Spring and autumn living coccolithophores in the Bohai Sea and Yellow Sea,China

The living coccolithophores （LCs） are an important class of calcified taxa of phytoplankton functional groups, and major producers of marine biogenic inorganic carbon, playing an important role in the marine carbon cycle. In this study, we report the two-demensional abundance, composition of LCs and its correlation with the environmental parameters in spring and autumn, in order to understand the ecological role of LCs in the Yellow Sea and the Bohai Sea. In spring, totally 9 taxa belonging to coccolithophyceae were identified using a polarized microscope at the 1 000x magnification. The dominant species were Emiliania huxleyi, Gephyrocapsa oceanica, Helicosphaera carteri, and Calcidiscus leptoporus. The abundance of coccosphores and coccoliths ranged 0-7.72 cells/mL, and 0-216.09 coccoliths/mL, with the average values of 0.21 cells/mL, and 11.36 coccoliths/mL, respectively. The Emiliania huxleyi distribution was similar to Gephyrocapsa oceanica. The highest abundance of coccoliths was observed in the east of Shandong Peninsula in northern Yellow Sea, whereas Helicosphaera carteri distributed more widely. Emiliania huxleyi and Gephyrocapsa oceanica were the two predominant species in LCs with higher abundances. The distribution of LCs was similar to that of coccoliths. In autumn, 14 taxa belonging to coccolithophyceae were identified with dominant species as Emiliania huxleyi, Gephyrocapsa oceanica, Helicosphaera carteri, Calcidiscus leptoporus and Oolithotus fragilis. The abundance of coccosphores and coccoliths ranged 0-24.69 cells/mL, and 0-507.15 coccoliths/mL, with the average values of 1.47 cells/mL, and 55.89 coccoliths/mL, respectively. The highest abundance of coccoliths was located in Qingdao coastal waters and south of the survey area. The distribution of LCs was similar to the coccoliths; in addition, LCs presented large abundance in the east of the central Yellow Sea area.

Living coccolithophores in the western Pacific Ocean with mesoscale eddies

Living coccolithophores(LCs)are regarded as a group of calcifiers and play important roles in global carbon cycle.This study used microscopic observations of LCs in the western Pacific Ocean to investigate their community structure and biodiversity,especially to test whether local physical traits(mesoscale eddies)could explain their biogeographic distributions during autumn of 2017.The coccolithophore calcite inventory based on carbon-volume transformation was estimated in this study.A total of 28 taxa of coccospheres and 19 types of coccoliths were identified from 161 samples.Gephyrocapsa oceanica was the most predominant species in all the coccolithophore community,followed by Florisphaera profunda,Emiliania huxleyi,Umbilicosphaera sibogae,Gladiolithusflabellatus and Umbellosphaera tenuis.The abundance of coccospheres and coccoliths ranged from 0 to 26.8×10^(3)cells/L and from 0 to 138.5×10^(3)coccoliths/L,averaged at 4.2×10^(3)cells/L and 10.9×10^(3)coccoliths/L,respectively.This study indicated that coccolithophore community in the survey area can be clustered into four groups.Three ecological niches of coccolithophores were characterized by their vertical profiles and multivariate statistical analysis.Coccolithophore abundance and species composition were remarkably different among warm-eddy region,G.oceanica dominated warm-eddy region,while F.profunda dominated warm-eddy and none-eddy region.The average values of estimated particulate inorganic carbon,particulate organic carbon were0.197μg/L and 0.140μg/L,respectively.The current field study widened the dataset of coccolithophores in western Pacific Ocean.

