SKELETAL PLANKTON AND NEKTON IN UPWELLING WATER MASSES

In this study we compare the distributions of the skeletal re­ mains of plankton and nekton organisms caught in water samples from the upwelling regions off northwest Africa and northwestern South America. In both regions the near-surface water masses were sampled continuously by means of a seawater pump with an attached filter sys­ tem effectively collecting all sand-sized material over sampling in­ tervals of limited regional extent. Close to 200 samples were avail­ able from ea.ch of the regions. The. samples were studied for their contents of shells and skeletons. Because the water flow was con­ trolled by means of a water meter, it was possible to calculate rela­ tive and absolute concentrations of all components within the sampled size fractions and their regional distributions could thus be determined. The quanti tati vely most important components of the collected grain assemblages are diatoms, planktonic and benthic foraminifers, radiolarians, larvae of benthic gastropods and bivalves, pelagic gas­ tropods and fish bones. Samples taken wi thin the coastal water masses of the upwelling regions are often characterized by the mas­ sive occurrence of large centric diatoms. Also, benthic foraminifers have frequently been found off south America and are believed to have lived as epi-benthos on drifting algae. The planktonic foraminifers and their distributional patterns can be related directly to the extent of upwelling water masses. Both off northwest Africa and off South America, the most important planktonic foraminiferal species of the upwelling water masses are Globigerina bulloide8~ Globigerinita glutinata and GloboquadPina