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A new project aims to use clams as bioindicators of the pH values in water.
In 2016, Australia faced the greatest coral bleaching in its Great Barrier Reef ever recorded. The whitened skeletons of the coral population, the largest of its kind in the world, showed in an eloquent way the consequences of the rising temperatures of the seas. That is, they worked as an environmental thermometer of global warming thanks to their high sensitivity to temperature variations. This is just another example of how the health of an ecosystem can be monitored through the behavior of one of its species. Technically, these species are known as bioindicators. The latest member to join the club is the Asian clam (Corbicula fluminea), which has been used in technological research to establish the quality of water affected by mining processes. The joint research by the University of Huelva in Spain and the University of Atacama in Chile has been published in the scientific journal Chemosphere.
The project comprises two main areas. Firstly, the development of a new low-cost and power-free filtering technology. Codenamed Disperse Alcaline Substrate, this passive filter uses a mixture of wood pieces and limestone sand. Acid water dissolves the sand, which in turn increases the pH and drives the precipitation of metals that are captured by the wood. These heavy metals can be retrieved and reused, which opens the door to circular economy alternatives in the mining industry.
The second area of work in this technological project is where the Asian clam takes the spotlight. The researchers placed specimens of this mollusk in each stage of the wastewater treatment process. All the clams in the acid waters close to the mine died, while 95% of them survived in the water-treatment plant and, once the water reached the river, the survival rate increased even more. Additionally, as clams are natural water filtering organisms, analyzing their accumulated heavy metals is another source of data. The Asian clam is just a starting point, as the research team is already assessing the possibility of analyzing the quality of water through other bioindicators such as fish, aquatic plants and algae.
Saline wetlands in arid and semiarid regions are another area of environmental concern that has become the focus of research of the AQUASALT European project. A team of scientists from Spain, Morocco, Algiers, Tunisia, France, and the USA are analyzing the microorganisms in these environments as another type of bioindicator. Microbes play a fundamental role in the breakdown of organic matter and pesticides. These wetlands are usually found in lower lands, which means they receive water filtered through the agricultural soil, both from irrigated and unirrigated crops. As this water contains fertilizers, herbicides, and pesticides, it can alter the balance of the ecosystem by affecting the salinity of these wetlands and the microorganisms living in them. Thus, these populations can provide an insight into the health of the ecosystem. This technological research aims to establish the evolution of wetlands over time and the consequences of changes implemented in the agricultural systems.