An overview of the planktonic foraminiferal fauna in waters off the Kerala Coast, south-west India during summer

Abstract

Twentyeight species of planktonic Foraminifera are recorded from 46 plankton samples collected from 27 stations of 5 traverses along the Kerala Coast. The mean abundance of total foraminiferal sepcimens of all the stations in each traverse shows that it increases from south to north. Two distinct foraminiferal assemblages have been noted in the fauna: first is the summer tropical one typified by species such as Globigerinella aequilateralis, Globigerinoides conglobatus, G. ruber and G. sacculifer, while second one known as summer tropical upwelling assemblage is formed by species, viz. Globigerina bulloides and Neogloboquadrina dutertrei. The spinose species of the genus - Globigerinoides - are the most abundant. A factor analysis of faunal data shows the grouping (Q-mode analysis) of foraminiferal species into (1) rare and (2) dominant species, besides a few rare ones; this study indicates that dominant forms in the area can addapt to a wide range of environmental conditions. The same study with R-mode analysis for stations depicts that traverses 5 (0-10m) and 4 (0-200m) are distinct in showing the least faunal abundance. The fauna in general has a close affinity with that of waters in tropical and subtropical zones of the north Atlantic in summer