Excessive nutrient loading is one of the major human pressures affecting lake water quality in the world. In Europe, most of the lakes are P-limited, and since the 80s, extensive effort has been accomplished to reduce P-loading in eutrophic lakes, to avoid massive algal blooms and to reduce excessive phytoplankton biomass. In spite of this effort, lake eutrophication remain a widespread problem in Europe. The enforcement of the Water Framework Directive requested to Member States to restore all significant water bodies close to their pristine conditions or to a "good reference" state. Defining reference conditions becomes then a major step in defining management goals and to calibrate restoration targets. A new palaeolimnological method for inferring past total phosphorus (TP) concentrations in lake water from sedimentary pigments, particularly total carotenoids (TC), was proposed. It is based on a strong statistical correlation (p<0.001) between total carotenoids (TC) in the surface sediment of a number of Italian lakes and TP concentrations measured in these lakes at overturn. This "training" set was used to obtain a transfer function to estimate past TP concentrations from sediment cores. Root mean square error of prediction (RMSEP) of the pigment model is lower than those derived from certain diatom inference models. Predicted and residual values are not related to the estimated values, and their average is not statistically different from zero. Errors were estimated via a 'leave-one-out' re-sampling technique. The results generally agreed with TP values as measured by long-term water quality monitoring programs. Contrasting results were obtained respect to diatom-inferred TP. Diatom model tend to overestimate TP values above 100 µg l-1, pigment model correctly estimated TP in lakes when TP was <100 µg l-1, but not when lakes were rich in macrophytes. Pigment method permits rapid and relatively inexpensive determination of reference trophic conditions.
Use of sedimentary pigments to infer past phosphorus concentration in lakes
Piero Guilizzoni;Aldo Marchetto;Andrea Lami;Stefano Gerli;Simona Musazzi
2011
Abstract
Excessive nutrient loading is one of the major human pressures affecting lake water quality in the world. In Europe, most of the lakes are P-limited, and since the 80s, extensive effort has been accomplished to reduce P-loading in eutrophic lakes, to avoid massive algal blooms and to reduce excessive phytoplankton biomass. In spite of this effort, lake eutrophication remain a widespread problem in Europe. The enforcement of the Water Framework Directive requested to Member States to restore all significant water bodies close to their pristine conditions or to a "good reference" state. Defining reference conditions becomes then a major step in defining management goals and to calibrate restoration targets. A new palaeolimnological method for inferring past total phosphorus (TP) concentrations in lake water from sedimentary pigments, particularly total carotenoids (TC), was proposed. It is based on a strong statistical correlation (p<0.001) between total carotenoids (TC) in the surface sediment of a number of Italian lakes and TP concentrations measured in these lakes at overturn. This "training" set was used to obtain a transfer function to estimate past TP concentrations from sediment cores. Root mean square error of prediction (RMSEP) of the pigment model is lower than those derived from certain diatom inference models. Predicted and residual values are not related to the estimated values, and their average is not statistically different from zero. Errors were estimated via a 'leave-one-out' re-sampling technique. The results generally agreed with TP values as measured by long-term water quality monitoring programs. Contrasting results were obtained respect to diatom-inferred TP. Diatom model tend to overestimate TP values above 100 µg l-1, pigment model correctly estimated TP in lakes when TP was <100 µg l-1, but not when lakes were rich in macrophytes. Pigment method permits rapid and relatively inexpensive determination of reference trophic conditions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
