ALBERT

Description: In laboratory culture experiments, phytoplankton species were exposed to a range of nickel concentrations at GEOMAR Helmholtz Centre for Ocean Research Kiel. The experiments were perfomed between Feburary and August 2021. Overall, three experiments were conducted, each with a different taxonomical species (the dinoflagellate Amphidinium carterae, the coccolithophore Emiliania huxleyi and the diatom Thalassiosira weissflogii). Cells were acclimated to experiment conditions for at least 1 week (under salinity 33, 18˚C, 12:12 light and dark cycle). Throughout the experiment cell density was recorded with BD Accuri C6 Flow Cytometer. After the experiment, nickel concentration was measured with ThermoFisher Scientific ElementXR. The study was supported by the OCEAN-ALK-ALIGN project funded by the Carbon to Sea and the Thistledown Foundation.

Description: Deposition of airborne ash from volcanic eruptions has the potential to inject a significant amount of bioavailable metals into seawater, affecting marine primary productivity and increasing or decreasing phytoplankton biomass in the open ocean. These effects can be the result of the release of fertilizing trace elements e.g. iron in limited areas, like high nutrient low chlorophyll areas, like the Southern Ocean or potentially toxic elements like cadmium, copper or lead. In previous studies, the diatom Thalassiosira pseudonanahas been shown to grow in contact with volcanic ash, whilst the growth of the coccolithophore Emiliania huxleyicame to a halt which was unclear why though and what the effects and thresholds could be 1. Different trace metals have been shown to be vital for different processes in coccoliths 2.Changes in coccolithophore productivity and coccolith numbers or sizes as a reaction to increased metal concentrations, could influence sinking rates and CO2uptake and could therefore alter the efficiency of organic carbon export to deep waters. For example, if volcanic material acts as a fertilizer in open ocean waters, it might stimulate phytoplankton growth, increasing the flux of CO2between the atmosphere and the surface ocean organic pool, and result in significant carbon sequestration.To clarify the potential impacts of volcanic ash on coccolithophores, we performed culturing experiments with two coccolithophore strains and different volcanic ashes at a range of concentrations. Here we present results from these experiments, showing the release of an array of metals from the volcanic ashes in Antarctic seawater and the physiological (growth, Fv/Fm) and morphological responses of both coccolithophore strains (SEM).Finally, from a broader perspective, we compare our results with paleo-data to increase the applicability of calcareous nannofossils (coccolithophore remains) as proxies for trace metal concentrations. In particular, the modeling of nannoplankton species-specific reactions/adaptations to excess volcanic trace metal released during different geological episodes is expected to open new scenarios on the characterization of critical past events.

Description: 〈jats:p〉Ocean alkalinity enhancement (OAE) can help mitigate climate change impacts by increasing the carbon storage capacity of the ocean. The technique involves addition of alkaline substances to the seawater to accelerate the natural rock weathering process. However, this will lead to sudden seawater chemistry changes, such as increased pH that might directly and/or indirectly (through trophic pathways) affect zooplankton, an important trophic link, by altering its metabolic state and community composition. In addition, varying dilution times of alkaline substances might impact organisms differently. To date, the possible influences of OAE on zooplankton communities are largely unexplored. To bridge the knowledge gap, we conducted mesocosm and laboratory experiments in simulated non-equilibrated, calcium-based (Ca(OH)2) OAE setups. An incrementally enhanced alkalinity gradient from 0 to 1250 µmol kg-1 in steps of 250 µmol kg-1 was used in all experiments. The wide-ranging enhanced total alkalinity (∆TA) was selected to assess the safety threshold. In addition, we compared immediate versus delayed dilution scenarios in our mesocosm study, where each scenario ended up with the same ∆TA gradient after mixing. We examined the multitrophic community response by monitoring twelve mesocosms for 39 days including the natural spring bloom community of Helgoland roads waters in the North Sea. Subsequently, the direct effect of alkalinity enhancement on the physiology (i.e., respiration and grazing) of Temora longicornis (predominant copepod in the mesocosms) was evaluated in the laboratory. The species-specific bottom-up effect was examined by culturing Rhodomonas salina in aforementioned ∆TA gradient and feeding them to the T. longicornis. We observed relatively lower zooplankton abundance, and growth rate in mesocosms with ∆TA1000 and 1250 µmol kg-1, which might be a bottom-up effect. In our lab experiments, though, we observed a negative impact on R. salina growth rate and nutritional quality from ∆TA750 µmol kg-1, we did not detect any substantial direct or indirect impact on the physiological performance of T. longicornis. Overall, our laboratory study provided a preliminary understanding of the direct and indirect effects of OAE on a key copepod species, and the mesocosm study gave insight into the zooplankton community response.〈/jats:p〉

