Urban lakes: interaction between phytoplankton dynamics and trace metal speciation

Urban lakes have a particular influence on the water cycle in urban catchments. Thermal stratification and a longer residence time of the water within the lake can boost the phytoplankton production. On the other hand, trace metals are naturally found in environment in trace amounts due to erosion and physic-chemical or biological alteration processes. Trace metals are essential to growth and reproduction of organisms. However, they are also well known for their toxic effects on animals and humans. Their ecotoxicity depends on metal properties and chemical speciation (particulate, dissolved: labile or bioavailable and inert fractions). The interaction between phytoplankton production and trace metal speciation is not well understood until present time. The aim of this research is twofold: (1) to analyze the driving processes of the phytoplankton production in an urban lake through physical-chemical and biological field data collection and (2) simultaneously to survey the chemical speciation of trace metals in this lake. To address these issues, a field survey and laboratory analysis, including physical-chemical, biological variables, organic matter and trace metal concentrations, have been designed and implemented in an urban study site: Lake Créteil in France