Limnetica 31

As early as 1951, Margalef speculated on the production of soluble phosphatases by zooplankton; “entomostracans” were producing their own phosphatases and so contributing to phosphate regeneration. After analytical techniques had been considerably improved and introduced into limnology laboratories, it was verified, almost three decades later, that the eminent scientist was right. The role of soluble phosphatase in fresh waters can be investigated either in straight relationship to plankton phosphatase producers or simply in connection with other chemical entities abundant in lake water, with capacity to condition enzyme activity. Such is the case of humic substances which complex with soluble phosphatase; the enzyme activity will be inactivated when making part of the complex (linked to the humic molecule) and reactivated again once the complex is broken down, e.g. by the action of UV light from the sun.