Distribution Of Coccolithophores Research Articles

Analysis of the latitudinal and longitudinal (coastal and pelagic zones) variability of coccolithophore assemblages in the water column of the Western Iberian Margin in late summer of 2022

This study investigates the abundance, composition, and biogeographical distribution of coccolithophores in the water column of the northwestern Iberian coastal upwelling system during late summer 2022. Coccolithophore data were compared with in situ measurements of physical, chemical, and biological parameters, as well as with satellite data and the upwelling index (UI) for the study area. Canonical Correspondence Analysis (CCA) was performed to determine the relationships between coccolithophore assemblages and environmental variables. The results reveal a latitudinal and longitudinal gradient in coccolithophore abundance, with higher concentrations towards the north and east, indicating a stronger influence of coastal upwelling near the coast (stations CA-7, CA-8, CA-4). Our data suggest that the source of upwelled water in the north (Eastern North Atlantic Central Waters of subpolar origin, ENACWsp) differs from that in the south (ENACWst, of subtropical origin). Significant correlations between UI and the total abundance of coccoliths and coccospheres underscore the role of upwelling in coccolithophore distribution. Additionally, correlations with fluorescence and turbidity indicate that coccolithophores contribute substantially to primary production in the region. Certain species are proposed as paleoenvironmental indicators due to their affinity for specific environmental conditions. The small Noëlaerhabdaceae group (small Gephyrocapsa group + Emiliania huxleyi) serves as a proxy for primary productivity and intense upwelling, while Florisphaera profunda is associated with upwelling relaxation and low productivity. Discrepancies with satellite data are attributed to their limitations in detecting subsurface biological processes. This study also supports the use of the N-ratio in water column samples, not just in sediments, and improves the understanding of primary productivity at the Western Iberian Margin during the upwelling season.

CASCADE: Dataset of extant coccolithophore size, carbon content and global distribution

Coccolithophores are marine calcifying phytoplankton important to the carbon cycle and a model organism for studying diversity. Here, we present CASCADE (Coccolithophore Abundance, Size, Carbon And Distribution Estimates), a new global dataset for 139 extant coccolithophore taxonomic units. CASCADE includes a trait database (size and cellular organic and inorganic carbon contents) and taxonomic-unit-specific global spatiotemporal distributions (Latitude/Longitude/Depth/Month/Year) of coccolithophore abundance and organic and inorganic carbon stocks. CASCADE covers all ocean basins over the upper 275 meters, spans the years 1964-2019 and includes 33,119 gridded taxonomic-unit-specific abundance observations. Within CASCADE, we characterise the underlying uncertainties due to measurement errors by propagating error estimates between the different studies. This error propagation pipeline is statistically robust and could be applied to other plankton groups. CASCADE can contribute to (observational or modelling) studies that focus on coccolithophore distribution and diversity and the impacts of anthropogenic pressures on historical populations. Additionally, our new taxonomic-unit-specific cellular carbon content estimates provide essential conversions to quantify the role of coccolithophores on ecosystem functioning and global biogeochemistry.

Environmental influences on coccolithophore distribution and abundance in the water column of the western Iberian margin (August 2022).

Environmental influences on coccolithophore distribution and abundance in the water column of the western Iberian margin (August 2022).