Autumn living coccolithophores in the Yellow Sea and the East China Sea

An investigation was carried out on living coccolithophores （LCs） distribution in the Yellow Sea and the East China Sea from October 17 to November 24, 2011. A total of 223 samples from different depths were col-lected at 48 stations. Totally 18 taxa belonging to coccolithophyceae were identified using a polarized micro-scope at the 1 000× magnification. The maximum species abundance was found at the outside of Transect P. The dominated species wereGephyrocapsa oceanica, Emiliania huxleyi,Helicosphaera carteri,andAlgiros-phaera robusta.The abundance of coccoliths and cells ranged 0-2 965.73 coccoliths/mL, and 0-119.16 cells/mL, with the average values of 471.00 coccoliths/mL and 23.42 cells/mL, respectively. The LCs in surface layer were mainly observed on the coastal belt and middle part of the survey area. The comparison among Transects A, F, P and E indicated lower species diversity and less abundance in the Yellow Sea than those of the East China Sea. The highest abundance of LCs was found in transect F and P. The coccolith abundance increased slightly from surface to bottom in the water column, but the highest value of the cell abundance was observed in the depth of 10-30 m. Temperature, depth and nutrient concentration were suggested as the major environmental factors controlling the distribution and species composition of LCs in the studying area based on canonical correspondence analysis （CCA）.

The metabolite profiling of coastal coccolithophorid species Pleurochrysis carterae(Haptophyta)

Pleurochrysis carterae is a calcifi ed coccolithophorid species that usually blooms in the coastal area and causes aquaculture losses. The cellular calcifi cation, blooming and many other critical species specifi c eco-physiological processes are closely related to various metabolic pathways. The purpose of this study is to apply the unbiased and non-destructive method of nuclear magnetic resonance(NMR) to detect the unknown holistic metabolite of P. carterae. The results show that NMR spectroscopic method is practical in the analysis of metabolites of phytoplankton. The metabolome of P. carterae was dominated by 26 metabolites involved in a number of dif ferent primary and secondary metabolic pathways. Organic acids and their derivatives, amino acids, sugars, nucleic aides were mainly detected. The abundant metabolites are that closely related to the process of cellular osmotic adjustment, which possibly refl ect the active ability of P. carterae to adapt to the versatile coastal niche. DMSP(dimethylsulphoniopropionate) was the most dominant metabolite in P. carterae, up to 2.065±0.278 mg/g lyophilized cells, followed by glutamate and lactose, the contents were 0.349±0.035 and 0.301±0.073 mg/g lyophilized cells respectively. Other metabolites that had the content ranged between 0.1–0.2 mg/g lyophilized cells were alanine, isethionate and arabinose. Amino acid(valine, phenylalanine, isoleucine, tyrosine), organic acid salts(lactate, succinate), scyllitol and uracil had content ranged from 0.01 to below 0.1 mg/g lyophilized cells. Trigonelline, fumarate and formate were detected in very low content(only thousandths of 1 mg per gram of lyophilized cells or below). Our results of the holistic metabolites of P. carterae are the basic references for the further studies when multiple problems will be addressed to this notorious blooming calcifying species.

The ecological response of natural phytoplankton population and related metabolic rates to future ocean acidification

Ocean acidifi cation(OA)and global warming-induced water column stratification can signifi cantly alter phytoplankton-related biological activity in the marine ecosystem.Yet how these changes may play out in the tropical Indian Ocean remains unclear.This study investigated the ecological and metabolic responses of the different phytoplankton functional groups to elevated CO_(2) partial pressure and nitrate deficiency in two different environments of the eastern Indian Ocean(EIO).It is revealed that phytoplankton growth and metabolic rates are more sensitive to inorganic nutrients rather than CO_(2).The combined interactive effects of OA and N-limitation on phytoplankton populations are functional groupspecific.In particular,the abundance and calcification rate of calcifying coccolithophores are expected to be enhanced in the future EIO.The underlying mechanisms for this enhancement may be ascribed to coccolithophore’s lower carbon concentrating mechanisms(CCMs)efficiency and OA-induced[HCO^(-)_(3)]increase.In comparison,the abundance of non-calcifying microphytoplankton(e.g.,diatoms and dinoflagellates)and primary productivity would be inhibited under those conditions.Diff erent from previous laboratory experiments,interspecifi c competition for resources would be an important consideration in the natural phytoplankton populations.These combined factors would roughly determine calcifying coccolithophores as“winners”and non-calcifying microphytoplankton as“losers”in the future ocean scenario.Due to the large species-specific differences in phytoplankton sensitivity to OA,comprehensive investigations on oceanic phytoplankton communities are essential to precisely predict phytoplankton ecophysiological response to ocean acidification.

