Sea warming, together with environmental changes caused by human activities, is causing a progressive decline in seagrass meadows in the northern Adriatic Sea. This is demonstrated by a new study recently published in the journal Estuarine, Coastal and Shelf Science. The research shows that the seagrass beds of Posidonia oceanica, Cymodocea nodosa and other marine plants, which are vital for biodiversity, coastal stability and carbon storage, are at risk from a variety of factors.

The study, coordinated by the National Institute of Oceanography and Applied Geophysics (OGS), involved an international group of researchers from the Miramare Marine Protected Area, the University of Trieste, the National Institute of Biology of Slovenia (NIB) and the University of Maribor (Slovenia). It highlighted how environmental change and sea warming contribute significantly to the decline of seagrass beds, particularly Cymodocea nodosa, in the coastal areas of the northern Adriatic. 

The analysis focused mainly on the Slovenian and Italian coasts of the Gulf of Trieste and used an integrated approach of field monitoring and statistical analysis to assess the relationship between anthropogenic pressure and marine vegetation response. The relationship between seagrass dynamics and environmental variations was studied by analysing the spatiotemporal patterns of environmental variables and applying mathematical models referring to two distinct time intervals: 2009-2013 and 2014-2018.

The study shows that the decline of seagrass beds in the gulf is caused by both impacts at the local level (pollution, urbanisation, hydrological alterations) and global climatic stresses (marine warming).

In the northern Adriatic, Cymodocea nodosa is the dominant species, while Posidonia oceanica and several species of Zostera show a much more fragmented distribution, often reduced to small isolated areas.

‘The results indicate that Cymodocea nodosa is still present in the Gulf, particularly along the coast from Monfalcone to the mouth of the Tagliamento, but in the period 2014-2018 there was a 30% regression in Slovenian waters and up to 89% along the coast near Trieste,’ explains Vinko Bandelj, oceanographer at OGS, adding that ‘analysis of physical and chemical variables revealed an increase in sea water temperature throughout the Gulf and a variation in nutrient load, with a particularly significant reduction in Slovenian waters’.

The group of researchers identified light in the water column, nutrient availability, temperature and sediment type as the main determinants of marine plant presence. However, other local factors, such as coastal anthropogenic interventions and urbanisation, have most likely also contributed to reducing the resilience of these species to environmental disturbances.

The conservation of these habitats is considered essential for mitigating climate change and safeguarding marine biodiversity in the Mediterranean. To achieve this goal, the study highlights the need to develop integrated spatial planning strategies, including the reduction of local anthropogenic pressures, the protection of less degraded coastal areas and the long-term monitoring of climatic and biological parameters. Although large-scale studies are useful for predicting the impact of climate change, local investigations, such as the one carried out in this study, remain equally essential for developing targeted conservation strategies.

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