Influence of changing carbonate chemistry on morphology and weight of coccoliths formed by <i>Emiliania huxleyi</i>

Abstract

Abstract. The coccolithophore Emiliania huxleyi is a marine phytoplankton species capable of forming small calcium carbonate scales (coccoliths) which cover the organic part of the cell. Calcification rates of E. huxleyi are known to be sensitive to changes in seawater carbonate chemistry. It has, however, not yet been clearly determined how these changes are reflected in size and weight of individual coccoliths and which specific parameter(s) of the carbonate system drive morphological modifications. Here, we compare data on coccolith size, weight, and malformation from a set of five experiments with a large diversity of carbonate chemistry conditions. This diversity allows distinguishing the influence of individual carbonate chemistry parameters such as carbon dioxide (CO 2 ), bicarbonate (HCO ] cannot be entirely ruled out. Changes in coccolith weight were proportional to changes in size. Increasing CaCO 3 production rates are reflected in an increase in coccolith weight and an increase of the number of coccoliths formed per unit time. The combined investigation of morphological features and coccolith production rates presented in this study may help to interpret data derived from sediment cores, where coccolith morphology is used to reconstruct calcification rates in the water column.

Influence of CO<sub>2</sub> and nitrogen limitation on the coccolith volume of <I>Emiliania huxleyi</I> (Haptophyta)

“…This value is in good agreement with the present estimates derived from the nitrogen limitation experiments. On the other hand, calculated coccolith masses from the nutrient replete experiments (4.1 to 7.8 pg CaCO 3 ) are higher than estimates from other laboratory studies (Paasche, 1998(Paasche, , 1999(Paasche, , 2002Bach et al, 2012) which report values from 1.5 up to 4 pg CaCO 3 per coccolith. Differences between the latter and the present study might be caused (1) by diverging experimental set up and the cultured strain/morphotype of E. huxleyi and/or (2) by the applied method to estimate coccolith mass (SEM, birefringence-based and resistive methods).…”

“…6) reveals that results from laboratory experiments (Bach et al, 2012, and this study) have a distinct pattern from field data Triantaphylloua et al, 2010). The difference between laboratory and field data is not surprising.…”

“…Increasing acidity (pH < 7.5 or pCO 2 > 1500 µatm), on the contrary, negatively affects the cell diameter (Bach et al, 2011). The combination of both effects results in an optimum curve response of the cell diameter to ocean acidification/carbonation (Bach et al, 2011(Bach et al, , 2012.…”

“…Field data are from Mediterranean waters (E. huxleyi dominated samples, Triantaphylloua et al, 2010) and from the chlorophyll maximum near the cost of Namibia . Laboratory data are from a carbonate chemistry manipulation experiment (Bach et al, 2012) and this study. Details about measurement procedure and inherent errors can be found in the original studies.…”

On culture artefacts in coccolith morphology

“…These measures ensure robust, unbiased results (Langer et al 2006;Langer and Benner 2009;Langer and Bode 2011;Langer et al 2012). Recently, it was shown that results based on an objective, biometrical malformation index compare well with the classical, subjective categorization (Bach et al 2012).…”