Chemical composition and the nitrogen-regulated trophic state of Patagonian lakes

• Published in: Limnologica 2007-01, Vol.37 (1), p.17-27
• Main Authors: Diaz, Mónica, Pedrozo, Fernando, Reynolds, Colin, Temporetti, Pedro
• Format: Article
• Language: English
• Subjects: Chemical composition; Freshwater; Lakes; Nitrogen; Patagonia; Trophic state
• ISSN: 0075-9511; 1873-5851
• DOI: 10.1016/j.limno.2006.08.006

Chemical composition and nutrient concentrations of 39 relatively poorly known Patagonian lakes (38–50°S and from 70° to 68°W) are described and analysed using principal component analysis (PCA). The general relationships between nutrients (total phosphorus, bioavailable phosphorus and dissolved inorganic nitrogen) and plankton biomass are examined. We seek to demonstrate that the extreme oligotrophy characterising many lakes and reservoirs of the Argentine Patagonian region of South America owes more to nitrogen deficiency than to a shortage of available phosphorus. The data show a range of trophic conditions with variable water chemistry characteristics. The first two axes of the PCA ordination explain most of the variance (63%). The first component of the variance in the environmental data is a trophic gradient, with positive correlations with the concentrations of nutrients (TP, SRP, DIN) and electrical conductivity and a negative correlation with transparency. For all the reservoirs considered, the calculated annual, summer and winter chlorophyll- a carrying capacities of the available phosphorus were consistently and significantly ( P