The Community increases six-fold the removal of biomass from the Mar Menor and avoids a “catastrophe”, according to fishermen and scientists

22_06_29_The Community increases six-fold the removal of biomass from the Mar Menor and avoids a catastrophe according to fishermen and scientistsThe Murcian Government has removed 10,509 tonnes of biomass from the Mar Menor since 1 January, an amount six times higher than the average extracted annually since 2017 and which has prevented a new “catastrophe” in the salt lagoon, as the Fishermen’s Guild of San Pedro del Pinatar and the Scientific Committee in charge of monitoring this ecosystem agree.

In statements to Europa Press, the spokesman for the Scientific Advisory Committee, Emilio María Dolores, recalled that the Community has been removing biomass for several years, but in values “much lower” than those of this 2022. The average amount of biomass removed in the last four years could be around 1,600 or 1,700 tonnes per year. Thus, so far in 2022 a figure of biomass has been removed six times higher than what was removed during previous full years.

María Dolores has put this difference down to the fact that “this year there is a greater proliferation of ova because there has been a greater influx of nutrients than in previous years”. For example, in 2021, around 720 tonnes of nitrogen entered the salt lagoon over the whole year, while in 2022 it has already exceeded 970 tonnes.

Therefore, this excess of nitrogen in the water, in different chemical forms, is favouring this algae proliferation. If these 10,509 tonnes of biomass had not been removed, María Dolores pointed out that the effect would have been “catastrophic” for the ecosystem because the extraction of algae “means removing organic matter”.

The algae removed were analysed after drying and the nitrogen and phosphorous they contained was estimated. Based on the results, these 10,509 tonnes of biomass “are equivalent to 219 tonnes of nitrogen and 7.29 tonnes of phosphorus” which, if they had not been removed, would be in the water and available to generate more problems.

“According to Maria Dolores, the removal of nitrogen and phosphorus reduces the availability of nutrients in the water column and therefore reduces the risk of phytoplankton proliferation.

The Scientific Advisory Committee has no estimate of the biomass that would remain to be removed from the Mar Menor because the ova is being generated every day and its proliferation depends on multiple factors such as nutrient levels, the competition of these nutrients with other living marine organisms, temperature and other oceanographic factors.

In this respect, the Community’s personnel clean a different area each day depending on the detection of the highest concentrations of biomass observed in the field. In total, it has an average of 150 people in brigades dedicated to this work every day. Of these, a hundred people carry out the task on foot and another 50 people at sea, belonging to the Fishermen’s Guild of San Pedro del Pinatar.

Right now, these brigades are responding to an emergency contract from the regional government, because the Committee warned that it was urgent to remove this biomass from a technical and scientific point of view. In total, the Community has invested between 5 and 7 million euros in emergency contracts for clean-up work.

Ángel Pérez Ruzafa, Professor of Ecology at the University of Murcia, confirmed that everything that can be biomass for proliferation or rapid growth is being extracted, especially the most nitrophilic species, which are the ones that have the greatest affinity with urban waste, nitrates and phosphorous.

He explained that these are species that take advantage of the available nutrients very quickly and have a tendency to accumulate. When they rot, they subsequently form a lot of organic matter. This is the biomass that has been causing beach silting in recent years.

“This sludge, which remains highly particulated on the beaches, moves with the waves and, in summer, these suspended particles are the ones that accumulate in the deep areas of the basin and end up causing anoxia,” according to Pérez Ruzafa, who points out that it is very important to remove them, as he has been warning for the last four or five years.

The problem emerged in the spring, when the water table began to rise and water began to flow not only through the Rambla del Albujón, but also through numerous watercourses and beach areas. At that time, the scientists advised removing the biomass with hand rakes “so as not to alter the sediment and not to harm the Cymodocea meadows, which not only do not cause any problems, but the biomass suffocates them and blocks the light”.

Pérez Ruzafa indicated that the task of extraction was carried out in 2022 in a “very methodical” way and a large amount of biomass was extracted. The most beneficial thing, in his opinion, is that “not only does it prevent the formation of organic matter and reduce the risk of anoxia when the high temperatures arrive, but the biomass has also sequestered many of the nutrients that have been entering” the salt lagoon.

In this way, a lot of nitrates, nitrogen and phosphorus are extracted from the biomass. “In this way, a double task of preventing the formation of sludge and removing these nutrients is carried out,” he added.

He stressed the importance of being “methodical” in the removal of this biomass, especially until a management infrastructure is in place to reduce water inflows and lower the water table. In fact, he predicted that, on the day that the water table is lowered below sea level, this type of task “will not be so necessary”.

“Any reduction in the nutrients that accumulate in the Mar Menor is fundamental to ensure that the ecosystem does not break down,” according to Pérez Ruzafa, who explains that the removal of biomass plays a “fundamental” role in this regard.

However, he also called for the Albujón wadi pumping station to be put into operation, which allows between 30% and 40% of what is coming in to be extracted, a percentage that “is already sufficient for the salt lagoon to begin to have control capacity”. However, when its operation is interrupted, the risk of a dystrophic crisis “increases tenfold”.

“Whether or not there will be an anoxia phenomenon will depend on whether the pumping station also works, on the weather conditions and on the amount of nutrients that enter between now and August,” according to Pérez Ruzafa, who assured, however, that the extraction of biomass “is fundamental to reduce the risks”.

The chief skipper of the Fishermen’s Guild of San Pedro del Pinatar, José Blaya, has pointed out that this removal of biomass “is a very positive action” for his group. In fact, he noted that the situation is “stable” and is improving thanks to this clean-up.

He pointed out that the fishermen are cleaning up, above all, in the southern area of the Mar Menor, which is where there is more localised ova. The Cofradía has 50 people on board some 35 boats deployed every day, which remove some 50 tonnes of ova daily.

If this biomass extraction task had not been carried out, Blaya acknowledged that fishing would have been more difficult because the nets fill up with ova and impede the task.



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