Chapter

The role of saltmarshes in reducing the concentration of nitrate and phosphorus in eutrophicated water: The mar menor lagoon, a case study in Semi-Arid Mediterranean areas of SE Spain

Book ch
Biogeochemistry and Pedogenetic Process in Saltmarsh and Mangrove Systems
  • Fecha: 01 December 2010
  • Páginas: 205-232
  • ISBN: 9781617282690
  • Source Type: Book
  • Document Type: Chapter
  • Publisher: Nova Science Publishers, Inc.
High concentrations of phosphorus and nitrogen are the main causes of eutrophication, which is defined as an increase in chemical nutrients in aquatic ecosystems. Although wetlands are among the ecosystems most affected by eutrophication on a worldwide scale, these environments also have a high capacity to combat eutrophication; the term green filters has been applied to wetlands and salt marshes to indicate their capacity to reduce pollution. In this chapter, a summary of the nutrient dynamics studies carried out in a coastal saltmarsh in the Mar Menor lagoon (semiarid SE Spain), is presented. A monitoring programme was established in order to characterize the contents of nitrogen and phosphorus in several watercourses that flow into the marsh, as well as to identify the possible role of this marsh as a sink for these two nutrients and thus in reducing eutrophication of the lagoon. The results are discussed and compared with data from other studies. Water samples were collected from the watercourses before they flowed into the salt marsh and in plots installed within the marsh. Soil samples were also collected in the same plots for analysis of the phosphorus. Eutrophicated water with high concentration of phosphorous (up to 12.3 mg L-1) and nitrates (up to 281.9 mg NO3- L-1) was found in the watercourses flowing into the saltmarsh. The contents of these two nutrients in the water within the salt marsh decreased towards the shoreline, indicating that the water is depurated as it flows across the marsh. However, this general spatial pattern of nutrient retention in the saltmarsh varied depending on the season. In the driest months, the marsh was 100% effective in reducing nutrient concentrations, but in rainy periods the effectiveness was reduced. On the basis of the values of redox potential obtained in the sampling plots, assimilation by vegetation appeared to be the main mechanism for reducing the concentration of nitrate in the water flowing across the marsh. However, fixation to the soil was the main mechanism whereby phosphorus was retained. Calcium and Mg compounds contributed to a great extent to phosphorus retention in the soils, except in some sectors affected by mine wastes in which the Fe- and Al-bound P fractions were the most abundant. The results indicate that coastal saltmarshes play an important role as filters in reducing contamination in the Mar Menor lagoon.© 2011 Nova Science Publishers, Inc. All rights reserved.

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