Causes of the disappearance of the aquatic plant Egeria densa and black-necked swans in a Ramsar sanctuary: comment on Mulsow & Grandjean (2006)

Abstract

In an attempt to demonstrate the ultimate causes of the massive mortality and emigration of blacknecked swans at the Ramsar site Carlos Anwandter Nature Sanctuary, Mulsow & Grandjean (2006, available at: www.int-res.com/articles/esep/2006/E66.pdf) used field data, microcosm experiments and basic chemical theory, to postulate that calcium bicarbonate is removed from water, due to the increase in sulphate by the effluent of the pulp mill of CELCO, Valdivia, Chile. This process is deemed to affect the photosynthetic rate of the plant Egeria densa, the main food of the black-necked swans, which in turn provokes the known mortality and emigration of these birds from this site. We critically analyzed the study of Mulsow & Grandjean (2006), and we found a serious lack of consistent arguments that precludes any fundamental statement about the effects of sulfate and bicarbonate on E. densa. Here we discuss our concerns.