KOPPRIO German Adolfo
congresos y reuniones científicas
Essential fatty acids as ecological indicators in plankton food webs: a case study in a brackish lake of Argentina
KOPPRIO, G. A.; KATTNER, G.; FREIJE, R. H.; LARA, R. J.
Figueira da Foz
Simposio; Integrative tools and methods in assessing ecological quality in estuarine and coastal systems worldwide; 2010
IMAR-Institute of Marine Research (U.Coimbra) and CO-Centre of Oceanography (U.Lisbon)
Lake Chasicó is an enclosed coastal water body and can be classified as eutrophic according to the Carlson index. This brackish lake has favored the exceptional growth and abundance of Odontesthes bonariensis, a zooplanktivorous and commercially important fish. Growth and reproduction of fish and zooplankton can be limited by essential fatty acids (EFA). EFA are mostly synthesized by phytoplankton and transferred unchanged through the aquatic food web. The most important EFA, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), vary strongly in seston with the trophic state of lakes. The short food web of Lake Chasicó from phytoplankton via a few species of zooplankton to fish allows tracing the fatty acid transfer from the seston fractions (microplankton and nanoplankton) to zooplankton. The percentage and content (µg mg C-1) of EFA were mostly higher in zooplankton. Higher concentrations (µg L-1) of EFA were found in the nanoplankton fraction, accounting for 53.3% of the total amount of all seston fractions. The EFA transference efficiency was high. The mean content of DHA and EPA (2.3 and 2.5 µg mg C-1, respectively) in the nanoplankton fraction in relation to the trophic state was higher than the values calculated by empirical relationships. This phenomenon could be associated to the high flagellate dominance, which are generally rich in DHA. Moreover, moderate salinities (~20) can also favor the fatty acids synthesis of phytoplankton. We propose to consider the efficiency of biomass and energy (lipid) transfer through the food web to assess the health of aquatic environments and suggest an index based on the EFA seston content.