CHELATABLE IRON IN THE SUBTROPICAL LAKE KINNERET - ITS SEASONAL-VARIATION AND IMPACT ON CARBON UPTAKE BY NATURAL ALGAL ASSEMBLAGES AND MONOALGAL CULTURES

The concentrations of chelatable iron in Lake Kinneret, defined as the fraction bound by 8-oxyquinoline (oxine) ranged in the euphotic zone between 0.24 and 2.36 mu g 1(-1). This iron species represented an ave rage of 8.1 and 5.0% of dissolved ionic (Fe-i) and total iron (Fe-t), respectively. Removal of the chelatable iron by oxine additions to lak e water samples reduced C-14 uptake by up to 87% of the control value. The impact of oxine addition was low when the lake phytoplankton was dominated by the dinoflagellate Peridinium gatunense and particularly high when the cyanophyte Aphanizomenon ovalisporum was the most abunda nt phytoplankton. The impact of oxine was most prominent near the wate r surface and declined with depth. Experiments showed that cultures of Peridinium and diatoms were significantly less sensitive to oxine iro n binding than chlorophytes and cyanophytes, thus matching the finding s with natural assemblages.