Environmental Science and Policy
Ocean acidification, Calcification, Coccolithus huxleyi, Coccolithophores, Scanning electron microscopy, Emiliania huxleyi
Increasing acidity in the oceans is a current cause for concern in populations of calcifying organisms. Reactions to increasing pCO2 by organisms are variable and unknown for many, including the small phytoplankton, coccolithophores. Strain CCMP2668 of the coccolithophore, Emiliania huxleyi, was grown in culture under three pCO2 treatments (~400 ppmv, ~750 ppmv, ~1000 ppmv) to understand the effects of increasing pCO2 on the calcification rate and morphological structure of the calcite coccoliths. Results indicated that cells held under control treatment conditions had a higher growth rate than the cells held under both the moderate and high pCO2 treatment conditions. However, no significant difference existed in the amount of particulate organic (POC) and inorganic carbon (PIC) among the control, moderate, and high treatments. Morphologically, after a visual inspection of scanning electron microscopy (SEM) images, an increase in the number of malformed coccoliths was observed in the enriched pCO2 (~15%) treatments in comparison to the control treatment (~3%). The discrepancy between the physiological and morphological results indicates that perhaps the physical structure of the coccolith is affected once exposed to a lower external pH, but that the process of producing the coccoliths remains unaffected by external pH. Variable responses by other species of coccolithophores, specifically other strains of Emiliania huxleyi, are common both in the geologic record and modern experiments. The results from the current experiment reiterate that effects of increasing pCO2 are likely to be strain and species specific, and adds to the knowledge by examining a strain not currently discussed in the literature. Coccolithophores are extremely important primary producers, in fact Emiliania huxleyi alone contributes 1-10% of total primary production, and bases for food webs. Therefore, despite the conflicting results to changing levels of pCO2, it is crucial to consider coccolithophores as a whole when developing political strategies to defend against changing atmospheric and seawater conditions.
Goethel, Christina L., "Effects of elevated pCO2 on the calcification and morphological characteristics of the coccolithophore Emiliania huxleyi : implications of ocean acidification" (2013). Honors Project, Smith College, Northampton, MA.
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