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N. Jayaraju ¹, I. Suryakumar ², K. R. Reddy ¹

Affiliations
1 Department of Geology, S. V. University, Tirupati - 517502, IN
2 Coastal Survey and Consultancy Services, 208 KB, Lal Industrial Estate, Santa Cruz (W), Mumbai - 400 054, IN

Abstract

This paper attempts to document the dominant living foraminiferal assemblages in 30 sampling stations in Pulicat lake during the four seasons of a year. Nearly 35 living species have been identified and their relative abundance was analyzed using Q-mode factor analysis programme. In each season, six faunal assemblages at an average of 64.5% of the observed variance emerged from the analysis. Statistical studies have revealed that the most significant assemblage is characterized by Florilus labrodoricum and F. grateloupi (av. 25.1%). Foraminiferal variation throws light on water mass characters such as salinity, water depth and the bottom sediments.

Keywords

Living Foraminifera, Seasonal Variation, Pulicat Lake, Bay of Bengal, Tamil Nadu.

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N. Jayaraju ¹, K. Srinivas ², K. R. Reddi ², I. Suryakumar ³

Affiliations
1 Department of Geology, Sri Venkateswara University, Tirupati-517 502 A.P., IN
2 Department of Geology, Sri Venkateswara University, Tirupati- 517 502 A.P., IN
3 Geonics (India) Pvt. Ltd., 501, Devavrata, Sector-17, Vashi, New Bombay-400 705, IN

Abstract

A total variance explaining 86% of the matrix is consituted by six factors where Florilus-Asterorotalia assemblage (46%) emerged significant. Asterorotalia-Florilus assemblage is more abundant (37%) in monsoon. These faunal assemblages were related to environmental ingredients Viz., texture of sediment substrate, the amount of locked-up organic matter content and bottom water salinity. The cross plot of first two factors for both seasons revealed the common genera found to occur in descending order i.e., Asterorotalia, Florilus, Elphidium and Ammobaculites which are confined especially in normal marine action of sea oscillations are noticed.

Keywords

Palaeontology, Foraminifera, Factor Analysis, East Coast.

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N. Jayaraju ¹, I. Suryakumar ¹, K. R. Reddy ¹

Affiliations
1 Department of Geology, Sri Venkateswara University, Tirupati - 517 502, IN

Abstract

Total (Dead + live) forarminiferal species have been studied for four seasons viz, pre monsoon (July-Sept), monsoon (Oct-Dec), post monsoon (Jan-Mar) and summer (April-June) in relation to ecological variables of Pulicat-Lake. Total population ranges from 298 to 1480/100 gms of sediment with an average of 615 per sample. Living crop ranges from 20 to 240/100 gms with an average of 86 per sample for the whole lake. The lowest L/D ratio (43%) was noticed at station 19 in monsoon and the highest (54 7%) was recorded at station 29 in pre monsoon. There IS no much significant difference in variability for all the four seasons with Co-Efficient of variation (CV) ranging from 41 to 46% Out of 50 species recorded, only 35 had living representatives, while the rest occurred as dead. The prominent stained (live) species in the decreasing importance are Ammonia beccan, A tepida, Elphidiurn hispidulum, Quinqueloculina agglutinans, Elphidium excavatum, Quinqueloculina hadav, Q oblonga and Elphidium milletti.

The coefficient correlation values for dissolved oxygen versus living fauna in monsoon (g = 0 33) and in summer (g=-0 26) are slightly below the significance level (g=O 36) at 95% confidence level. A high positive correlation and a high inverse relationship have been demonstrated between salinity and microbiota in monsoon and summer respectively. With the increase in organic matter fauna decreased in diversity and abundance in both the seasons. It may be concluded that in the Pulicat Lake as a whole, the environmental conditions are moderately favorable for the growth and survival of benthic foraminifera.

Keywords

Recent Forarminifera, Lake Environment, Ecology, Diversity And Density, Pulicat Lake.

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