Respiration rate and ammonium excretion data for the squat lobster Pleuroncodes monodon measured during METEOR cruise M93

Sampling was conducted during RV Meteor cruise M93 in austral summer 2013 in an area from 11ºS to 14ºS and approximately 120 km offshore to within 10 km of the Peruvian coast. Specimens were collected using a Hydrobios Multinet Maxi (0.5 m2 mouth opening, 330 µm mesh size, 9 nets) and a WP-2 net (Hydrobios, 0.26 m2 mouth opening, 200 µm mesh size). P. monodon were identified according to http://researchdata.museum.vic.gov.au/squatlobster/delta/deltakey.html. Specimens were transferred into filtered, well-oxygenated seawater immediately after the catch and maintained for 4 to 16 hours prior to physiological experiments. Maintenance and physiological experiments were conducted at 13°C as the temperature observed at 100 to 200 m depth in the OMZ ranged from 13.7 to 12.7°C.

Ammonium excretion and respiration rate of tropical copepods and euphausiids measured during METEOR cruise M93, M97 and Maria S. Merian cruise MSM22

Respiration and ammonium excretion rates at different oxygen partial pressure were measured for calanoid copepods and euphausiids from the Eastern Tropical South Pacific and the Eastern Tropical North Atlantic. All specimens used for experiments were caught in the upper 400 m of the water column and only animals appearing unharmed and fit were used for experiments. Specimens were sorted, identified and transferred into aquaria with filtered, well-oxygenated seawater immediately after the catch and maintained for 1 to 13 hours prior to physiological experiments at the respective experimental temperature. Maintenance and physiological experiments were conducted in darkness in temperature-controlled incubators at 11, 13 or 23 degree C (±1). Before and during experiments, animals were not fed. Respiration and ammonium excretion rate measurements (both in µmol h-1 gDW-1) at varying oxygen concentrations were conducted in 12 to 60 mL gas-tight glass bottles. These were equipped with oxygen microsensors (ø 3 mm, PreSens Precision Sensing GmbH, Regensburg, Germany) attached to the inner wall of the bottles to monitor oxygen concentrations non-invasively. Read-out of oxygen concentrations was conducted using multi-channel fiber optic oxygen transmitters (Oxy-4 and Oxy-10 mini, PreSens Precision Sensing GmbH, Regensburg, Germany) that were connected via optical fibers to the outside of the bottles directly above the oxygen microsensor spots. Measurements were started at pre-adjusted oxygen and carbon dioxide levels. For this, seawater stocks with adjusted pO2 and pCO2 were prepared by equilibrating 3 to 4 L of filtered (0.2 µm filter Whatman GFF filter) and UV - sterilized (Aqua Cristal UV C 5 Watt, JBL GmbH & Co. KG, Neuhofen, Germany) water with premixed gases (certified gas mixtures from Air Liquide) for 4 hours at the respective experimental temperature. pCO2 levels were chosen to mimic the environmental pCO2 in the ETSP OMZ or the ETNA OMZ. Experimental runs were conducted with 11 to 15 trial incubations (1 or 2 animals per incubation bottle and three different treatment levels) and three animal-free control incubations (one per experimental treatment). During each run, experimental treatments comprised 100% air saturation as well as one reduced air saturation level with and without CO2. Oxygen concentrations in the incubation bottles were recorded every 5 min using the fiber-optic microsensor system and data recording for respiration rate determination was started immediately after all animals were transferred. Respiration rates were calculated from the slope of oxygen decrease over selected time intervals. Chosen time intervals were 20 to 105 min long. No respiration rate was calculated for the first 20 to 60 min after animal transfer to avoid the impact of enhanced activity of the animal or changes in the bottle water temperature during initial handling on the respiration rates and oxygen readings. Respiration rates were obtained over a maximum of 16 hours incubation time and slopes were linear at normoxia to mild hypoxia. Respiration rates in animal-free control bottles were used to correct for microbial activity. These rates were < 2% of animal respiration rates at normoxia. Samples for the measurement of ammonium concentrations were taken after 2 to 10 hours incubation time. Ammonium concentration was determined fluorimetrically (Holmes et al., 1999). Ammonium excretion was calculated as the concentration difference between incubation and animal-free control bottles. Some specimens died during the respiration and excretion rate measurements, as indicated by a cessation of respiration. No excretion rate measurements were conducted in this case, but the oxygen level at which the animal died was noted.

