Abstract:Abstract. Coccolithophores, a diverse group of phytoplankton, make important contributions to pelagic calcite production and export, yet the comparative biogeochemical role of species other than the ubiquitous Emiliania huxleyi is poorly understood. The contribution of different coccolithophore species to total calcite production is controlled by interspecies differences in cellular calcite, growth rate and relative abundance within a mixed community. In this study we examined the relative importance of E. hux… Show more
“…We also present results from a previously unanalysed data set of exponential-phase coccosphere geometry in C. braarudii strain RCC 1198 and C. pelagicus strain RCC 4092, originally published as a data report by and available from http://www.pangaea.de (doi:10.1594/PANGAEA.836841). For that study, batch culture experiments were undertaken at multiple temperatures (6-12 • C in C. pelagicus and 12-19 • C in C. braarudii), and samples for coccosphere geometry analysis were collected on a single mid-exponential-phase experiment day (further details in Daniels et al, 2014). …”
Section: Additional Experimental Results From Coccolithusmentioning
confidence: 99%
“…Calcite production per cell per day (pmol C cell −1 d −1 ) can be calculated by multiplying cellular calcite (pmol C cell −1 ) by growth rate (d −1 ) (e.g. Daniels et al, 2014Daniels et al, , 2016. Calcite production in these four species is 6 to 20 times higher than in E. huxleyi at a comparable growth rate ( Fig.…”
Section: Implications Of Growth-driven Cellular Pic and Poc For Calcimentioning
confidence: 99%
“…For comparison purposes, we include data for C. braarudii and C. pelagicus that can be found in Gibbs et al (2013) and accompanying Daniels et al (2014).…”
Section: Statistical Analysesmentioning
confidence: 99%
“…All LM analysis was performed using a cross-polarised light microscope (Olympus BX51) with a colour camera attached (Olympus DP71). Coccosphere geometry data were obtained through LM following the same techniques applied by Gibbs et al (2013) and Daniels et al (2014) and described in detail here. Random transects across the widest section of the filter hemisphere were performed until 30 individual coccospheres per slide were located from slides corresponding to alternate day or, Figure 1.…”
Abstract. Coccolithophores are an abundant phytoplankton group that exhibit remarkable diversity in their biology, ecology and calcitic exoskeletons (coccospheres). Their extensive fossil record is a testament to their important biogeochemical role and is a valuable archive of biotic responses to environmental change stretching back over 200 million years. However, to realise the full potential of this archive for (palaeo-)biology and biogeochemistry requires an understanding of the physiological processes that underpin coccosphere architecture. Using culturing experiments on four modern coccolithophore species (Calcidiscus leptoporus, Calcidiscus quadriperforatus, Helicosphaera carteri and Coccolithus braarudii) from three long-lived families, we investigate how coccosphere architecture responds to shifts from exponential (rapid cell division) to stationary (slowed cell division) growth phases as cell physiology reacts to nutrient depletion. These experiments reveal statistical differences in coccosphere size and the number of coccoliths per cell between these two growth phases, specifically that cells in exponential-phase growth are typically smaller with fewer coccoliths, whereas cells experiencing growth-limiting nutrient depletion have larger coccosphere sizes and greater numbers of coccoliths per cell. Although the exact numbers are species-specific, these growth-phase shifts in coccosphere geometry demonstrate that the core physiological responses of cells to nutrient depletion result in increased coccosphere sizes and coccoliths per cell across four different coccolithophore families (Calcidiscaceae, Coccolithaceae, Isochrysidaceae and Helicosphaeraceae), a representative diversity of this phytoplankton group. Building on this, the direct comparison of coccosphere geometries in modern and fossil coccolithophores enables a proxy for growth phase to be developed that can be used to investigate growth responses to environmental change throughout their long evolutionary history. Our data also show that changes in growth rate and coccoliths per cell associated with growthphase shifts can substantially alter cellular calcite production. Coccosphere geometry is therefore a valuable tool for accessing growth information in the fossil record, providing unprecedented insights into the response of species to environmental change and the potential biogeochemical consequences.
