A &3C Study on Organic Matter in Semi-enclosed Mediterranean Marine System
107
phaeopigments (CHLa and Phaeo, p.g·l-l;
Lorenzen and Jeffrey 1980). carbon isotopic composition (Susp-013C, %0; Lajtha and Michener
1994) and particulate biopolymeric organic carbon (Susp-BPC, p.g C 1-1; Fabiano and Pusceddu
1998).
For sediment analysis, three replicate cores
per station and period were collected randomly
from three quadrats (20 cm length. 400 cm 2 surface area) belonging to a larger quadrat (1 m 2 ),
The top 0-1 em layer of each core was used for the
analysis of total organic matter (SOM, mg·g- 1 )
according to Parker (1983), chlorophyll a (CHLa,
p.g.g-l) and phaeopigments (Phaeo, p.g,trl) were
analysed according to Lorenzen and Jeffrey
(1980) and sedimentary biopolymeric organic
carbon (Sed-BPC, p.gCI-I) and isotopic composition (Sed-ol3C. %0) were analysed according to
Pusceddu et al. 1999. Phytoplankton (SuspCCHLa) and microphytobentmc (Sed-CCHLa)
carbon was calculated by converting CHLa concentrations to carbon content (C-Chla) according
to Nival et al, (1972). Zooplankton (> 125 p.m),
macro algae and seagrass isotopic analysis was
performed according to Jennings et al. (1997).
The isotopic contribution of each carbon
source to the organic matter bulk (sedimentary
and suspended) was calculated -3Ccording to
Dauby (1989). Isotopic data were compared with
frequency of resuspension calculated according
CERC (1977) model reported in Smaal and Haas
(1997). Temporal and spatial fluctuations were
assessed by analysis of variance (ANOYA;
Underwood 1997), while correlation between
parameters was ascertained by means of
Spearman-Rank correlation (Sokal and Rohlf
1981).
Results
Table 1 reports particulate and sedimentary
organic matter descriptors. Total sedimentary
organic matter (Fig. 2) mainly accumulated in
summer (l06 ± 0.9 mg·tr 1 ). Moving from open
sea (5.7 mg·g- 1 ) to the southern station (156
mg.g- 1 ). a marked gradient in SOM was observed
(ANOYA, P<0.05; Table 1). Total suspended
organic matter showed two peaks in May and
December (3.5 mg·I- 1 and 3.1 mg·I- 1 ) (Fig. 2).
Among stations no significant differences in
OSM were observed (ANOYA,P>0.05; Table 1).
The concentration of chlorophyll-a carbon in
the sediments (Fig. 3) ranged from 0 to 85 p.g C
15 1 , with the highest values in autumn and spring
(814.0 ± 536 p.gCg-l and 112.0 p.gCtrl, respectively). No significant differences were observed
between stations (ANOYA, P>0.05; Table 1).
Sedimentary phaeopigments peaked in late summer (August-October) and in December (2.95 ±
0.6 and 5.2 p.g.g-l, respectively), The concentrations of sedimentary phaeopigments were significantly higher in the southern than in the opensea station (ANOYA,P<0.05; Table 1).
Table 1. Statistics and ANOVA results of main trophic descriptors of sediments and suspended organic matter. See text for
acronyms. ns, no significant difference (P>O.05)
Variable/Station
Open-sea
North
South
ANOVA
Mean ±SD Min
Max
Mean ±SD
Min
Max
Mean ±SD
Min
Max
Fv..uI P
Resuspension
1.7
1.3
0.4
4A
4.4
2.6
1.9
11.5
2.9
1.7
1.1
6.4
6.0'**"
Water column
OSM (mg.I- I )
1.8
1.3
0.2
4.6
1.8
1.1
0.4
4.0
1.2
0.5
0.1
2.2
l.5/ns
CHLa (pg.I-I)
OA
0.2
0.1
0.8
0.4
0.3
0.0
1.1
0.3
0.1
0.1
0.5
O.5/ns
CCHLa (p.gCI-l) 15.6
8.1
3.2
31.0
15.1
12.5
0.4
45.9
12.1
4.0
3.7
18.6
0.6/ns
Phaeo (p.g.l-l)
0.2
0.3
0.0
0.9
0.3
0.5
0.0
1.7
0.1
0.2
0.0
0.5
O.Uns
BPC (pg.l-l)
223.3 168.4
75.0 596.4
246.3
157.3
86.7
542.9
179.7
103.4
77.7
357.0
0.6/ns
,s13C (%0)
-21.4
2.2 -25.1 -16.4
-18.3
1.8 -20.5
-15.8
-18.6
2.8
-24.7
-15.4
6.4/***
Sediment
80M (mg·g- 1 )
5.7
3.9
1.4
15.0
93.5
35.8
35.0
144.8
156.3
43.7
71.8
201.1
64.1/***
CHLa (p.g.g-l)
1.8
1.2
0.0
4.0
3.5
3.6
0.2
11.8
11.7
23.7
0.2
84.4
l.8/ns
CCHLa (p.gCg-l) 72.4
46.5
0.0 159.6
139A
142.2
9.6
473.9
467.9
947.2
8.7 3390.2
1.8/ns
Phaeo (Jlg.g-l)
0.0
0.2
0.0
0.5
2.3
1.0
0.0
3.8
4.6
3.8
0.0
13.0
12.0/***
BPC (pg.g-l)
1989.8 1926.9 104.5 7478.4 19011.1 11947.3 3907.9 42281.4 26619.2 18468.8 2749.9 59114.5
11.8/***
,suC (%0)
-15.8
3.1 -22.3 -10.6 -13.1
lA -15.3
-10.6
-10.0
1.2
-11.5
-8.0
22.91***
.. P$O.05; .... P$O.Ol; ...... P$O.OO1
107
phaeopigments (CHLa and Phaeo, p.g·l-l;
Lorenzen and Jeffrey 1980). carbon isotopic composition (Susp-013C, %0; Lajtha and Michener
1994) and particulate biopolymeric organic carbon (Susp-BPC, p.g C 1-1; Fabiano and Pusceddu
1998).
