Copepod species diversity and climate variability in the tropical Atlantic Ocean

A database synthesized from 19 oceanographic expeditions conducted by the former Soviet Union was used to analyse interannual patterns in copepod species diversity in the tropical Atlantic. Mesozooplankton was collected predominately in vertical hauls through the upper 100 m with Juday nets. The samples from 744 oceanographic stations were identified and enumerated to the species level. To assess species diversity, the Shannon diversity index was used. On the interdecadal scale, no statistically confirmed trend was found in species diversity change over the years sampled (1963-89). Multiple regression analysis indicated that interannual fluctuations of the South Atlantic High (pressure and latitude), the Azores High longitude and El Niño-Southern Oscillation (ENSO) index could explain 87% of species diversity fluctuations. Possible mechanisms that drive interannual fluctuations of species diversity are discussed.