Description: Morphological changes in coccoliths, tiny calcite platelets covering the outer surface of coccolithophores, can be induced by physiological responses to environmental changes. Coccoliths recovered from sedimentary successions may therefore provide information on paleo-environmental conditions prevailing at the time when the coccolithophores were alive. To calibrate the biomineralization responses of ancient coccolithophore to environmental changes, studies often compared the biological responses of living coccolithophore species with paleo-data from calcareous nannofossils. However, there is uncertainty whether the morphological responses of living coccolithophores are representative of those of the fossilized ancestors. To investigate this, we exposed four living coccolithophore species (Emiliania huxleyi, Gephyrocapsa oceanica, Coccolithus pelagicus subsp. braarudii, and Pleurochrysis carterae) that have been evolutionarily distinct for hundreds of thousands to millions of years, to a range of environmental conditions (i.e., changing light intensity, Mg∕Ca ratio, nutrient availability, temperature, and carbonate chemistry) and evaluated their responses in coccolith morphology (i.e., size, length, width, malformation). The motivation for this study was to test if there is a consistent morphological response of the four species to changes in any of the tested abiotic environmental factors. If this was the case, then this could suggest that coccolith morphology can serve as a paleo-proxy for that specific factor because this response is conserved across species that have been evolutionary distinct over geological timescales. However, we found that the four species responded differently to changing light intensity, Mg∕Ca ratio, nutrient availability, and temperature in terms of coccolith morphology. The lack of a common response reveals the difficulties in using coccolith morphology as a paleo-proxy for these environmental drivers. However, a common response was observed under changing seawater carbonate chemistry (i.e., rising CO2), which consistently induced malformations. This commonality provides some confidence that malformations found in the sedimentary record could be indicative of adverse carbonate chemistry conditions.

Description: The Cretaceous ocean witnessed intervals of profound perturbations such as volcanic input of large amounts of CO2, anoxia, eutrophication, and introduction of biologically relevant metals. Some of these extreme events were characterized by size reduction and/or morphological changes of a few calcareous nannofossil species. The correspondence between intervals of high trace metal concentrations and coccolith dwarfism suggests a negative effect of these elements on nannoplankton biocalcification process in past oceans. In order to verify this hypothesis, we explored the potential effect of a mixture of trace metals on growth and morphology of four living coccolithophore species, namely Emiliania huxleyi, Gephyrocapsa oceanica, Pleurochrysis carterae and Coccolithus pelagicus. These taxa are phylogenetically linked to the Mesozoic species showing dwarfism under excess metal concentrations. The trace metals tested were chosen to simulate the environmental stress identified in the geological record and upon known trace metal interaction with living coccolithophores algae. Our laboratory experiments demonstrated that elevated trace metal concentrations not only affect coccolithophore algae production but, similarly to the fossil record, coccolith size and/or weight. Smaller coccoliths were detected in E. huxleyi and C. pelagicus, while coccoliths of G. oceanica showed a decrease in size only at the highest trace metal concentrations. P. carterae coccolith size was unresponsive for changing trace metal amounts. These differences among species allow to discriminate most- (P. carterae), intermediate- (E. huxleyi), and least- (C. pelagicus and G. oceanica) tolerant taxa. The fossil record and the experimental results converge on a selective response of coccolithophores to metal availability. These species-specific differences must be considered before morphological features of coccoliths are used to reconstruct paleo-chemical conditions.

