- GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of Geology Exclusive of North America, Geological Society of America, Boulder, CO, United States
It is shown that relatively small variations in the measured environment exert major control in the population dynamics of this group, with temperature variations of as little as two degrees C, and salinity variations of as little as 0.2-0.5 ppm. exerting primary control of absolute and relative abundances of a number of species. Selected elements of the equatorial Atlantic current system may be defined by population variations in indigenous planktonic foraminiferal species. The use of planktonic foraminifera as indicator organisms for specific oceanic water masses and currents is established, and it is suggested that similar utilization of these forms in the geologic past, to define paleo-oceanographic conditions, is feasible.