UVR effects on nauplii from South Atlantic coastal waters (Patagonia, Argentina): Does food with high concentrations of UV-absorbing compounds make a difference?

RODRIGO J. GONÇALVES; MARIELA L. SPINELLI; RODRIGO D. HERNÁNDEZ MORESINO; VIRGINIA E. VILLAFAÑE; FABIANA L. CAPITANIO; E. WALTER HELBLING

Pucon

Simposio; 5th International Zooplankton Production Symposium; 2011

Zooplankton larvae are commonly considered to be sensitive to ultraviolet radiation (UVR, 280-400 nm), which may cause mortality, impaired locomotion, and impaired feeding. Zooplankton may obtain protection via bioaccumulation of UV-absorbing compounds from their prey. In order to test the importance of bioaccumulation of UV-absorbing compounds in protecting copepods against UVR, nauplii were collected in surface waters and fed, at in situ temperature for 24 hours, under one of four different food treatments: a) cells < 20 ìm from natural phytoplankton; b) cultures of Chaetoceros sp., c) cultures of Prorocentrum micans, and d) a control of filtered water (0.22 ìm). After feeding, the nauplii were exposed to UVR and PAR (400-700 nm) for 4 hours (irradiances of 0.7, 48 and 164 W m-2 for UVB, UVA and PAR, respectively), using two radiation treatments (UVR+PAR and PAR). Motility and behavior were recorded continuously before, during, and after exposure. The concentration of UVR-absorbing compounds (estimated spectrophotometrically) had higher values in larvae fed with natural phytoplankton (cells < 20 ìm) and with P. micans than in the other two treatments. There were no significant effects of UVR on mortality or swimming speed in any of the four food treatments, but UVR-exposed nauplii showed less activity near the surface than those exposed only to PAR. In the field, short term exposure (i.e., 24 hours) to algae rich in UV-absorbing compounds may not be enough for nauplii to bioaccumulate significant amounts of these substances, and thus they might rely on other alternatives such as swimming to deeper waters.