期刊
ECOLOGICAL APPLICATIONS
卷 19, 期 7, 页码 1791-1804出版社
ECOLOGICAL SOC AMER
DOI: 10.1890/08-0906.1
关键词
cyanobacteria; denitrification; grazing pressure; latitudinal gradient; nitrogen fixing; nutrient limitation; shallow lakes; South America
资金
- Netherlands Organization for Scientific Research (NWO) [W84-549]
- National Geographic Society [7864-5]
- Brazil by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) [480122, 490409, 311427]
Both nitrogen (N) and phosphorus (P) can limit primary production in shallow lakes, but it is still debated how the importance of N and P varies in time and space. We sampled 83 shallow lakes along a latitudinal gradient (5 degrees-55 degrees S) in South America and assessed the potential nutrient limitation using different methods including nutrient ratios in sediment, water, and seston, dissolved nutrient concentrations, and occurrence of N-fixing cyanobacteria. We found that local characteristics such as soil type and associated land use in the catchment, hydrology, and also the presence of abundant submerged macrophyte growth influenced N and P limitation. We found neither a consistent variation in nutrient limitation nor indications for a steady change in denitrification along the latitudinal gradient. Contrary to findings in other regions, we did not find a relationship between the occurrence of (N-fixing and non-N-fixing) cyanobacteria and the TN:TP ratio. We found N-fixing cyanobacteria (those with heterocysts) exclusively in lakes with dissolved inorganic nitrogen (DIN) concentrations of <100 mu g/L, but notably they were also often absent in lakes with low DIN concentrations. We argue that local factors such as land use and hydrology have a stronger influence on which nutrient is limiting than climate. Furthermore, our data show that in a wide range of climates N limitation does not necessarily lead to cyanobacterial dominance.
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