Diana Rojo analyzing river water samples. Credit: EHU

The Stream Ecology group of the University of the Basque Country (EHU) has tested various ways of measuring river quality in three streams in the Green Belt area of Vitoria-Gasteiz. Using these trials as the basis, the team designed a protocol with early warning indicators that allows environmental managers and agencies to assess the health of river environments more accurately.

Rivers perform a vital role in environmental balance. Keeping them in good condition depends not only on water quality, but also on the life they host and the processes that take place within them: plant respiration, decomposition of organic matter, and transformation of nutrients, among others.

“The good condition of a river means taking into account both the organisms that inhabit it and the way it functions,” explained Luz Boyero, an Ikerbasque Research Professor at the EHU. Human activity may alter this natural dynamic, so tools need to be available to enable its effects to be detected in a timely manner.

With the aim of standardizing methods for assessing river health and providing a simple, accessible guide for environmental management bodies, the researcher in the EHU’s Stream Ecology group Diana Rojo analyzed the performance of different materials that enable the decomposition processes and organic matter production to be measured in three streams located in agricultural areas in the Green Belt area of Vitoria-Gasteiz.

As Rojo explained, using various types of substrates, the team compared the differences between well-preserved sections and others more affected by agricultural activities. “We wanted to identify which ones best reflect the changes taking place in the river when there are human alterations,” the researcher pointed out.

The tests examined a wide variety of items, including marble tiles, alder and oak leaves, tongue depressors used in medicine, cotton strips, green and red tea bags, and even banana leaves, to determine which ones are most effective as ecological indicators.

The paper is published in the journal Ecological Indicators.

Communities of invertebrates, fungi, algae, and decomposition

Once they had selected altered and unaltered stretches of various streams on the outskirts of Vitoria-Gasteiz, they put experimental units containing the aforementioned substrates in the water and kept them incubating for four weeks, “so they could compare them afterwards and decide which substrates indicate changes in the condition of these streams most efficiently and within a short space of time,” they explained.

After collecting all the material, “we were able to analyze the communities of invertebrates, fungi and algae, as well as various decomposition variables, which indicate the state of the impacted areas compared with the unaltered stretches,” they added.

Broadly speaking, the researchers concluded that “to carry out efficient studies with limited resources, in terms of both time and money, alder is the best substrate for studying total decomposition and macroinvertebrate communities; banana leaves or cotton strips are very efficient for studying microbial decomposition; and finally, marble tiles are useful for studying algae or primary production. These three materials would provide us with a great deal of fairly immediate information about the state of the ecosystem.”

At the end of the day, this is a set of recommendations not only for the research community, but also for the administration and management bodies. What is more, the materials proposed are also quite universal, which makes it easier for this study to be replicated globally in different locations.

In the view of the EHU researchers, “Water is a vital resource for human beings. Healthy river communities need to be maintained and ecosystem processes need to function as they should. It is essential to know how to assess the health of ecosystems in order to address pollution.”

“This is always the first step: seeing where the conditions are good, where they are poor, and then deciding what to tackle, in particular to find out which sections are the most critical ones,” added Rojo.

“River ecosystems are fundamental in carbon cycles, nutrient cycles, and on Earth. And they are often the great forgotten,” concluded Professor Boyero.

More information: Diana Rojo et al, Decomposition of different organic matter substrates and algal biomass accrual as early warning indicators of human impacts on stream ecosystems, Ecological Indicators (2025). DOI: 10.1016/j.ecolind.2025.113998

Citation: Tiles, leaves and cotton strips examined to measure river health (2025, November 3) retrieved 3 November 2025 from https://phys.org/news/2025-11-tiles-cotton-river-health.html

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