ALBERT

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: Distinct facies types, classified in radiocarbon-dated sediments from the shelf of the Lazarev Sea, East Antarctica, reveal a detailed history of processes that have controlled sedimentation during the deglaciation over the last 10,000 yr. The ice retreat on this part of the Antarctic shelf started 9500 yr BP, marked by the deposition of laminated sediments, deposited from a floating ice shelf. These laminites, which occur on top of diamictons laid down from a grounded ice sheet, are the basal sediments of the postglacial sequence. The intensity of the Antarctic Coastal Current (ACC), directed by shelf morphology, controlled sedimentation of the postglacial facies. A residual glaciomarine sediment with the fine fraction winnowed by strong currents developed from 9000-8000 yr BP in the western part of the investigation area and from 9000-5000 yr BP in the eastern part, closer to the prominent 'Fenno Deep' trough. Current velocities apparently decreased between 8000 and 2000 yr BP due to a deflection of the ACC by advancing ice tongues to the east of the investigation area during the 'Hypsithermal'. This led to a deposition of fine-grained sediments, and clay mineralogy suggests a continental source, possibly near the grounding line of the Nivl Ice Shelf, rather than a winnowing of sediments near the shelf break or advection from deeper water. Current velocities intensified after 2000 yr BP, removed fine material from these sediments and led to a relict sediment, consisting of coarse bryozoan and molluscan debris.