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SEASONAL CHANGES IN BENTHIC FLUXES AND NET ECOSYSTEM METABOLISM IN THE RIA DE VIGO (NW SPAIN)
F. Alonso-Pérez, Carmen G. Castro, Zuñiga, D., B. Arbones y F.G. Figueiras
Instituto de Investigaciones Marinas (CSIC, Vigo)
Rías Baixas at the northern boundary of
the Canary Current upwelling system
Seasonal variation:
Upwelling: April to September
Downwelling: October to March
Ex(103 m3 s-1 Km-1)
-0.6-0.30.00.30.6
ME
S
A
M
F
E
D
N
O
SA
J
J
M
MO
NTH
Upwelling index (1987-2004)
Courtesy of RMS from PML
AVHRR Sea Surface TemperatureAugust 1998
UPWELLING
BACKGROUND
Fate of this high primary production?
NCP 0.84
Respiration0.56
Respiration?
Carbon flux0.18
aphoti
c zo
ne
photi
c zo
ne
sedimentRespiration
?
2-D non stationary box model for the Ria based on temporal variability of nutrient distributions
Units: gC m-2d-1
(Rosón et al. 1999)
BACKGROUND
To study the fate of fixed carbon on a seasonal scale
based on direct measurements of gross primary
production, pelagic and benthic respiration and vertical
export of organic matter in the Ria de Vigo.
OBJECTIVE
RIA DE VIGO: SAMPLING STATION
8 . 9 8 . 8 8 . 7 8 . 6
L o n g i t u d e ( W )
4 2 . 1 5
4 2 . 2 0
4 2 . 2 5
4 2 . 3 0
4 2 . 3 5La
titud
e (
N)
4 0 m 2 0 m1 0 m
V i g o
Reference Site
20 m depthmain ria channel
2 weeks campaign in April-04, July-04, October-04 and January-05.
METHODS
Seawater samples for nutrients and size-fractionated chlorophyll (0.2, 2 & 20 m) (5 depths)
Net Community Production (NCP) and Dark Community Respiration (DCR) by in situ 24 h light-dark bottle oxygen incubations (5 depths).
NCP = O2 (24h)light – O2 (t0)
DCR = O2 (t0) - O2 (24h)dark
Gross Primary Production:
GPP = NCP + DCR
Biogenic particle vertical fluxes by in situ 24 h deployment of a sediment trap
METHODS
Photos: Manuel E. Garci
External frame
Chamber
12 V Motor
Syringe water
sampler
Jet inflow
Outflow - Slotted tube
Lid
SEDIMENT
Rim
Water pump
80 cm
28 c
m
Sensor
Ele
ctro
nics
Chamber
Rim
Lead
Methacrylate base
Reed contact
LAND VERIFICATION ASSEMBLY
SEDIMENT8
cm
80 c
m
65 c
m
20 cm
Home made benthic chamberMeasuring oxygen and nutrient benthic fluxes
Cylindrical chape and incubating volume ~ 140 LStirring by 3 centrifugal pumps
Water samples at prefixed times by syringe sampler (50 mL)
Continuous recording of T, pH, turbidity and oxygen
METHODS
Ferrón et al, 2008
January
14 16 18 20 22 24 26 28
October
4 6 8 10 12 14 16 18
July
4 6 8 10 12 14 16
Upw
elli
ng
In
dex
April
17 19 21 23 25 27 29
-Qx
-4000
-2000
0
2000
4000
Up
wellin
g I
nd
ex
(m3/(
s k
m)
Tem
pera
ture
(ºC
)N
itr a
te(µ
M)
Ch
la(m
g/m
3)
APRIL JULY JANUARYOCTOBER
2004
19- apr 22- apr 26- apr 29- apr20
15
10
5
0
Dep
th (m
)
19- apr 22- apr 26- apr 29- apr20
15
10
5
0
Dep
th (m
)
19- apr 22- apr 26- apr 29- apr20
15
10
5
0
Dep
th (m
)
20046- j ul 8- j ul 12- j ul 15- j ul
20
15
10
5
0
6- j ul 8- j ul 12- j ul 15- j ul20
15
10
5
0
6- j ul 8- j ul 12- j ul 15- j ul20
15
10
5
0
07- oct 11- oct 14- oct 18- oct20
15
10
5
0
07- oct 11- oct 14- oct 18- oct20
15
10
5
0
07- oct 11- oct 14- oct 18- oct20
15
10
5
0
2004
17- j an 20- j an 24- j an 27- j an20
15
10
5
0
17- j an 20- j an 24- j an 27- j an20
15
10
5
0
17- j an 20- j an 24- j an 27- j an20
15
10
5
0
2005
HYDROGRAPHIC CONDITIONS
WATER COLUMN INTEGRATED SIZE-FRACTIONED CHLOROPHYLL-a
Units: mg Chl a m-2
Arbones et al, 2008
SEASONAL AVERAGES VERTICAL CARBON FLUXES
ABR JUL OCT JAN
C m
g m
-2 d
-1D
ata
0
200
400
600
800
1000
1200
1400
1600
1800
2000
ABR JUL OCT JAN
C:
N
0
2
4
6
8
10
12
14
16
ABR JUL OCT JAN
% O
rgC
/Dry
mas
s
0
2
4
6
8
APR JUL OCT JAN
O2
(mm
ol
m-2
d-1
)
-50
-40
-30
-20
-10
0
SEASONAL AVERAGES OF BENTHIC FLUXES
APR JUL OCT JAN
NO
3- (m
mo
l m-2
d-1
)
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
APR JUL OCT JAN
NH
4+ (
mm
ol
m-2
d-1
)
0
1
2
3
4
5
APR JUL OCT JAN
Si(
OH
) 4 (m
mo
l m
-2 d
-1)
0
2
4
6
8
10
SEASONAL AVERAGES OF BENTHIC FLUXES
APR JUL OCT JAN
Alk
co
rr (
mm
ol m
-2 d
-1)
0
10
20
30
APR JUL OCT JAN
Max
Co
x (m
mo
l m
-2 d
-1)
0
10
20
30
40
50
APR JUL OCT JAN
pH
un
its
m-2
d-1
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
0.02
APR JUL OCT JAN
Min
Co
x (m
mo
l m
-2 d
-1)
0
10
20
30
40
Using carbonic and boric dissociation constants (Luecker, 2000) TCO2 benthic fluxes =
MaxCoxTCO2 – ½ Alkcorr MinCox
APR JUL OCT JAN
Co
x A
vge
(mm
ol m
-2 d
-1)
0
10
20
30
40
Annual benthic carbon flux : 0.26 g C m-2 d-1 ~ 13 % GPP
NCP 1.00
Respiration1.25
Respiration0.11
Carbon flux0.96
APRIL-04
ap
hoti
c
zon
ep
hoti
c
zon
e
sedimentRespiration
0.30
NCP 4.06
Respiration1.07
Respiration0.32
Carbon flux1.12
JULY-04
sedimentRespiration
0.26
NCP 0.46
Respiration0.60
Respiration0.02
Carbon flux1.05
OCTOBER-04
ap
hoti
c
zon
ep
hoti
c
zon
e
sedimentRespiration
0.28
NCP 0.22
Respiration0.36
Respiration0.01
Carbon flux1.32
JANUARY-05
sedimentRespiration
0.19
44% 79%
43% 38%
56% 21%
56% 62%
5% 6%
2% 1%
27% 14%
23%31%
Su
mm
ary
& C
on
clu
sion
s: 1
D S
EA
SO
NA
L B
UD
GE
TS
Units: g C m-2 d-1