1 Marine Ecology, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, Netherlands. b.d.h.k.eriksson@rug.nl helmut.hillebrand@uni-oldenburg.de.
2 Institute for Chemistry and Biology of the Marine Environment, University of Oldenberg, Wilhelmshaven, Germany. b.d.h.k.eriksson@rug.nl helmut.hillebrand@uni-oldenburg.de.
3 Helmholtz Institute for Functional Marine Biodiversity Oldenburg and Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.