Lethal Effects of Ultraviolet Radiation Under Different Concentrations of Dissolved Organic Carbon On Neobosmina Chilensis (Daday, 1902) (Cladocera, Bosminidae)

Abstract

The increase in the penetration of ultraviolet radiation that has been reported lately for freshwater ecosystems in southern South America, would allegedly generate alterations in ecological processes. In the present study, the mortality of Neobosmina chilensis (Daday 1902), a small cladoceran distributed in South American lakes and ponds, was studied in this respect. Specimens were reared in five different concentrations of dissolved organic carbon, and subjected to 24 hrs of exposure to artificial ultraviolet radiation.An inverse correlation between the dissolved organic carbon concentration and individual mortality was found. This result supports the description of a screen effect of dissolved organic carbon against ultraviolet radiation. The data obtained describe a linear relation, in which LC 50 corresponded to 4.43 mg/l of dissolved organic carbon. The ecological implications of this result are discussed. RESUMENEl incremento de la penetración de la radiación ultravioleta ha sido reportado para ecosistemas lacustres en el sur de Sudamérica, y genera alteraciones en procesos ecológicos. En el presente trabajo, se estudió la mortalidad de Neobosmina chilensis (Daday, 1902), un cladócero de pequeño tamaño corporal distribuido en lagos y lagunas de América del Sur. Los especímenes fueron mantenidos por 24 horas bajo cinco concentraciones de carbono orgánico disuelto, y con exposición a radiación ultravioleta artificial.Se observó una relación inversa notoria entre la concentración de carbono orgánico disuelto y la mortalidad individual. Este resultado respalda la propuesta que el carbono orgánico disuelto genera un efecto protector contra la radiación ultravioleta. Los resultados describieron LC 50 correspondió a 4.43 mg/l of carbono orgánico disuelto. Se discutieron las implicancias ecológicas de los resultados obtenidos.

Short term effects of exposition to artificial ultraviolet radiation on Parabroteas sarsi (Copepoda, Calanoida)

“…The exposition to UV radiation in shallow Patagonian water bodies is enhances due the exposition to strong winds that generate mixing of the whole water column and exposing all planktonic living organisms to different levels of UV radiation (Zagarese et al 1998a, b). The results of this study indicate that P. sarsi is tolerant to exposition to UV radiation, and are consistent with other similar studies on calanoid species of water bodies of the southern part of South America (Zagarese et al 1997a, b;De los Ríos 2004, 2005a. Moreover, P. sarsi is more tolerant to UV radiation at starvation conditions ( (Zellmer 1998(Zellmer , 1996De los Ríos 2005a;De los Ríos & Soto 2005.…”