APPRAISAL OF CLAM BED SEDIMENT QUALITY IN TWO LAKES, A DEEP AND A SHALLOW

The study was carried out to assess the sediment parameters of two Lakes, a deep and a shallow, influencing the macrobenthos. A precise knowledge of the substratum is a prerequisite to manage the stock, culture and fishery of the clams. The sediment samples collected from the sampling sites of two Lakes were air dried and used for the analysis of soil parameters viz., soil texture, electrical conductivity, organic carbon, phosphorus, potassium and sediment pH. Sediment texture was analysed following pipette analysis. The sand-silt-clay distribution was determined using shepard-Ternary-Plot. Sediment pH measured using 1:1 soil water paste in Digital pH meter, electrical conductivity was determined by electrometric method using a digital electrical conductivity meter, soil organic carbon was analysed following Walkley-Black method, soil phosphorus estimated following sodium bicarbonate method and Flame photometric method employed for potassium estimation. In all the three seasons, deep Lake exhibited sandy loam sediment texture whereas the upper reaches of shallow Lake exhibited loamy sand texture throughout and its lower reaches depicted sandy loam texture in pre-monsoon and sandy clay loam texture in other two seasons. The sediment composition delineated similar trends in the two Lake. The mean values of various sediment parameters from deep Lake and shallow Lake were recorded. Sediment pH(6.34 ± 1.23 and 6.56 ± 1.25, (t(286)=- 1.462,P= .07) ), electrical conductivity ( 5.48 ± 3.79 mS cm-1 and 8.03 ± 4.49 mS cm-1, (t(286) = -5.195, P= .0001)), organic carbon( 0.57 ± 0.50 % and 0.61 ± 0.41%, (t(286) = -0.634, P= .26)), phosphorus (1.14 ± 0.36 mg g-1 and 1.59 ± 1.09 mg g-1, (t(286) = -5.943, P= .0001)) and sediment potassium (1.93 ± 1.09 mg g-1and 2.21 ± 0.99 mg g-1, (t (286) = - 2.275, P= .01) ) respectively. Both the estuarine sediments were fertile with ample amounts of nutrients and microbial activity. The results of the present study endorsed that both the Lakes are ecologically stable.