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Doñana's water quality, in danger due to intensive agriculture and a poor residual water treatment

Irene Paredes, researcher of the study

Eutrophication is a major cause of wetland degradation worldwide. In recent decades, reductions in nutrient inputs have led to improvements in water quality in many rivers and lakes in central and northern Europe, but long-term trends are less clear in southern Europe. The Doñana Biological Station conducted the first comprehensive study of water quality in Doñana, one of the most important wetland complexes in Europe and the Mediterranean region.

The core area of Doñana is a large shallow, seasonal marsh (UNESCO World Heritage Site—WHS) that floods during rainy, cool winter months, then dries out during the summer. The marsh is fed by three main streams whose catchments are within a Biosphere Reserve but are impacted by greenhouses (for cultivating fruit, irrigated with groundwater), poorly treated urban wastewaters and tourism.

From 2013 to 2016, the research team monitored nutrient and phytoplankton chlorophyll-a (chla) concentrations in surface waters of the Doñana marsh and the three main streams. They quantified changes in greenhouse cover since 1995 using satellite images. Nutrient concentrations in streams were consistently higher than in the marsh, particularly in the Partido and Rocina streams that regularly reached concentrations equivalent to a "bad physico-chemical status" under the EU Water Framework Directive (WFD), and whose catchments suffered a fivefold expansion of greenhouses from 1995 to 2016.

The Partido was the most polluted stream, and the most affected by wastewater effluents, and had particularly high concentrations of NH4+ and NO2? across seasons. Patterns in chla concentrations were less consistent, but streams generally had higher concentrations than the marsh. Nutrient concentrations in spot samples within the marsh largely depended on a combination of evaporation (as revealed by higher stable isotope ?2H values in the water column) and spatial processes (concentrations increase close to stream entry points, where conductivity is lower).

Anthropogenic nutrient pollution in entry streams is a serious problem in Doñana, with extensive stretches too toxic for fish. Reinforcement of policies aimed at reducing nutrient inputs to Doñana are urgently required to meet the biodiversity conservation and environmental objectives for the WHS and WFD, respectively. Paradoxically, the marsh is currently relied upon to purify the water entering from streams.

informacion[at]ebd.csic.es

Referencia: 

Paredes, I., Ramírez, F., Aragonés, D., Bravo, M.A., G. Forero, M., Green, A.J. (2021). Ongoing anthropogenic eutrophication of the catchment area threatens the Doñana World Heritage Site (South-west Spain). Wetlands Ecology and Management. https://doi.org/10.1007/s11273-020-09766-5

Read the full press release (Spanish)


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Light pollution and seabird fledglings

Light pollution and seabird fledglings

One of the most critical phases in the life of petrels is at fledging when young birds pass from parental dependence on land to an independent life at sea. To mitigate mortality at this time, rescue programs are implemented near breeding sites around the world, especially for birds grounded by artificial lights. This study evaluated the plumage and body condition of short-tailed shearwater (Ardenna tenuirostris) fledglings captured at colonies just before departure in comparison to fledglings washed up on beaches and to fledglings attracted by artificial light along roads. Beach-washed birds were underweight and in poor condition, suggesting their future survival probabilities at sea were low. Birds rescued on roads as a consequence of light attraction had lower body weights and condition indices than fledglings captured at the colony. However, more than 50% of light-attracted birds had attained similar weights to those of adults, suggesting they have higher probabilities of survival than beach-washed birds. Water-logged birds being washed onto beaches is a natural process, but birds grounded by lighting along roads is an increasing anthropogenic threat that requires management. Thus, management and conservation efforts should be directed to protect birds in the colonies and reduce light-induced mortality, ideally through the strategic reduction of light sources and lateral light spillage. información: [at]ebd.csic.es: Rodriguez et al (2017) Light pollution and seabird fledglings: Targeting efforts in rescue programs. J Wild Manage doi:10.1002/jwmg.21237


http://onlinelibrary.wiley.com/doi/10.1002/jwmg.21237/full