shown to be reduced in high-CO2 waters, limiting chances for survival under the combined effects of warming and acidification. An enhanced temperature sensitivity in a high-CO2 ocean has been confirmed by reduced O2 levels in the body fluids of large marine crustacea. The haemolymph O2 level is a function of oxygen supply and demand and largely influenced by the activities of ventilatory and circulatory systems. The present work highlights the impact of combined CO2 and temperature effects on the ventilatory and cardiovascular performance of the edible crab Cancer pagurus. It adds to previous mechanistic studies on the general synergistic effects of both drivers, revealing limitations in ventilatory performance and cardiac work. The relevance of these results is underlined by the non-invasive measurements on truly resting animals

pH-Bildgebung am Gehirn von polaren Fischen: eine TauCEST Anwendung

Chemical exchange saturation transfer (CEST) ist ein Bildkontrast, der die indirekte Detektion von Änderungen im pH ermöglicht. CEST bietet daher die Möglichkeit, die Säure-Basen-Regulation im Fischgehirn unter CO2-Konzentrationen, wie sie durch den Klimawandel bewirkt werden, zu verfolgen. Ziel dieser Studie war es, einen geeigneten Metaboliten zu finden, um Änderungen im intrazellulären pH-Wert mit hoher zeitlicher und räumlicher Auflösung im Fischgehirn bei 1.5°C zu detektieren. Der TauCEST-Effekt erwies sich als geeignet und wurde zum ersten Mal in vivo angewendet

CO2 induced pHi changes in the brain of polar fish: a TauCEST application

Chemical exchange saturation transfer from taurine to water (TauCEST) is primarily detectable in the low temperature range. Since, TauCEST asymmetry is bijective in the physiological pH-range (6.8-7.5), TauCEST is a potential candidate for in vivo studies on brain of polar fish. The specificity of TauCEST MRI on the brain of polar cod at 1.5°C shows a taurine contribution of 65%. TauCEST in brain of polar cod significantly increased under elevated CO2 concentrations by about 1.34%-3.17% in comparison to control, reflecting pHi changes since localized 1H NMR spectra show no significant changes in metabolite concentration for the different treatments

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