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Hydrobiologia (2012) 686:114 DOI 10.1007/s10750-012-1011-6
REVIEW PAPER
New paradigms in tropical limnology: the importance of the microbial food web
Hugo Sarmento
Received: 29 November 2011 / Revised: 10 January 2012 / Accepted: 15 January 2012 / Published online: 7 February 2012 Springer Science+Business Media B.V. 2012
Abstract Limnology has traditionally been a science of temperate regions. Long-term studies are not common in tropical regions despite the number of large tropical lakes that constitute a signicant proportion of global freshwater resources. A number of comparative studies have shown that tropical lakes are different from temperate lakes in some fundamental ways. Constantly high temperature and radiation have strong consequences for stratication and biological processes. Previous studies suggested that higher primary production on a given nutrient base in tropical lakes is related to their higher decomposition rates. Moreover, lower efciency in transforming primary production to higher trophic levels in tropical lakes also has been postulated as a difference. Data on the microbial processes in tropical lakes are scarce, but fail showing any signicant difference in epilimnetic decomposition (bacterial) processes between temperate and tropical aquatic systems. The most signicant differences found so far are in autotrophic and consumer community composition and body size, which constrain the upper compartments of the food web in a deterministic way. The reconciliation of ecological theory and observations yields a conceptual
framework that illustrates likely structural variations in food webs along the latitudinal gradient.
Keywords Heterotrophic prokaryote
Bacterial production Phototrophic picoplankton Latitudinal gradient Grazing Nanoagellates Metabolic theory of ecology Food-chain length
Introduction
So far, the most signicant advances in limnology were achieved in temperate regions. When compared to the proportion of surface fresh water in the world, the attention given by the scientic community to tropical aquatic systems is low (Descy & Sarmento, 2008). Nevertheless, numerous developing countries cover those latitudes and through regional limnology will improve our knowledge of tropical inland waters. It is likely that anthropogenic pressure on the aquatic systems in tropical countries will increase with economic growth, given that tropical lakes show a higher degree of adverse response to eutrophication or organic loading than temperate ones (Hecky, 2000; Lewis, 2000).
It is difcult to specify differences between temperate and tropical inland waters in a mechanistic way. An example of such...