No adaptation to warming after selection for 800 generations in the coccolithophore Emiliania huxleyi BOF 92
0
Citation
55
Reference
10
Related Paper
Abstract:
Ocean warming is suggested to exert profound effects on phytoplankton physiology and growth. Here, we investigated how the coccolithophore Emiliania huxleyi (BOF 92, a non-calcifying strain) responded to changes in temperature in short- and long-term thermal treatments. The specific growth rate after 10 days of acclimation increased gradually with increasing temperatures (14, 17, 21, 24, 28°C) and peaked at ~23°C, followed by a significant decrease to 28°C. Chlorophyll a content, cell size, photosynthetic rate, and respiratory rate increased significantly from 14°C to 24°C, but the cellular particulate organic carbon (POC) and nitrogen (PON) showed the lowest values at the optimal temperature. In contrast, during long-term thermal treatments at 17°C and 21°C for 656 days (~790 generations for 17°C treatment; ~830 generations for 21°C treatment), the warming significantly stimulated the growth in the first 34 days and the last 162 days, but there was no significant difference in specific growth rate from Day 35 to Day 493. Chlorophyll a content, cell size, cellular POC/PON, and the ratio of POC to PON, showed no significant difference between the warming and control for most of the duration of the long-term exposure. The warming-selected population did not acquire persistent traits in terms of growth and cell quotas of POC and PON, which resumed to the levels in the control temperature treatment after about 9 generations in the shift test. In summary, our results indicate that warming by 4°C (17°C and 21°C) enhanced the growth, but did not result in adaptative changes in E. huxleyi (BOF 92) over a growth period of about 800 generations, reflecting that mild or non-stressful warming treatment to E. huxleyi isolated from cold seas does not alter its phenotypic plasticity.Keywords:
Emiliania huxleyi
Coccolithophore
The composition of bacterial and phytoplankton communities during phytoplankton blooms, and their interactions, are important properties of the microbial food web, which can potentially have a strong impact on the fate of organic matter and hence carbon cycling in the world’s oceans.
During late spring (May-June 2006-2008) we investigated the relationship between the community structures of phytoplankton (pigment-based) and free-living and particle-associated bacterioplankton (denaturant gradient gel electrophoresis), and environmental constraints during natural coccolithophore blooms along the North East Atlantic continental margin (Bay of Biscay). The alternation between diatom and coccolithophore blooms (mainly Emiliania huxleyi) of similar biomass was partly driven by changes in nutrient stoichiometry (N:P and dSi:N). High concentrations of transparent exopolymer particles (TEP) were associated with stratified, coccolithophore-rich water masses. Free-living and particle-associated bacterial communities had different typical representatives but showed a considerable overlap in composition. Furthermore, the structure of the bacterial communities was significantly correlated to the abundance of phytoplankton groups and water column stratification. At selected stations, we assessed the relationship of dimethyl sulphide (DMS) and dimethylsulphonioproprionate (DMSP) concentrations and the fate of phytoplankton in terms of cell lysis rates and microzooplankton grazing. Coccolithophores constituted an important source of particulate DMSP, and cell lysis enhanced the release of dissolved DMSP. Finally, we assessed the role of bacterial activity and life cycle stage of the coccolithophore E. huxleyi on the dynamics of dissolved carbohydrates and TEP by measuring their production and composition during the stationary growth phase of batch cultures, and by tracing the fate of photosynthetically fixed carbon by stable isotope probing in non-axenic calcifying E. huxleyi cultures using liquid chromatographic separation of high molecular weight neutral aldoses (HMW NAld) combined with isotope ratio mass spectrometry. Bacteria favoured the accumulation of polysaccharides and the formation of TEP, and enhanced their aggregation in calcifying E. huxleyi cultures. The production of coccoliths was probably the main source of HMW NAld in our non-axenic calcifying E. huxleyi cultures. Extracellular release of carbon in the dissolved and the particulate pools reached up to 76% of total primary production during the stationary growth phase of E. huxleyi.
Emiliania huxleyi
Coccolithophore
Bacterioplankton
Exopolymer
Microbial loop
Bloom
Haptophyte
Cite
Citations (0)
Zinc is used extensively in the metabolism of higher organisms; cobalt's usage is minimal. We found an unusual pattern of requirement for these metals in marine phytoplankton in which the cyanobacterium Synechococcus bacillaris needed Co but not Zn for growth, the coccolithophore Emiliania huxleyi had a Co requirement that could be partly met by Zn, and the diatoms Thalassiosira pseudonana and Thalassiosira oceanica had Zn requirements that could be largely met by Co. These results indicate that Co and Zn can replace one another metabolically in the eucaryotic species. Associated with this replacement, there was up to a 700‐fold increase in cellular Co uptake rates with decreasing Zn ion concentration, indicating that Zn should have a major influence on biological scavenging of Co. This hypothesis is consistent with Zn and Co distributions within the oceanic nutricline which show Co depletion only after Zn has become depleted. Zn ion concentrations and Co : Zn ratios vary widely in the ocean, and these variations could influence the relative growth of diatoms and coccolithophores, with potential effects on global carbon cycles.
