Description: 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.

Description: 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.

Description: MRI of living edible crabs Cancer pagurus submerged in seawater were recorded at 9.4 T. The dataset contains the DICOM files for the respective figures. Anatomical images of the heart were recorded using gradient-echo sequences (FLASH). The structure of the cardiovascular system in vivo was investigated using time-of-flight angiography scans. Haemlymph flow in various vessels was quantified over time with phase-contrast angiography. Self-gated IntraGate CINE MRI could reveal the extent of the heart contraction. FLOWMAP measurements of haemolymph velocity in left and right gills are given, averaging three flow velocities for either side at a specific point in time. Signal and noise values were recorded from anatomical MRI. These values were used to calculate the signal-to-noise ratio for different radiofrequency hardware setups: Images were recorded with either the volume resonator in transmit-receive mode or using the volume resonator for signal excitation and a receive-only surface coil (SUC) for signal reception.

Description: Cancer pagurus from the North Sea were exposued to acute, step-wise warming under two levels of CO2. The exposure to either normocapnic (450 µatm CO2) or hypercapnic (1350 µatm CO2) conditions was randomized on a temperature ramp between 12 and 20°C. Steps of constant temperatures were 10 h every two °C (12, 14, 16, 18, 20°C). Seawater chemistry (temperature, salinity, ph, PCO2) was analysed at 12 and 20°C. pH is given on the free scale and used for subsequent calculation of totalk alkalinity (TA), bicarbonate concentration and dissolved inorganic carbon (DIC). Physiological parameters were recorded over the course of a temperature ramp: Whole-animal metabolic rate (MO2) via flow-through respirometry. Heart rates (HR) via infrared photoplethysmography (IR-PPG). The integral of the raw signal of the plethysmogrpah served as a proxy for cardiac stroke volume (SV). Is was normalized to a control SV of 0.2 mL, based on literature references. The product of HR and SV equals cardiac output (CO). The difference between logtime_MO2 and logtime is that MO2 (whole-animal metabolic rate) were sometimes recorded with an inconsistent temporal delay compared to the other parameters. For accurate correlation of the data, readers are kindly asked to use the correct logtimes for each parameter (i.e. "logtime_MO2" for "MO2" and "logtime" for the others). In a parallel experiment, ventilatory water flow in the excurrent channel of the gill chambers, as well as haemolymph flow in the arteria sternalis and branchial veins was determined via phase-contrast magnetic resonance imaging (MRI). The lateral contractility of the heart was determined from self-gated cardiac MRI movies at 12 and 20°C during diastole and systole.

Description: Edible crabs Cancer pagurus were subjected to acute severe hypoxia (15% air saturation). The cardiac responses were monitored with infra-red plethysmography (IR-PPG) and Magnetic Resonance Imaging (MRI). The oxygen partial pressure in the water was monitored using fibre-optic oxygen sensors. "PO2_record_IR-PPG_File_1" contains the recordings relevant for animals 1 (1st run), 3, and 4. "PO2_record_IR-PPG_File_2" contains the recordings for animals 1 (2nd run) and 2. IR-PPG recordings yielded heart rates as peak frequency. Data were also evaluated for signal peak area (integral, relative to a 1-minute minimum) and the average cyclic height as proxies for stroke volume changes. Cardiac MRI are from 4D (i.e. time-resolved 3D) stacks of images. The time series contains the entire contraction of one cardiac cycle. The volume stack covers the entire ventricle.

Description: Das untersuchte Sedimentmaterial stammt aus dem westlich des Gunnerus-Rückens liegenden Tiefseebereich des Riiser-Larsenmeeres aus ca. 4480 m Wassertiefe. An den unverfestigten Sedimentkernproben eines etwa 13,40 m langen Schwerelotes (PS1824-1) und eines ca. 50 cm langen Großkastengreifers (PS1824-2) wurden umfangreiche sedimentphysikalische und sedimentologische Untersuchungsmethoden angewandt. Neben zerstörungsfreien, sedimentphysikalischen Messungen zur Ermittlung von Suszeptibilität, elektrischen Widerstand, P-Wellengeschwindigkeit und Feuchtraumdichte, wurden unter anderem die Korngrößenverteilung, der Karbonat- und Corg-Gehalt sowie die Komponentenverteilung der Sandfraktion bestimmt. Die zeitliche Einstufung basiert auf biostratigraphischen Datierungsmethoden mit Hilfe von Radiolarien und Diatomeen. Die untersuchten Sedimente umfassen demnach einen Ablagerungszeitraum vom Pliozän bis in das Holozän. Die Abfolgen des Schwerelotkernes besitzen ein Mindestalter von ungefähr 4,5 Millionen Jahren, mit mittleren Sedimentationsraten von ca. 3 mm/1000 Jahre. Über einen Vergleich der Sedimente zu einem ca. 8 km östlich gewonnenen, 14 m langem Schwerelotkern (PS1823-6), der ein paläomagnetisch datiertes Mindestalter von ca. 1,7 Millionen Jahren aufweist, konnten die weitgehend fossilfreien, pleistozänen Abschnitte des untersuchten Schwerelotkernes PS1824-1 teilweise korreliert werden.