How many coccoliths are there in a coccosphere of the extant coccolithophorids? A compilation.

Abstract

Introduction As an important component in the biogeochemical cycling of carbon and sulphur, and of global climate change (Westbroek et al., 1993), production of coccolithophorids and their fluxes in the ocean have drawn much attention in recent years (e.g. Kleijne, 1991; Honjo, 1996; Andruleit, 1997; Ziveri & Broerse, 1997; Broerse et al., 2000a, b, c; Jordan & Winter, 2000; Sprengel et al., 2000; Ziveri & Thunell, 2000; Cortes et al., 2001; Haidar & Thierstein, 2001; Yang et al., 2001 ). To be able to quantitatively estimate the flux of coccolithophorids in the ocean system, it is often desirable to convert counts of coccoliths into coccospheres, or vice versa. For example, Kleijne (1991) and Knappertsbusch (1993) documented the distribution of standing crops of coccospheres of holococcolithophorids in the Indian Ocean, Red Sea, Mediterranean Sea and North Atlantic Ocean, and of coccolithophorids in the Mediterranean Sea, respectively, by converting the counted coccoliths to coccospheres using existing data of coccolith/coccosphere ratios. More recently, Broerse et al. (2000a, b, c) and Ziveri & Thunell (2000) compiled coccolith and coccolithophorid data, and converted the data eventually into carbonate mass flux, based upon the coccolith mass estimates ofYoung & Ziveri (2000). The conversions in these previous studies, however, were applied to limited numbers of species, based upon available data from published literature. To facilitate a more complete quantitative study of coccolithophorid standing crops, and their contribution to carbonate flux, not only ratios of coccoliths/coccosphere of all species needed to be documented, but also some basic questions needed to be addressed, for instance, is the ratio shown by each taxon constant? If not, does the ratio vary with different oceanographic settings, or is it solely a function of ontogenetic development? Furthermore, for some dimorphic and dithecate coccospheres, the number of different kinds of coccoliths should be converted separately depending upon whether the coccosphere is complete or not. Various functions of coccoliths have been hypothesised, including protection, biochemical convenience, flotation and light-regulation (see Young, 1994 for review, and references therein). Intraspecific variation is a notable phenomenon in cultured Emiliania huxleyi (Linschooten et al., 1991). They found that new daughter-cells were covered with an average of 8-10 coccoliths, but the number increased to 15-20 before the next cell-division. The number of coccoliths also varies with nutrient availability. Linschooten et al. (1991)