A satellite perspective on global blooms of coccolithophores
University of Southampton, Ocean and Earth Science,
Coccolithophores are a unique group of phytoplankton that produce calcium carbonate coccoliths. The production of
coccoliths can potentially reduce the carbon sink effect associated with phytoplankton photosynthesis. However, this may be offset by a coccolith ‘ballast’ effect that increases particulate organic carbon export efficiency. During a coccolithophore bloom, large quantities of coccoliths are shed into the water column. The unique light scattering properties of calcium carbonate particles of ~2 ?m in size (the size of an Emiliania huxleyi coccolith) have previously been used to develop an algorithm that enables estimates of particulate inorganic carbon (PIC) concentration to be made from space. Here, these satellite derived PIC data have been used to generate a unique set of
phonological characteristics, such as start date, peak date and bloom magnitude, for global coccolithophore blooms. A comparison of similar timings generated from chlorophyll data indicates that, contrary to conventional thinking, blooms of coccolithophores can co-?occur with other phytoplankton taxa. An assessment of the environmental conditions associated with coccolithophore blooms suggests that current understanding of coccolithophore bloom characteristics may be associated with the peak of the bloom and that conditions at the start of the bloom can be significantly different (i.e. deep mixed layers, moderate light levels and elevated silicic acid concentrations). A global PIC inventory of 29.0 ± 4.3 MT C was determined from satellite derived PIC and mixed layer depth data. The Great Calcite Belt and tropical Pacific were found to be regions that make a significant contribution to this budget. The data produced in this thesis provide the first multi-?year, global overview of coccolithophores and offer a novel means of monitoring coccolithophore populations over the long-term, global scales needed to identify the possible influences of climate change .
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