Coccolithophore Distribution in the Western Black Sea in the Summer of 2016

Coccolithophores are an important component of phytoplankton abundance and biomass in the brackish environments of the Black Sea. Here, the abundance, composition, and distribution of coccolithophores were investigated in water samples taken from the first 50 m at 18 stations in the western Black Sea during a coccolithophore bloom, in June 2016. The total cell abundances ranged from 2 to 763 × 104 coccospheres L−1; Emiliania huxleyi was the most dominant species, but also Syracosphaera spp. (S. dilatata and S. molischii), Acanthoica (A. acanthifera and A. quattrospina), and Algirosphaera robusta displayed remarkably high concentrations. The formation of the seasonal thermocline significantly affects the vertical distribution of coccolithophores. Emiliania huxleyi, Syracosphaera spp., and Acanthoica spp. were restricted to the upper part of the water column, whereas high abundances of Algirosphaera robusta occurred below the thermocline. Overall, our results show significant differences in the vertical (ANOSIM R = 0.50, p = 0.0001) and spatial (ANOSIM R = 0.18, p = 0.0006) distribution of coccolithophores. Higher abundances of E. huxleyi and Syracosphaera spp. were recorded in the northwestern inner shelf region when compared to the open-sea samples. The observed coccolithophore spatial distribution is suggested to be mostly associated with the influx of less saline river water with high nutrient concentrations.

Malformation in coccolithophores in low pH waters: evidences from the eastern Arabian Sea.

Oceanic calcifying plankton such as coccolithophores is expected to exhibit sensitivity to climate change stressors such as warming and acidification. Observational studies on coccolithophore communities along with carbonate chemistry provide important perceptions of possible adaptations of these organisms to ocean acidification. However, this phytoplankton group remains one of the least studied in the northern Indian Ocean. In 2017, the biogeochemistry group at the Council for Scientific and Industrial Research-National Institute of Oceanography (CSIR-NIO) initiated a coccolithophore monitoring study in the eastern Arabian Sea (EAS). Here, we document for the first time a detailed spatial and seasonal distribution of coccolithophores and their controlling factors from the EAS, which is a well-known source of CO2 to the atmosphere. To infer the seasonality, data collected at three transects (Goa, Mangalore, and Kochi) during the Southwest Monsoon (SWM) of 2018 was compared with that of the late SWM of 2017. Apart from this, the abundance of coccolithophores was studied at the Candolim Time Series (CaTS) transect, off Goa during the Northeast Monsoon (NEM). The most abundant coccolithophore species found in the study region was Gephyrocapsa oceanica. A high abundance of G. oceanica (1800 × 103cells L-1) was observed at the Mangalore transect during the late SWM despite experiencing low pH and can be linked to nitrogen availability. The high abundance of G. oceanica at Mangalore was associated with high dimethylsulphide (DMS). Particulate inorganic carbon (PIC) and scattering coefficient retrieved from satellites also indicated a high abundance of coccolithophores off Mangalore during the late SWM of 2017. Interestingly, G. oceanica showed malformation during the late SWM in low pH waters. Malformation in coccolithophores could have a far-reaching impact on the settling fluxes of organic matter and also on the emissions of climatically important gases such as DMS and CO2, thus influencing atmospheric chemistry. The satellite data for PIC in the EAS indicates a high abundance of coccolithophore in recent years, especially during the warm El Nino years (2015 and 2018). This warrants the need for a better assessment of the fate of coccolithophores in high-CO2 and warmer oceans.

Characterization of the coccolithophore community off Cabo Verde archipelago, including the Senghor Seamount (Eastern North Atlantic)

A systematic investigation of the extant coccolithophore community around Cabo Verde archipelago was performed during the cruise MSM49 of RV Maria S. Merian, which took place in the late fall of 2015. The description of the spatial and vertical distributions of coccolithophores was based on a survey performed to the north, east and south of Cabo Verde archipelago, between the surface and 150 m water depth. The total cell densities obtained for the studied region were relatively low, reaching to a maximum of 30 × 103 cell L−1 in the upper 50 m over the southeastern slope of the Senghor seamount. Emiliania huxleyi and Gephyrocapsa oceanica were the dominant species, followed by Florisphaera profunda. The coccolithophore distribution off Cabo Verde was essentially explained by relatively warm and nutrient-depleted waters in the region during the surveyed interval, in result of the weaker NE trade winds and the northward migration of the Intertropical Convergence Zone. In these conditions, a notable zonation of coccolithophores along depth was depicted, in consequence of the inferred general well-stratified water column. Four typical depth-related groups were identified: (i) a Shallow oligotrophic (10–30 m), represented by Discosphaera tubifera and Umbellosphaera spp.; (ii) an Intermediate (40–50 m), formed by the three placolith-bearing species E. huxleyi, G. ericsonii and G. oceanica, and by Algirosphaera robusta, Helicosphaera spp., Michaelsarsia spp., Syracosphaera spp. and Umbilicosphaera spp.; (iii) a Deep (60–75 m) with F. profunda, Ophiaster spp., Oolithotus spp. and Reticulofenestra sessilis as typical members; (iv) and The Deepest (>80 m), composed by Gladiolithus flabellatus and Syracosphaera lamina. In addition, high abundances of G. oceanica related with the Eddy station were attributed to the transport and thriving of the coastal coccolithophore community, dominated by this species, from the African coast towards Cabo Verde.

