Variation in nitrogen and carbon isotopes in the Bah¨ªa Blanca Estuary: Implications for ecological study in planktonic food web

BIANCALANA, F.; DUTTO, M. S.; KOPPRIO, G.; LARA, R. J.; HOFFMEYER, M.S.

Pucon, Chile

Simposio; 5th International Zooplankton Production Symposium; 2011

Variation in nitrogen and carbon isotopes in the Bah¨ªa Blanca Estuary:Implications for ecological studyin planktonic food web. Florencia Biancalana1, M. Sof¨ªa Dutto1, Germ¨¢n A. Kopprio2,Rub¨¦n J. Lara2andM¨®nica S. Hoffmeyer11Instituto Argentino de Oceanograf¨ªa (CONICET-UNS). La Carrindanga Km. 7,5, B8000FWB Bah¨ªa Blanca, Argentina. e-mail: biancaf@criba.edu.ar2 Wetland Biogeochemistry, Leibniz Center for Tropical Marine Ecology, Fahrenheitstrasse 6, 28359 Bremen, Germany. Although stable carbon and nitrogenisotopes are widelyused in marine ecosystemresearch, this study presents thefirst report on theirvariation in the Bah¨ªa Blanca Estuary. Sampling was carried out in stations with high (Canal Vieja:CV) and low human impact(Bah¨ªa del Medio: BM), during the phytoplankton bloom (winter) and in the post-bloomperiod (spring-summer). Surface water, plankton samples and environmental variables measurementswere obtained.Isotopic data were analysed using a multivariate approach.In winter, ¦Ä13Cvalues varied from -23.98to -19.706¡ëin CVand from -23.389 to -19.09¡ëin BM. In summer, ¦Ä13Crangedfrom-24.83to -18.66¡ë and from -23.43 to -16.20¡ë, in CVand BM stations,respectively. Generally, inboth seasons,¦Ä13Cshowed highervariability in consumers in BM than in CV.Inwinter, ¦Ä15N values ranged from 3.82to 11.11% in CVand 7.19 to 11.72¡ë in BM. In summer, ¦Ä15N ranged between 2.37-16.77¡ë and 9.02 -15.19¡ëin BM. ¦Ä15N valuesvaried from food sources at the base of the trophic level to consumers in both stations and seasons.Consequently, the suspended particulate matter (SPM) and primaryproducers showedvaluesslightlyhigher than consumers. While  ¦Ä13Cvalues of SPM, producersand consumers varied little between stations, ¦Ä15N variability was higher. These preliminary results indicatethat these stable isotopeswere useful as ecological and environmental indicators to assess thefood types and sources as well as changes in the structure of planktonic food webcould be caused by anthropogenicimpactin The Bah¨ªa Blanca Estuary.