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Biogeochemistry of Indian estuaries: Influence of Human Interferences
V.V.S.S. Sarma National Institute of Oceanography
India
2-4th April 2012
GEOSS, Miraikan, Japan
An estuary is… “a transition zone between river and sea in which fresh water gets mixed with seawater and tidal influence Is strongly felt ”
River
Fresh water
Seawater
Estuary Sea
A section along the main channel
A bird’s view of estuarine system
Estuaries significance… • important in hydrological cycles • sediment supplies to ocean • habitats for a large variety of life • highly productive among aquatic systems • food resources of socioeconomic relevance • influence ocean dynamics in the neighbourhood
Influence of different river discharges on oceans in our neighbourhood
INDIAN SUBCONTINENT
Bay of Bengal
Arabian Sea
1.6x1012 m3/y WATER 0.3x1012 m3/y
1.4x109 tons/y SPM 0.2x109 tons/y
River and estuarine systems facilitated human settlements on
their banks through the civilizations
However, human interference with these systems is a cause for worry!
ENVIRONMENTAL ISSUES IN ESTUARIES
• Changes in sediment load and water caused by clearing forests for agriculture and development
• Construction of dams • Waste disposal • Commercial fishing • Dredging • Shipping • Habitat destruction
Indian monsoonal river systems
Dis
char
ge (m
3 s-1
)
Dry Wet Dry Wet
Modification of organic matter in the Dam reservoir
DA
M
Dry Wet Dry Wet
ESTU
ARY
Influence on inorganic carbon system
Sarma et al., 2011; 2012
pCO2 (matm)
Enhanced coastal CO2 fluxes…
Sarma et al., 2011
Winter monsoon - -0.66 Intermonsoon - +0.06
Summer monsoon +7.8
Fluxes in mmolC m-2 d-1
4918
5798
8231
5806
1573
7262
3673
9608 721 17751
293
8616
686 516
1245
2423
10415
289 408
3388 1691
4126
2352
pCO2 in the Indian estuaries
CH4-Flux(µmole m-2 Day-1)
1.06
1.07
0.44
-0.04
-0.04 0.61
0.04
-0.37
1.24 0.04 -0.03
2.13
11.8 4.03
114
1.39
0.3
1.27
5.33
11.8
10.2
0.26 2.97 1.14
Fluxes of CH4 and N2O from the Indian Estuaries
-0.01 -0.03
-0.08
-0.17
0.16
-0.03
-0.17 -0.11
0.02
-0.04
0.08
-1.11
-0.03 -0.04
7.9
0.19
0.75
1.12
3.60
-0.6
0.16
1.27 1.05 0.71
N2O-Flux(µmole m-2 Day-1)
Estuaries (107 g y-1) East coast 1300 0.82 0.20 1.80 West coast 2300 1.04 8.43 0.80 TOTAL 3600 1.86 8.63 2.60 Coastal region (1012 g y-1) Bay of Bengal 1.30 -0.03 0.08 0.04 Arabian Sea 5.03 0.33 0.09 0.006 TOTAL 6.33 0.30 0.17 0.046
Region CO2 N2O CH4 DMS Fluxes of trace gases
Yearly Average Discharge (m3/sec)
Discharge versus phytoplankton blooms
Acharyya and Sarma, 2012
Magnitude and pattern of discharge has significant impact on phytoplankton bloom. Modification of this pattern may lead to change so far healthy Indian estuaries into eutrophicated.
Discharge versus phytoplankton
Impact of Fertilizer usage on Phytoplankton diversity in the
Indian estuaries
Estuarine systems under threat … Fertilizer washings – biological productivity
eutrophication & oxygen deficiency
Fertilizer usage in India
Source: Ministry of Agriculture
N. India S. India
74% 26%
Parameter N. India S. India
Nitrate 26.2±8 4.3±1 Ammonium 3.8±1 2.1±1 Silicate 32.8±8 157±48 DIN:DIP 8.3±2 1.9±2 Chl-a 2.1±1 4.3±1
Variable nutrients composition
9.0
9.9
9.0
9.7
3.7 1.8
3.5
0.9
1.9 4.1 2.5
3.9
16.6 5.8
5.2
5.8
9.7
6.5
8.1
8.6
15.0
10.2 9.1 9.9
d15NPN (per mil)
Nitrogen isotopic ratios in the Indian estuaries
2.9 8.8
Mean
3.61
0.79
0.49
0.58 0.67
0.41
0.06
0.09 1.09 0.16
8.96
0.49
1.01
0.15
0.05
0.25
0.00
0.31
0.13
0.07
0.02
0.04 1.36
0.12
1.36
2.95 0.27
0.08
0.54
0.16
0.21
0.78
0.24
0.46
0.15 1.06 0.15
0.05
0.41
0.53 0.5
Bacillariophy. Blue-green Alg. Fucoxanthin b-carotinoids
0.75 0.48 mg/L 0.28 1.68 mg/L
Variability in pigments composition in Indian estuaries
Fucoxanthin (mg/L) b-Carotinoid (mg/L)
Sarma et al, 2012
XII Five Year Plan (2012-2017)
Ocean Science for Forecasting Indian Marine Living Resource
Potential (OCEAN FINDER)
Forecasting Potential Fishery Zones (PFZ) : connection between sea surface temperature, chlorophyll & fish catch
What is the basis for this connection?
Forecast of PFZ for central west coast of India (2008)
From INCOIS
Schematic of an ecosystem model
Mesocosm (Expedition to Experiment)
Observations
Modelling
Glider Acoustic Doppler Current Profiler
Forecasting living resources Organism Habitat
Benthic/Pelagic
ü Expedition to experiment ü Spatial & temporal observations (to supplement information for
ecosystem analyses & forecasting)
Time-series locations
Estuarine time-series Coastal time-series
Coastal time-series ADCP moorings Sediment traps Profilling buoys Gliders Ship-based observations Mesocosm experiments
Thanks!
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