Seasonal living coccolithophore distribution in the enclosed coastal environments of the Thessaloniki Bay (Thermaikos Gulf, NW Aegean Sea)

Living coccolithophores collected from a yearly time interval, January to December 2016, at the SP1 station of the Thessaloniki Bay, an enclosed coastal environment located in the inner part of the Thermaikos Gulf (Northwestern Aegean Sea) were analyzed to determine their seasonal variation and evaluate the effects of environmental factors on their density, species composition and distribution. Our results showed that coccolithophores constituted a significant component of the phytoplankton community and were characterized by the dominance of few opportunistic species, as an impact of eutrophic environmental conditions. Temperature seasonal cycle and the variations in nutrient inputs from riverine and/or anthropogenic sources seem to control the seasonal pattern of coccolithophores. Emiliania huxleyi with densities as high as ∼4.0 × 105 cells l−1 predominated during the late spring–early summer, whereas a strong dominance of Gephyrocapsa oceanica with densities ∼2.0 × 105 cells l−1 was observed during the late summer and the autumn. Emiliania huxleyi appeared to dominate the coccolithophore assemblages once more during the winter; while Helicosphaera carteri was continuously present during the wintertime (exceeding ∼2.7 × 103 cells l−1). Emiliania huxleyi was entirely represented by morphotype type A in the studied samples. Morphometric analysis of E. huxleyi coccoliths indicated that the population is dominated by lightly calcified forms, although an increase of more heavily calcified coccoliths was observed during late autumn-early spring in line with the well-documented seasonal succession pattern of E. huxleyi type A forms in the Aegean Sea.

Coccolithophore distributions of the North and South Atlantic Ocean

We present average coccolithophore and associated biogeochemical results from ten Atlantic Meridional Transect (AMT) cruises between 50oN-50oS, results that show a number of unique observations across this massive data set. Lowest concentrations of coccolithophores were consistently found in equatorial waters. Highest concentrations of coccolithophore cells and coccoliths were associated with temperate, sub-polar environments. Concentrations of detached coccoliths were dispersed to ∼300m depth and show low inter-cruise variance. Coccolithophore cell concentrations in the subtropics remain highest at < 200m depth in the S. Atlantic and 100m in the N. Atlantic, near the 26.5 to 27 sigma-theta (σθ) isopycnal, within the Subantarctic Mode Water (SAMW). Diversity and species richness of coccolithophore cells was greater than for the detached coccoliths and generally greater in surface populations than in the deep chlorophyll maximum (DCM). Placolith-bearing coccolithophore species dominated over the umbelliform and floriform coccolithophore groups in surface waters of the Southern Ocean at 50oS, as well as the DCM from 50oS to the equator. The DCM was strongly associated with the σθ, of ∼27 kg m-3, coincident with the top of the nitracline, within the SAMW. Concentrations of coccolithophore cells and detached coccoliths were much less related to the density field than chlorophyll was. Highest integrated euphotic coccolith concentrations were observed when the integrated POC:chlorophyll ratio was highest. PIC:POC ratios increased with depth and approached maximum values near the top of the nitracline. Great Calcite Belt waters (upper 300m) showed biogenic silica:particulate inorganic carbon ratios (BSi:PIC) >1 while all other waters showed BSi:PIC ratios <1. Peaks in PIC and BSi were observed within, and above the SAMW, in waters with low phosphate and silicate concentrations. The results of this study suggest that coccolithophore-rich SAMW in the Southern Ocean is being conditioned after its formation, such that by the time it upwells in the Atlantic equatorial region, the water is no longer conducive to coccolithophore growth.

