Nannofossil assemblages from core MD02-2510 provide a ~ 22 ka record of past oceanographic variability in Alfonso Basin (Gulf of California, east subtropical Pacific). In this area, environmental conditions depend on a monsoonal system heavily influenced by changes in the location of the ITCZ and nearby atmospheric pressure centers. To reconstruct nutricline depth and ENSO-like variability, two ecological indexes were calculated based on the relative abundance of the three dominant coccolith species. The late glacial period is characterized by intensified wind-driven upwelling, high primary productivity and La Niña-like conditions. An environmental shift occurs during the glacial–interglacial transition, El Niño-like conditions intensify, nutricline deepens and surface productivity declines. The late Holocene is characterized by a persistent increase in nutricline depth and dominance of El Niño-like conditions. The fluctuations in the composition of the coccolith assemblages can be related to orbital-scale fluctuations in the average position of the ITCZ. However, while the ENSO-like signal that overprints the record varies in response to orbital forcing, on suborbital time scales the relation between ENSO-like conditions and the average position of the ITCZ and the North Pacific High changes, suggesting that the development of persistent El Niño-like conditions is strongly dependent on the specific climatic background.

Coccolithophores and Parmales are important functional groups of calcified and siliceous marine nanophytoplankton. Large-scale biogeographic distributions of the two groups were investigated based on 71 samples that were collected in the Atlantic Ocean. Using a scanning electron microscope, a total of 48 taxa of coccolithophores and eight taxa of Parmales were recorded, with Emiliania huxleyi, Tetraparma pelagica and Triparma strigata as the predominant forms. The highest abundances of coccolithophores (376 × 103 cells l−1) and Parmales (624 × 103 cells l−1) were observed in waters north-east of the Falkland Islands and the South Georgia Island, in close association with the Subantarctic Front and Polar Front, respectively. Three major biogeographic assemblages, i.e. the Falkland Shelf Assemblage, the Southern Ocean Assemblage and the Atlantic Ocean Assemblage, were revealed in cluster analysis. Additionally, canonical correspondence analysis indicated that temperature significantly affects the latitudinal patterns of the two algal groups. High abundances of Parmales were closely coupled with those of E. huxleyi in waters of the Southern Ocean with low temperature (<10°C). However, the number of coccolithophore species, along with the Shannon–Weaver diversity, significantly increased with elevated temperature, suggesting more diverse assemblages in tropical waters.

A total of twenty-seven species of marine-living coccolithophores were recorded from seawater samples that were collected during two spring cruises along the shelf regions of the Yellow Sea (YS) and the East China Sea (ECS). They were classified into ten families and four orders, with some additional species incertae sedis. Most of these species were heterococcolithophores, and no holococcolithophores were examined from the YS waters. Six species were recorded for the first time from the coastal waters of the China Seas and their morphological characteristics are described and photographically illustrated in this paper. They were Cyrtosphaera lecaliae, Syracosphaera histrica, Syracosphaera marginaporata, Pappomonas cf. sp. type 3, Calyptrolithophora papillifera and Corisphaera strigilis. Three types of Emiliania huxleyi, type A, type B/C and type C, were examined. Species of the genus Syracosphaera, in addition to E. huxleyi and Gephyrocapsa oceanica, frequently occurred at the surveyed sites. The coccolithophore assemblages in the offshore waters of the ECS were characterized by high species diversity—fourteen species in one sample. This finding indicated that the shelf waters adjacent to the Kuroshio path were ideal habitats for living coccolithophores. The variation in taxonomic composition of these algae could be associated with differences in their preferred habitats.