The dissolved oxygen in seawater is a critical requirement for the survival of marine organisms. The restricted circulation and high productivity are the primary factors that deplete the dissolved oxygen in several parts of the world ocean. One such zone of very low dissolved oxygen is in the northwestern Arabian Sea. A few marine organisms, especially foraminifera develop novel ways to survive in low dissolved oxygen environment. Therefore, it is important to understand foraminiferal distribution in low dissolved oxygen environment. A majority of the previous workers documented total foraminiferal distribution in the oxygen minimum zone (OMZ) of the Arabian Sea. The total population, however, is not a true representative of the recent modern ambient condition. Therefore, the living benthic foraminifera are more apt to understand foraminiferal response to low dissolved oxygen.
Results/Conclusions
Here, we document living benthic foraminiferal population from the OMZ of the northwestern Arabian Sea. The core top section of 13 multicore samples collected along a latitudinal transect at depths varying from 50 m to 4150 m were used. The surface samples were stained by ethanol rose-Bengal solution to distinguish living foraminifera. The total foraminiferal number (planktic + benthic + living) is very high in the OMZ as compared to depths above and below. Living benthic foraminifera are an order of magnitude higher throughout the OMZ. The maximum living benthic foraminifera are at 200 m with abundance as high as 63925 individuals per g sediment. Within the living benthic foraminifera, rectilinear forms dominate the population in the OMZ. We infer that the rectilinear benthic foraminifera are more adapted to survive in low dissolved oxygen condition and thus can be used as proxy to reconstruct past changes in the Arabian Sea OMZ.