Metabolism of mesozooplankton in the North-Eastern Aegean Sea during SES_GR2 in October 2008

The dataset is based on samples taken during October 2008 in the North-Eastern Aegean Sea. NH4 excretion rate: Mesozooplankton is collected by vertical tows within the Black sea water body mass layer in the NE Aegean, using a WP-2 200 µm net equipped with a large non-filtering cod-end (10 l). Macrozooplankton organisms are removed using a 2000 µm net. A few unsorted animals (approximately 100) are placed inside 8 bottles of 350 or 650 ml filled with GF/F or 0.2 µm Nucleopore filtered seawater and then on a wheell at dim light and maintaining the in situ temperature. 4 bottles without animals are used as control. After 24hours bottles are opened and water samples taken for NH4 chemical analysis. Then the bottle content is filtered on pre-combusted preweighted CF/F filters, which are then dried at 60 C and weighted. Calculations are made as described by Ikeda et al. (2000). Samples for the NH4 determination were collected in pre-cleaned 50 ml Duran bottles and analysed onboard immediately after collection. Ammonium concentration was measured on a Perkin Elmer Lambda 25 UV/VIS Spectrometer according to the method of Koroleff (1970). PO4 excretion rate: Mesozooplankton is collected by vertical tows within the Black sea water body mass layer in the NE Aegean, using a WP-2 200 µm net equipped with a large non-filtering cod-end (10 l). Macrozooplankton organisms are removed using a 2000 µm net. A few unsorted animals (approximately 100) are placed inside 8 bottles of 350 or 650 ml filled with GF/F or 0.2 µm Nucleopore filtered seawater and then on a wheell at dim light and maintaining the in situ temperature. 4 bottles without animals are used as control. After 24hours bottles are opened and water samples taken for PO4 chemical analysis. Then the bottle content is filtered on pre-combusted preweighted CF/F filters, which are then dried at 60 C and weighted. Calculations are made as described by Ikeda et al. (2000). Samples for the determination of PO4 were collected in pre-cleaned 50 ml polyethylene volumetric tubes and analysed on board immediately after collection. PO4 concentration was measured on a Perkin Elmer Lambda 25 UV/VIS Spectrometer following the protocol of Murphy and Riley (1962). O2 consumption rate: Mesozooplankton is collected by vertical tows within the Black sea water body mass layer in the NE Aegean, using a WP-2 200 µm net equipped with a large non-filtering cod-end (10 l). Macrozooplankton organisms are removed using a 2000 µm net. A few unsorted animals (approximately 100) are placed inside 8 bottles of 350 or 650 ml filled with GF/F or 0.2 µm Nucleopore filtered seawater and then on a wheell at dim light and maintaining the in situ temperature. 4 bottles without animals are used as control. After 24hours bottles are opened and water samples taken for O2 chemical analysis. Then the bottle content is filtered on pre-combusted preweighted CF/F filters, which are then dried at 60 C and weighted. Calculations are made as described by Ikeda et al. (2000). For the dissolved O2 determination, the samples were fixed immediately after collection and analysed with the Winkler method as modified by Carpenter (1965a and 1965b). Carbon specific CO2 respiration rate: O2 consumption rate was converted to CO2 production using a RQ value of 0.87 (Mayzaud et al. 2005). Conversion of mesozooplankton dry weight to carbon was done using the % of carbon content measured in the same station from the SESAME dataset of zooplankton biomass. Carbon specific NH4 excretion rate: Conversion of mesozooplankton dry weight to carbon was done using the % of carbon content measured in the same station from the SESAME dataset of zooplankton biomass. Carbon specific PO4 excretion rate: Conversion of mesozooplankton dry weight to carbon was done using the % of carbon content measured in the same station from the SESAME dataset of zooplankton biomass.

Seawater carbonate chemistry, calcification and respiration duirng experiments with a pteropod Creseis acicula, 2010

Among marine calcifiers, shelled pteropods are expected to be particularly sensitive to ocean acidification, generated by the uptake of anthropogenic CO2 by the ocean, and the associated decrease of the seawater saturation state with respect to aragonite (omega aragonite). The few available studies have mostly focused on polar species although pteropods are also important components of temperate and tropical ecosystems. It is also unknown which parameter of the carbonate system controls calcification. Specimens of the temperate Mediterranean species Creseis acicula were maintained under seven different conditions of the carbonate chemistry, obtained by manipulating pH and total alkalinity, with the goal to disentangle the effects of pH and omega aragonite. Respiration, excretion as well as rates of net and gross calcification were not directly affected by a decrease in pH but decreased significantly with a decrease of omega aragonite. The decrease of gross calcification rates is consistent with that reported for polar species. Although the organisms were apparently able to maintain gross calcification rates under slightly undersaturated aragonite conditions, the clear net dissolution signal observed below saturation suggests that they are not able to build a shell in seawater corrosive to aragonite. The decrease in respiration and excretion, and the low O:N molar ratio, could be due to the short time that the organisms were allowed to acclimatize to their new environment.

