ALBERT

Description: During the HALO-(AC)³ campaign in March-April 2022 airborne observations were performed with the High Altitude and LOng range research aircraft (HALO) covering the Fram Strait and north polar regions. The flight tracks covered open ocean areas, the marginal sea ice zone, and closed sea ice cover. Furthermore, cloud conditions were observed during air mass transformation events as marine cold air outbreaks and warm air intrusions. This data set summarizes the flight tracks of HALO and provides longitude, latitude, and altitude defined as position above WGS84. All data are measured by the Basic HALO Measurement and Data System (BAHAMAS) and resampled to 1 Hz temporal resolution.

Description: Oil polluted and not oil polluted soils (crude oil hydrocarbons contents: 20-92500 mg/kg dry soil mass) under natural grass and forest vegetation and in a bog in the Russian tundra were compared in their principal soil ecological parameters, the oil content and the microbial indicators. CFE biomass-C, dehydrogenase and arylsulfatase activity were enhanced with the occurrence of crude oil. Using these parameters for purposes of controlling remediation and recultivation success it is not possible to distinguish bctween promotion of microbial activity by oil carbon or soil organic carbon (SOC). For this reason we think that these parameters are not appropriate to indicate a soil damage by an oil impact. In contrast the metabolie quotient (qC02), calculated as the ratio between soil basal respiration and the SIR biomass-C was adequate to indicate a high crude oil contamination in soil. Also, the ß-glucosidase activity (parameter ß-GL/SOC) was correlated negatively with oil in soil. The indication of a soil damage by using the stress parameter qCO, or the specific enzyme activities (activity/SOC) minimizes the promotion effect of the recent SOC content on microbial parameters. Both biomass methods (SIR, CFE) have technical problems in application for crude oil-contaminated and subarctic soils. CFE does not reflect the low C_mic level of the cold tundra soils. We recommend to test every method for its suitability before any data collection in series as well as application for cold soils and the application of ecophysiological ratios as R_mic/C_mic, C_mic/SOC or enzymatic activity/SOC instead of absolute data.

Description: The reliability of Arctic climate predictions is currently hampered by insufficient knowledge of natural climate variability in the past. A sediment core from Lake El'gygytgyn (NE Russia) provides a continuous high-resolution record from the Arctic spaning the past 2.8 Ma. The core reveals numerous "super interglacials" during the Quaternary, with maximum summer temperatures and annual precipitation during marine benthic isotope stages (MIS) 11c and 31 ~4-5 °C and ~300 mm higher than those of MIS 1 and 5e. Climate simulations show these extreme warm conditions are difficult to explain with greenhouse gas and astronomical forcing alone, implying the importance of amplifying feedbacks and far field influences. The timing of Arctic warming relative to West Antarctic Ice Sheet retreats implies strong interhemispheric climate connectivity.

Description: 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.

Description: Anthropogenic climate change confronts marine organisms with rapid trends of concomitant warming and CO2 induced ocean acidification. The survival and distribution of species partly depend on their ability to exploit their physiological plasticity during acclimatization. Therefore, in laboratory studies the effects of simulated future ocean acidification on thermal tolerance, energy metabolism and acid-base regulation capacity of the North Sea population of the blue mussel Mytilus edulis were examined. Following one month of pre-acclimation to 10 °C and control CO2 levels, mussels were exposed for two weeks to control and projected oceanic CO2 levels (390, 750 and 1120 µatm) before being subjected to a stepwise warming protocol between 10 °C and 31 °C (+ 3 °C each night). Oxygen consumption and heart rates, anaerobic metabolite levels and haemolymph acid-base status were determined at each temperature. CO2 exposure left oxygen consumption rate unchanged at acclimation temperature but caused a somewhat stronger increase during acute warming and thus mildly higher Q10-values than seen in controls. Interestingly, the thermally induced limitation of oxygen consumption rate set in earlier in normocapnic than in hypercapnic (1120 µatm CO2) mussels (25.2 °C vs. 28.8 °C), likely due to an onset of metabolic depression in the control group following warming. However, the temperature induced increase in heart rate became limited above 25 °C in both groups indicating an unchanged pejus temperature regardless of CO2 treatment. An upper critical temperature was reached above 28 °C in both treatments indicated by the accumulation of anaerobic metabolites in the mantle tissue, paralleled by a strong increase in haemolymph PCO2 at 31 °C. Ocean acidification caused a decrease in haemolymph pH. The extracellular acidosis remained largely uncompensated despite some bicarbonate accumulation. In all treatments animals developed a progressive warming-induced extracellular acidosis. A stronger pH drop at around 25 °C was followed by stagnating heart rates. However, normocapnic mussels enhanced bicarbonate accumulation at the critical limit, a strategy no longer available to hypercapnic mussels. In conclusion, CO2 has small effects on the response patterns of mussels to warming, leaving thermal thresholds largely unaffected. High resilience of adult North Sea mussels to future ocean acidification indicates that sensitivity to thermal stress is more relevant in shaping the response to future climate change.

