Relationship between Seston Composition and Water Transparency in Spanish Reservoirs

Abstract

AbstractIn the context of an extensive study of 101 Spanish reservoirs, we have explored the relationship between transparency (0.11 ≤ SD ≤ 8.6 m) and a number of general limnological parameters. Principal components analysis has been used as a means to summarize these relationships in two distinct periods, winter and summer, revealing the grouping of variables associated to abioseston or with biomass. Multiple regression analysis has been used to quantify these relationships. Total labile iron, calcium and chlorophyll appeared to be the best regressors of turbidity among our variables. The association between total labile iron and turbidity can be explained by the widespread adsorption of metals onto particles. Total labile manganese and phosphorus showed a similar behaviour, especially in winter. The presence of a relatively large proportion of detrital matter in low‐biomass eutrophic reservoirs in winter has been revealed by the analysis of Chla:C and Chla:N ratios. The fact that low ratios were associated with high iron concentrations gives support to this view. Also the C:P and N:P particulate atomic ratios differed from winter to summer. All these ratios appear to be very sensitive to the presence of a variable detrital component and, therefore, their use as indicators of the physiological state of phytoplanktonic populations is highly discouraged for these reservoirs.