Dr Shannen Smith1, Andrej Fućak1, Edi Gljušćić1, Andrea Bilajac1, Dr Ljiljana Iveša1
1Institut Ruđer Bošković, Center for Marine Research, Rovinj, Croatia
Globally, the structure of marine forest habitat is changing, and in many bioregions the cover of large canopy forming macroalgal species has declined. In the Mediterranean region, mixed species assemblages once formed belts of canopy cover across much of the coastline, however, coastal development and pollution have negatively affected these assemblages in recent decades. In many cases, rocky reefs in this region are now dominated by less complex algal assemblages that often do not form true canopies. In the southern part of the Istrian peninsula (northern Adriatic Sea), Šćuza Lagoon represents one of the last known significant populations of the canopy forming species Gongolaria barbata, which was once prolific throughout shallow reefs along the Istrian coast. Here, we present the results of a field study within Šćuza Lagoon that describes how the benthic topography and complexity within the lagoon, including the presence of structural seagrass meadows, positively influences growth and settlement patterns of G. barbata. Within seagrass habitat, we observed a higher number of G. barbata individuals, which also grew taller than those in more exposed habitat, thus creating a more dense canopy in those areas. In addition, we present the results of a transplant experiment, that show how herbivore exclusion influences the persistence of this species at a nearby location where G. barbata was once prolific. The results of both experiments aid in understanding the biological mechanisms that contribute to canopy loss and help inform best practises for future restoration trials.
