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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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Reducing light-induced mortality of seabirds: High pressure sodium lights decrease the fatal attraction of shearwaters

Reducing light-induced mortality of seabirds: High pressure sodium lights decrease the fatal attraction of shearwaters

The use of artificial light at night and its ecological consequences are increasing around the world. Light pollution can lead to massive mortality episodes for nocturnally active petrels, one of the most threatened avian groups. Some fledglings can be attracted or disoriented by artificial light on their first flights. Studies testing the effect of artificial light characteristics on attractiveness to seabirds have not provided conclusive results and there is some urgency as some endangered petrel species experience high light-induced mortality. A field experiment to test the effect of three common outdoor lighting systems with different light spectra (high pressure sodium, metal halide and light emitting diode) on the number and the body condition of grounded fledglings of the short-tailed shearwater was designed. A total of 235 birds was grounded during 99 experimental hours (33 h for each treatment). 47% of birds was grounded when metal halide lights were on, while light emitting diode and high pressure sodium lights showed lower percentages of attraction (29% and 24%). No differences in body condition were detected among the birds grounded by the different lighting systems. The adoption of high pressure sodium lights (or with similar spectra) into petrel-friendly lighting designs together with other light mitigation measures such as light attenuation, lateral shielding to reduce spill and appropriate orientation are recommended. informacion[at]ebd.csic.es: Rodríguez et al (2017) Reducing light-induced mortality of seabirds: High pressure sodium lights decrease the fatal attraction of shearwaters. J Nature Conservation Doi 10.1016/j.jnc.2017.07.001


http://www.sciencedirect.com/science/article/pii/S1617138117300390