Publication Details

Category Text Publication
Reference Category Journals
DOI 10.1073/pnas.2130696100
Title (Primary) Mixotrophs combine resource use to outcompete specialists: implications for aquatic food webs
Author Tittel, J.; Bissinger, V.; Zippel, B.; Gaedke, U.; Bell, E.; Lorke, A.; Kamjunke, N.
Source Titel Proceedings of the National Academy of Sciences of the United States of America
Year 2003
Department SEEFO; FLOEK; UV
Volume 100
Issue 22
Page From 12776
Page To 12781
Language englisch

The majority of organisms can be grouped into those relying solely on photosynthesis (phototrophy) or those relying solely on the assimilation of organic substances (heterotrophy) to meet their requirements for energy and carbon. However, a special life history trait exists in which organisms combine both phototrophy and heterotrophy. Such "mixotrophy" is a widespread phenomenon in aquatic habitats and is observed in many protozoan and metazoan organisms. The strategy requires investment in both photosynthetic and heterotrophic cellular apparatus, and the benefits must outweigh these costs. In accordance with mechanistic resource competition theory, laboratory experiments revealed that pigmented mixotrophs combined light, mineral nutrients, and prey as substitutable resources. Thereby, they reduced prey abundance below the critical food concentration of competing specialist grazers [Rothhaupt, K. O. (1996) Ecology 77, 716-724). Here, we demonstrate the important consequences of this strategy for an aquatic community. In the illuminated surface strata of a lake mixotrophs reduced prey abundance steeply. The data suggest that, as a consequence, grazers from higher trophic levels, consuming both the mixotrophs and their prey, could not persist. Thus, the mixotrophs escaped from competition with and losses to higher grazers. Furthermore, the mixotrophs structured prey abundance along the vertical light gradient, creating low densities near the surface and a pronounced maximum of their algal prey at depth. Such deep algal accumulations are typical features of nutrient-poor aquatic habitats, previously explained by resource availability. We hypothesize instead that the mixotrophic grazing strategy is responsible for deep algal accumulations in many aquatic environments.

Persistent UFZ Identifier
Tittel, J., Bissinger, V., Zippel, B., Gaedke, U., Bell, E., Lorke, A., Kamjunke, N. (2003):
Mixotrophs combine resource use to outcompete specialists: implications for aquatic food webs
Proc. Natl. Acad. Sci. U.S.A. 100 (22), 12776 - 12781 10.1073/pnas.2130696100