Is Doñana sick? We look for symptoms in mice and crabs

Along with climate change, pollution is an increasingly worrying global problem. The unbridled human activity (agricultural, industrial, mining, urban) releases a large amount of chemicals into the environment.

Compounds such as heavy metals, dioxins, aromatic hydrocarbons, fertilizers, pesticides, drugs, cyanide and detergents are mostly toxic. They can produce harmful effects on living organisms in general, and be particularly harmful to people's health.

If the pollution is intense and / or persists over time, harmful effects may affect the structure and function of terrestrial and aquatic ecosystems. Therefore, diagnosing episodes of contamination is essential to apply early corrective or restorative measures. In this way we can prevent the damages from becoming greater and with irreversible consequences.

Mechanisms to measure environmental quality

Assessing environmental quality is a complex and difficult task. Chemical analysis techniques need a previous idea about the contaminants involved. Its effectiveness is limited, since it allows analyzing some contaminants, but not others.

In addition, these tools do not take into account the possible interactions of some contaminants with others, nor the influence of physicochemical factors of the environment (temperature, humidity, pH, salinity, etc.). Nor do they report their biological effects.

Living things such as animals, plants, fungi and microorganisms can be used as sentinel organisms, indicators or bioindicators. They allow you to evaluate the biological effects of pollution and measure the consequences on your health and well-being.

Its application dates back to Roman times, when the Canaries went down to the coal mines. Being much more sensitive than humans to the presence of gases (carbon monoxide), the birds served to warn of an imminent danger and give the miners time to escape.

In an example of disastrous news, the reduction and progressive deterioration of coral reefs are warning about climate change and global warming of the planet.

Pollution Bioindicators in Doñana

Located southwest of the Iberian Peninsula (Andalusia), the Doñana National Park is a protected natural area of ​​great environmental and ecological importance. It stands out as a place of passage, breeding and wintering for thousands of birds and the habitat of several endangered species, such as the Iberian lynx or the imperial eagle. Therefore, among other considerations, Doñana was declared a World Heritage Site in 1994.

However, various pollutants and sources of pollution threaten the balance and environmental health of the area. The following stand out:

  • Metals from pyrite mines located in the north of the region.
  • Pesticides used for the production of rice, citrus and strawberries in the nearby fields.
  • Waste from chemical and petrochemical industries located near the city of Huelva.

Rio Agrio at the height of the municipality of Aznalcóllar. The turquoise color is due to the residual contamination that comes from the runoff from the debris from the old pyrite mines (on the right).

Rio Agrio at the height of the municipality of Aznalcóllar. The turquoise color is due to the residual contamination that comes from the runoff from the debris from the old pyrite mines (on the right).

Wwal / Wikimedia Commons

The fragility of this ecological system was revealed when the Aznalcóllar mining raft breaks on April 25, 1998. The accident seriously endangered Doñana's integrity. If not for the rapid and effective intervention, it could have devastating and incalculable environmental consequences.

Our group It has evaluated for more than 20 years the environmental situation of Doñana and its surroundings by measuring the biological effects of pollution on different sentinel animals that inhabit the area.

Despite being an area of ​​maximum protection, and that the catalog of species that can be used in the studies is very limited, we have used different bioindicators to evaluate the diverse ecosystems of the Park.

These are unprotected species such as dark mouse (terrestrial ecosystems), considered both in our last work and in one that we published last year. The latter was about the effects of a model pesticide (DDE, by-product of DDT) on the testicles of this small rodent.

We have also studied other sentries of environmental health in Doñana such as american red crab (freshwater courses) and mud coquina (estuary of the Guadalquivir). The study of biological responses at the biochemical level in these organisms has allowed the environmental evolution of the area to be evaluated over time, as well as the recovery after the Aznalcóllar mining disaster.

American red crab

American red crab

MikeMurphy / Wikipedia

Sentinels from the invisible world

Among the organisms that inhabit the Earth, the greatest diversity is found in the microscopic world. The microorganisms are here from the beginning of life and will undoubtedly remain until the end of time, long after humanity disappears.

Given their great plasticity and extraordinary capacity for genetic adaptation, microbes have colonized, without exception, all possible ecosystems on our planet, including extreme environments. No less than 1 million bacteria can be found in a single gram of soil (100,000 microbes per m3 of air and 10,000 per ml of water).

Microorganisms have great potential as indicators in environmental diagnosis. Widely distributed, they are actively involved in the biogeochemical cycles of main elements (carbon, nitrogen, phosphorus and sulfur), in the function of ecosystems and in the degradation and immobilization of pollutants.

Microbes are organisms especially sensitive to environmental conditions. Its abundance, diversity and biological activity are significantly modified in response to harmful agents. The changes warn about pollution episodes.

We have been able to verify this early detection system in the most recent studies we are doing in Doñana. For this we are using techniques that analyze different biomolecules (DNA, proteins) globally to evaluate changes in microbial diversity and its metabolic processes caused by pollution.

This article was originally published in The Conversation. You can read the original here.


José Alhama Carmona

University Professor. Department of Biochemistry and Molecular Biology, University of Córdoba

Ana María Herruzo Ruiz

Predoctoral student of Biochemistry and Molecular Biology, University of Córdoba

Carmen María Michán Doña

Professor in Biochemistry and Molecular Biology, University of Córdoba

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