(Introduction):

Shallow wetlands are relevant for waterfowl; they are currently affected by climatic changes and nutrients derived from agriculture. This has been associated with outbreaks of avian botulism.

(Objective):

Identify changes in wetlands that can lead to botulism outbreaks, as well as identify the source of nutrients that may contribute to an eutrophic state.

(Methodology):

Evaluation of biotic characteristics (diversity of zooplankton and macroinvertebrates) and physicochemical characteristics (dissolved oxygen, temperature, total dissolved solids and transparency) in 3 shallow wetlands (Silva, Coyote and Trancas) in central Mexico, as well as evaluation of values of stable isotopes of carbon (δ13C) and nitrogen (δ15N) from organisms, in order to detect the input of nutrients to the aquatic ecosystem.

(Results):

There was a decrease in zooplankton and invertebrate diversity as well as a decrease in water level and transparency at all 3 sites. The values of dissolved oxygen, temperature and total dissolved solids were different in the 3 sites. Values of stable carbon (δ13C) and nitrogen (δ15N) isotopes from Silva and Coyote organisms coincide with values of stable isotopes found in sewage, fertilizers and grains such as corn and wheat.

(Conclusion):

Wetlands in the study site registered biotic and physicochemical changes along the year. In Silva and Coyote water fluctuations, human activities and finally the arrive of thousands of migratory birds, produce an accumulation of dead organic matter and nutrients that made the system eutrophic and therefore more prone to present recurrent avian botulism outbreaks.