Days before the death of thousands of fish that hit the beaches of the mar Menor on the 12th of October, they came to the lagoon between 500 and 1,000 tonnes of nitrates in the aftermath of the last drop of cold, esteem a final report signed by scientific experts in the environment of the Spanish Oceanographic Institute, several universities and the Consejo Superior de Investigaciones Científicas (CSIC). These, together with that already contained the lagoon, led to the horrific episode with fish and crustaceans asfixiándose in the banks. The nitrates come from, above all, of the credits of the irrigated crops that have multiplied in the area of Campo de Cartagena (the basin that discharges into the mar Menor). As a result, “an area of more than 9,000 hectares –the mar Menor occupies 17,000 hectares– has been again devastated at the bottom of the lagoon”, calculated by the researchers.

The samples were taken days after the passage of the temporary give concentrations of nitrates in around 13 milligrams per liter, “100 times above that can be considered normal”, specifies the report. Also had 35 tons of ammonium, and more than 100 of phosphates. The contaminants were in the 100,000 tons of sediment that are swept away by the flood into the lagoon, which was already a “profound degradation”.

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“The problem is not a consequence of the entry into itself of the fresh water, but nutrients (nitrate) carried by the water, they are the fuel of the process eutrophic (increase in nutrients causes an excess phytoplankton, which leads to lack of oxygen)”, clarify the researchers. In fact, have pointed out, the avenue of November 1987, and accumulated a precipitation of one-third superior to the Dana (depression isolated at high levels) this year, “despite which there were no episodes of mass mortality in the lagoon.”

The report looks at the process of deterioration in the mar Menor, which receives “from the decade of the eighties, large quantities of organic matter and nutrients from both diffuse as a point of the agricultural activity”. This contamination has affected the groundwater in the aquifer of the Quaternary, and to the surface. Sewage discharges (sewage) and agricultural have been, however, focused on points and at certain times. Until 2015, the values of chlorophyll were low, own the system, although in the decade of 2000 because there were some peaks which drew attention to the risk of eutrophication. From the end of 2015, confirmed an unusual growth of phytoplankton, which are shot in the summer of 2016. The clear water turned into a paste green, light left to get to the bottom and 85% of the vegetation benthic sea Less disappeared.

In this scenario, the authors warn that the process of recovery of the mar Menor will be “long and complex”, because even by stopping all of the inputs of nutrients present, “the funds will continue releasing nitrates for quite some time.” The first step for them is to “curb the entry of sediments and nutrients, improving techniques and efficiency of fertilization of agricultural”. They also advocate for the recovery of the water courses of the hydrological network of the basin of the mar Menor, the implementation of systems of tillage less aggressive, the recovery of wetlands or the use of groundcovers and hedges to reduce flooding.

Put in doubt the effectiveness of the Plan of Zero Discharge submitted by the Ministry for the Ecological Transition because its main measures are based on the construction of a public work and does not point to the source of the problem. The scientists warn, at the same time, that solutions that have been shuffled as to increase the input of water from the Mediterranean are “not an option”, for the same reason and because it “would cause side effects completely undesirable.”

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