Land-use  effects  on  ecosystem  structure  and  function of tropical Cerrado streams (2005-2008)

(Project together with Björn Gücker)

The  tropical  Cerrado  savannah,  the  second-largest  of  all  South American  ecosystems, is undergoing the most rapid land-use changes on the  continent,  including  wholesale  shift  from  native vegetation to grazing  and  cropland,  but the consequences for ecosystem health are largely  unknown. In this project, we investigate the effects of  land-use changes and contemporary cultural eutrophication on ecosystem structure and function (community composition, elemental stoichiometry and biochemistry of aquatic biofilms, as well as whole-stream nutrient uptake  and ecosystem metabolism) in as-yet unstudied tropical Cerrado streams.

Variation in the rate at which organic carbon is transferred across trophic levels in aquatic food webs is quite large. This may be partially related to differences in the nutritional quality of planktonic prey organisms. Organic carbon is allocated into various biochemical molecules that differ greatly in their energy content and essentiality for zooplankton predators. Thus, the biochemical composition of planktonic prey organisms is an efficient tool to evaluate their nutritional quality. Among the most important compounds conferring nutritional quality on planktonic prey organisms are essential fatty acids, amino acids, and sterols. Although it has been widely accepted that heterotrophic protists are an important link between the microbial and the classical food web, relatively little is known about their biochemical composition and resulting nutritional quality as prey.

In my PhD thesis I have investigated two main aspects of the biochemical composition of protists: (1) whether the biochemical composition of the protists depends on their dietary resources or on their trophic mode; and (2) how the biochemical composition of protists determines their nutritional quality as prey for rotifers.

Full Text (PDF):

http://edoc.hu-berlin.de/dissertationen/goncalves-boechat-iola-2005-02-15/PDF/Goncalves-Boechat.pdf