Preservation of the endemic alga Fucus virsoides J. Agardh: Ecological factors responsible for its regression and extinction

Gljušćić, Edi (2025) Preservation of the endemic alga Fucus virsoides J. Agardh: Ecological factors responsible for its regression and extinction. Doctoral thesis, Prirodoslovno-matematički fakultet.

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Abstract

Fucus virsoides (order Fucales), known also as the Adriatic Fucus, is an endemic Mediterranean perennialthat inhabits exclusively the intertidal zone of the Adriatic Sea, where it naturally forms dense belts or patchystands of significant ecological importance. Over the past decades, populations of F. virsoides haveundergone almost complete collapse, disappearing from most of the Adriatic coast from Italy to Albania,though the causes of this regression are still uncertain. This study investigated the historical and recentdistribution of F. virsoides along the Istrian coast and adjacent parts of the northern Adriatic Sea,documenting the systematic decline of populations and their replacement by opportunistic, ephemeralspecies. Population structure, morphology, and the influence of external biotic factors were also analysedwithin the study sites. In-situ temperature measurements in Fucus populations revealed sharp and rapidfluctuations caused by alternating aerial exposure and submersion, with the greatest extremes recordedduring spring daytime low tides. Experimental trials further confirmed that periodic exposure of F. virsoidesapices to the elevated air temperatures of 34°C can cause permanent thallus damage, biomass loss, andreduced photosynthetic efficiency, with markedly weakened recovery potential. Based on all these findings,a protocol for ex-situ cultivation and restoration of F. virsoides was developed and successfully tested.Although early thallus growth remains slow, juvenile individuals transplanted into suitable habitats, whenprotected from grazers, can reach reproductive maturity within 10 months, confirming the method’spotential for future conservation efforts.

Item Type:	Thesis (Doctoral thesis)
Uncontrolled Keywords:	Fucus virsoides; historical distribution; regression; community structure; population structure;thermotolerance; restoration
Subjects:	NATURAL SCIENCES > Interdisciplinary Natural Sciences NATURAL SCIENCES > Interdisciplinary Natural Sciences > Marine Science
Divisions:	Center for Marine Research
Depositing User:	Edi Gljušćić
Date Deposited:	09 Jan 2026 06:50
URI:	http://fulir.irb.hr/id/eprint/10758

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