Mangroves in the Change: The Need of New Synthesis of Climate, Ecohydrology and Biomedical Research

LARA, R.J.

Mangroves: Ecology, Biology and Taxonomy

. Nova Science Publishers, Inc.

Lugar: New York; Año: 2010; p. 287 - 295

Besides the classical ecological, hydrological and biogeochemical studies, microbiological investigations in mangroves have been hitherto mostly related to material transformation and fluxes, and little is known about pathogen dynamics in their different compartments. South Asia and Brazil embrace the largest unitary mangroves worldwide. Although Sunderbans mangroves have been related since ancient times to endemic cholera, there are no systematic studies establishing causal links between the yearly hydrological and biogeochemical cycles in its waters and the seasonal dynamics of Vibrio cholerae. In Amazonia, although this region has been affected by cholera in the past, the disease never developed an endemism as around the Bay of Bengal.A comparison between Sunderbans and Amazonian mangroves as Vibrio habitats would provide a deeper insight into the links between wetland dynamics, pathogen diversity and incidence of diarrheal diseases. The environmental setting of both regions is similar: large mangroves, high riverine discharge and sediment load. Thus, a major question is: Why is cholera endemic in mangrove regions in South Asia and not in tropical South America? Is this mainly a biodiversity, biogeochemical or social/demographic issue? Mangrove waters and sediments are rich in chitinaceous organisms, such as zooplankton, shrimps and crabs. V. cholerae can acquire new genetic material by natural transformation during growth on chitin. Thus, natural competence occurring in chitin-attached bacterial communities can act as driver of V. cholerae?s evolution, and the natural chitin abundance in mangroves can favor pathogen mutations. Further, aquaculture in or close to mangroves is increasing worldwide and vibrioses are common diseases affecting shrimp ponds. Thus, aquaculture can play a double role in Vibrio dynamics in mangroves: by the high density of chitinaceous substrate and by the pathogen abundance in the ponds. Further, dam construction ?and likely sea-level rise- facilitates salt intrusion into Bay of Bengal estuaries, resulting in land use shifts from rice cultivation to shrimp farming. Nothing is known about these interactions or about the effect of increasing eutrophication on pathogen dynamics in mangroves. Another knowledge gap is the dynamics of mangrove regeneration under conditions of increasing storm frequency and intensity or after a tsunami. A discussion about a new paradigm on the stability of aquatic ecosystems is urgently needed. Natural mangrove regeneration may not keep pace with a higher incidence of catastrophic events and with the dynamics of human communities relying on coastal resources for subsistence. Sustainability is necessary but not enough, and it is crucial to get endangered coastal regions on a pathway to increased robustness. Thus, the knowledge on techniques for regeneration of degraded mangrove ecosystems or creation of new forests along endangered coastal stripes has to be improved, as well as the understanding of the consequences of introducing such changes in the environmental setting.