Ljiljana Iveša1, Andrea Bilajac1, Edi Gljušćić1, Shannen Smith2
1Center for Marine Research, Rovinj, Croatia - 2South Australian Research and Development Institute, Australia
The northern Adriatic Sea provides ideal conditions for marine forests dominated by fucalean canopy forming algae. Along the western Istrian coast, the species Gongolaria barbata in particular, was documented forming extensive forests between 2003-2013. However, since 2016, these forests have experienced a rapid decline, culminating in local extinctions in recent years. A comparison of historical and recent distribution data revealed that G. barbata now persists in three distinct habitats: shallow subtidal areas, a coastal lagoon, and rockpools scattered along the coastline. Morphological analyses further revealed significant differences in thalli structure between these habitats. Settlements in the lagoon and rockpools maintain higher abundances, acting as refugia despite extreme environmental conditions. In contrast, shallow water settlements near known historical sites are severely degraded, with underdeveloped and unhealthy thalli suffering from intense grazing and fouling. Restoration trials for G. barbata utilized both ex-situ and in-situ approaches. In the ex-situ approach, laboratory grown individuals reintroduced to their natural habitat showed noticeable growth and development over a year, demonstrating the potential of using existing refugia as natural incubators. In the in-situ approach, transplantation of adult thalli was attempted into a location that had previously hosted G. barbata assemblages. This trial revealed that such locations may no longer be suitable for restoration due to persistent stressors, such as grazing. Conversely, fertile individuals transplanted into an existing mixed algal forest provided insight into recruitment, juvenile growth and adult survival within these habitats. This trial demonstrated considerable potential for improving or restoring existing fucalean forests through both recruitment and transplantation. Future studies will focus on recruitment patterns and herbivore impacts to identify key donor populations and viable restoration targets. Active conservation of remaining habitats, combined with targeted restoration efforts and continuous monitoring, is crucial for preserving G. barbata and the biodiversity of the Adriatic in the face of escalating climate change and habitat degradation.
Biography
Ljiljana Iveša is a senior scientist at the Center for Marine Research in Rovinj, Ruđer Bošković Institute, Croatia. Her field of research includes taxonomy and ecology of macrophytobenthos (seaweeds and seagrasses), the ecology of coastal habitats on natural rocky shores and artificial hard substrates, and the assessment of the ecological status of coastal waters using macroalgal assemblages. Her current research is focused on the ecology of canopy-forming species of the order Fucales.