Post on 30-Jan-2016
description
Which factors determine spring biological bloom in the China Sea?
Xiaohong Yao
Key Laboratory of Marine Environment and Ecology
(Ministry of Education), Ocean University of China,
Qingdao, 266100, P.R. China
2012.5.10, SOLAS OPENSCIENCE CONFERENCE
Objectives
• 1) In the China Sea, which factors determine spring biological bloom (not always occur)? This is a “yes” or “no” question
• 2) In the China Sea, which factors enhance spring biological bloom? This is “how much” question
• 3) Roles of Asian dust deposition on spring biological bloom in the China Sea
Fertilization incubation experiments in the Yellow Sea in March 2011
Surface sea water
200μm filtering
bottles
Dust and nutrientscontrol
Photo of incubation box, each of bottle is 16 L , recycling sea water is used for controlling temperature
Route of incubation experiment in March, 2011
Sea water was collected in the mid of the Yellow sea (red star), then direct to East China sea;
Atmospheric deposition, including nature and anthropogenic pollutants, was reported to be the major source of nutrients in the Yellow sea.
Initial nutrients in sea water:
NO3-=1.05 umol/L; NH4
+=0.31 umol/L; PO4
3-=0.15 umol/L;NO2
-=0.09 umol/L.
Nutrients added in incubation experiment in March, 2011
ID Nutrients added Amount or concentration
A control No
B dust 20 mg/L based on episodic observations
C FeSO4 2nmol/L just a guessD NaH2PO4 0.2μmol/L close to sea waterE FeSO4+NaH2PO4 2nmol/L+0.2μmol/LF NaNO3 2μmol/L close to sea water
G rainwater 2ml/L assuming 10 cm rainfall in a 50 m mixed layer
20 mg/L dust contains 0.14 umol/L Fe (total, Fe2+ could be much less than 2 nmol/L) + 0.005 umol/L PO4
3-+ (0.14 umol/L NO3-+0.08
umol/L NH4+);
Chemical composition of Rainwater was not measured.
What determined spring biogenic bloom in the Yellow Sea?
A weak biogenic bloom was observed at A2 station from satellite data;
Much strong biogenic bloom occurred in the control incubation experiment ;
Temperature and PAR (photosynthetically active radiation) were likely the most important limitation factors for biogenic bloom.
0.00
3.00
6.00
9.00
12.00
15.00
18.00
0 2 4 6 8 9 10 11 13 15
Cho
loph
yll-
a (μ
g/L
)
Days
Control
Dust in 20mg/L
NO3- in 2umol/L
What can enhance spring biogenic bloom?
In Dust and NO3- fertilization
incubation experiments, CHLA was statistically higher than in the control experiment
A net increase of CHLA in dust experiment relative
to the control was 1/3 of that in NO3- experiment
1) Doubling NO3- in sea
water doubles the concentration of CHLA;
2) Added 20 mg/L dust to sea water increased the concentration of CHLA by about 30% relative to the control;
3) Bio-availability Nitrogen in Dust experiment was only 1/10 of that in NO3
- experiment;
4) What caused high efficiency in dust fertilization experiment?
0.00
2.00
4.00
6.00
8.00
10.00
0 2 4 6 8 9 10 11 13 15
Cho
loph
yll-
a (μ
g/L
)
Days
Control
Fe in 2nmol/l
P in 0.2umol/L
Fe in 2nmol/L+ P in 0.2umol/L
Can Fe, P, Fe+P and rainwater enhance spring biogenic bloom?
In Fe, P, (Fe+P) and Rain water fertilization incubation experiments, CHLA was higher than that in the control during the most of experiment times;
However, the difference was not statistically significant;
More experiments might be needed.
0.00
2.00
4.00
6.00
8.00
10.00
0 2 4 6 8 9 10 11 13 15
Cho
loph
yll-
a (μ
g/L
)
Days
Control
Rain
Why dust has a high efficiency?-Nutrients in dust
fertilization experiment
Fe2+ was not measured in this study
Dust increased concentration of NH4
+;
Dust decreased PO4
3- at the initial stage, then released;
Minor influences on NO3
- and NO2- too
much;
Overall, unexpected increase of NH4
+ relative to NH4
+ in sea water; is high efficiency of dust associated with NH4
+ input?
0.00
0.20
0.40
0.60
0.80
0 2 4 6 8 9 10 11 13 15Days
NH
4+ con
cent
ratio
n, μ
mol
L-1
0.00
0.04
0.08
0.12
0.16
0 2 4 6 8 9 10 11 13 15Days
PO43-
con
cent
ratio
n, μ
mol
L-1
0.00
0.03
0.06
0.09
0.12
0 2 4 6 8 9 10 11 13 15Days
NO
2- con
cent
ratio
n, μ
mol
L-1
0.00
0.40
0.80
1.20
1.60
0 2 4 6 8 9 10 11 13 15Days
NO
3- con
cent
ratio
n, μ
mol
L-1 Control
Dust20
Nutrition in NO3- and PO4
3- fertilization experiment
Only about 50% of added NO3
- and PO43-
were detected in experiments;
Reverse daily variations of NH4
+ between the control and the NO3
- experiment;
More NH4+ was
released in the NO3-
and PO43- experiment
than in the control.
