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The Las Tablas de Daimiel National Park currently presents, according to the entity, an anomalous biodiversity with a low population of herbivorous waterfowl, such as the red-crested duck, together with a high population of invasive exotic fish. They show an abrupt change in the state of the wetland, going from clear waters with submerged vegetation, to a state of turbid waters and absence of vegetation. This new scenario would be causing significant changes in the ecosystem.

This initiative promotes the improvement of the knowledge necessary for the management of the National Park (present in the Priority Action Framework for the Natura 2000 Network in Spain), in the search for sustainable ecological restoration.

The project aims to analyse the causes that have led the wetland to reach a critical threshold, which has caused a change in the state of its ecosystem, with the consequent loss of biodiversity. The initiative has set the following objectives:

• Assessment of the water situation of the wetland since 2010.
• Evaluation of water quality and its influence on the development of benthic vegetation.
• Study of the nature of the inorganic and biogenic suspended particle as a cause of turbidity.
• Study of the attenuation of solar radiation in the water column and evaluation of the light conditions of the lake bottom and its influence on the development of benthic vegetation.

• Determine the geological and hydrogeological framework of the wetland and the relationship of the wetland with the groundwater body.

• Study of the chemistry of the main water inputs to the wetland: Cigüela and Guadiana rivers.

• Installation and maintenance of a device for recording variations in water level and temperature in the wetland.

• Evaluation of physical-chemical variables of the water column at several representative points of the wetland, and evaluation. Knowledge of water chemistry at various points.

• Assessment by means of a detailed sampling of the distribution of nutrients in the wetland, their trophic status and their incidence in the development of phytoplankton. In addition to the study of phytoplankton as a bioindicator of pollution.

• Sampling and assessment of the nature of the suspended particle as a cause of water turbidity in the wetland. Analysis of the seasonal activity cycle of benthic fish (invasive alien species) in nutrient concentration and turbidity. In addition to the analysis of the incidence of wind on the turbidity values of the wetland.

• Action to find out how PAR radiation is attenuated in the water column.

• Continuous recording of the luminosity of the lake bottom, to assess its daily and seasonal fluctuation and study of the influence of fish activity on the recording of this parameter.

• Dissemination of the data to the National Park management and dissemination of the results of the project through scientific articles and participation in national congresses.

• In recent years, much of the existing diversity in this ecosystem has been lost, materializing in a decrease in the presence of a duck, an emblematic bird such as the red-crested duck (Netta rufina) that receives its food from algae of the genus Chara sp., which are also disappearing in this environment, due among other factors to the increase in the turbidity of the water and the consequent absence of light.

• The increase in the turbidity of the wetland water may have a direct relationship with eutrophication (excess supply of inorganic nutrients) that the park is suffering and with important populations of invasive species of fish with benthic habits such as carp and catfish.

• Las Tablas de Daimiel has two main water inlets through the Cigüela and Guadiana rivers. In this environment, there are two areas, one that retains the Morenillo Dam, and that receives the waters of the aforementioned rivers, and another area that floods the waters retained by the Puente Navarro dam, both bodies of water, with important hydrochemical differences.

• On the one hand, after analysing the water retained by the Navarro Bridge , it was found that it had little turbidity and low values of chlorophyll and nutrients. Due to the transparency of the water , a greater penetration of light was verified, favoring the development of aquatic algae.

• On the other hand, the water retained by the Morenillo Dam has greater turbidity, higher values of type A chlorophyll, and nutrients, such as phosphorus and nitrogen. In addition, during its analysis in the summer months, this mass presented an algal bloom with very high turbidity values.

• After the study of microbial biodiversity, it was possible to confirm the presence of three types of cyanobacteria, which, together with photosynthetic algae, form mats that make it impossible for the entry of light necessary for the development of benthic vegetation, since it prevents photosynthesis from taking place, which means that primary production cannot exist at depth.

• The entity has been able to determine that this environment can be considered eutrophic, being able to reach the level of hypereutrophic in the second zone listed with greater turbidity, nutrients and chlorophyll of type A, which indicates the current ecological status. A eutrophication that indicates, according to the Geological and Mining Institute of Spain (IGME), the degradation it is suffering. With this information, the Tablas de Daimiel National Park has a scientific basis that will help it improve the management of the wetland.