EFFECT OF SOLAR RADIATION ON THE DISAPPEARANCE OF EGERIA DENSA (HYDROCHARITACEAE) IN THE WETLANDS OF THE CRUCES RIVER (VALDIVIA, CHILE)

Abstract

Background: The submersed macrophyte Egeria densa Planch., locally known as "luchecillo", disappeared from the wetlands of Rio Cruces or Nature Sanctuary Carlos Anwandter (Valdivia, Chile) in October 2004. It was established that this phenomenon occurred due to the chemical pollution coming from industrial origin. Objectives: Analyze an alternative hypothesis that identifies the increase in the intensity of solar radiation as the cause of the reduction of Egeria densa populations, especially in the UV region. Methods: Cultures of Egeria densa were covered by Raschel mesh, mylar filter, acetate filter, while one of the cultures was not covered. During the experiment the Egeria densa chlorophyll content was determined by a SPAD-meter. Results: The experimental study showed that the damage was not likely to be attributed to UV radiation. However, it was determined that the intensity of solar radiation affected the development of Egeria densa by reducing chlorophyll content in direct proportion to exposure time. Conclusions: An increase in sunlight intensity or other unknown radiation could have caused the death of Egeria densa in shallow waters. The absence of a protective epidermis that filters certain wavelengths in Egeria densa leaves could facilitate the deleterious effect of radiation under prolonged exposure at low tide.