Biogeochemical response of Emiliania huxleyi (PML B92/11) to elevated CO2 and temperature under phosphorous limitation: A chemostat study

Abstract

The present study investigates the combined effect of phosphorous limitation, elevated partial pressure of CO 2 (pCO 2 ) and temperature on a calcifying strain of Emiliania huxleyi (PML B92/11) by means of a fully controlled continuous culture facility. Two levels of phosphorous limitation were consecutively applied by renewal of culture media (N:P = 26) at dilution rates (D) of 0. . CO 2 and temperature conditions were 300, 550 and 900 μatm pCO 2 at 14°C and 900 μatm pCO 2 at 18°C. In general, the steady state cell density and particulate organic carbon (POC) production increased with pCO 2 , yielding significantly higher concentrations in cultures grown at 900 μatm pCO 2 compared to 300 and 550 μatm pCO 2 . At 900 μatm pCO 2 , elevation of temperature as expected for a greenhouse ocean, further increased cell densities and POC concentrations. In contrast to POC concentration, C-quotas (pmol C cell , a reduction of C-quotas by up to 15% was observed in the 900 μatm pCO 2 at 18°C culture. As a result of growth rate reduction, POC:PON:POP ratios deviated strongly from the Redfield ratio, primarily due to an increase in POC. Ratios of particulate inorganic and organic carbon (PIC:POC) ranged from 0.14 to 0.18 at D = 0.3 d , cell volume was reduced by up to 22% in cultures grown at 900 μatm pCO 2 . Our results indicate that changes in pCO 2 , temperature and phosphorus supply affect cell density, POC concentration and size of E. huxleyi (PML B92/11) to varying degrees, and will likely impact bloom development as well as biogeochemical cycling in a greenhouse ocean.

Emiliania huxleyi increases calcification but not expression of calcification-related genes in long-term exposure to elevated temperature and p CO 2

“…POC content was significantly higher in the future ocean condition only at the 703 generation point, whereas primary production was the same. The data in this study (figures 2b and 3b) are in agreement with prior studies that examined the combined effect of elevated pCO 2 and temperature on POC content [21][22][23] and primary production [22] (table 6). Only the POC bulk production rate calculated from data reported by Feng et al [23] increases under elevated pCO 2 and temperature (table 6).…”

“…Chemostats were run with a dilution rate (equivalent to growth rate) of 1.1 d 21 using 0.2 mm filtered nutrient-poor, aged seawater with a salinity of 33.5 + 0.3 (collected offshore of Half Moon Bay, CA, USA; 378 29 0 31 0 N, 1228 30 0 02 0 W), enriched with phosphate (14 mM), and with a metal and vitamin mix according to f/2 concentrations [33]. To archive a cell concentration of approximately 500 000 cells ml 21 , nitrate concentrations were raised to 30 mM in the 'present ocean condition' media and 35 mM in the 'future ocean condition'. These nitrate concentrations were found in prior tests to yield the target cell concentration.…”

“…While there have been tests of E. huxleyi responses to multiple variables [14,[21][22][23], only one study has tested the effect of multiple environmental factors in long-term experiments [24] and found a synergistic effect of pCO 2 and nitrogen source on carbon partitioning in E. huxleyi.…”

Phosphorus limitation and heat stress decrease calcification in <i>Emiliania huxleyi</i>

“…Müller et al, 2008;Langer et al, 2012Langer et al, , 2013bGerecht et al, 2014;Oviedo et al, 2014;Perrin et al, 2016). In a (semi-)continuous culturing setup, growth rate is constant over the course of the experiment and production rates can be calculated (Paasche and Brubak, 1994;Paasche, 1998;Riegman et al, 2000;Borchard et al, 2011). Ratio data such as coccolith morphology, on the other hand, should be comparable between batch and (semi-)continuous culture experiments (Langer et al, 2013b), as has been shown for C. pelagicus (Gerecht et al, 2014.…”

Size-fractionated dissolved primary production and carbohydrate composition of the coccolithophore <i>Emiliania huxleyi</i>

“…A more detailed description of the chemostat principle and the experimental setup are given by Borchard et al (2011), respectively. Temperature was set to 14.0 ± 0.1 • C. Irradiance was provided at a 16 h / 8 h light / dark cycle with a photon flux density of 19 µmol photons m −2 s −1 (TL-D Delux Pro, Philips; QSL 100, Biospherical Instruments Inc.).…”