Renuka Lake ecosystem and wetland protection, Lesser Himalaya ...
Renuka Lake ecosystem and wetland protection, Lesser Himalaya ...
Renuka Lake ecosystem and wetland protection, Lesser Himalaya ...
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samples close to the hotel, temples, bathingghat where human activity viz-a-vizpollution is maximum (Fig.2; Table 1). Incomparison to lake water, samples alongthe contact of wetl<strong>and</strong> <strong>and</strong> riparian zoneshow depletion in metal ion concentrationexcept relative enhancement of Sr. Thelatter may indicate higher carbonate inwater as Sr has chemical affinity withcarbonate minerals <strong>and</strong> enter into latticestructure of calcite. Other metal ions Cu, Cdetc. do not show significant variation.4.1 Water quality <strong>and</strong> phytoplanktonThe phytoplankton being the primaryproducers constitute the basic food sourceof the lake which supports fish <strong>and</strong> otheraquatic animals. As the lake is rich innutrients it supports a high biologicaldiversity(Melkania,1988) 7 .The macrophyticvegetation covers an area of 39,969 sq. min <strong>Renuka</strong> lake. According to Singh <strong>and</strong>Mahajan (1987) 8 the chief macrophyticgenera are Phragmites, Acorus, Typha,Carex, Pontederia <strong>and</strong> Veronica whichtotals to 42 in number. It is observed thatthe total number of phytoplankton werehigher in April <strong>and</strong> October which areindicators of pollution. In addition bluegreen algae developed in large number inOctober when the temperature of lake waterwas between 19 0 to 24 0 C but their numberdecrease in August when the temperature ofwater increased. It is observed that thenumber of Myxophycean members weredirectly correlated to the concentrations ofnitrate-nitrogen (NO 3 -N) <strong>and</strong> inorganicphosphate phosphorus. Phosphorous <strong>and</strong>nitrogen are transported into the lakethrough soil particles from agriculture l<strong>and</strong>s,animals dung, sewage discharge, <strong>and</strong>cultural activities. The higherconcentrations of dissolved inorganicphosphate phosphorus was recorded inApril <strong>and</strong> October <strong>and</strong> low in June <strong>and</strong>August which corresponds to the high <strong>and</strong>low number of phytoplankton population inthe lake (Singh <strong>and</strong> Mahajan, 1987) 8 . Weedinfestation also leads to oxygen depletion<strong>and</strong> consequent fish mortality particularlyin morning hours.5. Sediment geochemistry of <strong>Renuka</strong> <strong>Lake</strong><strong>and</strong> wetl<strong>and</strong>Among the major elements Al 2 O 3 , Fe 2 O 3 ,K 2 O <strong>and</strong> TiO 2 are enriched in wetl<strong>and</strong>compared to lake sediments <strong>and</strong> as theseshow positive correlation with Al 2 O 3 inboth the cases, it indicates a commonsource viz., phyllosilicates. The traceelements Y, Zr, Ni, Th, U <strong>and</strong> Nb areenriched in wetl<strong>and</strong> compared to lake <strong>and</strong>show similarity with Post ArcheanAustralian Shale (PAAS) indicating clayrich sediment in the wetl<strong>and</strong>. A high Zr/Hfratio of 30 for lake sediments <strong>and</strong> 33 forwetl<strong>and</strong> suggests that these elements arecontrolled by zircon since these values aresimilar to those reported by Murali et al(1983) 9 from the analysis of zircon crystals.The Zr/Yb, Zr/Th ratio are higher inwetl<strong>and</strong> sediments as compared to lakesediments though these ratios are expectedto be higher in s<strong>and</strong>stones than in shales butas the wetl<strong>and</strong> is enriched in alumina itindicates more of shale component. Thisshows mineral sorting (fractionation)during process of lighter particles (clays)being trapped in the wetl<strong>and</strong> soilconcentrating heavy minerals (zircon) insediments. This is also reflected fromnegative correlation of Gd N /Yb N with Al 2 O 3<strong>and</strong> a strong positive correlation with SiO 2in wetl<strong>and</strong> sediments. This shows that thewetl<strong>and</strong> restricts the flow of nutrients, metalions to the lake basin during catchment runoff, due to precipitation in the monsoonseason <strong>and</strong> also checks the flood water flowin the lake (Das, Birgit <strong>and</strong> Parkash,4
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