Description: Physiological sensitivity of cold-water corals to ocean change is far less understood than of tropical corals and very little is known about the impacts of ocean acidification and warming on degradative processes of dead coral framework. In a 13-month laboratory experiment, we examined the interactive effects of gradually increasing temperature and pCO2 levels on survival, growth, and respiration of two prominent color morphotypes (colormorphs) of the framework-forming cold-water coral Lophelia pertusa, as well as bioerosion and dissolution of dead framework. Calcification rates tended to increase with warming, showing temperature optima at ~ 14°C (white colormorph) and 10–12°C (orange colormorph) and decreased with increasing pCO2. Net dissolution occurred at aragonite undersaturation (ΩAr 〈 1) at ~ 1000 μatm pCO2. Under combined warming and acidification, the negative effects of acidification on growth were initially mitigated, but at ~ 1600 μatm dissolution prevailed. Respiration rates increased with warming, more strongly in orange corals, while acidification slightly suppressed respiration. Calcification and respiration rates as well as polyp mortality were consistently higher in orange corals. Mortality increased considerably at 14–15°C in both colormorphs. Bioerosion/dissolution of dead framework was not affected by warming alone but was significantly enhanced by acidification. While live corals may cope with intermediate levels of elevated pCO2 and temperature, long-term impacts beyond levels projected for the end of this century will likely lead to skeletal dissolution and increased mortality. Our findings further suggest that acidification causes accelerated degradation of dead framework even at aragonite saturated conditions, which will eventually compromise the structural integrity of cold-water coral reefs.

Description: Dinitrogen (N2) fixation is a major source of bioavailable nitrogen to oligotrophic ocean communities. Yet, we have limited understanding how ongoing climate change could alter N2 fixation. Most of our understanding is based on short-term laboratory experiments conducted on individual N2-fixing species whereas community-level approaches are rare. In this longer-term in situ mesocosm study, we aimed to improve our understanding on the role of rising atmospheric carbon dioxide (CO2) and simulated deep water upwelling on N2 and carbon (C) fixation rates in a natural oligotrophic plankton community. We deployed nine mesocosms in the subtropical North Atlantic Ocean and enriched seven of these with CO2 to yield a range of treatments (partial pressure of CO2, pCO2 = 352–1025 μatm). We measured rates of N2 and C fixation in both light and dark incubations over the 55-day study period. High pCO2 negatively impacted light and dark N2 fixation rates in the oligotrophic phase before simulated upwelling, while the effect reversed in the light N2 fixation rates in the bloom decay phase after added nutrients were consumed. Dust deposition and simulated upwelling of nutrient-rich deep water increased N2 fixation rates and nifH gene abundances of selected clades including the unicellular diazotrophic cyanobacterium clade UCYN-B. Elevated pCO2 increased C fixation rates in the decay phase. We conclude that elevated pCO2 and pulses of upwelling have pronounced effects on diazotrophy and primary producers, and upwelling and dust deposition modify the pCO2 effect in natural assemblages.

Description: This data is part of the BMBF projects CUSCO (Coastal Upwelling Systems in a Changing Ocean) and BioTip subproject Humboldt Tipping. Data was collected during cruise number MSM80 with research vessel Maria S. Merian from 23.12.2018 - 30.01.2019 (from Panama to Valparaiso) in the Humboldt Upwelling system off the Eastern Tropical south Pacific. Samples were taken by CTD- rosette sampler from different depths and analysed onboard for dissolved inorganic nutrients and total dissolved nutrients. Triplicate nutrient samples were analysed for concentrations with an autosampler (XY-2 autosampler, SEAL Analytical) and a continuous flow analyzer (QUAAtro Autoanalyzer, SEAL Analytical) using standard colorimetric and flourometric methods by Kastriot Qelaj. Dissolved organic nutrients were calculated as the difference of the two for respective nitrogen and phosphorous nutrients. Phosphate was measured according to Murphy and Riley (1962). Ammonium was measured fluorometrically based on Holmes et al. (1999). An empty cell means that corresponding nutrient samples were not taken for the respective depth.

Description: Physio-chemical data from the mesocosms experiment conducted in the Canary Islands in autumn 2019. Values are depth-integrated averages in (mostly) 2-days intervals over the course of 33 days. The upwelling treatment started on day 6. Oxygen (O2), salinity, temperature, photosynthetically active radiation (PAR) and pH were measured from 0.3 to 2.5 m depth via three replicate CTD casts. Dissolved inorganic carbon (DIC) and the inorganic nutrients nitrite (NO2), combined nitrate and nitrite (NO3 + NO2), ammonia (NH4), phosphate (PO4) and silicate (Si(OH)4) were measured in triplicates on depth integrated water samples from 0 to 2.5 m depth. Total alkalinity (TA) was measured from the same water samples but in duplicates. Then, pCO2 and nitrate was calculated. Methodological details in Goldenberg et al. (doi:10.3389/fmars.2022.1015188).

