Basic HTML Version
International Journal of Marine Science 2013, Vol.3, No.20, 158-165
http://ijms.sophiapublisher.com
161
of 2011 compared to the other two years. The years
2005 and 2006 plotted on the negative semiaxis, being
characterised by the species described in point b),
confirming their similarity in terms of presence of
certain species, and dissimilarity with respect to 2011.
Figure 2 Result of correspondence analysis of the data
Note: biplot of row (species) and column (years) scores. a) The
species coded as 6, 8, 14, 15, 18, 20, 21, 22, 40, 43, 44, 46 and
39 (superimposed on the graph) were abundant in August 2011
and absent in July 2005 and July 2006; b) the species coded as
34, 25, 11 and 9 were present in 2005 and 2006 and absent in
2011; c) species 19 was present in 2005; d) species 17 was
present in 2006 and 2011; e) the species coded 1, 2, 5, 10, 12,
16, 24, 26, 28, 30, 31, 32, 33, 36, 37, 38, 41, 42, 45 and 47
(superimposed on the graph) were insignificant for the
purposes of the analysis (they were always present or always
absent)
According to Boudouresque (1984), the species that
developed in the back-reef (LB in Figure 1) in the
three years (Table 1) mostly belong to the following
ecological groups: Photophilous–Infralittoral-Thermo-
philous (PhIT), Photophilous–Infralittoral-soft bottom
(PhISt), Photophilous–Infralittoral–Quiet environment
(PhIQ), Photophilous–Infralittoral–Harbours (PhIH),
Antisciaphilous (AS), Sciaphilous–Infralittoral–relatively
Quiet environment (SIQ), Sciaphilous–relatively Quiet
environment (SQ) and Sciaphilous-Infralittoral (SI).
The conditions in the study area were therefore
relatively calm and subject to considerable summer
warming, in some respects similar to a harbour
environment. The species observed for the first time in
2011 also had these characteristics. The ratio of the
number of photophilous species to sciaphilous species
(Ph:Sc) was 1.6, 1.9 and 1.3 in 2005, 2005 and 2011,
respectively.
Macroalgal biomass is reported in Table 2. Total
biomass showed a large increase between July 2005
and July 2006, while in August 2011 it dropped
sharply (about
-
65%).
C. racemosa
showed the same
trend, its biomass increasing by two orders of
magnitude (+8173%) between 2005 and 2006 and
decreasing by 96% between 2006 and 2011, the worst
performance of all macroalgae. These variations of
C.
racemosa
were clearly reflected by
C.r
.:T ratios
(Table 2).
During the observations conducted in the whole
back-reef area,
C. racemosa
proved widespread but
with few small thalli, in line with the results shown by
Table 2 Biomass (g dry weight m
-2
± SD) of
Caulerpa racemosa
v.
cylindracea
(
C. r.
), other macroalgal species (O) and total species
(T), and percentage weight ratios
C.r
.:T (%
C.r
.) estimated for each plot (LB-a, LB-b) and as average of plot data (m, values in bold)
of the Santa Liberata back-reef area
C. r.
O
T
%
C. r.
2005
LB-a
0.73 ±0.90
240.58±47.3
241.32±48.06
0.27
LB-b
1.00 ±0.54
81.5±55.67
82.50±56.32
1.24
M
0.87 ±0.78
161.04±109.95
161.91±110.17
0.67
2006
LB-a
60.39 ±28.7
236.05±104.39
296.43±115.31
20.37
LB-b
58.63 ±13.56
110.86±25.1
169.49±32.16
34.59
M
59.51 ±20.1
173.45±96.5
232.96±102.79
25.54
2011
LB-a
2.65 ±3.09
95.18±20.21
97.83±17.75
2.71
LB-b
1.81 ±2.09
73.69±16.03
73.49±14.95
2.46
M
2.55 ±2.48
83.43±21.04
85.66±20.00
2.98
Note: From the survey of August 2011, compared with July 2005 and July 2006 surveys (Lenzi et al., 2007)