ALBERT

Description: The simulation of deep-sea conditions in laboratories is technically challenging but necessary for experiments that aim at a deeper understanding of physiological mechanisms or host-symbiont interactions of deep-sea organisms. In a proof-of-concept study, we designed a recirculating system for long-term culture (〉2 yr) of deep-sea mussels Gigantidas childressi (previously Bathymodiolus childressi). Mussels were automatically (and safely) supplied with a maximum stable level of ~60 μmol L−1 methane in seawater using a novel methane–air mixing system. Experimental animals also received daily doses of live microalgae. Condition indices of cultured G. childressi remained high over the years, and low shell growth rates could be detected, too, which is indicative of positive energy budgets. Using stable isotope data, we demonstrate that G. childressi in our culture system gained energy, both, from the digestion of methane-oxidizing endosymbionts and from digesting particulate food (microalgae). Limitations of the system, as well as opportunities for future experimental approaches involving deep-sea mussels, are discussed.

Description: Air-sea interaction in late boreal winter is studied over the extratropical North Atlantic (NA) during 1960–2020 by examining the relationship between sea-surface temperature (SST) and total turbulent heat flux (THF). The two quantities are positively correlated on interannual timescales over the central-midlatitude and subpolar NA, suggesting the atmosphere on average drives SST and THF variability is independent of SST. On decadal timescales and over the central-midlatitude NA the correlation is negative, suggesting ocean processes on average drive SST and THF variability is sensitive to SST. The correlation is positive over the subpolar NA. There, interannual and decadal THF variability is governed by the North Atlantic Oscillation (NAO). During the major late 20th and early 21st century SST increase in the subpolar NA diminishing oceanic heat loss associated with a weakening NAO was observed. This study suggests that the atmosphere is more sensitive to SST over the central-midlatitude than subpolar NA. Key Points: - Regional variation in the nature of air-sea interaction over the extratropical North Atlantic (NA) north of 35°N - Timescale dependence in relationship between sea-surface temperature (SST) and turbulent heat flux over the central-midlatitude NA - The atmosphere is more sensitive to SST variability over the central-midlatitude than subpolar NA

Description: The disturbance of marine organism phenology due to climate change and the subsequent effects on recruitment success are still poorly understood, especially in migratory fish species, such as the Atlantic herring (Clupea harengus; Clupeidae). Here we used the commercial catch data from a local fisher over a 50-year period (1971–2020) to estimate western Baltic spring-spawning (WBSS) herring mean arrival time Q50 (i.e., the week when 50% of the total fish catches had been made) at their spawning ground within the Kiel Fjord, southwest Baltic Sea, and the duration of the spawning season for each year. The relationship between the seawater temperature in the Kiel Bight and other environmental parameters (such as water salinity, North Atlantic and Atlantic multidecadal oscillations) and Q50 was evaluated using a general linear model to test the hypothesis that fish arrived earlier after warm than cold winters. We also estimated the accumulated thermal time to Q50 during gonadal development to estimate the effects of seawater temperature on the variations of Q50. The results of this study revealed a dramatic decrease in herring catches within the Kiel Fjord since the mid-1990s, as documented for the whole southwestern Baltic Sea. Warmer winter seawater temperature was the only factor related to an earlier arrival (1 week for one January seawater temperature degree increase) of herring at their spawning ground. The relationship was found for the first time on week 52 of the year prior to spawning and was the strongest (50% of the variability explained) from the fourth week of January (8 weeks before the mean Q50 among the studied years). A thermal constant to Q50 (~316°C day) was found when temperatures were integrated from the 49th week of the year prior to spawning. These results indicate that seawater temperature enhanced the speed of gonadal maturation during the latest phases of gametogenesis, leading to an early fish arrival under warm conditions. The duration of the spawning season was elongated during warmer years, therefore potentially mitigating the effects of trophic mismatch when fish spawn early. The results of this study highlight the altering effects of climate change on the spawning activity of a migratory fish species in the Baltic Sea where fast global changes presage that in other coastal areas worldwide

