Variation in nitrogen and carbon isotopes in the Bahía Blanca Estuary: Implications for ecological studies in a human-disturbed system

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

Pucón

Simposio; 5th International Zooplankton Production and Population Symposium.; 2011

International Council for the Exploration of the Seas

Although stable carbon and nitrogen isotopes are widely used in marine ecosystem research,this study presents the first report on their variation in the Bahía Blanca Estuary. Sampling wascarried out at stations where human impact was high (Canal Vieja: CV) and low (Bahía delMedio: BM), during both the winter phytoplankton bloom and spring-summer post-bloom period.Surface water, plankton samples, and environmental variable measurements were obtained.Isotopic data were analyzed using a multivariate approach. In winter, d13C values varied from -23.98 to -19.706? in CV and from -23.389 to -19.09? in BM. In summer, δ13C ranged from-24.83 to -18.66? and from -23.43 to -16.20?, in CV and BM stations, respectively. Generally,in both seasons, d13C showed higher variability in consumers in BM than in CV. In winter, d15Nvalues ranged from 3.82 to 11.11% in CV and 7.19 to 11.72? in BM. In summer, d15N rangedbetween 2.37-16.77? and 9.02 -15.19? in BM. The d15N values indicated food sources variedfrom the base of the food web to consumers at both stations and in both seasons.Consequently, suspended particulate matter (SPM) and primary producer δ15N values wereslightly higher than consumers. While d13C values of SPM, producers, and consumers variedlittle between stations, d15N variability was higher. These preliminary results indicate that stableisotopes are useful indicators of food types and sources, and can be used to study changes inthe structure of the planktonic food web caused by anthropogenic impact in the Bahía BlancaEstuary.