Description: The Cretaceous ocean witnessed intervals of profound perturbations such as volcanic input of large amounts of CO2, anoxia, eutrophication and introduction of biologically relevant metals. Some of these extreme events were characterized by size reduction and/or morphological changes of a few calcareous nannofossil species. The correspondence between intervals of high trace metal concentrations and coccolith dwarfism suggests a negative effect of these elements on nannoplankton biocalcification processes in past oceans. In order to test this hypothesis, we explored the potential effect of a mixture of trace metals on growth and morphology of four living coccolithophore species, namely Emiliania huxleyi, Gephyrocapsa oceanica, Pleurochrysis carterae and Coccolithus pelagicus. The phylogenetic history of coccolithophores shows that the selected living species are linked to Mesozoic species showing dwarfism under excess metal concentrations. The trace metals tested were chosen to simulate the environmental stress identified in the geological record and upon known trace metal interactions with living coccolithophore algae.Our laboratory experiments demonstrated that elevated trace metal concentrations, similarly to the fossil record, affect coccolithophore algae size and/or weight. Smaller coccoliths were detected in E. huxleyi and C. pelagicus, while coccoliths of G. oceanica showed a decrease in size only at the highest trace metal concentrations. P. carterae coccolith size was unresponsive to changing trace metal concentrations. These differences among species allow discriminating the most- (P. carterae), intermediate- (E. huxleyi and G. oceanica) and least-tolerant (C. pelagicus) taxa. The fossil record and the experimental results converge on a selective response of coccolithophores to metal availability.These species-specific differences must be considered before morphological features of coccoliths are used to reconstruct paleo-chemical conditions.

Description: The Toarcian Oceanic Anoxic Event (T-OAE) interval was cored at Colle di Sogno and Gajum in the Lombardy Basin (Southern Alps, northern Italy). The Sogno and Gajum cores recovered 26.83 and 31.18 stratigraphic metres, respectively, of pelagic sediments consisting of marly limestones, marlstone, marly claystone, and black shale. Drilling at both sites resulted in 100 % recovery of unweathered material. The pelagic succession comprises a relatively expanded black shale interval of 4.98 m in the Sogno core and 15.35 m in the Gajum core, with lower and upper boundaries without evidence of hiatuses. The Sogno and Gajum cores can be considered reference sections for the pelagic lower Toarcian interval of the western Tethys and will provide high-resolution micropaleontological, inorganic and organic geochemical, isotopic multiproxy data. Integrated stratigraphy and cyclostratigraphy are predicted to result in estimates of durations and rates to model the ecosystem resilience to the extreme perturbations of the T-OAE and gain a better understanding of current global changes and help provide better projections of future scenarios.

Description: Morphological changes in coccoliths, tiny calcite platelets covering the outer surface of coccolithophores, can be the result of physiological responses to environmental changes. Coccoliths recovered from sedimentary successions may therefore provide information on paleo-environmental conditions prevailing at the time when the coccolithophores were alive. To calibrate the biomineralization responses of ancient coccolithophore to climatic changes studies often compared the biological responses of living coccolithophore species with paleo-data from calcareous nannofossils. However, there is uncertainty whether the morphological responses of living coccolithophores are representative for those of the fossilized ancestors. To investigate this, we cultured four living coccolithophore species (Emiliania huxleyi, Gephyrocapsa oceanica, Coccolithus pelagicus subsp. braarudii, and Pleurochrysis carterae) that have been evolutionarily distinct for millions of years, exposed them to changing environmental conditions (i.e. changing light intensity, Mg / Ca ratio, nutrient availability, temperature and carbonate chemistry) and evaluated their responses in coccolith morphology (i.e. size, length, width, malformation). The motivation for this study was that if the species show the same morphological response to changes in any of the tested abiotic environmental factors, then there is a reason to assume that this response is conserved over geological timescales and that coccolith morphology can serve as a paleo-proxy for that specific factor. In contrast with this concept, we found that the four species responded differently to changing light intensity, Mg / Ca ratio, nutrient availability and temperature in terms of coccolith morphology. The lack of a common response reveals the difficulties in using coccolith morphology as a proxy for paleo-environmental conditions. However, a common response was observed under changing seawater carbonate chemistry (i.e. rising CO2) which consistently induced malformations. This commonality provides some confidence that malformations found in the sedimentary record could be indicative for high CO2 levels.