NIOZ discovers new predator-prey relation in the sea

14-02-2013  It all started with a failed experiment. When Dr Louis Peperzak (NIOZ, IVM and VU University Amsterdam) wanted to analyse the growth of Emiliania huxleyi in a lab experiment, the microscopic algae did not grow, but disappeared from the water. After the most likely causes had been ruled out, such as the absence of the nutrient nitrogen, microscopic research showed that the water had been contaminated with a species of zooplankton. Experts identified this organism as Uronema marinum. Is Uronema a predator feeding on Emiliania?

No, it cannot be, as Uronema feeds on much smaller bacteria. A follow-up study with Fokje Schaafsma, student at the University of Groningen, solved the mystery. Today (14 February 2013), the journal Marine Ecology Progress Series will publish the results of this study.* Uronema turns out to secrete a poisonous substance that kills algae that are too big to be eaten. Dead algae secrete organic carbon, a source of food for bacteria. Uronema then eats these bacteria. In this roundabout way, Uronema can feed on algae that are too big to eat directly. This new predator-prey relation raises a number of further questions for a new research project, such as what is the Uronema poison made up of and what are its effects.


* Marine Ecology Progress Series 2013-475, pp. 35-48: ‘Phytoplankton growth inhibition by the toxic and bacterivorous ciliate Uronema marinum (Protozoa, Ciliophora)’. F.L. Schaafsma and L. Peperzak.
http://www.int-res.com/articles/meps2013/475/m475p035.pdf
or DOI: 103354/meps10124











Figure: Uronema marinum (ciliates) secretes poison that kills phytoplankton. Organic carbon (DOM) is subsequently released into the water, which enables bacteria eaten by Uronema to grow.