Water is a precious resource, but is often threatened by pollution. The aquatic environments they frequently suffer, in fact, the spinning of chemical pollution deriving from industrial discharges or even atmospheric depositions and agricultural outflow. It is fundamental monitor and protect the sources of drinking water From these contaminations, which can be unpredictable and cause serious risks to human health, but identifying these dangers in time is not always easy. For this reason, special sensors have been developed to monitor the level of health of the water. Conventional methods based on physical sensors And chemists I am expensive and often ineffective in detecting sudden pollution events or unexpected chemicals in a short time. Bioindicators, such as i bivalves (as for example mussels And clams), on the other hand, provide a continuous monitoringeffective and immediate: large quantities of water filter, they are extremely sensitive to one Wide range of pollutants and their toxic effects in a very short time and react in real time to any change. Among these, the fresh water mussels They are particularly used for biomonitoring thanks to their ability to accumulate and report the presence of contaminants, making them precious ecological sentinels for the quality of internal waters. In short, nature itself offers us a sophisticated alarm system, helping us to protect the water and, consequently, our health.
Mussels: the bivalves used as water quality biosensors
For optimal water monitoring have been developed biological systems of early alert (Biological Early Warning Systems – Bewss), to provide anvery rapid identification negative variations in water quality, real “Natural Sentinels”. The most used and ideal bivalve molluscs for waters biomonitoring are the mussels (Mytilus spp.).
The latter are particularly suitable for the BEWSS because:
- Have one high filtration capacity water, which makes them very sensitive to pollutants.
- They have one Long life expectancyallowing long -term monitoring.
- Have one Wide geographical distribution and ease of manipulation.
- Provide a diversity of physiological and behavioral responses to pollutants.
How the bivalves are monitored
The parameters (metrics) main ones that are taken into account in monitoring the activity of the bivalves used in the BEWSS are above all the Movements of the valves and theheart activity. They are all absolutely harmless metrics for the crossroads, non -invasive and low energy consumption. Both technologies allow you to collect data in real time, improving the ability to detect pollutants and prevent environmental disasters. Then there are other behaviors of the less studied, but promising bivalves, which include the growth and dissolution of the shell, the premature release of eggs or larvae, and horizontal movements or the burial.
Movements of the valves
THE Movements of the valves they are one of the most indicators reliable and easy To be measured for biomonitoring: just think that the BEWSS based on this metric already exist on a commercial scale and are used by various countries. Are mainly detected through electromagnetic techniquesand provide information on closing or opening of the valves in response to environmental stress.
In normal conditions, the valves remain ajar to allow breathing. Yes open and close in response to several environmental factors. Variations in movements can indicate exposure to toxic substances, for example:
- there prolonged closure delle Valve is a response to the presence of heavy metals (like Mercury and Copper), pesticides And other polluting agents, since these bodies completely close the valves to protect themselves and avoid their absorption. The closure can last from a few minutes to several hours, depending on the concentration of the supply.
- The flapping (rapid opening and closing movement) indicates chemical stress. It is the moment when the bivalves try to quickly eliminate harmful substances from their body.
- If the valves remain open, it is to filter the water and capture nutritional particles, however theexcessive opening is a sign of imminent death. It can be an answer to the oxygen deficiency (hypoxia) or prolonged exposures to toxic substances.
The techniques for monitoring the movements of the valves include electromagnetic induction sensorsi.e. magnetic switches that record the open or closed state of the valves (each bivalve is equipped with a Small magnet on one valves and one sensor on the otherwhen the valves open and close, the magnetic field changes and the sensor records the movement). Or they are used optical fibersThat is, two coils are positioned on each valva, when the valves approach or move away, an electrical signal proportional to their distance is generated. Finally, the laser triangulationtechnique in which a laser The reflected light measures is projected on the valva and a sensor measures: when the valves open and close, the reflection changes and is recorded.
Monitoring of the heart activity of the mussels
THE’heart activity It is another powerful indicator of the state of health of the crossroads. In fact, heartbeat changes can reveal exposure to toxic substances.
- The bradycardia, that is the slowdown of the beat It is a typical response to pollutants such as copper.
- Tachycardia, that is theIncrease in the beat It is a compensatory response to environmental stress.
- THE’temporary cardiac arrest instead is frequent in conditions of hypoxia or toxic exposure.
Among the techniques to detect heart activity we find a scary name technique: the Infrared photopletismographyin which some sensors on the shell of the bivalve Above the cardiac region. During the heartbeat, the shape and volume of the heart changemodifying the amount of reflected light. These variations are converted into an electrical signal that can be analyzed in real time to determine the heartbeat.
There are then Alternative optical techniques (laser and ultrasound imaging or magnetic resonance imaging), in which a low power laser It is focused on the cardiac area of the crossroads: the reflection of the light is captured by a optical sensor and analyzed. Changes in the position of the reflection indicate the movement of the heart And they allow you to measure the heartbeat.
Future alternatives and developments of water control with mussels
To obtain the maximum result, there is certainly the need to integrate more measurement metrics simultaneouslybut also to develop New technologies To reduce the impact on monitored species. Some future directions can be, for example:
- the use of unquired bivalves (without any device), with detection through techniques of acoustic telemetry.
- the implementation of advanced algorithms to distinguish natural responses from those induced by contaminants
- The monitoring of several species at the same time For a more complete evaluation of the water quality
- the application of the BEWSS to improve the sustainability of aquaculture e protect the populations of bivalves at risk.
A virtuous example of biomonitoring
Among the many examples, emblematic is that of the aqueduct of Warsaw. Here biomonitoring is a resource that ensures the quality and safety of drinking water. The mussels used are those belonging to the species of river mussels in the sharp margin (Mytilus Galloprovinalis).
Before going into action, the mussels are collected by the lakes of Wielkopolska and brought in laboratorywhere they are selected and adapted to a new environment to prepare them for their role of sentinels environmental. Subsequently they are included in the aqueduct monitoring system, where for three months they work silently. After three months of “work” at the Warsaw Aqueduct, the mussels they come homein the lakes of Wielkopolska, from where they were taken. Here they resume their natural life, contributing to the balance of the ecosystem and being able to live for many years, sometimes even decades.
