The responses of habitat-forming brown macroalgae of the genus Cystoseira on local and global stressors
The northern Adriatic represents the northernmost biogeographic sector of the Mediterranean Sea. The sea bottom along the west Istrian Coast is mainly rocky and therefore particularly suitable for the growth of habitat-forming brown macroalgae of the genera Cystoseira, Gongolaria and Ericaria.
The west Istrian coast spans approximately 100 km air line in the north-south direction. This particular orientation produces large-scale gradients of oceanographic variables and wave action intensities. In its less disturbed state, the Istrian coast hosted lush forests of fucalean species, including Cystoseira, Ericaria, Gongolaria, Sargassum species, but also the endemic Fucus virsoides.
In the proposed project, we will inspect its distribution and abundance along the whole Istria Coast with special attention on determining the different fucalean species habitat architecture. Starting from 2015, a general regression of Cystoseira, Gongolaria and Ericaria species in the subtidal zone was observed along the west Istrian Coast. Before 2015, mixed stands of Cystoseira compressa, Gongolaria barbata, Ericaria crinita, Cystoseira foeniculacea and Cystoseira humilis formed flourishing forests, which predominantly covered the rocky bottom, while the intertidal zone was characterized by the endemic Fucus virsoides (although already regressed), Cystoseira compressa, Ericaria crinita and Ericaria amentacea stands.
The die-off chronology of Cystoseira, Gongolaria and Ericaria forests was followed from spring 2015 to autumn 2018 at several stations. Based on those observations, in the proposed project we will evaluate the current status of the genera Cystoseira, Gongolaria and Ericaria and possible first signs of regression of these forests due to local and global stressors, among which we prioritize assessing the impact of high temperatures during summer, benthic mucilage formation and sea urchin grazing.
Furthermore, we will inspect more in details the reproductive phenology of Cystoseira, Gongolaria and Ericaria species as well as Fucus virsoides that leads to the successful recruitment and we will test some cost-effective restoration methods for successfully restoring some degraded forests along the Istria coast.