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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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Multiple mating as bet-hadging strategy

Multiple mating as bet-hadging strategy

Polyandry (female multiple mating) has profound evolutionary and ecological implications. Despite considerable work devoted to understanding why females mate multiply, no convincing empirical evidence explains the adaptive value of polyandry. In this study it is provided a direct test of the controversial idea that bet-hedging functions as a risk-spreading strategy that yields multi-generational fitness benefits to polyandrous females. Unfortunately, testing this hypothesis is far from trivial, and the empirical comparison of the across-generations fitness payoffs of a polyandrous (bet hedger) versus a monandrous (non-bet hedger) strategy has never been accomplished because of numerous experimental constraints presented by most ‘model' species. In this study, authors take advantage of the extraordinary tractability and versatility of a marine broadcast spawning invertebrate to overcome these challenges. Multi-generational (geometric mean) fitness among individual females assigned simultaneously to a polyandrous and monandrous mating strategy has been simulated. These approaches, which separate and account for the effects of sexual selection and pure bet-hedging scenarios, reveal that bet-hedging, in addition to sexual selection, can enhance evolutionary fitness in multiply mated females. In addition to offering a tractable experimental approach for addressing bet-hedging theory, this study provides key insights into the evolutionary ecology of sexual interactions. informacion[at]ebd.csic.es: Garcia-Gonzalez et al (2015) Mating portfolios: bet-hedging, sexual selection and female multiple mating. Proc. R. Soc. Lond. B 282:20141525. http://dx.doi.org/10.1098/rspb.2014.1525