MEPS 193:85-93 (2000)  -  doi:10.3354/meps193085

Impact of solar ultraviolet radiation on hatching of a marine copepod, Calanus finmarchicus

Carolina Alonso Rodriguez1,2, Howard I. Browman1,*, Jeffrey A. Runge1, Jean-François St-Pierre1

1Maurice-Lamontagne Institute, Department of Fisheries and Oceans Canada, Division of Ocean Sciences, PO Box 1000, 850 Route de la Mer, Mont-Joli, Québec G5H 3Z4, Canada
2Département d'océanographie, Université du Québec à Rimouski, 310, allée des Ursulines, Rimouski, Québec G5L 3A1, Canada
*Corresponding author. Present address: Institute of Marine Research, Aquaculture Centre, Austevoll Aquaculture Research Station, 5392 Storebø, Norway. E-mail:

ABSTRACT: The calanoid copepod Calanus finmarchicus is a key component of the zooplankton community in the estuary and Gulf of St. Lawrence, Canada. During the spring and summer months, C. finmarchicus 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 ultraviolet radiation (UV = 280 to 400 nm) penetrate into the mixed surface layer. Thus, C. finmarchicus eggs are potentially susceptible to UV-induced mortality. This possibility was evaluated by incubating C. finmarchicus 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]. Control groups were kept in the dark. Incubations were conducted at depths of 2 and 60 cm and the percentage of eggs that hatched was determined following 2 to 3 d exposures in 3 independent experiments. Both the UV-B+UV-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. finmarchicus 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, UV-A radiation appeared to be more detrimental to C. finmarchicus embryos than UV-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.

KEY WORDS: UV-B · UV-A · Ozone depletion · Estuary and Gulf of St. Lawrence · Secondary production

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