Description: Organic carbon (OC) in permafrost interacts with the mineral fraction of soil and sediments, representing 〈 1% to ~80% of the total OC pool. Quantifying the nature and controls of mineral-OC interactions is therefore crucial for realistic assessments of permafrost-carbon-climate feedbacks, especially in ice-rich regions facing rapid thaw and the development of thermo-erosion landforms. Here, we analyzed sediment samples from the Batagay megaslump in East Siberia, and we present total element concentrations , mineralogy, and mineral-OC interactions in its different stratigraphic units. Our findings indicate that up to 34 ± 8% of the OC pool interacts with mineral surfaces or elements. Interglacial deposits exhibit enhanced OC-mineral interactions, where OC has undergone greater microbial transformation and has likely low degradability. We provide a first-order estimate of ~12,000 tons of OC mobilized annually downslope of the headwall (i.e., the approximate mass of 30 large aircrafts), with a maximum of 38% interacting with OC via complexation with metals or associations to poorly crystalline iron oxides. These data imply that over one-third of the OC exposed by the slump is not readily available for mineralization, potentially leading to prolonged OC residence time in soil and sediments under stable physicochemical conditions.

Description: The data presented herein originates from a mesocosm study conducted as part of the EU H2020 OceanNETs project, aimed at investigating the ecological ramifications of ocean alkalinity enhancement. Nine mesocosms were deployed in Taliarte Harbour, Gran Canaria, Spain, and systematically sampled using integrated water samplers over the period spanning from September 10th to October 25th, 2021. Alkalinity was employed in a gradient design, ranging from ambient (0 µeq kg-1 added alkalinity, OAE0) to elevated levels of 2400 µeq kg-1 additional alkalinity (OAE2400) in increments of 300 µeq kg-1. The dataset encompasses a spectrum of sediment trap particle flux data, water column biogeochemistry variables, including inorganic nutrients, carbonate chemistry parameters, and particulate matter, alongside chlorophyll a concentrations. The study and data set offer insights into impacts of alkalinity enhancement on marine ecosystems and their associated biogeochemistry.

Description: Upward transport and/or mixing of trace gas-enriched subsurface waters fosters the exchange of nitrous oxide (N2O) and methane (CH4) with the atmosphere in the Eastern-South Atlantic (ESA). To date, it is, however, unclear whether this source is maintained by local production or advection of trace-gas enriched water masses. So, the meridional and zonal variability of N2O and CH4 in the ESA were investigated to constrain the contributions of the major regional water masses to the overall budget of N2O and CH4. The fieldwork took place during the cruises M99 (July 31st - August 23rd, 2013) and M120 (October 17th - November 18th, 2015) onboard the R/V METEOR, which encompassed close-coastal and open ocean regions off Angola and Namibia. To investigate the regional concentration gradients of N2O and CH4 and corresponding sea-air fluxes, seven hydrographic sections (six zonal transects and one alongshore transect) were conducted between ~10°S and 26°S. Concentrations of dissolved N2O and CH4 in surface waters were continuously measured by using the Mobile Equilibrator Sensor System. To evaluate, the oceanic-atmospheric trace gas exchange, the atmospheric N2O and CH4 in ambient air were measured at several sporadic locations, with an inlet installed at 35 m height. The data were quality controlled by comparing with the data generated by NOAA in the nearest atmospheric sampling station (23.58° S, 15.03°E, Station NMB (Gobabeb, Namibia)). Also, to better understand the underlying patterns of the trace gas in the ESA, the vertical profiles were investigated by measuring discrete samples of N2O using the dynamic headspace method on M99. N2O and CH4 concentrations were also measured using a purge and trap system during M120 expedition.

Description: This dataset contains energy content measurements performed on zooplankton collected in the Arctic Ocean during the MOSAiC expedition (PS122) from November 2019 untill September 2020. Energy content measurements were done on Apherusa glacialis, Themisto abyssorum, Chaetognatha, Thysanoessa longicaudata and Calanus hyperboreus. These species are all known prey of polar cod (Boreogadus saida), and their energy content was measured to be included in a bioenergetic model of the growth rate of this predator and to gain insight in the differences between prey species. The meaurements were performed on freeze-dried specimens using a 6725 semi-micro oxygen calorimeter (Parr, USA) connected to a 6772 calorimetric thermometer (Parr, USA).