Neptune seagrass (Posidonia oceanica), a marine plant endemic to the Mediterranean Sea, has gone from being a great (un)known to the general public to a hot topic we often hear about. Its growing relevance is well justified due to its crucial role in the proper functioning of the marine environment and in mitigating the effects of climate change.
Neptune seagrass is a type of seagrass, a marine plant that is vital to our health and the health of the ocean. Their role is so important that there is even a day dedicated to them. Every year in March, awareness of seagrasses, including Posidonia oceanica, is promoted internationally.
However, despite their growing recognition, we still need to continue raising awareness about its importance and promote its conservation. Why? The answer lies in a worrying reality: Neptune seagrass is regressing throughout the Mediterranean. Recent studies suggest that in the last 50 years, the area occupied by Neptune seagrass has decreased by more than 30% in the western Mediterranean. This drastic reduction raises serious concerns about the future of this underwater habitat and the overall health of our seas.
Causes of regression:
Posidonia oceanica is subject to many pressures and impacts that have contributed to its regression in the Mediterranean. These pressures fall into two main categories: physical and biological. Both are largely related to human activities and have had a significant impact on the status and extent of Neptune grass meadows.
Physical pressures:
- Illegal trawling: trawling, a practice involving the use of weighted nets dragged along the seabed, can cause a direct physical impact on seagrass meadows. Despite being an illegal practice at depths of less than 50 metres, this type of practice still occurs occasionally.
- Coastal activities: human activities in coastal areas, such as the construction of breakwaters, sand dredging for beach regeneration or the building of marinas, can lead to the degradation of Neptune seagrass habitat. These actions can result in direct destruction of the habitat or alteration of the environmental characteristics of the area, such as natural sedimentation dynamics or currents, negatively affecting the distribution and health of the meadows.
Concrete block used for anchoring on Neptune seagrass
- Mooring of boats: the anchoring of recreational boats, either by anchoring or by incorrectly placed anchoring buoys, in areas of Neptune grass has a direct physical impact on the seagrass meadows.
Biological pressures:
- Marine pollution: Marine pollution, which can include (accidental or voluntary) wastewater discharge and spillage of chemicals and agricultural nutrients, directly affects Posidonia oceanica meadows, which are highly sensitive to water conditions.
- Loss of water quality: Decreasing water quality due to pollution, eutrophication, and sedimentation can negatively affect the health and survival of Neptune seagrass as light and nutrients become less available.
- Invasive species: The introduction of non-native species can alter the ecological balance of marine ecosystems and cause competition with Neptune seagrass, leading to its regression. As an example, the proliferation of algae such as Caulerpa cylindracea or more recently, the Rugulopteryx okamurae, which grows much faster than Neptune grass, can colonise areas that would be favourable for its development.
Many of these factors are strongly related to and aggravated by our mass tourism model, which is not very respectful of the environment. Excessive mooring of recreational boats, over-exploitation of beaches and waste generation from tourism put additional pressure on Neptune seagrass meadows and the marine environment in general. The cumulative impact of these activities accelerates and worsens many of the threats posed to Posidonia oceanica, leading to its regression.
In summary, Neptune seagrass regression results from a series of physical and biological pressures and impacts, many of which are closely related to and exacerbated by human activity. The conservation of this species and the critical habitat it forms requires a holistic approach that addresses both the direct and underlying causes of its decline. In this sense, SUBMON works on integral projects for the conservation of marine biodiversity, such as the BlueLab project, which involves the study and preservation of Posidonia oceanica.