Description: This dataset contains the results of a lab experiment performed in Ny Ålesund (Arctic, Svalbard, 78° 55′ N, 11° 56′ O) from 22.–29. August 2013. We collected early-stage thecosome pteropods (Limacina spp.) in Kongsfjord to investigate the response of their lipid metabolism (response variables: total lipids, lipid classes, fatty acids, fatty alcohols) to ocean warming and acidification (OWA). Pteropods were collected on August 21 with a 100 µm plankton net (0.2 square meter mouth opening, 1 L cod end) integrated from 300 m depth in Kongsfjord. The OWA experiment was designed to cover end-of the century projections for temperature and pCO2 and included two temperature treatments (3.5°C = mean in situ temperature averaged over the depth range where pteropods where collected from, and 5.5°C resembling a 2°C temperature increase projected for the Arctic Ocean in the upper 100-200 m, Steinacher et al. 2009, https://doi.org/10.5194/bg-6-515-2009) and three pCO2 levels chosen according to the RCP 8.5 scenario (present day = 400 µatm, year 2080 = 750 µatm, and 〉2100 = 1100 µatm). Temperature treatments were realized in temperature controlled rooms. pCO2 levels were established by bubbling filtered seawater (20 µm filtered) with Wösthoff gas mixing pumps (Wösthoff, Germany). For each treatment level six replicates (one vessel á 300 ml = one experimental unit = one replicate) were established with 200 incubated early-stage pteropods (ca. 300 µm shell length of individual pteropods). To assure that oxygen concentrations in the vessels did not fall below critical saturation levels of oxygen partial pressure for marine mollusks due to respiration of the incubated pteropods, the experimental seawater was changed regularly. Along with the analyzed lipid data, this dataset also includes the carbonate chemistry data of the perturbed experimental seawater and of that in the experimental units (start/end measurements as well as pH development in the experimental units).

Description: Pigment concentration and pigment-based phytoplankton community composition data from a KOSMOS mesocosm experiment carried out in the frame work of the Ocean Artificial Upwelling project. The experiment was performed in the North-East Atlantic Ocean off the coast of Gran Canaria in autumn 2018 and lasted for 39 days. In this study we investigated the effect of different intensities of artificial upwelling combined with two upwelling modes (recurring additions versus one singular addition) on the phytoplankton community. Filters were analysed for a range of photosynthetic pigments using reverse-phase high-performance liquid chromatography (HPLC). Based on pigment concentrations, phytoplankton community composition was approximated using the CHEMTAX software with the original pigment ratios from Mackey et al (1996, doi:10.3354/meps144265). The input included Chl a, b, c2, and c3, peridinin, 19'-butanoyloxyfucoxanthin, fucoxanthin, neoxanthin, prasinoxanthin, violaxanthin, 19'-hexanoyloxyfucoxanthin, alloxanthin, diadinoxanthin, diatoxanthin and zeaxanthin. Divinyl Chl a was instead fully associated with Prochlorophyceae. The presence of the main phytoplankton groups is expressed in Chl a equivalents.

Description: Size fractionated primary productivity rate measurements through 14C radioisotope incorporation rates from a KOSMOS mesocosm experiment carried out in the frame work of the Ocean Artificial Upwelling project. The experiment was performed in the North-East Atlantic Ocean off the coast of Gran Canaria in autumn 2018 and lasted for 39 days. In this study we investigated the effect of different intensities of artificial upwelling combined with two upwelling modes (recurring additions versus one singular addition) on the phytoplankton community. Data shown includes production rates of dissolved organic carbon, particulate organic carbon in 3 size fractions (0.2-2 µm, 2-20 µm, 〉20 µm) and total organic carbon.

Description: Export data from the mesocosm experiment conducted in the Canary Islands in autumn 2019. Sinking matter was collected in 2-days intervals over the course of 33 days from the mesocosm sediment traps (4 m depth). Sediment samples were processed and subsampled for duplicate measurements of particulate organic carbon (POC), nitrogen (PON), phosphorus (POP) and biogenic silica (BSi). Elemental mass fluxes in µmol L-1 were calculated by normalizing to the mesocosm volume. They were then either normalized to the time between sample collection (48 h) to obtain daily mass fluxes (µmol L-1 d-1), or added up to obtain cumulative mass fluxes (µmol L-1). Another set of sediment subsamples was analyzed for particle sinking velocities, sizes and porosities (bidaily) and microbial remineralization rates (every 4 days).