A New Approach to Estimating Coccolithophore Calcification Rates From Space

AbstractThe production and ultimate fate of calcium carbonate in the global ocean has implications for the efficiency of the biological carbon and alkalinity pumps. Historically, sediment trap flux data and/or mass balance equations have been used to estimate the rate of particulate inorganic carbon production in the ocean. More recently, satellite data have been used to provide a more comprehensive global overview of this important biogeochemical process based on relationships determined from multilinear regression of measured calcification rates against a number of measurable variables. Here we describe a simple model to estimate calcification rate based around elements of coccolithophore physiology that can be easily parametrized with satellite ocean color data. The model output conforms to our understanding of the spatial and temporal distribution of coccolithophores and performs relatively well at reproducing global rates that are of the correct order of magnitude, while capturing the variability in such a complex, natural process when compared to field calcification rate measurements (slope = 0.98; R2 = 0.28; p &lt; 0.05; RMSE = 0.53 mg C · m−3 · day−1). Average, global, euphotic zone depth‐integrated calcification rate is estimated to be 1.42 ± 1.69 Pg particulate inorganic carbon/year with the oceanic gyres contributing the greatest influence.

Distribution of planktonic biogenic carbonate organisms in the Southern Ocean south of Australia: a baseline for ocean acidification impact assessment

Abstract. The Southern Ocean provides a vital service by absorbing about one-sixth of humankind's annual emissions of CO2. This comes with a cost – an increase in ocean acidity that is expected to have negative impacts on ocean ecosystems. The reduced ability of phytoplankton and zooplankton to precipitate carbonate shells is a clearly identified risk. The impact depends on the significance of these organisms in Southern Ocean ecosystems, but there is very little information on their abundance or distribution. To quantify their presence, we used coulometric measurement of particulate inorganic carbonate (PIC) on particles filtered from surface seawater into two size fractions: 50–1000 µm to capture foraminifera (the most important biogenic carbonate-forming zooplankton) and 1–50 µm to capture coccolithophores (the most important biogenic carbonate-forming phytoplankton). Ancillary measurements of biogenic silica (BSi) and particulate organic carbon (POC) provided context, as estimates of the biomass of diatoms (the highest biomass phytoplankton in polar waters) and total microbial biomass, respectively. Results for nine transects from Australia to Antarctica in 2008–2015 showed low levels of PIC compared to Northern Hemisphere polar waters. Coccolithophores slightly exceeded the biomass of diatoms in subantarctic waters, but their abundance decreased more than 30-fold poleward, while diatom abundances increased, so that on a molar basis PIC was only 1 % of BSi in Antarctic waters. This limited importance of coccolithophores in the Southern Ocean is further emphasized in terms of their associated POC, representing less than 1 % of total POC in Antarctic waters and less than 10 % in subantarctic waters. NASA satellite ocean-colour-based PIC estimates were in reasonable agreement with the shipboard results in subantarctic waters but greatly overestimated PIC in Antarctic waters. Contrastingly, the NASA Ocean Biogeochemical Model (NOBM) shows coccolithophores as overly restricted to subtropical and northern subantarctic waters. The cause of the strong southward decrease in PIC abundance in the Southern Ocean is not yet clear. The poleward decrease in pH is small, and while calcite saturation decreases strongly southward, it remains well above saturation ( &gt; 2). Nitrate and phosphate variations would predict a poleward increase. Temperature and competition with diatoms for limiting iron appear likely to be important. While the future trajectory of coccolithophore distributions remains uncertain, their current low abundances suggest small impacts on overall Southern Ocean pelagic ecology.

