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Breathing water bodies

Rivers are complex and fascinating ecosystems that are constantly evolving and are the habitat of different life forms, much of which are not directly visible by eye

One method for sampling fish is to generate an electric field in the water, which induces a norcosis to the specimens and allows ichthyologists to catch them more easily

Drought and reduced flows endanger life and biodiversity in rivers. Watch the video interview.

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If the ecosystem is not healthy, the impacts of human activities are stronger and more challenging to manage

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According to available data, less than half of Italian water bodies are in good ecological status. The goal is to significantly increase this percentage by 2030

Rivers are habitats full of life. Unfortunately, the rapid change in the climatic conditions and human impacts are preventing the ability of the biota to adapt

How do you recognise a healthy river habitat?

HIGH
GOOD
MODERATE
POOR
BAD

Index of Habitat Integrity (IH)

Macroinvertebrates are fascinating creatures. Some have adapted their body shapes to withstand fast flow velocities or to improve their grip on the riverbed

To collect samples, a fine-meshed net mounted on a metal frame is used. This operation requires patience and experience

The organisms are then analyzed in the laboratory to characterize species and families present in the aquatic habitat

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Larvae and adults of insects, molluscs, crustaceans, and leeches are considered 'bioindicators' because their presence can indicate the health of a river environment

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Macroinvertebrates, such as insect larvae, crustaceans and many other organisms which are found in rivers and lakes, offer valuable insight into water quality. Based on the organic load present, macroinvertebrates indicate whether the waters are uncontaminated, purified, or polluted. Therefore, scientists refer to them as ‘bioindicators’.

To monitor a water system’s health, researchers go into the field and use nets to collect a certain number of macroinvertebrates from the riverbed.  The collected organisms are taken to the laboratory and identify at the species or family level .

The MesoHABSIM methodology currently is not  only focusing on fish, as was previously done, but also considers macroinvertebrates as part of the river habitat. Indeed,  macroinvertebrates can provide important information about the alteration of the flow rate and velocity, if one looks at their functional traits and morphological adaptations to survive and thrive in different environmental conditions.

For instance, in waters with low levels of oxygen, some species have adapted to resurface to take a breath of atmospheric oxygen before diving back in.

In fast-moving waters, some species have developed a streamlined body to adapt to the strong current. For example, the Ecdyonurus has a “spoiler” that redirects water, while others, like the blepharicerids, have suckers on their abdominal wall. Some species, such as blackflies, build small silk bases on river stones and attach to them using hooks. When a river or a section of it dries up for a prolonged period, the presence of bioindicators helps to understand how long it takes for an ecosystem to recover. The speed of the recolonization process depends on the length and geographical position of the river stretch involved, as well as the duration of the dry period.

Rivers and their ecosystems are at risk due to human activities. For instance,  the wastewater from both large and small inhabited areas flows into the river network. According to the data provided by Utilitalia (the federation that brings together the special companies operating in the public services of Water, the Environment, Electricity and Gas), approximately 60% of wastewater undergoes purification processes before being released into the environment. However, a significant amount of untreated wastewater still flows into rivers. In Italy, water bodies during the  low flow period can become overloaded with nutrients (such as nitrogen and phosphorus) or other pollutants (pesticides, herbicides, heavy metals), leading to a loss of natural self-purification capacity and causing severe degradation of the river environment.

Recent monitoring of the application of the Water Framework Directive 2000/60/EC (which aims, before 2030, to “prevent the deterioration of the status of all water bodies and highly modified ones in order to achieve good ecological status“) has shown that there is still much work to be done to improve the ecological state of our rivers. In Italy, only 43% of the 7,494 surveyed water bodies have achieved “good ecological status” to date.

Actions also need to be intensified to protect biodiversity. According to the IUCN Red List (International Union for Conservation of Nature) over 25% of freshwater fish species in Italy are endangered, and for over 30% of native species, we do not have sufficient information on their environmental requirements in terms of habitat.

The climate crisis is the third major threat to rivers. It accelerates the hydrological cycle and alters the frequency, intensity, and location of extreme events, leading to both water scarcity and sudden floods. Global warming not only causes ice melting but is also expected to reduce water availability in the Mediterranean area and semi-arid regions by up to 30%. Additionally, the presence of invasive species in waterways is a significant concern. For example, the catfish, introduced from Eastern Europe in the 1950s for fish repopulation, has become highly invasive in Italy. As a result, specific laws have been enacted in different regions to control and eliminate this species.