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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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The structure of waterbird seed dispersal networks is not mediated by functional traits

The structure of waterbird seed dispersal networks is not mediated by functional traits

Plants and their dispersers form interaction networks whose structure has important implications for the persistence and stability of the community. Frugivory is vital for the dispersal of many plants, but the dispersal interactions between plants and non-frugivorous animals, such as waterfowl, are poorly studied. In this study, the authors characterized the structure of networks for seed dispersal by waterfowl, considered whether their structure is similar to that of the networks formed between frugivorous birds and plants with fleshy fruits, and searched for functional traits of birds or plants that are important for maintenance of network structure. Data from four European community-level studies on the content of the digestive tracts of ducks and rallids, including 12 species of birds and 88 of plants, were used. Waterbird seed dispersal networks shared some organizational patterns with those of frugivores, but unlike frugivores, their underlying structure was not related to functional traits. This is likely related to fundamental differences between waterfowl and frugivores in the way they ingest seeds. Differences in the functional role of particular waterbird species for seed dispersal are likely due to other processes, such as differences in population size, movement patterns, microhabitat selection, or gut processing of seeds. informacion[at]ebd.csic.es: Sebastián-González et al (2020) Waterbird seed-dispersal networks are similarly nested but less modular than those of frugivorous species, and not driven by species ecological traits. Funct Ecol https://doi.org/10.1111/1365-2435.13657


https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2435.13657