Living coccolithophores community from Southern Tyrrhenian Sea (Central Mediterranean — Summer 2009)

Abstract We present data on distribution patterns of living coccolithophores at 18 selected hydrographic stations, and oceanographic measurements collected at 68 stations during the TIR09 cruise carried out on board of R/V Urania in the southern Tyrrhenian Sea (central part of the Mediterranean Sea) during summer 2009. The survey enabled us to provide indications on the structure of calcareous phytoplankton associations in relation to oceanographic parameters and vertical water column stratification. The total number of coccospheres ranged from − 1 to ~ 6.8 ∗ 10 4 cells l − 1 (mean 8.28 ∗ 10 3 cells l − 1 ). Emiliania huxleyi dominated the assemblages, followed by Gephyrocapsa spp., small placoliths, Calciosolenia spp., Florisphaera profunda , Holococcolithophores spp., Syracosphaera pulchra and Umbellosphaera tenuis . The coccolithophore community showed a typical vertical zonation, with K-strategist taxa in the upper 75 m and the deep community down to 200 m. The local water circulation and summer stratification significantly affected the spatial and vertical distribution of coccolithophores.

Coccolithophore and benthic foraminifera distribution patterns in the Gulf of Cadiz and Western Iberian Margin during Integrated Ocean Drilling Program (IODP) Expedition 339

For the first time during an Integrated Ocean Drilling Program (IODP) Expedition (Exp. 339, Mediterranean Outflow) water samples for living coccolithophore distributions and mudline samples for coccoliths, benthic foraminifera, and geochemical analyses in the underlying surface sediments were collected. In total, 14 water samples (from 5 to 20 m water depth) and 7 mudline samples were gathered at the drill sites. Coccolithophore distributions show spatial variations in species diversity. In particular, assemblages that characterize the Western Iberian Margin differ from those in the Gulf of Cadiz, indicative of oceanographic and environmental controls on the community in the upper ocean (0–20 m depth). Comparison of the living assemblages to those in surface sediments shows differences in the presence of some species, suggesting the influence of post deposition sedimentary processes. Other factors such as the season of sampling and the limited sampling depth may also have a role in the differences recorded. Benthic foraminiferal assemblages seem to be primarily determined by source, quantity and quality of available food. Sites in the Gulf of Cadiz are bathed by Mediterranean Outflow Water (MOW) and characterized by a considerable amount of advected food particles. Elevated epibenthic foraminifera exploit this niche, while arborescent epifaunal and infaunal taxa thrive on food particles falling out of MOW. The combined data suggest different flow speeds and settling of MOW suspension load in the Gulf of Cadiz. In contrast, assemblages from the Western Iberian Margin located farthest from or outside of MOW are determined by local export productivity and mirror trophic conditions in the surface waters. Both assemblages reveal variation in the composition at intermediate and deep water depths along the southern and western Iberian Margins with distance from the Strait of Gibraltar.

Large-scale distribution of coccolithophores and Parmales in the surface waters of the Atlantic Ocean

Coccolithophores and Parmales are important functional groups of calcified and siliceous marine nanophytoplankton. Large-scale biogeographic distributions of the two groups were investigated based on 71 samples that were collected in the Atlantic Ocean. Using a scanning electron microscope, a total of 48 taxa of coccolithophores and eight taxa of Parmales were recorded, withEmiliania huxleyi, Tetraparma pelagicaandTriparma strigataas the predominant forms. The highest abundances of coccolithophores (376 × 103cells l−1) and Parmales (624 × 103cells l−1) were observed in waters north-east of the Falkland Islands and the South Georgia Island, in close association with the Subantarctic Front and Polar Front, respectively. Three major biogeographic assemblages, i.e. the Falkland Shelf Assemblage, the Southern Ocean Assemblage and the Atlantic Ocean Assemblage, were revealed in cluster analysis. Additionally, canonical correspondence analysis indicated that temperature significantly affects the latitudinal patterns of the two algal groups. High abundances of Parmales were closely coupled with those ofE. huxleyiin waters of the Southern Ocean with low temperature (&lt;10°C). However, the number of coccolithophore species, along with the Shannon–Weaver diversity, significantly increased with elevated temperature, suggesting more diverse assemblages in tropical waters.

