P. Fink et al.
Archiv für Hydrobiologie 165(2): 146-165 (2006)
Stoichiometric mismatch between littoral invertebrates and their periphyton food.
P. Fink1, L. Peters2 and E. Von Elert2
1Department of Physiological Ecology, Max-Planck-Institute for Limnology, Ploen, Germany
2Limnological Institute, University of Konstanz, Konstanz, Germany
Ecological stoichiometry is considered a key concept in understanding constraints in energy
transfer at the plant-herbivore interface. However, whether this concept is relevant for benthic
freshwater ecosystems is not fully known. Therefore, a field survey was conducted in 2003 during
the growing season in the littoral zone of Lake Constance, a large pre-alpine lake in central Europe.
The aim was to assess temporal variation in the elemental stoichiometric composition in both
herbivorous macroinvertebrates and their food resource, the periphyton in two different lakes.
The periphyton showed large temporal and spatial variation in carbon, nitrogen, and phosphorus
content, with particularly high molar C:P ratios of up to 1225:1. Periphyton C:P and C:N ratios
were often high and constantly above the Redfield ratio that is considered optimal for autotrophic
growth. In contrast to the pronounced fluctuations in the nutrient ratios of their food resource,
the herbivorous macroinvertebrates showed only very little variation in their nutrient ratios,
which indicated that they are homeostatic, i.e., physiologically restricted to a comparatively
narrow range of C:P and C:N ratios. Distinct species-specific C:P and C:N ratios were found for
different taxonomic groups of macroinvertebrates, which indicated different requirements of optimal
dietary C:P and C:N ratios and which might influence the ability of the taxa to compete for limiting
elemental nutrients. Considering the temporally very high C:P and C:N ratios of the periphytic
resource and the very low ratios of the consumer body tissue, this stoichiometric mismatch is
likely to constrain growth and reproduction of these littoral invertebrates. Therefore, the concept
of stoichiometric food quality limitation might also be applicable to the littoral food web in lakes.