Warnings over deterioration of water quality in the Mar Menor

Residents organize protests at Mar Menor beaches as ecologists warn that conditions in the lagoon are worsening

Alarm bells are ringing once again in respect of the water quality in the Mar Menor, the largest saltwater lagoon in, with both observers and scientists warning that there is a risk of another severe deterioration in the marine environment like the one which occurred in 2019.

In some parts of the lagoon the water is already turning green as it has done during numerous episodes in the past, with chlorophyll levels rising rapidly as water continues to run off from the farmland of the Campo de Cartagena via the aquifer below the surface and the “rambla” drainage channels which cut across the countryside. In this context Ángel Pérez Ruzafa, Professor of Ecology at the University of Murcia, is quoted in the regional press as warning that a heavy late-summer storm could easily lead to a repetition of the events following the gota fría storm of September 2019, when thousands of dead fish and shellfish were washed ashore as a result of a dramatic drop in the level of oxygen in the water.

Due to the runoff of water into the Mar Menor the level of salinity in the lagoon also remains low, and is now at under 43 grams per litre – well under the level of 45 or 46 which was the norm from the late 20^th century onwards. This is attributed by Sr Pérez Ruzafa to the continuing runoff of freshwater containing nutrients into the Mar Menor, particularly during episodes such as the bursting of a water pipe in Santiago de la Ribera in late July.

As for chlorophyll levels, the maximum acceptable level of 4 micrograms per litre is being exceeded in practically all of the lagoon, and it is at above 5 micrograms that the water begins to turn green. At the measuring point near Los Urrutias the reading has reached 5.41, and other readings of up to 10 and 11 have been reported near the southern end of the Mar Menor.

In consequence, average transparency has lessened considerably from the average of 5 metres during the spring to under 3 metres at the end of July, and in the area of the mouth of the Rambla del Albujón and Los Urrutias the figure has fallen to below 2 metres, according to data quoted in La Verdad.

How the situation develops in the coming weeks will depend to a large extent on meteorological conditions, but also on the rate at which runoff water continues to bring nutrients derived from agricultural fertilizers into the lagoon. At present it is calculated that the amount of water making its way into the Mar Menor via the Rambla del Albujón is 176.81 litres per second, according to figures quoted in La Opinión, and with each litre containing an average of 119 milligrams of nutrients this equates to an astonishing 2,892 kilos of nitrates every day.

Lower rates of runoff are reported at the Rambla de Miranda and the Rambla las Matildes as well as in El Carmolí, but they also contribute to the problem.

When these substances meet the warm water of the Mar Menor, which is currently at close to 30ºC, the result is an algal bloom which, unfortunately, is once again leading to bathing in the lagoon becoming extremely unappetizing.

In response, demonstrations are being organized at various beaches around the Mar Menor on Friday August 13 to protest at the “collapse of the lagoon and the inactivity of public administration bodies”, with all members invited to take part between 18.00 and 20.00.

Images: SOS Mar Menor Facebook