Understanding Nutrient Loads from Catchment and Eutrophication in a Salt Lagoon: The Mar Menor Case

Abstract

Eutrophication is a significant threat to aquatic ecosystems worldwide, and the Mar Menor hypersaline lagoon exemplifies a coastal lagoon at risk of algal blooms due to excessive nutrient loads, nitrogen, and phosphorus. These nutrients originate from various sources within the lagoon’s catchment area, including urban, agricultural, and livestock activities. Regular and occasional loads—during flood events—produce algal blooms that can significantly reduce the water oxygen content and cause massive mortalities, as observed in recent years. A daily algal growth model (Mmag) was developed to better understand the processes and determine key elements such as the phosphorus water–sediment interchange and deep water plants that effect the entire ecosystem and algal growth. The analysis developed can be applied in other wetlands around the world facing similar challenges. In the Mar Menor, both nitrogen and phosphorus have high relevance depending on the period of the year and the phosphorus legacy in the sediments. Floods are the main phosphorus input to the lagoon (80–90%), which goes to the sediment and is released after during the warm months in the following years. At the end of summer, phosphorus released from the sediment and the regular nitrate inputs to the lagoon increase the algal bloom risk. The good status of deep water plants, which reduces the phosphorus release in summer, is a key element to reduce the algal bloom risk. An integrated set of measures is required to reduce the mean chlorophyll to levels under 1 or 0.5 µgChla/L that can make the Mar Menor more robust and resilient.

Green Manuring and Irrigation Strategies Positively Influence the Soil Characteristics and Yield of Coriander (Coriandrum sativum L.) Crop under Salinity Stress

“…Similar results were found by Benidire et al [44]. On the other hand, the NO 3 − dynamics observed in the lysimeters confirm its decrease in the surface horizons during the coriander vegetative cycle, a trend clearly attributable to the absorption of this constituent, but also to leaching towards deeper horizons, which is confirmed by the increase in the lysimeters installed at 60 cm during some stages of cultivation in treatments with optimal and surplus irrigation, a process that may be behind the eutrophication observed in nearby aquatic ecosystems [45][46][47] and which satisfies the third hypothesis of this paper.…”

Adapting Water Resources Management to Climate Change in Water-Stressed River Basins—Júcar River Basin Case

“…On the other hand, irrigation modernisation significantly reduces agricultural returns, with high concentrations of nitrate, phosphorus, and pesticides. This measure, accompanied by fertigation, can be the main measure applied to recover nitrate-polluted aquifers [43] and to reduce the eutrophication risk in rivers and lakes [44,45].…”