Recent marine diatom taphocoenoses off Peru and off Southwest Africa

Abstract

Abstract taken from Dissertation Abstracts International, vol 41, no 04, October 1980, p. 1286-B:

Delphineis karstenii is characteristically found in newly upwelled waters and, correspondingly, it occurs in highest abundance in the sediments in nearshore patches. Chaetoceros resting spores generally occur in highest relative abundance outside these nearshore patches. The overlapping but distinct distribution patterns for these two dominant species may record a sequence of diatom assemblages which is related to the dynamics of coastal upwelling off South West Africa

The final chapter is a comparison of the findings for the two areas and a characterization of coastal upwelling influence on sediment composition. Those features are discussed which are common to both upwelling areas and which differentiate upwelling-influenced diatom taphocoenoses: (1) abundant remains of well-preserved diatoms, (2) high percentages of meroplanktic species and species groups, and (3) coherent distribution patterns for diatom assemblages which represent subenvironments within the coastal upwelling area

The second chapter reports the findings from the study of 124 sediment samples from the South East Atlantic, including 85 surface samples located within the coastal upwelling area. In this study the shallow water depths of the inner shelf off South West Africa allow the preservation of many diatom species prominent in the phytoplankton of the overlying surface waters. Diatom rich samples (75 - 800 x 10 to the power of 6 valves per gram dry sediment) occur between 19°S - 24°S in water depths less than about 130 meters. The species composition of these samples contrasts markedly with that of the offshore sediment samples and is dominated by Chaetoceros resting spores and Delphineis karstenii