This would be expected to occur in situations with a low carbon: mineral nutrient ratio in the bacteria (Jurgens and Gude 1990), situations where the mixotroph would benefit greatly from its ability to compensate for the lack of carbon in the prey by photosynthesis.
We found that, when the rest of the environment and the physiology of the other trophic partners in the ecosystem are defined, there are specific mixotroph strategies that would be optimal to the mixotrophs in the sense that mixotroph biomass is maximized.
All protists will have a loss rate equal to the dilution rate, and the algal or mixotroph uptake of mineral nutrients will therefore keep the nutrient concentration low (from the requirements that [[Mu].sub.A](N) = D and/or [[Mu].sub.M](N, B) = D where [Mu] is the specific growth rate).
M: Concentration limiting nutrient conained in mixotroph biomass
Because mixotrophs play a minor role in the conceptual framework, they are most often not considered.
The relative importance of the photoautotrophic and phagotrophic modes of nutrition in the mixotrophs is species specific and varies as a function of environmental parameters like particle density, light (Sanders et al.
In the field, mixotrophs can compete with heterotrophs for the uptake of food particles and with phototrophs for light and mineral nutrients.
Two qualitatively different interactions between mixotrophs and obligate phototrophs are possible.
The possibility of both competition and facilitation by mixotrophs has implications for nutrient dynamics in microbial food webs.
At low light intensities (sectors II and III), the heterotrophic flagellates are predicted to be superior and to exclude the mixotrophs, With sufficient light intensities and low bacterial supply (sectors V and VI), the mixotrophic flagellates should be superior.
Depending on the growth conditions, mixotrophs can take up or release SRP (Rothhaupt 1996).