Effect of microcrustaceans on blue-green algae in flooded soil

The ostracod Cypris sp., when present in large numbers, prevented the development of inocula of Tolypothrix tenuis and suppressed inocula of Anabaena sp. added to flooded soil. The waterflea Daphnia magna, when present in large numbers, only had a minor influence on the growth rate or extent of development of these algae. Anabaena sp. was less susceptible than T. tenuis to the two microcrustaceans. It is suggested that grazing by certain microcrustaceans may limit nitrogen fixation by algae in flooded rice fields.