Classical and microbial pathways remain as a useful dichotomy for distinguishing the several fates of primary production in aquatic ecosystems. In most of our idealized concepts of food-web, we tend to separate profoundly between the photosynthetic and the heterotrophic organisms in the predatory food-web. This division is not necessarily adequate descriptions of reality since there are known ... organisms able to combine nutrition types, and complicate our traditional view about aquatic food-webs. One complicating factor that is receiving increasing attention is the influence of ?mixotrophs?, organisms that defy traditional trophic concepts classification by both photosynthesizing and grazing. In addition, ?omnivory?, the consumption of resources from more than one trophic level, is a widespread behavior among planktonic organisms.
Evidences for shifting trophic roles of various types of planktonic organisms and multiple levels of feeding interactions within mixotrophs and omnivorous components, which typically have been regarded as a single trophic level have increased during the last decade. By using field and experimental approaches, we propose to elucidate the potential role of ?mixotrophy? and ?omnivory? to the carbon flows in a river-influenced and non-river influenced continental shelf off Central Chile. Primary production, bacterial production, autotrophic, heterotrophic and mixotrophic biomasses, as well as, measurements of grazing by nanoflagellates, microzooplankton, and mesozooplankton are conducted under contrasting conditions during sprig and winter. Ongoing food-web analysis of the spring condition during coastal upwelling events, and under the influence of the river discharge will be discussed, as well as, the implications of mixotrophy and omnivory in the structure and ecosystem functioning.