Environmental drivers of coccolithophore abundance and calcification across Drake Passage (Southern Ocean)

Abstract. Although coccolithophores are not as numerically common or as diverse in the Southern Ocean as they are in subpolar waters of the North Atlantic, a few species, such as Emiliania huxleyi, are found during the summer months. Little is actually known about the calcite production (CP) of these communities or how their distribution and physiology relate to environmental variables in this region. In February 2009, we made observations across Drake Passage (between South America and the Antarctic Peninsula) of coccolithophore distribution, CP, primary production, chlorophyll a and macronutrient concentrations, irradiance and carbonate chemistry. Although CP represented less than 1 % of total carbon fixation, coccolithophores were widespread across Drake Passage. The B/C morphotype of E. huxleyi was the dominant coccolithophore, with low estimates of coccolith calcite (∼ 0.01 pmol C coccolith−1) from biometric measurements. Both cell-normalised calcification (0.01–0.16 pmol C cell−1 d−1) and total CP (&lt; 20 µmol C m−3 d−1) were much lower than those observed in the subpolar North Atlantic where E. huxleyi morphotype A is dominant. However, estimates of coccolith production rates were similar (0.1–1.2 coccoliths cell−1 h−1) to previous measurements made in the subpolar North Atlantic. A multivariate statistical approach found that temperature and irradiance together were best able to explain the observed variation in species distribution and abundance (Spearman's rank correlation ρ = 0.4, p &lt; 0.01). Rates of calcification per cell and coccolith production, as well as community CP and E. huxleyi abundance, were all positively correlated (p &lt; 0.05) to the strong latitudinal gradient in temperature, irradiance and calcite saturation states across Drake Passage. Broadly, our results lend support to recent suggestions that coccolithophores, especially E. huxleyi, are advancing polewards. However, our in situ observations indicate that this may owe more to sea-surface warming and increasing irradiance rather than increasing CO2 concentrations.

The summer distribution of coccolithophores and its relationship to water masses in the East China Sea

Coccolithophores are calcifying phytoplankton belonging to the phylum Haptophyta, and are thought to play an important role in the marine carbon cycle through the production and export of organic carbon and calcite. A quantitative scanning electron microscope study of coccolithophores was conducted to survey the spatial distribution of coccolithophore communities in surface water covering the continental shelf of the East China Sea (ECS) during the summer of 2014. The abundance of haptophytes was also revealed by fluorescence in situ hybridization with an 18S rRNA-specific probe. The abundance of coccolithophores in the surface-water ranged from 3.7 to 82.8 cells mL−1, contributing a mean 7.0 % to haptophyte abundance. Four distinct coccolithophore groups (A, B, C, and D) were categorized based on similarities of the coccolithophore communities among the stations. Group A was located in the north of the ECS in the Yellow Sea Mixed Water area, where coccolithophore abundance was low. Group B was dominated by Gephyrocapsa oceanica and was located in the south of the ECS in the Taiwan Warm Current. Group C represented the inner shelf assemblages, with Emiliania huxleyi as the major dominant species, and was influenced by the Changjiang discharges. Group D represented the Kuroshio assemblages, with communities dominated by E. huxleyi and Umbellosphaera tenuis in the outer shelf region. These results suggest that coccolithophores tend to migrate with the water masses in the ECS during the summer.

