Population dynamics of rotifers in the floodplain of river Ravi,Pakistan

The population dynamics of rotifers of a flood plain ecosystem are supposed to change with mixing of flood water from riverine system,during floods. with respect to biodiversity,floodplain ecosystem remained ignored and no work has been done in pakistan. with the aim to identify monthly changes in the population of rotifer communities in a flood plain,rotifers were estimated through studying the monthly variations of density and diversity of rotifers,from january to december 2012,in the floodplain of river ravi near balloki headworks,pakistan. a total of 101 species belonging to 32 genera,15 families and 3 orders were identified from 15 different sites. family brachionidae dominated among all (56%) with the brachionus,anuraeopsis and keratella being the most important genera in family brachionidae. rotifer density was highest from april to june 2012. rotifer density showed a positive correlation with air and water temperature,ph,turbidity and total hardness and strong positive correlation with electrical conductivity,total dissolved solids (tds) and total alkalinity. similarly a negative correlation existed between rotifer density and visibility and chlorides and strong negative correlations with dissolved oxygen. analysis of variance showed a significant difference in rotifers between different months and sites. shannon diversity index (h) showed high species diversity in august and lowest diversity in november. simpson index of dominance showed lowest diversity in november. species richness was highest in august and lowest in april. species evenness was highest in april and lowest in november. it is summarized that density of rotifers remain highest during summer,when plenty of food is available where as diversity of rotifers reaches to its maximum when riverine water,carries variety of rotifers,mixes with the stagnant and isolated flood plain water.