Environmental controls on the geographic distribution of zooplankton diversity

Proposed explanations for the geographic distribution of zooplankton diversity include control of diversity by geographic variation in: physical and chemical properties of the near-surface ocean(1-3); the surface area of biotic provinces(4); energy availability(5); rates of evolution and extinction(6); and primary productivity(7). None of these explanations has been quantitatively tested on a basin-wide scale. Here we used assemblages of planktic foraminifera from surface sediments to test these hypotheses. Our analysis shows that sea-surface temperature measured by satellites explains nearly 90% of the geographic variation in planktic foraminiferal diversity throughout the Atlantic Ocean. Temperatures at depths of 50, 100 and 150 m (ref. 9) are highly correlated to sea-surface temperature and explain the diversity pattern nearly as well. These findings indicate that geographic variation in zooplankton diversity may be directly controlled by the physical structure of the near-surface ocean. Furthermore, our results Show that planktic foraminiferal diversity does not strictly adhere to the model of continually decreasing diversity from equator to pole. Instead, planktic foraminiferal diversity peaks in the middle latitudes in all oceans.