Coccolithophore assemblage distribution along a temperate to polar gradient in theWest Pacific sector of the Southern Ocean (January 2005)

We document surface coccolithophore species composition along a N-S transect from New Zealand to the Ross Sea, across the fronts of the Antarctic Circumpolar Current. Emiliania huxleyi is the most abundant coccolithophore species throughout, with high concentration in the northernmost samples, in the Polar Frontal Zone and at the Polar Front. Three E. huxleyi morphotypes, A, B/C and O were recognized and show different biogeographic distributions along the investigated transect. Coccolithophore distribution appears to be strongly controlled by the location of oceanographic fronts, with minor species (Calcidiscus leptoporus, Syracosphaera spp., Acanthoica quattrospina, Umbellosphaera tenuis, Corisphaera strigilis and other holococcolithophores) largely restricted to the northern Sub-Antarctic Zone, only showing minor occurrence in the southern Sub-Antarctic Zone and being very rare in the Polar Frontal Zone. Our data confirm previous findings and add new information on the biogeography of minor coccolithophore species in relation with oceanographic features. Overall, integration with previous data on the southern extent distribution of E. huxleyi showed no significant temporal shifts in the polar dynamic perspective of the species since early observations.

Comparison of living and surface sediment coccolithophore assemblages in the Pacific sector of the Southern Ocean

This study examined recent coccolith surface sediment assemblages across the Pacific sector of the Southern Ocean (from Punta Arenas, Chile to Wellington, New Zealand). Twenty five stations located within 44.4°S to 65.4°S and 80.1°W to 174.5°E were selected in order to assess if and how the surface sediment assemblages reflect the present-day coccolithophore community and surface- water oceanographic conditions. The highest numbers of coccoliths in the surface sediments are reached near the East Pacific Rise and close to the Subtropical Front, at the New Zealand Margin (&gt;6x109 coccoliths/g of sediment). The dominant taxa are Emiliania huxleyi (including types A, B, B/C and C), Calcidiscus leptoporus, Gephyrocapsa spp. (including G. muellerae, G. oceanica and G. ericsonii), Umbellosphaera tenuis and Coccolithus braarudii. Despite the recognition of species morphotypes being hampered by carbonate dissolution at some locations, we observed that numbers generally decrease southward until almost a monospecific and sporadic record of E. huxleyi (types B/C and C) and C. leptoporus south of the Polar Front occurs. The recent coccolithophore distribution was compared to already published living coccolithophore distributions (i.e., water column samples collected at the same specific locations) showing a fairly similar pattern. Combining the numbers of cells/l and coccoliths/g of sediment, different coccolithophore assemblages were established coincidentwith areas bounded by the major surface oceanographic fronts, i.e. the Subantarctic Zone and the Polar Front Zone.

Distribution of coccolithophores as a potential proxy in paleoceanography: The case of the Oman Sea monsoonal pattern

Abstract High abundances of coccoliths have been observed in surface sediment samples from near the coasts of the Oman Sea in February 2011. At the end of the NE monsoon, the locally observed high Gephyrocapsa oceanica production is hypothesized to respond to local injections of nutrient-rich deep water into the surface water due to sea-surface cooling leading to convection. The most abundant coccolithophore species are G. oceanica followed by Emiliania huxleyi, Helicosphaera carteri, Calcidiscus leptoporus. Some species, such as Gephyrocapsa muellerae, Gephyrocapsa ericsonii, Umbilicosphaera sibogae, Umbellosphaera tenuis and Florisphaera profunda, are rare. The G. oceanica suggested a prevalence of upwelling conditions or high supply of nutrients in the Oman Sea (especially West Jask) at the end of the NE monsoon. E. huxleyi showed low relative abundances at the end of the NE monsoon. Due to the location of the Oman Sea in low latitudes with high temperatures, we have observed low abundances of G. muellerae in the study area. Additionally, we have identified low abundances of G. ericsonii at the end of the NE monsoon. Helicosphaera carteri showed a clear negative response with decreasing amounts (relative abundances) at the end of the NE monsoon. C. leptoporus, U. sibogae and U. tenuis have very low relative abundances in the NE monsoon and declined extremely at the end of the NE monsoon. F. profunda, which is known to inhabit the lower photic zone (&lt;100 m depht) was rarely observed in the samples.

