Jasmine FERRARIO, TAMBURINI M., LO VULLO M., OCCHIPINTIAMBROGI A.
Department of Earth and Environmental Sciences, University of Pavia, Italy.
E-mail: jasmine.ferrario@universitadipavia.it
A TRANSPLANT EXPERIMENT TO TEST THE BIOTIC
RESISTANCE IN NATIVE FOULING COMMUNITIES TO
BIOINVASION
Abstract
The introduction of non-indigenous species (NIS) poses a threat to marine ecosystems and is a
major cause of biodiversity loss. Globally, shipping is considered one of the most important
vectors of NIS introduction, and ports the relative hotspot areas. In ports, NIS can easily
colonise artificial substrates and displace native species, becoming an important component of
biofouling communities. The ecological interactions behind the success of a NIS introduction
are still unclear, including the capability of communities characterized by high native species
richness to limit the success of NIS (i.e., biotic resistance hypothesis).
To test this hypothesis, communities rich in native species from a “low-impact” site were
transplanted in two marinas (“high-impact”) in the Gulf of La Spezia (in 2019), expecting to
assess a difference in NIS number and cover between transplanted and non-transplanted panels.
A total of 25 PVC panels were deployed and after three months a subset of the panels that had
grown in the low-impact sites was moved into marinas, for an additional period of two months.
In general, fouling communities were significantly different among treatments (control,
transplanted and not-transplanted panels) at the end of the experiment, suggesting the
maintenance of peculiar assemblages in the transplanted panels. On the other hand, newly
recruited species after the transplant were not significantly different between transplanted and
no-transplanted panels, thus indicating a null effect of mitigation by native species to NIS
settlement. In literature, contradictory results were obtained when testing the hypothesis of
biotic resistance, but the use of native communities in eco-engineering infrastructures is an
interesting future prospect and should deserve further investigation.
Keywords: Alien species, colonization success, biofouling, ports, Mediterranean Sea
Introduction
The marine urbanization sprawl is globally replacing natural habitats with hard artificial
infrastructures, a physical aspect that can strongly modify the structure of marine
communities (Airoldi et al., 2015). Ports are the main artificial habitats involved in
marine urbanization and provide new available substrates for opportunistic and tolerant
fouling species, which are mostly composed by NIS (Mineur et al., 2012). In fact, ports
are considered hotspot areas for NIS, due to the influence of one of the most important
vectors of introduction of these species, namely maritime shipping (including large
commercial and small recreational vessels; Bailey et al., 2015; Ulman et al., 2019). In
particular, species can be transported by vessels into ballast waters or as fouling on their
hulls; while the first vector is now regulated on large vessels in most countries, the
second one is still largely underestimated and considered the most dangerous
unregulated vector of NIS worldwide (Drake et al., 2021; Ulman et al., 2019). The
recreational boating has been now largely acknowledged as an important vector of NIS
spreading worldwide and the management of fouling should be implemented urgently,
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
29
Department of Earth and Environmental Sciences, University of Pavia, Italy.
E-mail: jasmine.ferrario@universitadipavia.it
A TRANSPLANT EXPERIMENT TO TEST THE BIOTIC
RESISTANCE IN NATIVE FOULING COMMUNITIES TO
BIOINVASION
Abstract
The introduction of non-indigenous species (NIS) poses a threat to marine ecosystems and is a
major cause of biodiversity loss. Globally, shipping is considered one of the most important
vectors of NIS introduction, and ports the relative hotspot areas. In ports, NIS can easily
colonise artificial substrates and displace native species, becoming an important component of
biofouling communities. The ecological interactions behind the success of a NIS introduction
are still unclear, including the capability of communities characterized by high native species
richness to limit the success of NIS (i.e., biotic resistance hypothesis).
To test this hypothesis, communities rich in native species from a “low-impact” site were
transplanted in two marinas (“high-impact”) in the Gulf of La Spezia (in 2019), expecting to
assess a difference in NIS number and cover between transplanted and non-transplanted panels.
A total of 25 PVC panels were deployed and after three months a subset of the panels that had
grown in the low-impact sites was moved into marinas, for an additional period of two months.
In general, fouling communities were significantly different among treatments (control,
transplanted and not-transplanted panels) at the end of the experiment, suggesting the
maintenance of peculiar assemblages in the transplanted panels. On the other hand, newly
recruited species after the transplant were not significantly different between transplanted and
no-transplanted panels, thus indicating a null effect of mitigation by native species to NIS
settlement. In literature, contradictory results were obtained when testing the hypothesis of
biotic resistance, but the use of native communities in eco-engineering infrastructures is an
interesting future prospect and should deserve further investigation.
Keywords: Alien species, colonization success, biofouling, ports, Mediterranean Sea
Introduction
The marine urbanization sprawl is globally replacing natural habitats with hard artificial
infrastructures, a physical aspect that can strongly modify the structure of marine
communities (Airoldi et al., 2015). Ports are the main artificial habitats involved in
marine urbanization and provide new available substrates for opportunistic and tolerant
fouling species, which are mostly composed by NIS (Mineur et al., 2012). In fact, ports
are considered hotspot areas for NIS, due to the influence of one of the most important
vectors of introduction of these species, namely maritime shipping (including large
commercial and small recreational vessels; Bailey et al., 2015; Ulman et al., 2019). In
particular, species can be transported by vessels into ballast waters or as fouling on their
hulls; while the first vector is now regulated on large vessels in most countries, the
second one is still largely underestimated and considered the most dangerous
unregulated vector of NIS worldwide (Drake et al., 2021; Ulman et al., 2019). The
recreational boating has been now largely acknowledged as an important vector of NIS
spreading worldwide and the management of fouling should be implemented urgently,
2nd Mediterranean Symposium on the Non-Indigenous Species (Genoa, Italy, 22-23 September 2022)
29