Researchers warn of the lack of protection of Posidonia meadows from dumping
European directives prohibit anthropogenic discharges, i.e. those derived from human activity, in marine areas where Posidonia is present. However, because of a legal vacuum, they do not specify how far away from its meadows it is permitted to do so, and there is a generally accepted consensus among scientists and managers that a distance of 500 metres is more than enough. As a result, spills have been shifting in recent years from shallower coastal areas to deeper, more open marine areas. A recent study carried out by the Department of Marine Sciences of the University of Alicante and the Marine Angiosperm Ecology Group of the Spanish Institute of Oceanography (IEO-CSIC) shows that Posidonia meadows are affected by spills far beyond this safety distance. In particular, the researchers warn that a distance of at least 2.5 kilometres from the point of emission should be respected.
A critical gap in seagrass protection: impact of Anthropogenic off-shore nutrient discharges on deep posidonia oceánica Meadows is the title of the article published in the journal Plants, which reflects an alarming reality, as the decline of Posidonia meadows is accelerating and, thus, the disappearance of habitats essential for the life of hundreds of species of marine flora and fauna. According to Professor José Luis Sánchez Lizaso, one of the researchers who took part in the study, it, was carried out over a year at four points along the coast between the south of the province of Alicante and the north of Murcia. During this time, samples have been taken periodically in order to analyse the nutrients discharged and, as the professor explains, molecular markers have been used to discern which nutrients do not originate in the plant itself. The amount of light in the water has been measured and, in addition, another series of descriptors have been taken into account, such as the density of its leaves, or how it carries out photosynthesis.
The result shows that plants within this area of influence of the landfill experience morphological and physiological changes that affect their growth and survival, causing significant habitat alteration. Therefore, despite efforts to move landfills away from the coastline, these results highlight the vulnerability of the deeper Posidonia meadows.
As explained by Juan Manuel Ruiz, researcher at the Spanish Institute of Oceanography (IEO-CSIC) and co-author of the study, the distances between spills and vulnerable habitats have been underestimated and should be revised if we want to guarantee their conservation. Also, Sánchez Lizaso pointed out that if action is not taken quickly, many Posidonia meadows will be lost, and these are essential in the Mediterranean ecosystem as they oxygenate the water and a wide variety of organisms and benthic species depend on them, many of them commercial.
Posidonia oceanica is a plant endemic to the Mediterranean, the most abundant and most common in the coastal strip, which can form extensive meadows from a depth of 0.5 metres to a maximum of 40 metres. This plant is an organism that is highly sensitive to environmental deterioration, such as a decrease in water transparency, eutrophication (excess supply of inorganic nutrients from human activities), pollution and erosion, so its presence on the coast is considered an indicator of water quality.
More information:
Judit Jiménez-Casero et al, A Critical Gap in Seagrass Protection: Impact of Anthropogenic Off-Shore Nutrient Discharges on Deep Posidonia oceanica Meadows, Plants (2023). DOI: 10.3390/plants12030457
Provided by Asociacion RUVID
