A total of 23 surface sediment samples collected from north-south stretch along the Indian Ocean have been examined for their planktonic foraminiferal faunas. Among the other planktonic foraminiferal faunas, Neogloboquadrina pachyderma was found substantially in all samples. Census data of N. pachyderma were obtained for different parameters (average size, mean proloculus size, coiling direction and number of chamber) and were analyzed using a Q-mode cluster analysis. Samples were segregated into three clusters, each reflecting particular environmental conditions. These clusters are: (1) Cluster A comprised of 14 samples from tropical to sub-tropical zone, characterized by a moderate range of foraminiferal and ecological parameters; (2) Cluster B comprised of 8 samples mainly from sub-polar zone, characterized by lowest range of foraminiferal parameters with lowest range of sea surface temperature and salinity; (3) Cluster C comprised of a single sample (northernmost sample from our study area) from tropical zone, characterizing higher range of foraminiferal parameters along with highest value of sea surface temperature and lowest value of nutrient and dissolved oxygen. The study suggests that sea surface temperature, sea surface salinity and nutrients are the main ecological factors controlling the morphological characteristics of planktonic foraminiferal species N. pachyderma.
Keywords
South Western Indian Ocean, Planktonic Foraminifera, Neogloboquadrina pachyderma, Morphological Characters, Q-Mode Cluster Analysis, Ecological Factors.
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