Feeding habits of Noctiluca scintillans in coastal waters off Buenos Aires Province, Argentina

The diet of Noctiluca scintillans was determined using samples collected monthly at a permanent coastal station off Buenos Aires Province, Argentina (Station EPEA) from March 2000 through April 2001. A total of 1100 individuals were examined. Diatoms (27.7%), copepod eggs (24,1%), and tintinnids (17.9%) were the main prey items. The genus/species of the most abundant preys found in the N. scintillans food vacuoles were, in declining order, the tintinnids Tintinnopsis spp., Codonellopsis spp., and Tintinnidium spp.; copepod eggs of Calanoides carinatus, Ctenocalanus vanus, and Oithona nana; and the diatoms Coscinodiscus wailesii, Paralia spp., Guinardia flaccida, Thalassiosira spp., Pinnularia spp., Pleurosigma normanii, and Triceratium spp. The alimentary incidence varied between 27.5% and 77.0%, with an average of 50.2%. This index reached a high value in the month of September 2000. The correlation between the volumes of predators and preys was highly significant (r = 0.1921; P < 0.00000). The results indicated that N. scintillans is a predator opportunist.