Chapter Seven - Biology of Haptophytes: Complicated Cellular Processes Driving the Global Carbon Cycle.

Haptophytes are one of the photosynthetic microalgae with red-algal-derived chloroplasts, and thought to be among the most important primary producers in oceans. Calcifying haptophytes (coccolithophores) have a significant effect on the global carbon cycle, as they fix dissolved inorganic carbon through photosynthesis and calcification. Given that these two processes occur in a single cell, intracellular ion and metabolite traffic is expected to be more complex than in other algae. Haptophytes synthesise and accumulate various compounds during photosynthesis, such as long chain unsaturated ketones (alkenones), β-glucan, mannitol, acid polysaccharides (APs), and dimethylsulphoniopropionate. Some compounds are not equally produced in all haptophytes but are produced by specific species or groups. For example, APs are produced only in coccolithophores and suggested to support morphogenesis of calcite scales. The structure of APs is highly species-specific. Alkenones are produced in only five haptophyte species regardless of their calcification ability. The occurrence of such variations in carbon metabolism across species is also a marked characteristic of haptophytes. This chapter introduces basic cellular features of haptophytes and focuses on features of their carbon metabolism and calcification. [ABSTRACT FROM AUTHOR]