Rethikala K.R¹, V. Kumar^2,, B. Satish³

The study investigates the relationship between the bottom water variables and temporal distribution of benthic foraminifera in the southern part of the Gulf of Mannar. For the study, a systematic collection of sediment and bottom water samples have been made along four traverses from off the coast of Theresapuram, Sippikulam, Mookaiyur and Valinokkam. The samples were collected from 7 stations each, along the 4 traverses and thus the total amounted to 28, ranging in depth from 0.8 to 15.0 metres. The collections were carried out once in four months starting from October 2016 to April 2017, representing the three seasons viz. October (pre-monsoon), January (post-monsoon/winter) and April (summer) and thus the collection amounted to a total of 84 samples. Faunal analysis led to the recognition of 124 foraminiferal species belonging to 59 genera, 39 families, and 21 super families of 5 suborders. The population size both as living and total (living + dead) in each of the stations during different seasons revealed that the maximum living population size was found in stations between 3 and 5 during all the collections and the living population was maximum in summer (April) and was minimum during monsoon (October). Among the 124 foraminiferal species, the following species were considered widespread and abundantly occurring viz. Ammonia beccarii, A. tepida, Asterotalia inflata, Elphidium advenum, Noninoides boueanum and Quinqueloculina seminulum. Various bottom water parameters of all the samples have been estimated and correlated with foraminiferal population. Higher temperature, salinity, pH and dissolved oxygen content noticed during April favoured higher reproduction and abundance of foraminiferal population.

Benthic foraminifera, temporal distribution, bottom water characters, Theresapuram, Sippikkulam, Valinokkam, Mookkaiyur, Gulf of Mannar