Recent Large Scale Environmental Changes in the Mediterranean Sea and Their Potential Impacts on Posidonia Oceanica

Climate related changes can have significant effects on Posidonia oceanica, an endemic seagrass species of the Mediterranean Sea (MEDIT). This seagrass is very important for many aspects of functioning of the sea but there is an increasing number of reports about the ongoing loss of its biomass and area coverage. We analysed multiyear data of the sea surface temperature (SST), sea level anomalies, ocean colour MODIS-A and ERA-Interim reanalysis. The results provide a description of current environmental conditions in the MEDIT and their spatial and temporal variability, including long-term trends. We defined regions where the extent of the P. oceanica meadows may be limited by specific environmental conditions. Light limitation is more severe near the northern and western coasts of the MEDIT, where the vertical diffuse attenuation coefficient is large. In the zone extending from the Gulf of Lion towards the south, significant wave heights reach large values. Wave action may destroy the plants and as a result the shallow water depth limit of P. oceanica meadows is most likely deeper here than in other regions. The highest SST values are documented in the south-eastern part of the Mediterranean Sea. In this area P. oceanica meadows are more endangered by the climate warming than in other regions where SSTs are lower. The absence of P. oceanica meadows in the south-eastern edge of the Mediterranean Sea can be attributed to high temperatures. Our conclusions are partly confirmed by the information about P. oceanica from the literature but more monitoring efforts are needed to fully describe current extent of the meadows and their shifts. Results presented in this paper can help with designing special programs to confirm the role of environmental conditions on the spatial distribution of P. oceanica and their future trends in the Mediterranean Sea

Review on the conservation status of autochthonous marine angiosperms in the Mediterranean Sea

Seagrasses are globally declining. They form important ecosystems, providing food and shelter for other marine organisms and services such as protection from coastal erosion and regulation of coastal water quality. For these reasons, their conservation should be of primary importance. A critical review was carried out determining whether the conservation efforts for autochthonous marine angiosperms in the Mediterranean Sea were consistent with their status based on their distribution, habitat, population dynamics, main threats, and the conservation strategies applied to each one of them. In general, seagrasses in the Mediterranean are declining and the conservation efforts applied to them vary substantially depending on the species. The species that have been studied the most between the years 2000 and 2020 were Posidonia oceanica (L.) Delile and Cymodocea nodosa (Ucria) Asch. On the contrary, little information was available for Ruppia maritima L. The in situ conservation strategies implemented for these species are considerably more advanced than the ex situ. P. oceanica is the species that benefits from the highest level of legal protection, while the other species are mostly protected by actions directed to all seagrasses in general. Not many studies were developed for the ex situ conservation strategies and especially not for every species. Specimens in gene banks were only present for Zostera marina L., Ruppia cirrhosa (Petagna) Grande and R. maritima.Las angiospermas marinas están regresando globalmente. Forman ecosistemas de elevada importancia debido a que procuran comida y refugio para muchos organismos marinos, y también llevan a cabo servicios como la protección de la erosión costera y la regulación de la calidad del agua. Por estas razones, su conservación debería ser de importancia primaria. Para determinar el estado de conservación de las angiospermas marinas autóctonas del Mar Mediterráneo se ha llevado a cabo una revisión bibliográfica, en función de su distribución, dinámica poblacional, hábitat, amenazas y estrategias de conservación in situ y ex situ aplicadas a cada especie. Por lo general, las angiospermas marinas en el Mar Mediterráneo están en declive y las medidas de conservación varían considerablemente dependiendo de la especie. Las especies que más han sido estudiadas entre los años 2000 y 2020 han sido Posidonia oceanica (L.) Delile y Cymodocea nodosa (Ucria) Asch. Las estrategias de conservación in situ para estas especies están considerablemente más desarrolladas que las estrategias de conservación ex situ. P. oceanica es la especie que beneficia de la protección legal más elevada, mientras que otras especies están protegidas principalmente por legislaciones dirigidas a todas las angiospermas marinas en general. Los estudios que se han llevado a cabo para las estrategias de conservación ex situ son escasos y no existen para todas las especies. La presencia de material conservado en bancos genéticos sólo es disponible para Zostera marina L., Ruppia cirrhosa (Petagna) Grande and Ruppia maritima L..Ciencias del Ma