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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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Seed dispersal by neotropical waterfowl depends on bird species and seasonality

Seed dispersal by neotropical waterfowl depends on bird species and seasonality

Waterbirds have an important ecological function as vectors of plant dispersal between different wetlands. In the Neotropical region, there is very limited information about this dispersal. In southern Brazil, seed dispersal by endozoochory was studied by five waterfowl, including Brazilian teal, yellow-billed teal, ringed teal, coscoroba swan, and whitefaced whistling-duck. Over 2000 diaspores were recovered from 40 different plants, including seeds of 37 angiosperms, and diaspores of mosses, ferns and charophytes. Seeds of the threatened grass Zizaniopsis bonariensis were the most abundant. The species richness and abundance of seeds dispersed varied between bird species, and between the cold and warm seasons, with a strong interaction between these two factors. 12 plant species were indicators of particular bird species or seasons. The largest bird, the coscoroba, dispersed a larger proportion of relatively large seeds. The coscoroba and the smallest bird (ringed teal) differed from each other, and from the other three ducks, in the community composition of plants dispersed. All five species make daily movements between wetlands and are widely distributed in South America, ranging from the sedentary Brazilian teal to the long-distance migratory coscoroba. informacion[at]ebd.csic.es: Silva et al. (2020) Seed dispersal by neotropical waterfowl depends on bird species and seasonality.  Freshwater Biology https://doi.org/10.1111/fwb.1361


https://onlinelibrary.wiley.com/doi/10.1111/fwb.13615