QUANTITATIVE IMPORTANCE OF PARTICULATE MATTER RETENTION BY THE ROOTS OF EICHHORNIA-CRASSIPES IN THE PARANA FLOODPLAIN

The amounts of organic and inorganic particulate matter retained by th e roots of the floating macrophyte Eichhornia crassipes (Mart.) Solms were followed for 17 months at two sites in the floodplain of the Para na river. The average particulate matter burden associated with the ro ots was 925 g m-2 in a lake located near (0.3 km) the main river chann el, and 511 g m-2 in the lake located farther (2 km) from the river. A t low water, floating meadows in the distal lake retained more coarse particulate organic matter than those of the proximal lake. At high wa ters, inorganic sediment retention by the roots was much higher (1326 g m-2) in the proximal lake than in the distal lake (179 g m-2). Illit e was the most abundant clay mineral associated with the roots and was supplied by the Paraguay-Bermejo rivers. Organic and inorganic sedime nt retention by the roots of E. crassipes floating meadows may represe nt a significant fraction of the annual nutrient demand by the meadows .