0.00
0.05
0.10
0.15
0.20
0.25
0 2 4 6 8 9 10 11 13 15Days
PO
43- c
once
ntra
tion,
μm
ol L
-1
Control
PO43- in 0.2 umol/L
0.00
0.50
1.00
1.50
2.00
2.50
0 2 4 6 8 9 10 11 13 15Days
NO
3- con
cent
ratio
n, μ
mol
L-1
Control
NO3- in 2umol/L
0.00
0.20
0.40
0.60
0.80
0 2 4 6 8 9 10 11 13 15Days
NH
4+ con
cent
ratio
n, μ
mol
L-1
Control
NO3- in 2umol/L
0.00
0.20
0.40
0.60
0 2 4 6 8 9 10 11 13 15Days
NH
4+ con
cent
ratio
n,
μm
ol L
-1
Control
PO43- in 0.2umol/L
Daily variations of NH4+ implied: grew and degrade, then grew and degrade…
NO3- and NH4
+ were used to synthesize organic, then decomposed into NH4+,
NH4+ was further used to synthesize organic, then decomposed into NH4
+ …
Nutrients in rain water fertilization experiment
Rainwater did not add the detectable amount of PO4
3-;
Added rainwater increased N by 50%; When considered only 50% of added nutrients can be detected, N added by rainwater could be close to that in NO3
- fertilization experiment ; then why low CHLA?
NO3- could be
partially converted to NH4
+? and vice verse?
NO3- NH4
+ ?
0.00
0.40
0.80
1.20
1.60
0 2 4 6 8 9 10 11 13 15Days
NO
3- con
cent
ratio
n, μ
mol
L-1
Control
Rain
0.00
0.30
0.60
0.90
1.20
0 2 4 6 8 9 10 11 13 15Days
NH
4+ con
cent
ratio
n, μ
mol
L-1
0.00
0.04
0.08
0.12
0.16
0 2 4 6 8 9 10 11 13 15Days
PO43-
con
cent
ratio
n, μ
mol
L-1
0.00
0.03
0.06
0.09
0.12
0 2 4 6 8 9 10 11 13 15Days
NO
2- con
cent
ratio
n, μ
mol
L-1
Experiment in the East China Sea in summer
No bloom for the control and no synthesized effect by DustMuch low concentration of CHLA, only three days for CHLA reaching the maximum.
0.2
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 2 4 5 6 7 8 9 10 11 12 13 15
Days
Chl
-a c
once
trat
ion,
μg/
L
Control
Dust20
NO3-2
2
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0 2 4 5 6 7 8 9 10 11 12 13 15
Days
Chl
-a c
once
trat
ion,
μg/
L
Control
Dust20
NO3-2
20
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0 2 4 5 6 7 8 9 10 11 12 13 15
Days
Chl
-a c
once
trat
ion,
μg/
L
Control
Dust20
NO3-2
T
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
0 2 4 5 6 7 8 9 10 11 12 13 15
Days
Chl
-a c
once
trat
ion,
μg/
L
Control
Dust20
NO3-2
N limitation; not limited by Fe, P and Fe+P (not shown)
<0.2 um CHLA
>20 um CHLA
2-20 um CHLA
Total CHLA
Conclusion
• 1) Temperature and PAR were likely the most important limitation factors for biogenic bloom in the Yellow sea;
• 2) Since the ratio of N/P is less than 10 at the ocean zone, the concentration of chlorophyll-a was very sensitive to the external input of N; the concentration also increased with increasing external input of P, but not statistically significant;
• 3) N in Dust fertilization experiment was only 1/10 of that in NO3-
fertilization experiment, but the net increase of CHLA in the former experiment relative to the control was 1/3 of that in the later experiment; Does this imply that any unknown X could enhance bloom?
• 4) In the rainwater fertilization experiment, N increased by about 100%. However, relative to the control, no significant increase of the concentration of chlorophyll-a was observed. Again, Does this imply any unknown X limitation? X appeared to be absent in rainwater and it seems to play a key role for the use of NH4
+.
Acknowledgement
• This study is a team work by my colleagues and students, they are Prof. Huiwang Gao, Jinhui, Shi, Jianhua Qi, students include Tianran Zhang, YangFan, Ying Liu,…
Not SiO32-
0.00
2.00
4.00
6.00
8.00
0 2 4 6 8 9 10 11 13 15Days
SiO
32- c
once
ntra
tion,
μm
ol L
-1 Control
Dust in 20mg/L
SEEDSSERIES
EisenEx SOIREE
, II
SOFeX
IronEx I
In situ Fe fertilizer experiments in N.Pac
SAGE
SEEDS II
LNLC
Most of areas in China Sea is subject to EOZ
HNLC
LNLCEOZ
Surface Chl.a concentration
EOZ: Eutrophic Ocean Zone; HNLC: High-Nutrient Low-Chlorophyll; LNLC: Low -Nutrient Low-
Chlorophyll
China
Biological bloom in the China Sea occurred frequently in spring, but not yet well understand; the process could provide a clue to understand dynamics of carbon transfer in the China sea.
US