For sediment analysis, three replicate cores
per station and period were collected randomly
from three quadrats (20 cm length. 400 cm 2 surface area) belonging to a larger quadrat (1 m 2 ),
The top 0-1 em layer of each core was used for the
analysis of total organic matter (SOM, mg·g- 1 )
according to Parker (1983), chlorophyll a (CHLa,
p.g.g-l) and phaeopigments (Phaeo, p.g,trl) were
analysed according to Lorenzen and Jeffrey
(1980) and sedimentary biopolymeric organic
carbon (Sed-BPC, p.gCI-I) and isotopic composition (Sed-ol3C. %0) were analysed according to
Pusceddu et al. 1999. Phytoplankton (SuspCCHLa) and microphytobentmc (Sed-CCHLa)
carbon was calculated by converting CHLa concentrations to carbon content (C-Chla) according
to Nival et al, (1972). Zooplankton (> 125 p.m),
macro algae and seagrass isotopic analysis was
performed according to Jennings et al. (1997).
The isotopic contribution of each carbon
source to the organic matter bulk (sedimentary
and suspended) was calculated -3Ccording to
Dauby (1989). Isotopic data were compared with
frequency of resuspension calculated according
CERC (1977) model reported in Smaal and Haas
(1997). Temporal and spatial fluctuations were
assessed by analysis of variance (ANOYA;
Underwood 1997), while correlation between
parameters was ascertained by means of
Spearman-Rank correlation (Sokal and Rohlf
1981).
Results
Table 1 reports particulate and sedimentary
organic matter descriptors. Total sedimentary
organic matter (Fig. 2) mainly accumulated in
summer (l06 ± 0.9 mg·tr 1 ). Moving from open
sea (5.7 mg·g- 1 ) to the southern station (156
mg.g- 1 ). a marked gradient in SOM was observed
(ANOYA, P<0.05; Table 1). Total suspended
organic matter showed two peaks in May and
December (3.5 mg·I- 1 and 3.1 mg·I- 1 ) (Fig. 2).
Among stations no significant differences in
OSM were observed (ANOYA,P>0.05; Table 1).
The concentration of chlorophyll-a carbon in
the sediments (Fig. 3) ranged from 0 to 85 p.g C
15 1 , with the highest values in autumn and spring
(814.0 ± 536 p.gCg-l and 112.0 p.gCtrl, respectively). No significant differences were observed
between stations (ANOYA, P>0.05; Table 1).
Sedimentary phaeopigments peaked in late summer (August-October) and in December (2.95 ±
0.6 and 5.2 p.g.g-l, respectively), The concentrations of sedimentary phaeopigments were significantly higher in the southern than in the opensea station (ANOYA,P<0.05; Table 1).
Table 1. Statistics and ANOVA results of main trophic descriptors of sediments and suspended organic matter. See text for
acronyms. ns, no significant difference (P>O.05)
Variable/Station
Open-sea
North
South
ANOVA
Mean ±SD Min
Max
Mean ±SD
Min
Max
Mean ±SD
Min
Max
Fv..uI P
Resuspension
1.7
1.3
0.4
4A
4.4
2.6
1.9
11.5
2.9
1.7
1.1
6.4
6.0'**"
Water column
OSM (mg.I- I )
1.8
1.3
0.2
4.6
1.8
1.1
0.4
4.0
1.2
0.5
0.1
2.2
l.5/ns
CHLa (pg.I-I)
OA
0.2
0.1
0.8
0.4
0.3
0.0
1.1
0.3
0.1
0.1
0.5
O.5/ns
CCHLa (p.gCI-l) 15.6
8.1
3.2
31.0
15.1
12.5
0.4
45.9
12.1
4.0
3.7
18.6
0.6/ns
Phaeo (p.g.l-l)
0.2
0.3
0.0
0.9
0.3
0.5
0.0
1.7
0.1
0.2
0.0
0.5
O.Uns
BPC (pg.l-l)
223.3 168.4
75.0 596.4
246.3
157.3
86.7
542.9
179.7
103.4
77.7
357.0
0.6/ns
,s13C (%0)
-21.4
2.2 -25.1 -16.4
-18.3
1.8 -20.5
-15.8
-18.6
2.8
-24.7
-15.4
6.4/***
Sediment
80M (mg·g- 1 )
5.7
3.9
1.4
15.0
93.5
35.8
35.0
144.8
156.3
43.7
71.8
201.1
64.1/***
CHLa (p.g.g-l)
1.8
1.2
0.0
4.0
3.5
3.6
0.2
11.8
11.7
23.7
0.2
84.4
l.8/ns
CCHLa (p.gCg-l) 72.4
46.5
0.0 159.6
139A
142.2
9.6
473.9
467.9
947.2
8.7 3390.2
1.8/ns
Phaeo (Jlg.g-l)
0.0
0.2
0.0
0.5
2.3
1.0
0.0
3.8
4.6
3.8
0.0
13.0
12.0/***
BPC (pg.g-l)
1989.8 1926.9 104.5 7478.4 19011.1 11947.3 3907.9 42281.4 26619.2 18468.8 2749.9 59114.5
11.8/***
,suC (%0)
-15.8
3.1 -22.3 -10.6 -13.1
lA -15.3
-10.6
-10.0
1.2
-11.5
-8.0
22.91***
.. P$O.05; .... P$O.Ol; ...... P$O.OO1