Implications of global climate change for the development and ecological interactions between two key Amazonian aquatic macrophytes

ABSTRACT Amazon wetlands are among the most vulnerable ecosystem to be impacted by climate change, which may increase the frequency of extreme droughts and floods. We used Eichhornia crassipes and Pistia stratiotes, two abundant aquatic plants in the Amazon floodplains, to evaluate the effects of combined temperature and [CO2] increase on growth, physiology and ecological interactions. Individual and paired plants were deposited for three weeks in a microcosm under four IPCC scenarios: control (current temperature/CO2), mild (control + 1.5 ºC, 200 ppm CO2), intermediate (control + 2.5 ºC, 450 ppm CO2) and extreme (control + 3.5 ºC, 850 ppm CO2). P. stratiotes died after three weeks in the intermediate and extreme treatments; E. crassipes experienced no mortality or change in any of the measured variables during the same period. P. stratiotes reduced root length in the mild treatment and reduced total dry biomass in intermediate and extreme treatments, revealing less tolerance to climate change. Ecological interactions between the two species changed with increasing [CO2] and temperature neutral interaction changed to facilitation for E. crassipes, while competitive interaction changed to neutral for P. stratiotes. Global climate change may alter the composition, biomass and ecological interactions of Amazonian aquatic plant species.