Coccolithophorid blooms in the global ocean

Abstract

Abstract. The global distribution pattern of coccolithophorid blooms was mapped in order to ascertain the prevalence of these blooms in the world's oceans and to estimate their worldwide production of CaCO 3 and dimethyl sulfide (DMS). Mapping was accomplished by classifying pixels of 5-day global composites of coastal zone color scanner imagery into bloom and nonbloom classes using a supervised, multispectral classification scheme. Surface waters with the spectral signature of coccolithophorid blooms annually covered an average of 1.4 x 10 6 km 2 in the world oceans from 1979 to 1985, with the subpolar latitudes accounting for 71% of this surface area. Classified blooms were most extensive in the Subarctic North Atlantic. Large expanses of the bloom signal were also detected in the North Pacific, on the Argentine shelf and slope, and in numerous lower latitude marginal seas and shelf regions. The greatest spatial extent of classified blooms in subpolar oceanic regions occurred in the months from summer to early autumn, while those in lower latitude marginal seas occurred in midwinter to early spring. Though the classification scheme was efficient in separating bloom and nonbloom classes during test simulations, and biogeographical literature generally confirms the resulting distribution pattern of blooms in the subpolar regions, the cause of the bloom signal is equivocal in some geographic areas, particularly on shelf regions at lower latitudes. Standing stock estimates suggest that the presumed Emiliania huxleyi blooms act as a significant source of calcite carbon and DMS sulfur on a regional scale. On a global scale, however, the satellite-detected coccolithophorid blooms are estimated to play only a minor role in the annual production of these two compounds and their flux from the surface mixed layer.

Phytoplankton community dynamics during late spring coccolithophore blooms at the continental margin of the Celtic Sea (North East Atlantic, 2006–2008)

“…Yet, the N:P ratio per se does not seem to determine absolute biomass development, and hence the magnitude of the blooms (see also Table 4). Our results are in general agreement with other studies investigating the conditions conducive to coccolithophore bloom development, such as a low dSi:N ratio, shallow mixed layer depth, and increased irradiances (Brown and Yoder, 1994;Painter et al, 2010b). A higher proportion of coccolithophore biomass was associated with higher N:P ratios, even though these ratios were not that high (Table 3).…”

The hydrography and biology of a bloom of the coccolithophorid Emiliania huxleyi in the northern North Sea

“…Coccolithophores may generate large oceanic blooms exceeding 100 000 km 2 in area (Brown and Yoder, 1994;Fernández et al, 1993). Coccolithophore blooms may persist for 3-6 weeks, can act as passive tracers of water movement, and have a variable distribution from year to year (Holligan et al, 1993b).…”

Biological Oceanography by Remote Sensing

“…48 Another consequence is that, in the case of ocean color sensors, a different algorithm needs to be used to estimate their abundance from satellite data. 47 It also means that it is possible to monitor one specific species of phytoplankton, whereas the standard chlorophyll measurements obtained from ocean color do not allow discrimination between different species of phytoplankton. Two effects of the presence of large numbers of coccoliths in the water are first, an increase in the ocean's albedo, and, second, a shading effect that reduces the light level in deeper water (while the scattering of photons increases the light level in the surface waters).…”

“…46 Their importance is probably greatest during a bloom, where their concentrations can reach up to 115 million cells per liter. 47 The most abundant of the species is Emiliania huxleyi, which can be found throughout most of the world's oceans, with the exception of the polar oceans. 48 They can be detected in satellite imagery because the presence of the coccoliths leads to high reflectance in the surface waters due to their intense scattering of light.…”

“…48 They can be detected in satellite imagery because the presence of the coccoliths leads to high reflectance in the surface waters due to their intense scattering of light. 47 Essentially they act like small mirrors suspended in the water and cause a significant portion of the incoming light to be reflected back out from the water.…”