Seawater carbonate chemistry and biological processes of Mytilus edulis during experiments, 2010

Marine organisms are exposed to increasingly acidic oceans, as a result of equilibration of surface ocean water with rising atmospheric CO2 concentrations. In this study, we examined the physiological response of Mytilus edulis from the Baltic Sea, grown for 2 months at 4 seawater pCO2 levels (39, 113, 243 and 405 Pa/385, 1,120, 2,400 and 4,000 µatm). Shell and somatic growth, calcification, oxygen consumption and excretion rates were measured in order to test the hypothesis whether exposure to elevated seawater pCO2 is causally related to metabolic depression. During the experimental period, mussel shell mass and shell-free dry mass (SFDM) increased at least by a factor of two and three, respectively. However, shell length and shell mass growth decreased linearly with increasing pCO2 by 6-20 and 10-34%, while SFDM growth was not significantly affected by hypercapnia. We observed a parabolic change in routine metabolic rates with increasing pCO2 and the highest rates (+60%) at 243 Pa. excretion rose linearly with increasing pCO2. Decreased O:N ratios at the highest seawater pCO2 indicate enhanced protein metabolism which may contribute to intracellular pH regulation. We suggest that reduced shell growth under severe acidification is not caused by (global) metabolic depression but is potentially due to synergistic effects of increased cellular energy demand and nitrogen loss.

Seawater carbonate chemistry and resource allocation and extracellular acid-base status in the sea urchin Strongylocentrotus droebachiensis during experiments, 2012

Anthropogenic CO2 emission will lead to an increase in seawater pCO2 of up to 80-100 Pa (800-1000 µatm) within this century and to an acidification of the oceans. Green sea urchins (Strongylocentrotus droebachiensis) occurring in Kattegat experience seasonal hypercapnic and hypoxic conditions already today. Thus, anthropogenic CO2 emissions will add up to existing values and will lead to even higher pCO2 values >200 Pa (>2000 µatm). To estimate the green sea urchins' potential to acclimate to acidified seawater, we calculated an energy budget and determined the extracellular acid base status of adult S. droebachiensis exposed to moderately (102 to 145 Pa, 1007 to 1431 µatm) and highly (284 to 385 Pa, 2800 to 3800 µatm) elevated seawater pCO2 for 10 and 45 days. A 45 - day exposure to elevated pCO2 resulted in a shift in energy budgets, leading to reduced somatic and reproductive growth. Metabolic rates were not significantly affected, but ammonium excretion increased in response to elevated pCO2. This led to decreased O:N ratios. These findings suggest that protein metabolism is possibly enhanced under elevated pCO2 in order to support ion homeostasis by increasing net acid extrusion. The perivisceral coelomic fluid acid-base status revealed that S. droebachiensis is able to fully (intermediate pCO2) or partially (high pCO2) compensate extracellular pH (pHe) changes by accumulation of bicarbonate (maximum increases 2.5 mM), albeit at a slower rate than typically observed in other taxa (10 day duration for full pHe compensation). At intermediate pCO2, sea urchins were able to maintain fully compensated pHe for 45 days. Sea urchins from the higher pCO2 treatment could be divided into two groups following medium-term acclimation: one group of experimental animals (29%) contained remnants of food in their digestive system and maintained partially compensated pHe (+2.3 mM HCO3), while the other group (71%) exhibited an empty digestive system and a severe metabolic acidosis (-0.5 pH units, -2.4 mM HCO3). There was no difference in mortality between the three pCO2 treatments. The results of this study suggest that S. droebachiensis occurring in the Kattegat might be pre-adapted to hypercapnia due to natural variability in pCO2 in its habitat. We show for the first time that some echinoderm species can actively compensate extracellular pH. Seawater pCO2 values of >200 Pa, which will occur in the Kattegat within this century during seasonal hypoxic events, can possibly only be endured for a short time period of a few weeks. Increases in anthropogenic CO2 emissions and leakages from potential sub-seabed CO2 storage (CCS) sites thus impose a threat to the ecologically and economically important species S. droebachiensis.

Physiological response of the cold-water coral Desmophyllum dianthus to thermal stress and ocean acidification

Rising temperatures and ocean acidification driven by anthropogenic carbon emissions threaten both tropical and temperate corals. However, the synergistic effect of these stressors on coral physiology is still poorly understood, in particular for cold-water corals. This study assessed changes in key physiological parameters (calcification, respiration and ammonium excretion) of the widespread cold-water coral Desmophyllum dianthus maintained for 8 months at two temperatures (ambient 12 °C and elevated 15 °C) and two pCO2 conditions (ambient 390 ppm and elevated 750 ppm). At ambient temperatures no change in instantaneous calcification, respiration or ammonium excretion rates was observed at either pCO2 levels. Conversely, elevated temperature (15 °C) significantly reduced calcification rates, and combined elevated temperature and pCO2 significantly reduced respiration rates. Changes in the ratio of respired oxygen to excreted nitrogen (O:N), which provides information on the main sources of energy being metabolized, indicated a shift from mixed use of protein and carbohydrate/lipid as metabolic substrates under control conditions, to less efficient protein-dominated catabolism under both stressors. Overall, this study shows that the physiology of D. dianthus is more sensitive to thermal than pCO2 stress, and that the predicted combination of rising temperatures and ocean acidification in the coming decades may severely impact this cold-water coral species.