Lake fertility: effects of nutrient pulses

Posted on May 26, 2009

How does the timing of nutrient inputs, as opposed to the total nutrient input over a given period, affect the make-up of freshwater communities? U.S.scientists ran an experiment in which 24 wetland mesocosms containing topsoil and well water were first inoculated with phytoplankton, periphyton, macrophytes, zooplankton, benthic invertebrates and associated microbes, and then fertilized with different nutrient regimes.  As the nutrient load was increased, the biomass of filamentous algae rose but the biomass of macrophytes fell.  However, these responses were strongest when nutrients were added at regular intervals, rather than all at one time.  It seems possible that when supplies of dissolved nutrients are more continuous, algae in the water column are better placed to exploit them than the roots of macrophytes below the sediment surface.

Reference: Butzler, J. & Chase, J.  2008.  The effects of variable nutrient additions on a pond mesocosm community.  Hydrobiologia, 617, 65-73.

Posted in: nutrients, production