“…We also present results from a previously unanalysed data set of exponential-phase coccosphere geometry in C. braarudii strain RCC 1198 and C. pelagicus strain RCC 4092, originally published as a data report by and available from http://www.pangaea.de (doi:10.1594/PANGAEA.836841). For that study, batch culture experiments were undertaken at multiple temperatures (6-12 • C in C. pelagicus and 12-19 • C in C. braarudii), and samples for coccosphere geometry analysis were collected on a single mid-exponential-phase experiment day (further details in Daniels et al, 2014). …”
Section: Additional Experimental Results From Coccolithusmentioning
confidence: 99%
“…Calcite production per cell per day (pmol C cell −1 d −1 ) can be calculated by multiplying cellular calcite (pmol C cell −1 ) by growth rate (d −1 ) (e.g. Daniels et al, 2014Daniels et al, , 2016. Calcite production in these four species is 6 to 20 times higher than in E. huxleyi at a comparable growth rate ( Fig.…”
Section: Implications Of Growth-driven Cellular Pic and Poc For Calcimentioning
confidence: 99%
“…For comparison purposes, we include data for C. braarudii and C. pelagicus that can be found in Gibbs et al (2013) and accompanying Daniels et al (2014).…”
Section: Statistical Analysesmentioning
confidence: 99%
“…All LM analysis was performed using a cross-polarised light microscope (Olympus BX51) with a colour camera attached (Olympus DP71). Coccosphere geometry data were obtained through LM following the same techniques applied by Gibbs et al (2013) and Daniels et al (2014) and described in detail here. Random transects across the widest section of the filter hemisphere were performed until 30 individual coccospheres per slide were located from slides corresponding to alternate day or, Figure 1.…”
Abstract. Coccolithophores are an abundant phytoplankton group that exhibit remarkable diversity in their biology, ecology and calcitic exoskeletons (coccospheres). Their extensive fossil record is a testament to their important biogeochemical role and is a valuable archive of biotic responses to environmental change stretching back over 200 million years. However, to realise the full potential of this archive for (palaeo-)biology and biogeochemistry requires an understanding of the physiological processes that underpin coccosphere architecture. Using culturing experiments on four modern coccolithophore species (Calcidiscus leptoporus, Calcidiscus quadriperforatus, Helicosphaera carteri and Coccolithus braarudii) from three long-lived families, we investigate how coccosphere architecture responds to shifts from exponential (rapid cell division) to stationary (slowed cell division) growth phases as cell physiology reacts to nutrient depletion. These experiments reveal statistical differences in coccosphere size and the number of coccoliths per cell between these two growth phases, specifically that cells in exponential-phase growth are typically smaller with fewer coccoliths, whereas cells experiencing growth-limiting nutrient depletion have larger coccosphere sizes and greater numbers of coccoliths per cell. Although the exact numbers are species-specific, these growth-phase shifts in coccosphere geometry demonstrate that the core physiological responses of cells to nutrient depletion result in increased coccosphere sizes and coccoliths per cell across four different coccolithophore families (Calcidiscaceae, Coccolithaceae, Isochrysidaceae and Helicosphaeraceae), a representative diversity of this phytoplankton group. Building on this, the direct comparison of coccosphere geometries in modern and fossil coccolithophores enables a proxy for growth phase to be developed that can be used to investigate growth responses to environmental change throughout their long evolutionary history. Our data also show that changes in growth rate and coccoliths per cell associated with growthphase shifts can substantially alter cellular calcite production. Coccosphere geometry is therefore a valuable tool for accessing growth information in the fossil record, providing unprecedented insights into the response of species to environmental change and the potential biogeochemical consequences.
“…The phytoplankton Emiliania huxleyi (coccolithophore, Strain RCC1228 from the Roscoff Collection) was cultured in artificial seawater at 16 • C, under light conditions of 100 µE. The chlorophyll concentration in the stock solution was calculated based on a chlorophyll concentration per cell (Daniels et al, 2014), and the counted cell concentration of the stock solution. The culture was diluted with artificial seawater to 100 ml, with final chlorophyll concentrations of 0.1, 1, 2, 2.5, 5, 10 µg L −1 .…”
The ocean is a major sink for anthropogenic carbon dioxide (CO 2 ), with the CO 2 uptake causing changes to ocean chemistry. To monitor these changes and provide a chemical background for biological and biogeochemical studies, high quality partial pressure of CO 2 (pCO 2 ) sensors are required, with suitable accuracy and precision for ocean measurements. Optodes have the potential to measure in situ pCO 2 without the need for wet chemicals or bulky gas equilibration chambers that are typically used in pCO 2 systems. However, optodes are still in an early developmental stage compared to more established equilibrator-based pCO 2 systems. In this study, we performed a laboratory-based characterization of a time-domain dual lifetime referencing pCO 2 optode system. The pCO 2 optode spot was illuminated with low intensity light (0.2 mA, 0.72 mW) to minimize spot photobleaching. The spot was calibrated using an experimental gas calibration rig prior to deployment, with a determined response time (τ 63 ) of 50 s at 25 • C. The pCO 2 optode was deployed as an autonomous shipboard underway system across the high latitude North Atlantic Ocean with a resolution of ca.10 measurements per hour. The optode data was validated with a secondary shipboard equilibrator-based infrared pCO 2 instrument, and pCO 2 calculated from discrete samples of dissolved inorganic carbon and total alkalinity. Further verification of the pCO 2 optode data was achieved using complimentary variables such as nutrients and dissolved oxygen. The shipboard precision of the pCO 2 sensor was 9.5 µatm determined both from repeat measurements of certified reference materials and from the standard deviation of seawater measurements while on station. Finally, the optode deployment data was used to evaluate the physical and biogeochemical controls on pCO 2 .
Coccolithophores are recognized as having a significant influence on the global carbon cycle through the production and export of calcium carbonate (often referred to as particulate inorganic carbon or PIC). Using remotely sensed PIC and chlorophyll data, we investigate the seasonal dynamics of coccolithophores relative to a mixed phytoplankton community. Seasonal variability in PIC, here considered to indicate changes in coccolithophore biomass, is identified across much of the global ocean. Blooms, which typically start in February-March in the low-latitude (~30°) Northern Hemisphere and last for~6-7 months, get progressively later (April-May) and shorter (3-4 months) moving poleward. A similar pattern is observed in the Southern Hemisphere, where blooms that generally begin around August-September in the lower latitudes and which last for~8 months get later and shorter with increasing latitude. It has previously been considered that phytoplankton blooms consist of a sequential succession of blooms of individual phytoplankton types. Comparison of PIC and chlorophyll peak dates suggests instead that in many open ocean regions, blooms of coccolithophores and other phytoplankton can co-occur, conflicting with the traditional view of species succession that is thought to take place in temperate regions such as the North Atlantic.
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