Emiliania huxleyi
Thalassiosira pseudonana
Coccolithophore
Biological pump
Cite
Citations (327)
Growth of a high-calcifying strain of Emiliania huxleyi (Lohmann) Hay & Mohler was investigated in cultures aerated with varying concentrations of CO2 in air and compared with growth in 0.03 % (v/v) CO2.Cultures aerated with 0.1 % (v/v) C02/air under identical conditions resulted in approximately 40% reduction in cell number and final cell yield.A concentration of 0.5% (v/v) CO2 completely inhibited growth.In the virtual absence of CO,, cells could grow to the same levels as in those cultures aerated with air-equilibrated levels of CO2, i.e. 0.03% (v/v) CO2.Measurement of internal pH (pH,) gave comparable results using either the 5,5-dimethyl-2['4C]oxazalidine-2,4-dione (DMO) method or a fluorescent probe technique (BCECF-AM).At external pH 8.3, intracellular pH of cells aerated with air was 6.9 whilst pH, of cells aerated with 0.1 % (v/v) CO2 was 6.4.Lowering external pH decreased growth rate for cultures aerated with 0.03 "., (v/v) CO2.A 30 "/o reduction in cell number and final cell yield occurred at pH 7.8 increasing to almost 60°0 at pH 7.0; pH, decreased at more acidic external pH down to 6.38 at pH 7.0.Carbon dioxide concentration and external pH appear to be equally important in the growth of high-calcifying cells.The significance of these results is considered in relation to the development of mesoscale blooms of E. huxleyi.
Emiliania huxleyi
Coccolithophore
Total inorganic carbon
Coccolith
Carbon fibers
Cite
Citations (65)
Summary A combined increase in seawater [CO 2 ] and [H + ] was recently shown to induce a shift from photosynthetic HCO 3 − to CO 2 uptake in Emiliania huxleyi . This shift occurred within minutes, whereas acclimation to ocean acidification (OA) did not affect the carbon source. To identify the driver of this shift, we exposed low‐ and high‐light acclimated E. huxleyi to a matrix of two levels of dissolved inorganic carbon (1400, 2800 μmol kg −1 ) and pH (8.15, 7.85) and directly measured cellular O 2 , CO 2 and HCO 3 − fluxes under these conditions. Exposure to increased [CO 2 ] had little effect on the photosynthetic fluxes, whereas increased [H + ] led to a significant decline in HCO 3 − uptake. Low‐light acclimated cells overcompensated for the inhibition of HCO 3 − uptake by increasing CO 2 uptake. High‐light acclimated cells, relying on higher proportions of HCO 3 − uptake, could not increase CO 2 uptake and photosynthetic O 2 evolution consequently became carbon‐limited. These regulations indicate that OA responses in photosynthesis are caused by [H + ] rather than by [CO 2 ]. The impaired HCO 3 − uptake also provides a mechanistic explanation for lowered calcification under OA. Moreover, it explains the OA‐dependent decrease in photosynthesis observed in high‐light grown phytoplankton.
Emiliania huxleyi
Coccolithophore
Total inorganic carbon
Ocean Acidification
Cite
Citations (49)
Phytoplankton pigment signatures from a cruise in 2005 are herein presented and used as a chemotaxonomic tool for phytoplankton diversity in the Svalbard marine archipelago. Studies from these waters have until recently reported only a few groups of phytoplankton, and while this paper is the first to show that the diversity around Svalbard includes all major phytoplankton pigment groups, the results are seen in relation to other similar studies from the Arctic. We present two potentially important marker pigments: prasinoxanthin, originating from prasinophytes, and gyroxanthin-diester, possibly originating from the temperate- and bloom-forming coccolithophore Emiliania huxleyi. Pigment identification by HPLC revealed a significant amount of Chlorophyll b-containing chlorophyceae, euglenophyceae and prasinophyceae. Prasinoxanthin was present at 50% of the examined stations, typically at Chl a maximum (15–25 m depth), in both Atlantic and Arctic water masses. Gyroxanthin-diester, in contrast to prasinoxanthin, was found only in Atlantic water masses and at low concentrations. Our data may be important for the identification and verification of remotely sensed images of different pigment groups of phytoplankton and their corresponding biomass, typically estimated from Chl a. Remotely sensed presence of coccoliths, indicating E. huxleyi at sea surface, is discussed in relation to water masses and pigment signatures at sea surface and Chl a maximum depths.
Emiliania huxleyi
Coccolithophore
Archipelago
Picoplankton
Cite
Citations (13)
Emiliania huxleyi
Coccolith
Coccolithophore
Ocean Acidification
Cite
Citations (17)