Portal de Cartagena
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Researchers from the Polytechnic University of Cartagena (UPCT) and the Spanish Institute of Oceanography (IEO) of Murcia coordinate a study to analyze the seabed of the Mar Menor.
According to the first conclusions of the work carried out last March, the contribution of nutrients from the sediment to the water column can increase during this summer as a result of the rise in temperature.
Given these data, experts warn of a possible new explosion of phytoplankton and increased water turbidity.
The objective of the work is to obtain for the first time a biogeochemical characterization of the bottoms of the Menor that includes sediment, vegetation and water.
This will allow us to analyze in detail the processes that involve the exchange of nutrients and possible contaminants between water and funds and to evaluate the role of seagrasses in the sayings and flows of the mentioned elements, says José Álvarez, researcher responsible for the Edaphology group Environmental, Chemical and Agricultural Technology of the UPCT.
The results of the winter season, according to Álvarez, coordinator of the UPCT, show that most of the lake's bottoms are strongly anoxic (lacking oxygen), there is a large accumulation of organic matter from vegetation remains .
Researchers have also found high concentrations of nitrogen and dissolved organic carbon in the sediment, detecting flows into the water column.
Juan Manuel Ruíz, coordinator for the IEO, indicates that in areas where vegetation is present, there is evidence of a greater flow of oxygen to the sediments, as well as a greater accumulation of nitrogen, phosphorus, sulfur and carbon.
These preliminary results of the winter conditions show the known functions of these habitats as a storage and sink of the aforementioned elements, a fundamental aspect for the proper functioning of the Mar Menor ecosystem, the control of nutrients, sediments and water quality.
The nutrient that could limit the phenomenon of proliferation of plankton is phosphorus, whose concentration in water was very scarce when the winter analysis was carried out, although it was abundant in the sand and mud particles and in the remains of organic matter accumulated in the bottom .
The release of a small portion of said accumulated phosphorus, or the entry of the nutrient due to wastewater discharges or sewage leaks, could trigger the process.
In fact, available data indicate that in their current conditions, the concentrations of phosphorus and nitrogen in the water are significantly higher than those found at this time in 2017, just before the phytoplankton bloom observed in the summer of that year. .
According to this, data from the IEO have already detected a rise in chlorophyll levels well above those observed at this time last summer.
Therefore, although it is unknown how the process will evolve in the coming weeks, everything seems to indicate that we could observe a new explosion of phytoplankton.
The next stage of the project will determine the extent to which the sediments contribute to explaining these summer developments of the phytoplankton communities.
Multidisciplinary group
The researchers of the UPCT and the IEO, together with experts from the Universities of Cádiz and Santiago de Compostela, are evaluating the effect of the vegetation on the nutrients and heavy metals of the sediment.
For this, they will carry out field and experimental works.
Knowing the biological, nutritional and geochemical state of the funds will help to evaluate the potential risks associated with pollution / eutrophication, predict possible short and medium term consequences, assess with more criteria the possible corrective measures and estimate the recovery times of the ecosystem, according to the experts consulted.
Source: UPCT
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