Abstract. Ocean alkalinity enhancement (OAE) is a proposed method for removing carbon dioxide (CO2) from the atmosphere by the accelerated weathering of (ultra-)basic minerals to increase alkalinity – the chemical capacity of seawater to store CO2. During the weathering of OAE-relevant minerals relatively large amounts of trace metals will be released and may perturb pelagic ecosystems. Nickel (Ni) is of particular concern as it is abundant in olivine, one of the most widely considered minerals for OAE. However, so far there is limited knowledge about the impact of Ni on marine biota including phytoplankton. To fill this knowledge gap, this study tested the growth and photo-physiological response of 11 marine phytoplankton species to a wide range of dissolved Ni concentrations (from 0.07 to 50 000 nmol L−1). We found that the phytoplankton species were not very sensitive to Ni concentrations under the culturing conditions established in our experiments, but the responses were species-specific. The growth rates of 6 of the 11 tested species showed generally limited but still significant responses to changing Ni concentrations (36 % maximum change). Photosynthetic performance, assessed by measuring the maximum quantum yield (Fv/Fm) and the functional absorption cross-section (σPSII) of photosystem II (PSII), was sensitive to changing Ni in 3 out of 11 species (35 % maximum change) and 4 out of 11 species (16 % maximum change), respectively. The limited effect of Ni may be partly due to the provision of nitrate as the nitrogen source for growth as previous studies suggest higher sensitivities when urea is the nitrogen source. Furthermore, the limited influence may be due to the relatively high concentrations of synthetic organic ligands added to the growth media in our experiments. These ligands are commonly added to control trace metal bioavailability and therefore for example “free Ni2+” concentrations by binding the majority of the dissolved Ni. Our data suggest that dissolved Ni does not have a strong effect on phytoplankton under our experimental conditions, but we emphasize that a deeper understanding of nitrogen sources, ligand concentrations, and phytoplankton composition is needed when assessing the influence of Ni release associated with OAE.
A Gram-stain-negative and facultatively anaerobic bacterial strain, designated GUOT, was isolated from surface water collected from the South China Sea. Cells were non-flagellate, yellow, non-spore-forming and rod-shaped. The 16S rRNA gene sequence comparisons with species in the genus Arenibacter showed that strain GUOT shares the highest similarity of 97.5 % with Arenibacter echinorum and Arenibacter palladensis . Average nucleotide identity and digital DNA–DNA hybridization values between strain GUOT and its related type strains were 77.1–78.4% and 20.8–26.2 % respectively. Growth of strain GUOT occurred at 15–50°C (optimum, 20–25°C), pH 5–7.5 (pH 6) and in media containing 0–7 % NaCl (optimum, 0–1 %). Cells contained methanol-soluble yellow-coloured pigments but flexirubin-type pigments were absent. The major fatty acids (>5 %) were iso-C17 : 0 3-OH, iso-C15 : 0, anteiso-C15 : 0, C16 : 0, summed feature 3, iso-C15 : 1 G and iso-C15 : 0 3-OH. The dominant polar lipids comprised phosphatidylethanolamine and some unidentified polar lipids. The main respiratory quinone was menaquinone-6. The DNA G+C content of strain GUOT was 40.1 %. Based on the presented data, we consider strain GUOT to represent a novel species of the genus Arenibacter , for which the name Arenibacter aquaticus sp. nov. is proposed. The type strain is GUOT (=KCTC 62629T=MCCC 1K03559T)
A Gram-stain-negative and aerobic bacterial strain, designated as JL3514T, was isolated from surface water of the hydrothermal system around Kueishan Island. The isolate formed red colonies and cells were non-flagellated, rod-shaped and contained methanol-soluble pigments. Growth was observed at 10–50 °C (optimum, 30 °C), at pH 5.0–9.0 (optimum, pH 7.0) and in the presence of 0–9 % (w/v) NaCl (optimum, 2 %). Strain JL3514T was positive for catalase and weakly positive for oxidase. Results of 16S rRNA gene sequence analyses showed highest similarities to species in the family Erythrobacteraceae , namely Croceibacterium atlanticum (96.1 %), Pelagerythrobacter marensis (96.0 %), Tsuneonella rigui (96.0 %) and Altericroceibacterium xinjiangense (96.0 %). Phylogenetic analysis based on core gene sequences revealed that the isolate formed a distinct branch with the related species and it had a lower average amino acid identity value than the suggested threshold for genera boundaries. The major fatty acids (>5 %) were summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), C16 : 0, C17 : 1 ω6c, C14 : 0 2-OH and C12 : 0. The dominant polar lipids comprised diphosphatidylglycerol, sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, glycolipid, two unidentified lipids and one unidentified phospholipid. The main respiratory quinones were ubiquinone-10 (95.7 %) and ubiquinone-9 (4.3 %). The DNA G+C content from the genome was 63.0 mol%. Based on the presented data, we consider strain JL3514T to represent a novel genus of the family Erythrobacteraceae , with the name Pseudopontixanthobacter vadosimaris gen. nov., sp. nov. The type strain is JL3514T (=KCTC 62623T=MCCC 1K03561T).
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