Calcareous nannofossil changes in the Early Oligocene linked to nutrient and atmospheric CO2

Rapid changes on nutrient supply and CO2 concentration that occurred in the northern South China Sea(SCS)during the Early Oligocene,provides an ideal natural laboratory,allowing us to peer into the coccolithophores’physiology in the geological records.In this study,we established a new nannofossil assemblage index,termed as E^*ratio,which is calculated by the relative abundance of eutrophic taxa and meso-oligotrophic taxa(E^*=e/e+c,where e is eutrophic taxa,and c is meso-oligotrophic taxa)Eutrophic taxa include small Reticulofenestra,Reticulofenestra lockeri group,Reticulofenestra bisecta group and Coccolithus pelagicus group,while meso-oligotrophic taxa include Cyclicargolithus spp.The E^*ratio is well correlated with nutrient proxy during the Early Oligocene,while with different covarying patterns under the higher and lower CO2 condition.By comparing the assemblage changes to the published data,we suggest that coccolithophores may change the way they use carbon source and nutrient with the decline of CO2.Furthermore,this implies a possible initiation of the carbon concentrating mechanism.

Calcification response of Pleurochrysis carterae to iron concentrations in batch incubations： implication for the marine biogeochemical cycle

Calcified coccolithophores, a diverse and widely distributed group of marine microalgae, produce biogenic calcite in the form ofcoccoliths located on the cell surface. Using batch incubations of the coccolithophorid Pleurochrysis carterae, we investigated the responses of this calcification process to iron concentrations by changing the iron supply in the initial culture media from a normal concentration to 1 ppm （parts per million）, 5 ppm, and 10 ppm. Time-dependent measurements of cell population, production of inorganic carbon （coccoliths）, and organic carbon （organic cellular components） showed that elevated iron supply in the growth medium of P. carterae stimulates carbon sequestration by increasing growth along enhanced photosynthetic activity and calcification. In addition, the acquired time-dependent UV-Vis and FT-IR spectra revealed that iron fertilization- enhanced coccolith calcification is accompanied by a crystalline phase transition from calcite to aragonite or amorphous phase. Our results suggest that iron concentration has a significant influence on the marine carbon cycle of coccolithophores.

Distribution of aromatic bio-markers in pyrolysates of co-ccolithophore

Analyses of the original and pyrolytic products of coccolithophore at various temperatures suggest that the contribution of coccolithophore to the formation of large immature oil reservoirs should attract keen interest. Through biochemical processes algae can change inorganic sulphur into organic sulphur, which could be one of the most important precursors of organic sulphur compounds in oil and source rocks. When Methylphenanthrene Index (MPI) and Methylphenanthrene Ratio (MPR) indices were used to evaluate the evolution degree of source rocks and oil maturity, other maturity indices must be used together for correction. In low maturity, the relative abundances of diben-zothiophene (DBT), fluorine (F) and dibenzofuran (DBF) can be used to identify the oxidation-reduction environments.

Patterns of coccolithophore pigment change under global acidification conditions based on in-situ observations at BATS site between July 1990-Dec 2008

Coccolith production is an important part of the biogenic carbon cycle as the largest source of Calcium carbonate on earth, accounting for about 75% of the deposition of carbon on the sea floor. Recent studies based on laboratory experiment results indicated that increasing anthropogenic CO2 in the atmosphere triggered global ocean acidification leading to a decrease of calcite or aragonite saturation and calcium carbonate, and to decreasing efficiency of carbon export/pumping to deep layers. In the present study, we analyzed about 20 years of field observations of coccolithophore pigment, dissolved inorganic carbon （DIC）, nutrients, and temperatures from the Bermuda Atlantic Time-series Study （BATS） site and satellite remote sensing to investigate the variable tendency of the coccolithophore pigment, and to evaluate the influence of ocean acidification on coccolithophore biomass. The results indicated that there was a generally increasing tendency of coccolithophore pigment, coupled with increasing bicarbonate concentrations or decreasing carbonate ion concentration. The change of coccolithophore pigment was also closely associated with pH, nutrients, mixed layer depth （MLD）, and temperature. Correlation analyses between coceolithophores and abiotic parameter imply that coccoliths production or coccolitho- phore pigment has increased with increasing acidification in the recent 20 years.