Uptake of [32P]orthophosphate by algae adn bacteria in Lake Kinneret

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Abstract
Differential filtration was used to apportion [ 32 p]orthophosphate (P 1 ) uptake to predominantly bacterial (3 μm) components of Lake Kinneret microplankton. Bacteria generally showed preferential 32 P i uptake in comparison with algae. Nevertheless, in most cases, the relative proportion of 32 P counts retained on 3 μm filters was greater than the proportion of 14 C counts from heterotrophic bacterial incorporation of [ 14 Clglucose, indicating that algae were competing for P i with bacteria with some measure of success. Most time course experiments did not show any consistent transfer of 32 P from bacteria to algae. The addition of a bacterial inhibitor (garamycin) caused a relative increase in the proportion of algal to bacterial 32 P i uptake. Added organic P substrates lowered the amount of 32 P i uptake and appeared to be preferentially utilized by bacteria. Apparent residence times for P i in Lake Kinneret ranged from 0.4 h (prior to overturn) to 17.4 h during bomothermy. Despite low ambient P i concentrations, P limitation in Lake Kinneret is not as extreme as in many other aquatic environments.