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International Journal of Marine Science 2013, Vol.3, No.20, 158-165
http://ijms.sophiapublisher.com
158
Research Article Open Access
Can the Marine Ecosystem of a
Posidonia oceanica
Back-reef React and Defend
Itself against the Spread of
Caulerpa racemosa
var.
cylindracea
?
Mauro Lenzi
1
, Francesca Birardi
1
, Maria Grazia Finoia
2
1. Lagoon Ecology and Aquaculture Laboratory OPL Company, via G. Leopardi 9, 58015 Orbetello (Gr) Italy
2. Institute for Environmental Protection and Research (ISPRA), via Casalotti 300, 00166 Roma, Italy
Corresponding author email: lealab1@gmail.com
International Journal of Marine Science, 2013, Vol.3, No.20 doi: 10.5376/ijms.2013.03.0020
Received: 16 Mar., 2013
Accepted: 18 Apr., 2013
Published: 22 Apr., 2013
Copyright
©
2013 Lenzi, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:
Lenzi et al., 2013, Can the Marine Ecosystem of a
Posidonia oceanica
Back-reef React and Defend Itself against the Spread of
Caulerpa racemosa
var.
cylindracea
?, International Journal of Marine Science, Vol.3, No.20 158
-
165 (doi: 10.5376/ijms.2013.03.0020)
Abstract
A back-reef of
Posidonia oceanica
(Santa Liberata, Orbetello, Italy)
subject to degradation lost its typical mixed meadow
of
Cymodocea nodosa
,
Nanozostera noltii
and
Caulerpa prolifera
and was colonised by the invasive chlorophycea
Caulerpa
racemosa
var.
cylindracea
(
C. racemosa
) between 2003 and 2004. When the submerged flora behind the
P. oceanica
barrier reef was
studied between 2005 and 2006,
C. racemosa
constituted 25% of the macroalgal biomass and showed high cover (>50%). Residual
dead patches of the mixed meadow had been colonized by
Penicillus capitatus
. By 2011,
C. racemosa
had fallen to about 3% of total
algal mass and its cover had also dropped (5-25%), while other typical species predominated:
P. oceanica
dead
mattes
were covered
by thin dense mats of photophile species dominated by
Jania rubens
and
Cladophora
sp
.
Periodically, the latter produced balls that
floated freely on the bottom. We compared the lists of phytobenthic flora for 2005, 2006 and 2011 by explorative correspondence
analysis. The 2011 list showed a 27% increase in autochthonous species. The results suggest that the invasion of allochthonous
fast-spreading
C. racemosa
may occur in degraded ecosystems after events that altered the original community. The community can
recover through a succession of vegetation changes.
Keywords
Caulerpa racemosa
v.
cylindracea
;
Posidonia oceanica
back reef; Invasive species; Tyrrhenian Sea
Introduction
Various factors can modify coastal phytobenthic
populations. In recent decades, such changes have
been correlated with various human activities along
the coast, the introduction of exotic species and global
climate change. Increasing human impact on coasts
includes residential settlements, ports, breakwaters,
docks and discharge of urban and industrial waste
water. Pleasure boating and mooring in areas populated by
marine phanerogams is another disturbing factor. All
this has undoubtedly reduced the area of meadows
of
the seagrass
Posidonia oceanica
, which are now
believed to be decreasing significantly throughout
the Mediterranean Sea. Finally, warming of the
Mediterranean by the greenhouse effect (Bradley,
2000) may already have caused changes in phytobenthic
populations and favoured allochthonous species that
have largely been introduced and spread by shipping
(Boudouresque and Verlaque, 2002).
In recent years, the number of introduced macroalgal
species has risen in all marine ecosystems with
increasing marine traffic (through fouling and
deballasting of water), aquaculture and commercial
activities (Boudouresque and Ribera, 1994; Verlaque,
2001; Sfriso and Curiel, 2007). In the Mediterranean
Sea, 85 introduced macroalgae have been listed and
eight of them are considered invasive (Boudouresque
and Verlaque, 2002a). The invasive
Caulerpa racemosa
var.
cylindracea
(Sonder) Verlaque, Huisman,
Boudouresque (Bryopsidales, Chlorophyta) (hereafter:
C. racemosa
), introduced in the early 1990s from the
south-western coast of Australia (Verlaque et al
.
,
2003), has spread swiftly along Mediterranean coasts
in the last 15 years (Ruitton et al., 2005a; Piazzi et al.,
2005). The ecological role of
C. racemosa
is still
debated, however most authors consider it harmful to
autochthonous phytobenthic communities, especially
to algae constituting turfs and to a lesser extent to
taller species (Boudouresque and Verlaque, 2002b;
Piazzi and Balata, 2007). There is some consensus
that dense cover of a large number of established
indigenous species can be a major factor in reducing
the probability of successful invasion (Ceccherelli et