047 | Halophila stipulacea: population dynamics in the oriented nature reserve “Laghetti di Marinello”, Sicily, Italy

Ilaria Nusco¹, Mattia Soppelsa¹, Fabio Mondello¹, Antonio Manghisi¹, Salvatore Giacobbe², Marina Morabito¹ | ¹Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Italy; ²CNR-IRBIM, Messina, Italy.

The Oriented Nature Reserve (ONR) “Laghetti di Marinello” was established by the Sicilian Region in 1998 (Regional Decree 745/44), being listed among the Nature Reserve Areas since 1991. The lagoon rises at the base of the Tindari cliff, set in the gulf of Patti, northern coast of Sicily, where it plays a relevant biogeographical role due to biological and phytocentric values [1]. Because of storm surges, the sandy bank has been interested in continuous modifications that led to the formation of several ponds, different in number and shape, variously connected with the sea. In 2023 a biomonitoring program (visual surveys and sampling) has started, coupled with an extensive review of published and gray literature about the area. As a result of this activity, it has been possible to evaluate distribution and seasonal dynamic of seagrasses. Among them, Halophila stipulacea (Forssk.) Asch. belongs to the family Hydrocharitaceae and it is the only non-native seagrass currently settled in the Mediterranean Sea [2]. In marine environment H. stipulacea has the tendency to supplant native seagrasses, such as Posidonia oceanica and Cymodocea nodosa [3]. In the ONR “Laghetti di Marinello”, H. stipulacea occurs in lake Porto Vecchio as a well-established patch since 1995. Furthermore, in the last three years, ephemeral patches of it have been found in lake Marinello and lake Verde, alternating few months of rapid development with sudden disappearance. Noteworthy, in lake Porto Vecchio it co-occurs with other seagrasses, namely C. nodosa and Ruppia spp., without supplanting them, while in both lake Verde and lake Marinello all seagrass meadows are highly interrupted by a huge presence of both Caulerpa spp. and Cladophoraceae (Chlorophyta). Well established meadows of H. stipulacea are present since 1999 in the facing bay of Marinello, which might be the source of the ephemeral patches in the ponds, supplied by sea storms. Even if the ecological interrelations among macrophytes in the lagoon needs more observations to be fully disentangled, physic-chemical gradients among and within the different ponds could be major drivers to the mutual distribution and interactions among seagrasses. Especially differences in salinity among the ponds and the salinity gradient cliff-to-sea in lake Porto Vecchio might influence directly and eventually limit the expansion of H. stipulacea.