Ilaria MANCINI, AZZOLA A., BIANCHI C.N., MORRI C., OPRANDI A.,
MONTEFALCONE M.
SEL (Seascape Ecology Laboratory), DiSTAV, Department of Earth, Environment and
Life Sciences, University of Genoa, Corso Europa 26, 16132 Genova, Italy
E-mail: ilamancini@yahoo.it
THE STORY OF A SUCCESSFUL INVASION: CAULERPA
CYLINDRACEA IN THE MARINE PROTECTED AREA OF
PORTOFINO (LIGURIAN SEA)
Abstract
The green alga Caulerpa cylindracea, one of the worst invasive species in the Mediterranean Sea,
was first recorded in the Ligurian Sea (NW Mediterranean) in 1996 and in the Portofino Marine
Protected Area in 2008. Monitoring at Portofino between 2012 and 2017 showed that it was
widespread between 1 m and 45 m depth. A new period of monitoring, 2018 to 2021, roughly
confirmed previous information, but also evidenced that in the infralittoral zone C. cylindracea
cover exhibited little intra- and interannual variability, while in the circalittoral zone it was more
variable within and among years. A reduction in cover was observed at all depths in 2019. On
the whole, our results indicate that C. cylindracea is now fully established on the rocky reefs of
Portofino MPA.
Key-words: Alien alga; Monitoring; Algal reefs; Coralligenous reefs; NW Mediterranean Sea.
Introduction
The green alga Caulerpa cylindracea Sonder, 1845, of SW Australian origin, is one of
the worst invasive species in the Mediterranean Sea: first recorded in 1990 off Libya, it
reached the Ligurian Sea in 1996 (Montefalcone et al., 2015). Its presence remained
mostly restricted to anthropized areas until 2008, when the species was observed also in
the Marine Protected Area (MPA) of Portofino, especially on biodetritic bottoms (Morri
et al., 2019). A yearly monitoring activity between 2012 and 2017 showed that it was
widespread between 1 m and 45 m depth, with the highest substratum cover (up to 25%)
at about 20 m (Morri et al., 2019). Here we report on the results of a second monitoring
period, 2018 to 2021, in order to see whether C. cylindracea has somewhat receded after
a first bloom or has remained similarly abundant as in the previous period.
Materials and methods
Cover data of C. cylindracea were estimated visually by scuba diving between 1 m and
45 m depth. Data were analyzed separately according to two different depth ranges: the
infralittoral zone, 1 m to 20 m, and the circalittoral zone, 21 m to 45 m.
Results
The information obtained during the monitoring activity between 2018 and 2021
confirmed that C. cylindracea has remained roughly as abundant as in the previous period.
However, different trends between infralittoral algal communities and circalittoral
coralligenous communities were apparent. In the infralittoral zone (Fig.1a), C.
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
105
MONTEFALCONE M.
SEL (Seascape Ecology Laboratory), DiSTAV, Department of Earth, Environment and
Life Sciences, University of Genoa, Corso Europa 26, 16132 Genova, Italy
E-mail: ilamancini@yahoo.it
THE STORY OF A SUCCESSFUL INVASION: CAULERPA
CYLINDRACEA IN THE MARINE PROTECTED AREA OF
PORTOFINO (LIGURIAN SEA)
Abstract
The green alga Caulerpa cylindracea, one of the worst invasive species in the Mediterranean Sea,
was first recorded in the Ligurian Sea (NW Mediterranean) in 1996 and in the Portofino Marine
Protected Area in 2008. Monitoring at Portofino between 2012 and 2017 showed that it was
widespread between 1 m and 45 m depth. A new period of monitoring, 2018 to 2021, roughly
confirmed previous information, but also evidenced that in the infralittoral zone C. cylindracea
cover exhibited little intra- and interannual variability, while in the circalittoral zone it was more
variable within and among years. A reduction in cover was observed at all depths in 2019. On
the whole, our results indicate that C. cylindracea is now fully established on the rocky reefs of
Portofino MPA.
Key-words: Alien alga; Monitoring; Algal reefs; Coralligenous reefs; NW Mediterranean Sea.
Introduction
The green alga Caulerpa cylindracea Sonder, 1845, of SW Australian origin, is one of
the worst invasive species in the Mediterranean Sea: first recorded in 1990 off Libya, it
reached the Ligurian Sea in 1996 (Montefalcone et al., 2015). Its presence remained
mostly restricted to anthropized areas until 2008, when the species was observed also in
the Marine Protected Area (MPA) of Portofino, especially on biodetritic bottoms (Morri
et al., 2019). A yearly monitoring activity between 2012 and 2017 showed that it was
widespread between 1 m and 45 m depth, with the highest substratum cover (up to 25%)
at about 20 m (Morri et al., 2019). Here we report on the results of a second monitoring
period, 2018 to 2021, in order to see whether C. cylindracea has somewhat receded after
a first bloom or has remained similarly abundant as in the previous period.
Materials and methods
Cover data of C. cylindracea were estimated visually by scuba diving between 1 m and
45 m depth. Data were analyzed separately according to two different depth ranges: the
infralittoral zone, 1 m to 20 m, and the circalittoral zone, 21 m to 45 m.
Results
The information obtained during the monitoring activity between 2018 and 2021
confirmed that C. cylindracea has remained roughly as abundant as in the previous period.
However, different trends between infralittoral algal communities and circalittoral
coralligenous communities were apparent. In the infralittoral zone (Fig.1a), C.
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
105