Description: Ocean acidification increases the amount of dissolved inorganic carbon (DIC) available in seawater which can benefit photosynthesis in those algae that are currently carbon limited, leading to shifts in the structure and function of seaweed communities. Recent studies have shown that ocean acidification-driven shifts in seaweed community dominance will depend on interactions with other factors such as light and nutrients. The study of interactive effects of ocean acidification and warming can help elucidate the likely effects of climate change on marine primary producers. In this study, we investigated the ecophysiological responses of Cystoseira tamariscifolia (Hudson) Papenfuss. This large brown macroalga plays an important structural role in coastal Mediterranean communities. Algae were collected from both oligotrophic and ultraoligotrophic waters in southern Spain. They were then incubated in tanks at ambient (ca. 400-500 ppm) and high CO2 (ca. 1200-1300 ppm), and at 20 °C (ambient temperature) and 24 °C (ambient temperature +4 °C). Increased CO2 levels benefited the algae from both origins. Biomass increased in elevated CO2 treatments and was similar in algae from both origins. The maximal electron transport rate (ETRmax), used to estimate photosynthetic capacity, increased in ambient temperature/high CO2 treatments. The highest polyphenol content and antioxidant activity were observed in ambient temperature/high CO2 conditions in algae from both origins; phenol content was higher in algae from ultraoligotrophic waters (1.5-3.0%) than that from oligotrophic waters (1.0-2.2%). Our study shows that ongoing ocean acidification can be expected to increase algal productivity (ETRmax), boost antioxidant activity (EC50), and increase production of photoprotective phenols. Cystoseira tamariscifolia collected from oligotrophic and ultraoligotrophic waters were able to benefit from increases in DIC at ambient temperatures. Warming, not acidification, may be the key stressor for this habitat as CO2 levels continue to rise.

Description: Sediment samples for measuring N2 production rates and for the characterization of the sediment system were taken in three seasons (winter, spring, summer) from sand and mud sediments of the Vistula Estuary and the open Bay of Gdansk at the Polish coast, Southern Baltic Sea. Sediment was sampled with a HAPS bottom corer (coarse sand), a Multicorer and a Boxcorer (fine sand, mud). Porosity was analyzed both from sediment slices and from entire core subsamples, which means that sediment in a sampling core (heights 15-20 cm, iD 2.3 cm) was mixed and sub sampled, assuming vertical homogeneity; sediment was dried overnight at 105°C and calculations followed Burdige (2006). Sediment organic matter content was analyzed as loss on ignition (LOI), for which dried sediment was combusted at 550°C for 4h. Sediment permeability was measured from pooled surface sediments (~1-2 cm homogeneous surface layer) with a permeameter cell following the constant head method for laminar flow of water through granular soil; calculations were derived from Darcy's Law. The oxygen penetration depth (OPD) was determined by manual (EMB 77, AL 449) and automated (EMB 123) profiling at bottom water temperature, electrode tip 100 µm: EMB 123, AL 449 (mud) and 250 µm: EMB 77, AL 449 (sand), EMB 123 (VE05, VE49). Denitrification rates were measured with the revised isotope pairing technique (r-IPT; Risgaard-Petersen et al. 2003, 2004) that accounts for the potential contribution of anammox (anaerobic ammonium oxidation) to total N2 production. Incubations were done in acrylic cores (heights 15-20 cm, iD 2.3 cm) in a concentration series of 30, 60, 90, 120 µM 15NO3- (n=3, EMB 77, AL 449) and 40 (n=4), 80 (n=4), 120 (n=12) µM 15NO3- for 3-5h at in situ bottom water temperature and darkness. In the presence of significant advective pore water flow, an advective incubation design was used. Dw gives denitrification of nitrate from the water column; Dn gives denitrification of nitrate from sediment nitrification (coupled nitrification-denitrification). If no contribution of anammox to total N2 production was found, columns hold a zero (0). The sediment silicate content (ASi =amorphous, biogenic Si (Na2CO3-extractable), Ca-Si = easily available Si (CaCl2-extractable), Ox-Si = oxide-bound Si (extractable by acid oxalate)) was analyzed from the top sediment layer.

