Nutrient and sediment dynamics in a Mediterranean shallow lake in southwest Spain
Temporal and spatial variations in the nutrient concentrations of lake water and surface sediments and in settling and resuspension rates were assessed in a Mediterranean shallow lake (Medina Lake, southern Spain) using a combination of short- term and long-time monitoring. Our results confi rmed th...
| Autores: | , , , |
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| Formato: | artículo |
| Fecha de publicación: | 2012 |
| País: | España |
| Recursos: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/63222 |
| Acesso em linha: | http://hdl.handle.net/10261/63222 |
| Access Level: | acceso abierto |
| Palavra-chave: | Mediterranean shallow lakes phosphorus sediment resuspension |
| Resumo: | Temporal and spatial variations in the nutrient concentrations of lake water and surface sediments and in settling and resuspension rates were assessed in a Mediterranean shallow lake (Medina Lake, southern Spain) using a combination of short- term and long-time monitoring. Our results confi rmed the high temporal (inter- and intra-annual) variability characterising Mediterranean shallow lakes, which is also enhanced by water level fl uctuations. The results also underlined the crucial role of phosphorus (P) exchange across the sediment-water interface in controlling P dynamics in lake water. This statement is supported by (i) the existence in the upper 1 cm of the sediment of 18 times the mass of TP of the whole water column and, hence, the high potential impact of P released from the sediment into the overlying column and by (ii) the strong P limitation of planktonic primary production, as refl ected by a DIN:TP atomic ratio much higher than 16. Resuspension, co-precipitation with CaCO3 and adsorption onto iron hydroxides (FeOOH) all had major effects on the P exchange across the sediment-water interface. Wind-induced resuspension (31 ± 13 % of the settled matter) explained the extremely high gross sedimentation rates (40 ± 11 g m–2 d–1 ) recorded for a 24 h period. P adsorption onto FeOOH controlled internal P loading during the winter (FeOOH: Pmobile > 15). During the summer, the low availability of FeOOH (Fe:Pmobile < 15) refl ected the inability of FeOOH to control P adsorption. The SRP concentrations in lake water were much higher than necessary for CaCO3 and P co-precipitation, explaining the high contribution of P bound to CaCO3 (PHCl ) to the total P in the sediment of the study site and demonstrating the importance of CaCO3 precipitation for removing P from lake water. |
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