Is coccolithophore distribution in the Mediterranean Sea related to seawater carbonate chemistry?

Abstract. The Mediterranean Sea is considered a "hot spot" for climate change, being characterized by oligotrophic to ultra-oligotrophic waters and rapidly increasing seasurface temperature and changing carbonate chemistry. Coccolithophores are considered a dominant phytoplankton group in these waters. As marine calcifying organisms they are expected to respond to the ongoing changes in seawater carbonate chemistry. We provide here a description of the springtime coccolithophore distribution in the Mediterranean Sea and relate this to a broad set of in situ-measured environmental variables. Samples were taken during the R/V Meteor (M84/3) oceanographic cruise in April 2011, between 0 and 100 m water depth from 28 stations. Total diatom and silicoflagellate cell concentrations are also presented. Our results highlight the importance of seawater carbonate chemistry, especially [CO32−] but also [PO43−] in unraveling the distribution of heterococcolithophores, the most abundant coccolithophore life phase. Holo- and heterococcolithophores respond differently to environmental factors. For instance, changes in heterococcolithophore assemblages were best linked to the combination of [CO32−], pH, and salinity (ρ = 0.57), although salinity might be not functionally related to coccolithophore assemblage distribution. Holococcolithophores, on the other hand, showed higher abundances and species diversity in oligotrophic areas (best fit, ρ = 0.32 for nutrients), thriving in nutrient-depleted waters. Clustering of heterococcolithophores revealed three groups of species sharing more than 65% similarities. These clusters could be assigned to the eastern and western basins and deeper layers (below 50 m), respectively. In addition, the species Gephyrocapsa oceanica, G. muellerae, and Emiliania huxleyi morphotype B/C are spatially distributed together and trace the influx of Atlantic waters into the Mediterranean Sea. The results of the present work emphasize the importance of considering holo- and heterococcolithophores separately when analyzing changes in species assemblages and diversity. Our findings suggest that coccolithophores are a main phytoplankton group in the entire Mediterranean Sea and can dominate over siliceous phytoplankton. They have life stages that are expected to respond differently to the variability in seawater carbonate chemistry and nutrient concentrations.

Coccolithophores from near the Volturno estuary (central Tyrrhenian Sea)

We present the distribution pattern of living and surface sediment coccolithophores, the main phytoplankton calcifying group, from 22 stations set in a neritic environment (from 10 to 50 m water depth), adjacent to the shelf area of the Volturno River mouth (Gulf of Gaeta — central part of the Tyrrhenian Sea). The survey conducted in June 2012 included five transects perpendicular to the coast, which enabled us to provide indications on the structure of calcareous phytoplankton associations in relation to coastal dynamics and the Volturno River runoff. The total number of coccospheres ranged from 15 to 64 ∗ 103 ∗ l− 1 coccolithophores. Emiliania huxleyi dominates the assemblages, followed by Rhabdosphaera xiphos, holococcolithophores and Syracosphaera pulchra. The coccolithophore community shows a typical vertical zonation, with K-strategist taxa in the upper 15 m and the deep community developed down to 40 m. The local water circulation significantly affects the spatial and vertical distribution of coccolithophores. The river discharge influences the distribution of coccolithophore taxa, resulting in a north–south gradient. In the northern sector, outside the influence of the Volturno River, the high values of R. xiphos suggest a negative correlation with river runoff. The surface sediment assemblages reflect the overall composition of the living coccolithophore communities. The distribution of abundant reworked species, both in water and sediment, provides useful information about coastal dynamics and sediment transport in the study area.