Untangling the effect of organic matter and dissolved oxygen on living benthic foraminifera in the southeastern Arabian Sea.

We studied the relationship between organic carbon in sediments (%C), bottom water dissolved oxygen and living benthic foraminifera in a marginal marine upwelling setting from the southeastern Arabian Sea to develop proxy indicator for marine productivity as well as oxygen deficient zones. The surface sediments from 43 stations covering a depth range of 25 to 2980 m were used. The relationship between living benthic foraminifera and ambient environmental parameters (seawater temperature, salinity, dissolved oxygen, organic carbon and C/TN and depth) was assessed by multivariate analysis. A majority of the living benthic foraminifera were significantly affected by several ambient parameters. We report that the living benthic foraminiferal assemblage comprising of Epistominella umbonifera, Uvigerina auberiana, Reophax longicollis and Osangularia bengalensis is significantly affected only by %C in the sediment. Additionally, we also found that the assemblage including Bolivina obscuranta, Bulimina arabiensis, Bulimina pseudoaffinis and Cancris penangensis is significantly affected only by the bottom water dissolved oxygen. The living benthic foraminifera assemblages can be used to reconstruct marine productivity and dissolved oxygen concentration in the past.