January 20, 2022 5:10 pm

“You cannot change the situation of the Mar Menor from one day to the next, not even from one year to the next”

Julia Martinez Fernandez, technical director of the New Culture of Water Foundation (In yet), is a founding partner and member of the group of 100 signatory experts of the “European Declaration for a New Culture of Water”. In addition, he has extensive national and international research experience in integrated management of water resources and water sustainability from interdisciplinary perspectives.

To his experience in these issues must be added an intense work for years in environmental movements and other citizen groups in the defense of environmental and heritage values, sustainability and the new culture of water.

He is currently working on the sustainability of the socioecological system from the Mar Menor. In fact, this September, a thesis is read under his co-direction on this subject and the governance process for the improvement of the current situation of the lagoon.

How did we get to the current situation of the Mar Menor?

The excess of nutrients provided by fertilizers of agricultural origin for many years and, above all, its great increase due to the increase in irrigation in the countryside of Cartagena, which is very intensive, has led to this.

Also the contribution of brines loaded with these agricultural nutrients. All this has overcome the ecological resilience mechanisms of the lagoon ecosystem, which has led to an enormous proliferation of phytoplankton and, therefore, a eutrophic crisis that has already led to three major episodes of mass mortality of specimens of all types of species in 2016 , 2019 and 2021. Each of these episodes has an increasing severity with respect to the previous one.

We have reached this situation due to fertilizers of agricultural origin and the increase in irrigation in the countryside of Cartagena

These episodes of anoxia are seasonal. Why doesn’t the same thing happen in winter?

Mass mortality episodes are produced by the presence of large amounts of nutrients, which are the fuel of the eutrophic process. The proliferation of phytoplankton needs, in addition to food (which are those nutrients), adequate temperatures that do not occur in winter, because they are too low.

For this reason, although there is a situation of deep degradation, especially in the deepest layers of the Mar Menor lagoon, the visualization and emergence of these acute episodes, of a situation that is chronic, occur in summer. It is at this time that this combination occurs for a sufficient number of weeks and months to give rise to episodes in which oxygen is completely depleted and mass mortality occurs.

In the event that nutrient discharges to the lagoon were abruptly stopped, how much would it cost Mar Menor to regain ecological balance?

Well, it must be specified that we are not talking only and mainly about discharges, we are talking about diffuse agricultural pollution. Therefore, the bulk of this contamination does not go through a pipe or a canal, or through a discharge as such, but occurs in each square meter of intensive irrigation, then through different natural flows, both surface and underground, and ends up reaching the Mar Menor.

The bulk of this contamination does not go through a pipe or a canal, or by a discharge as such, but occurs in every square meter of intensive irrigation

It seems like a slow recovery process …

You cannot change the eutrophic situation of such a large lagoon – bear in mind that it is the most important salty coastal lagoon in Europe – from one day to the next, not even from one year to the next. We are talking about what could begin to be visible in the medium term, but that it will take the long term, possibly 10 years for it to really be a significant recovery. This as long as the measures were started at the source, not with emergency, provisional, badly thought out measures, or those that do not address the root of the problem.

The solutions at source are to eliminate part of the intensive irrigated area and drastically reduce the contribution of fertilizers to the remaining irrigation.

Mortality episodes in the Mar Menor are increasingly serious. / Juan Carlos Caval (EFE)

Is cleaning the bottom sludge a viable option or would it be worse?

No, first it is necessary to change the agrarian model of the Cartagena countryside and, in addition, reinforce the capacity of the basin itself to eliminate its own nutrients. The measures have to be based on nature, such as green hedges between crops and recover the surface of all coastal wetlands in the environment.

How are these wetlands today?

There are natural wetlands, but they have lost a very important part of their surface that should be recovered. It is essential to exclude any type of irrigation and intensive agricultural activity in a wide, perimeter band, in the entire environment of the Mar Menor. This would act in a buffer and nutrient elimination band formed by natural wetlands and natural vegetation.
From that moment on, the lagoon has its own mechanisms to recover, so that the grasslands of phanerogams such as the cymodocea nodosa recover, because that recovery is the key mechanism to prevent further explosions of phytoplankton.

Only if it is seen that this recovery of the meadows has difficulties, it would be necessary to consider whether it is necessary to carry out some type of action, of active restoration

Would you then rule out that option?

You have to do a follow-up. Only if it is seen that this recovery of the meadows has difficulties, is paralyzed, or cannot be overcome by itself, would it be necessary to consider, if it is necessary to carry out some type of action, of active restoration. They are very complex in large ecosystems and it would be necessary to study it very carefully, doing previous pilot tests.

Another emergency measure that has been considered is to dredge the Gola de Marchamalo. Can it be effective?

All the studies that have been done on the effectiveness of this measure by the Spanish Institute of Oceanography, which has also been analyzed by other universities and was already analyzed by the scientific committee years ago, they came to the conclusion that its effect in increasing the renewal of the water in the lagoon was very small.

Even if Marchamalo and Las Encañizadas were dredged together, an effect of around 10% increase in the renewal of the lagoon would be seen. It would hardly have an effect. If it is done only in Marchamalo it would be insignificant, but also that can put the conservation of certain species and habitats at risk.

Keep in mind that we are talking about a place of community importance where there are habitats and species. These removal and dredging actions, in addition to being useless, could be counterproductive.

What would happen if the lagoon becomes a permanent dead zone?

We would maintain a state of more eutrophic water, where we would lose the unique species of the lagoon that are the reason why it has deserved multiple protection status at a regional, national, European and international level. Not to mention the enormous ecological impacts it entails. It would aggravate the economic crisis — the value of homes has been greatly reduced due to the poor condition of the Mar Menor — it would ruin the tourism sector.

It would also have a very serious impact on fisheries and we would face European sanctions for non-compliance with the Habitats Directive, the Water Framework Directive and of the European directive on nitrates.


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