Rodriguez, C.A., H.I. Browman, J.A. Runge & J.F. St. Pierre. (2000). Impact of solar ultraviolet radiation on hatching of a marine copepod, Calanus finmarchicus. Marine Ecology Progress Series. 193:85-93.

110885

Rodriguez, C.A., H.I. Browman, J.A. Runge & J.F. St. Pierre

2000

193:85-93.

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The calanold copepod Calanus finmarchicus 1s a key component of the zooplankton com- munity in the estuary and Gulf of St. Lawrence, Canada. During the spring and summer months, C. fir- marchicus eggs are released into the shallow (0 to 15 m) mixed surface layer, where they incubate for 1 to 3 d. Radiometric measurements in this region show that biologically significant levels of solar ultra- violetradiation (UV=280to400nm)penetrate intothemixedsurfacelayer.Thus,C.finmarchicuseggs are potentially susceptible to UV-induced mortality. This possibility was evaluated by incubating C.fin- marchicus eggs in an outdoor reservoir under natural sunlight. There were 3 spectral exposures regimes [UV-B(280-320 nm)+UV-A (320-400 nm)+PAR (400-700 nm);UV-A+PAR;PAR only].Con- trol groups were kept in the dark. Incubations were conducted at depths of 2 and 60 cm and the per- centage of eggs that hatched was determined following 2 to 3 d exposures in 3 independent experi- ments. Both the UV-BtUV-A+PAR and the UV-A+PAR treatments exhibited low percent hatching compared to the PAR and dark treatments: UV radiation had a strong negative impact on C. fin- marchicus eggs. Further, percent hatching in UV-B-exposed eggs was not significantly lower than that in eggs exposed to UV-A only: under natural sunlight, W - A radiation appeared to be more detrimen- tal to C. finmarchcus embryos than W - B . UV penetration into the experimental reservoir was similar to that observed in estuarine waters of this region, but lower than the clearer waters of the Gulf of St. Lawrence. This suggests that, at current levels of exposure, UV radiation has a negative effect on C. finmarchicus eggs residing in the first few meters of the water columns in this geographic region.

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