FATTY-ACIDS AS TROPHIC MARKERS OF PHYTOPLANKTON BLOOMS IN THE BAHIA-BLANCA ESTUARY (BUENOS-AIRES, ARGENTINA) AND IN TRINITY BAY (NEWFOUNDLAND, CANADA)

The fatty acid compositions of phytoplankton and major primary consume rs were analyzed during the development of seasonal algal blooms in th e Bahia Blanca estuary, situated on the southern coast of the province of Buenos Aires (Argentina), and Trinity Bay. at Sunnyside, on the ea stern coast of Newfoundland (Canada). Primary consumers in the Bahia B lanca estuary were zooplankton dominated by the calanoid copepod Acart ia tonsa. At Sunnyside, the primary consumers were the sea scallop Pla copecten magellanicus. an ecological and economical important benthic bivalve. The study shows that in spite of obvious differences between the two environments and the analytical approaches employed in each ca se, the analyses of fatty acid biomarkers can provide relevant ecologi cal information. The fatty acid composition of the lipids of Bahia Bla nca phytoplankton (high concentrations of the fatty acids 14:0. 16:1 o mega 7, 16:4 omega 1, and 20:5 omega 3) reflected the presence of diat oms as a major component throughout the bloom. Patty acid markers of t he post-bloom phytoplankton in Bahia Blanca indicated a decline of phy toplankton biomass, and a relatively high input of detritus and terres trial plant materials to the particulate organic matter of the estuary . Linoleic acid (18:2 omega 6), a typical ''terrestrial'' fatty acid, was conspicuous in the lipids of the post bloom particulate matter of the Bahia Blanca estuary; 18:2 omega 2 was subsequently incorporated i nto zooplankton lipids. Diatom markers were also prominent in the lipi ds of pre-bloom and bloom phytoplankton at Sunnyside: post-bloom phyto plankton showed higher proportions of 18:0, 18:1 omega 9, and 18:4 ome ga 3, characteristic and often major fatty acids of dinoflagellates. T he fatty acids of the digestive gland of P. magellanicus reflected the fatty acid composition of the phytoplankton, whereas those of the add uctor muscle were practically unaffected by the composition of the foo d. This organ-specific response of an animal to the fatty acid composi tion of the diet is examined in terms of different applications of the fatty acid marker concept. (C) 1997 Elsevier Science Ltd.