Description: Ocean warming and acidification are two important environmental drivers affecting marine organisms. Organisms living at high latitudes might be especially threatened in near future, as current environmental changes are larger and occur faster. Therefore, we investigated the effect of hypercapnia on thermal tolerance and physiological performance of sub-Arctic Mytilus edulis from the White Sea. Mussels were exposed (2 weeks) to 390 µatm (control) and 1,120 µatm CO2 (year 2100) before respiration rate (MO2), anaerobic metabolite (succinate) level, haemolymph acid-base status, and intracellular pH (pHi) were determined during acute warming (10-28°C, 3°C over night). In normocapnic mussels, warming induced MO2 to rise exponentially until it levelled off beyond a breakpoint temperature of 20.5°C. Concurrently, haemolymph PCO2 rose significantly 〉19°C followed by a decrease in PO2 indicating the pejus temperature (TP, onset of thermal limitation). Succinate started to accumulate at 28°C under normocapnia defining the critical temperature (TC). pHi was maintained during warming until it dropped at 28°C, in line with the concomitant transition to anaerobiosis. At acclimation temperature, CO2 had only a minor impact. During warming, MO2 was stimulated by CO2 resulting in an elevated breakpoint of 25.8°C. Nevertheless, alterations in haemolymph gases (〉16°C) and the concomitant changes of pHi and succinate level (25°C) occurred at lower temperature under hypercapnia versus normocapnia indicating a downward shift of both thermal limits TP and TC by CO2. Compared to temperate conspecifics, sub-Arctic mussels showed an enhanced thermal sensitivity, exacerbated further by hypercapnia, indicating their potential vulnerability to environmental changes projected for 2100.

Description: Coralline algae (Rhodophyta) play a key role in promoting settlement of other benthic organisms, being the food source for herbivores, being involved in the stabilization of reef networks, and in carbonate production. They are considered a vulnerable group to ocean acidification due to the potential dissolution of their high-Mg calcite skeleton at lower pH. Nevertheless, different species of coralline algae showed different responses to low-pH/high-pCO2 environment. Here, we studied the physiological response of Jania rubens to the pH condition predicted for the year 2100. We used a natural CO2 vent system as natural laboratory to transplant J. rubens from pH 8.1–7.5 for 3 weeks. Maximal PSII photochemical efficiency showed a significant reduction in transplanted thalli at low pH (7.5-T) compared to other conditions; consistent with that result, also the pigments involved in the light-harvesting spectrum of J. rubens (i.e., chlorophylls, carotenoids, and phycobilins), exhibited a significant decrease under water acidification, highlighting the strong sensitivity of this species to the environmental change. A major understanding of the response of coralline algae at high CO2 will go through the impact of OA on benthic ecosystems in the next future. This contribution is the written, peer-reviewed version of a paper presented at the Conference “Changes and Crises in the Mediterranean Sea” held at Accademia Nazionale dei Lincei in Rome on October 17, 2017.