ARCHIVED - Pockets of anoxic water still threaten fish and crustaceans in the Mar Menor

Analysts warn another episode of phytoplankton growth could turn the lagoon green again as sea grass vegetation alters

The layer of anoxic water (i.e. water lacking in oxygen) which caused the mass death of tens of thousands of fish and crustaceans on the beaches of the Mar Menor last weekend is reported to be still present in the lagoon, although according to the scientists monitoring the situation the probability of a second episode like that of a week ago has decreased significantly.

The latest data reveal that the oxygen level in the Mar Menor is still very low at depths of greater than 5 metres in “a couple of areas” where the water is at its deepest in the north and the centre of the lagoon but it is also believed that lower air temperatures and an increase in wind speeds have contributed to an improvement as they help different layers of water to mix.

However, the danger is far from over. Freshwater continues to run off into the lagoon due to the rise in the water table after the heavy rain and flooding of September, much of it bearing nitrates from the crop land of the Campo de Cartagena, and the level of salinity in the Mar Menor is still lower than usual. These conditions, the experts warn, could lead to a massive growth in the amount of phytoplankton in the water – in other words, the lagoon could see the process of eutrophication which turned the water green in 2016 repeated as 2019 draws to a close.

The regional government continues to attribute the recent deterioration in the condition of the Mar Menor almost exclusively to the gota fría storm of last month, but others insist that the storm was merely a catalyst and that all of the ingredients for the disaster have been steadily accumulated over a period of decades.

Some sources report that in 90 per cent of the area where Cymodocea sea grass normally grows it has been replaced over the last month by Caulerpa, that mud is forming on the sea bed where it is not usually seen, and that needlefish, prawns, crabs and other species are gathering on or close to rocks so that when a wave breaks there is more oxygen in the water. With another gota fría storm possibly on its way to the Costa Cálida next week there are worries that, as government sources warned earlier this week, the worst may yet be to come.

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