Communication

Researchers at the IMEDEA (CSIC-UIB) study how to stop the deterioration of the Portocolom marine ecosystem

  • Results got so far point out a lack of oxygen, excessive nutrients and global temperature increase as the main problems of conservation of the bay

Mallorca, 7th  June  2012. A scientific study conducted by researchers at Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB) reports that the combination of local factors due to human pressure and the gradual global warming endanger marine ecosystems in Portocolom (Felanitx, Mallorca). 

One of the observed factors for diagnosing health status of the port is oxygen. As stated by Dr. Raquel Vaquer, «we must remember that if the oxygen concentration decreases, organisms cannot survive. This phenomenon of lack of oxygen is called hypoxia, and makes life impossible for most species, with more negative effects for species that cannot move quickly and flee to safe areas. The study shows how the probability of hypoxia increases as water temperature rises». When the water temperature increases, marine organisms need increase their breathing in order to survive. This means a higher oxygen decrease.

 The study, published in the journal Estuaries and Coasts, is authored by researchers at the IMEDEA (CSIC-UIB) Raquel Vaquer-Sunyer, Carlos M. Duarte, Gabriel Jordà and Sergio Ruiz-Halpern, and has been carried out in Portocolom. Researchers measured several parameters (water salinity, temperature, dissolved oxygen, etc.) along 2009 and 2010. All these data were recorded continuously by a sounding line attached at the bottom of the bay. Records include, among other things, an elevated deep water temperature: 29 degrees Celsius were reached, and an even higher surface temperature.


More temperature, lack of oxygen and excess nutrients: a very bad combination

By adding eutrophication (excess of nutrients that reach the sea from treatment plants or fertilizers used in agriculture) to these factors, the result is an extremely negative combination, which makes life almost impossible during long periods. The study of IMEDEA (CSIC-UIB) has documented episodes with proliferation of seaweeds that indicate poor water quality. These seaweeds «explosions» are caused by an excess of nutrients and organic matter coming from land, causing oxygen depletion. This phenomenon is visible to the naked eye and repeats itself whenever the conditions are met, as occurred in April 2010.

«The conclusions of the study, -Dr. Vaquer specifies-, suggest the Portocolom marine water quality will worsen even more if wastewater discharges are not fixed. These discharges have been increasing, mainly by the poor condition of the sewer, population growth (residential and seasonal), and increased vessel activity within the port. The measures to be taken locally to prevent a worsening of the native ecosystem include fixing leaks in the sewer system, minimizing spills from ships, limiting urban and dock sprawl, and reducing the use of chemical fertilizers».

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Citation: Temperature Dependence of Oxygen Dynamics and Community Metabolism in a Shallow Mediterranean Macroalgal Meadow (Caulerpa prolifera). Raquel Vaquer-Sunyer, Carlos M. Duarte, Gabriel Jordà and Sergio Ruiz-Halpern. Estuaries and Coasts 2012, DOI: 10.1007/s12237-012-9514-y