Latitudinal Diversity of Planktic Foraminfera
Latitudinal Gradients in Planktic Foraminferal Diversity
The diagram below shows planktic foraminiferal species richness for core top samples from the Atlantic. One of the basic tenets of ecology is that species richness increases from the poles to the equator. This is not true for planktic foraminifera, however. Notice the in the plot of richness versus latitude species richness peaks in the midlatitudes then decreases toward the eqautor.
In trying to link the observed diversity profile, we have examined a number of physical variables including, sea surface temperature (SST), mixed layer depth, chlorophyll concentration, primary productivity, topographic height, and salinity. In addition, we have investigated the effect of seasonal differences in many of these variables. It appears the best predictor of planktic foraminiferal species richness is SST. The diagram below shows the relationship between species richness and mean annual SST. The SST data were provided by Ken Casey and are 4 year averages of satellite (AVHRR) measurements.
