Abstract
Impacts on wetlands are becoming more pressing every day. Among them, habitat loss, overexploitation of aquifers and changes in land use are considered the most important. However, the impacts linked to wastewater discharges are increasing worldwide. In this context, this study analyses the impacts of input of wastewater to a Mediterranean Ramsar temporary wetland (Fuente de Piedra, south of Spain). To this end, systematic sampling was carried out in the Charcón stream which receives water from a wastewater treatment plant (WWTP) and discharges it into the wetland. The results showed a slight decrease in the nutrient concentrations, particularly for nitrogen compounds. Heterotrophic and fecal bacteria concentration, as well as phytoplankton and zooplankton abundance and biomass, all significantly decreased from the treatment plant to the wetland. When comparing the effect of this discharge with other similar occurring to the same wetland, it was evident that the Charcón stream was responsible for a greater impact. At this point, it is relevant to note that the main difference among both treated wastewater discharges lies in the different water retention time once the wastewater was released from the WWTP. In fact, we recommend an increase in the water retention time by building seminatural ponds, together with the use of biofilters, which will notably contribute to improve the processes of assimilation of nutrients and to decrease the impact generated in the wetland by this spill.
Highlights
Inland freshwater ecosystems are hotspots of biodiversity as they show higher relative species richness than marine or terrestrial ecosystems [1]
This ecosystem receives the discharge of three wastewater treatment plants (WWTP); two from the Fuente de Piedra village [12] and the other one from the Humilladero village through the Charcón stream, this last being the objective of the present study (Figure 1)
The main variables related to the cultural eutrophication of aquatic ecosystems (TN and total phosphorus (TP)) show similar values at the outlet of the wastewater treatment plant and at the in-put to the wetland
Summary
Inland freshwater ecosystems are hotspots of biodiversity as they show higher relative species richness than marine or terrestrial ecosystems [1]. They provide important ecosystem services, with a global estimated annual economic value of USD 44,000 per Sustainability 2021, 13, 3540. The global Living Planet Index (LPI) shows that 60% of species have shown population declines between 1970 and 2014, with freshwater species showing an 83% decline [3] These authors and others indicate that the biggest drivers of biodiversity decline are habitat loss, habitat degradation, and overexploitation [4,5]. Wetlands biodiversity is mostly affected by changes in land use and eutrophication processes [6,7,8,9]
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