A Spatial Ecological Study Based on Benthic Foraminifera off Central West Coast of India: An Approach through Cluster Analysis with Special Reference to Oxygen Minimum Zone

Abstract

Fifty-two surface samples collected from a depth range between 15 and 3300 m from the Vijaydurg-Karwar sector off the central west coast of India were analyzed for benthic foraminifera. A total of 386 benthic foraminifera were identified to species level. The relative abundances of 21 major genera (>5% in at least two stations) were plotted on a distribution map as well as on a kite diagram. Most of the genera show correlation to water depth in the study area. For better understanding and to draw meaningful conclusions from the assemblages out of the surface distribution of major genera, Q-mode cluster analysis was performed with the total number of species as variables. The clusters (namely A & B) and their subclusters (namely B1, B2 & B3) also exhibit a preference to water depth. Considering the position of the Oxygen Minimum Zone (OMZ) in this region extends from 150 to 1500 m water depth, it was noticed that the stations in smaller subcluster within cluster B3 fall below the OMZ, while most of the stations in cluster B2 fall above the OMZ. From the cluster analysis, the major benthic foraminiferal species from within the OMZ are identified as Bolivina silvestrina, Bulimina marginata, Globocassidulina oriangulata and Melonis pompilioides. Hence, cluster analysis based on the benthic foraminiferal assemblage is useful to detect the position of the OMZ in the study area.