- The atlas presents an analysis of relative abundances of
extant planktic foraminifera (>150 µm) in surface sediments
of the Indian Ocean and the North Atlantic, based on CLIMAP data.
Relative abundances of each species are plotted against latitude,
and winter, summer, mean values, and a seasonality parameter
of temperature, salinity, and water density at the sea surface
and at 200 m depth, the vertical temperature gradient and the
density contrast (stratification) between the sea surface and
200 m depth, based on data from Levitus (1982).
The analysed species are: C. nitida, D. anfracta, G. bulloides,
G. falconensis, G. digitata, G. calida, G. siphonifera (syn.
G. aequilateralis), G. glutinata, G. conglobatus, G. ruber, G.
sacculifer, G. conglomerata, G. crassaformis, G. hirsuta, G.
inflata, G. menardii, G. scitula, G. truncatulinoides, G. tumida,
G. hexagonus, G. rubescens, G. tenella, H. pelagica, N. dutertrei,
N. pachyderma, O. universa, P. obliquiloculata, S. dehiscens,
T. humilis, T. quinqueloba; and with sporadic occurrences in
a few samples: B. pumilio, G. adamsi, G. uvula (syn. G. bradyi),
T. iota, and H. digitata. Some species were not recorded due
to their small size (<150µm): G. vivans, G. minuta,
O. riedeli, S. globigerus, T. clarkei, T. fleisheri, T. parkerae;
or for other reasons: G. cavernula, G. theyeri, and G. ungulata.
The biogeographic ranges, suboptima, and optima with respect
to the analysed parameters are presented in tabular form for
each species with continuous occurrences.
The six dominant species have broad relations with sea surface
temperature, with optima in the various biogeographic provinces,
or preferences for productive marine environments. Other species
show specific relations with combinations of physical parameters
which reflect specialisation and individual niches. A third group
is part of bloom successions or seasonal productivity variation
and is differentiated by their preferences for conditions in
high latitudes and upwelling zones, tropical environments, or
processes related to the deep chlorophyll maximum. Species with
known ontogenetic cycles show closest relations with physical
conditions in their time of reproduction, suggesting a dominance
of reproduction-related processes for control of relative abundances
in sediment assemblages.
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