Description: This data is part of the BMBF projects CUSCO (Coastal Upwelling Systems in a Changing Ocean) and BioTip subproject Humboldt Tipping. Here we report water column nitrogen fixation, carbon fixation rates and particulate organic matter composition from the upper 300 m. Data was collected during cruise number MSM80 with research vessel Maria S. Merian from 23.12.2018 - 30.01.2019 (from Panama to Valparaiso) in the Humboldt Upwelling system off the Eastern Tropical south Pacific. Samples were taken by CTD- rosette sampler from different depths, injected with 15N labelled N2 gas based on the modified dissolution method (Großkopf et al., 2012 and Mohr et al., 2010) and additionally 13C labeled sodium bicarbonate. Samples were incubated for 24 hours at light intensities that resemble the in situ light conditions. After incubation a volume of the sample (20 - 1500 ml) was filtered onto a pre-combusted Whatman GF/75 filter. Filters were frozen, transported to the institute on dry ice and measured on a mass spectrometer for Delta15N and 13C (Delta V Advantage Isotope Ratio MS, ThermoFisher) with the ConFlo IV interface (ThermoFisher). Nitrogen fixation rates were calculated based on Montoya et al (1996) while carbon fixation rates were calculated based on the equation by Slawyk et al. (1977). Limits of detection (LOD) and minimum quantifiable rates (MQR) for Nitrogen fixation rates were calculated according to the criteria described by White et al. (2020) and standard error propagation methods described in Gradoville et al. (2017) respectively. POP and Biogenic silica concentrations were measured spectrophotometrically following Hansen and Koroleff (1999).

Description: In a 13-months laboratory experiment conducted in 2014/2015, the interactive effects of gradually increasing temperature and pCO2 levels on survival, growth and respiration of two prominent colour morphotypes (white and orange) of the framework-forming cold-water coral Lophelia pertusa (also known as Desmophyllum pertusum), as well as bioerosion and dissolution of dead coral framework were assessed. In six-week intervals, three treatments (T1: acidification, T2: warming, T3: combined acidification and warming) were gradually increased in their respective manipulated parameters by 1°C and/or 200 µatm pCO2 after an initial two intervals under ambient (near in-situ) conditions. Each treatment consisted of 7 replicates that were manipulated over the course of the experiment and 3 control replicates that remained at ambient conditions throughout the entire duration of the experiment. Each replicate tank consisted of one live coral fragment of the white morphotype, one fragment of the orange morphotype and one dead framework fragment (naturally bioeroded framework material). Dead framework was examined with regard to attached bioeroders and calcifying organisms, the latter being removed prior to the experiment. All coral samples were collected from an inshore Norwegian cold-water coral habitat in the outer Trondheim-Fjord near Nord-Leksa (63°36.4'N, 09°22.7'E) between 150 to 230 m water depth using the manned submersible JAGO (GEOMAR, 2017; doi:10.17815/jlsrf-3-157) during RV POSEIDON (GEOMAR, 2015; doi:10.17815/jlsrf-1-62) cruise POS455 in June/July 2013. In situ conditions at the time of sampling near the corals were 7.7°C in temperature, 35.2 in salinity and ~6 mL/L oxygen concentration. Prior to the experiment, corals were kept in a closed recirculating system of 1,700 L in a climate-controlled laboratory facility at GEOMAR in Kiel at near in situ conditions of temperature and salinity (7.8 145 ± 0.2 °C and 35.8 ± 0.6) for half a year. Calcification/dissolution rates of live corals and bioerosion/dissolution rates of dead coral framework were determined using the buoyant weighing technique (Davies, 1989; doi:10.1007/BF00428135) with a high precision analytical balance (Sartorius CPA225D, readability = 0.1 mg) placed above every individual aquarium for each measurement. Respiration rates were determined via oxygen consumption measurements using an optode-based oxygen analyser (Oxy-10 mini, PreSens GmbH). Mortality was examined during every six-week interval by visual inspection of all live fragments. Dead polyp counts were calculated as percentage of total polyps counts of every individual fragment. Carbonate system parameters were calculated from the two measured parameters total alkalinity (TA) and dissolved inorganic carbon (DIC). TA and DIC samples were taken at the end of every 6-week interval and analyzed via potentiometric open-cell titration (862 Compact Titrosampler, Metrohm) in case of TA and by infrared detection of CO2 using an Automated Infra-Red Inorganic Carbon Analyzer (AIRICA with LI-COR 7000, Marianda) in case of DIC. TA and DIC were corrected against Certified Reference Material from A.G. Dickson (Scripps Institution of Oceanography) and density-corrected. The purpose of this study was to examine thresholds and optima of live corals under gradual increases of ocean acidification and warming and to quantify dissolution and bioerosion rates of dead coral framework to ultimately assess the balance between live coral calcification and degradation of dead coral framework under future ocean conditions.