Physical and chemical characterization of a protected wetland area in El Fondo d'Elx (Alicante, Spain)

Abstract

Two shallow ponds (Southeast and Southwest ponds) of El Fondo d'Elx wetland and their contributing inflows are described in their physico-chemical features during one year (November 1994 to October 1995). Conductivity increased as water level decreased due to high evaporation and minimal water inputs under drought conditions caused both by the weather and over-exploitation of groundwater resources in the area. Initially considered mesohaline, the waters were re-classitied as polyhaline from July 1995. Extensive agricultural activities and the intensive use of nitrogenous fertilizers occur in surrounding lands have resulted in high nitrate concentrations, and frequently high N/P ratios, in inflow waters. Other human activities, such as reed burning and the opening of paths have disturbed the sediment, also leading to phosphorus enrichment, which has also been followed by large algal blooms at some sites. The Southeast Pond was subject to successive dessication-flooding cycles. After the flooding of the dry sediment, high concentrations of nitrogen compounds and soluble reactive phosphorus were detected, which were quickly depleted, possibly due to uptake by phytoplankton. The Southwest Pond, which did not dry out had lower nutrient concentrations, lower salinity, higher water transparency and the continuous presence of aquatic macrophytes throughout the year. © Asociación Española de Limnología.