CLIMATE CHANGE IMPACTS ON PHYTOPLANKTON BIODIVERSITY

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CLIMATE CHANGE IMPACTS ON PHYTOPLANKTON
BIODIVERSITY IMPACTS ON THE ECOSYSTEM OF THE
ARABIAN SEA
Joaquim I. Goes Helga Gomes, Bigelow Lab. USA
Prabhu Matondkar Sushma Parab NIO, India
Prasad Thoppil, John Kindle Sergio de Rada,
NRL, USA
John Fasullo, NCAR, USA, Fei Chai, Univ. Maine,
USA
Richard Barber, Duke Univ., USA
Adnan Al Azri, Sultan Qaboos Univ., Oman
R. M. Dwivedi, Space Applications, Centre, India
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UNIQUE FEATURES OF THE ARABIAN SEA
Is a tropical sea and the northwestern landlocked
arm of the Indian Ocean
Comes under the influence of the monsoon winds
which reverse their direction seasonally driving
one the most energetic current systems and the
greatest seasonal variability of phytoplankton
biomass
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Reversal of the winds and their intensity is
strongly regulated by thermal gradient between
land and sea
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WINTER MONSOON
Schematic showing snow cover extent and wind
direction superimposed on an ocean color
chlorophyll image for the northeast monsoon
season (Nov-Feb).
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SUMMER MONSOON
Schematic showing the reversal in wind direction
during the southwest monsoon (Jun-Sept),
superimposed on satellite derived chlorophyll
fields
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Schematic showing the SW Monsoon response of the
Arabian Sea to snow cover over the
Himalayan-Tibetan Plateau
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SW Eurasian-Land Warming
Warming of SW Eurasia mirrors the global-land
signal, but recent warming anomalies are gt50
larger than global temperature trends.
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Trend line showing anomalies (departures from
monthly means) of snow cover extent over
Southwest Asia and Himalayas-Tibetan Plateau
between 1967 and 2003.
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70 years of global warming? Photograph of the
Pindari glacier in the Himalayas taken on October
7, 1936, by then Deputy Conservator of Forests F
W Champion. 70 years later at the exact spot, his
grandson James Champion photographed the same
glacier. (Source Sunday Indian Express, 29th Dec.
2006).
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Interannual changes in chlorophyll along coast of
Somalia since 1997 (Goes et
al., Science, 2005 )
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SeaWiFS derived chlorophyll fields during the
peak southwest monsoon growth season of 1997 and
2006
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The Arabian Seas permanent oxygen minimum zone
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FISH MORTALITY OMAN NOV 2005
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Air-temperature and Relative humidity for the
northern Arabian Sea (60E-70E, 14N-25N).
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Annual trends of net heat flux (NCEP-NCAR)
(60-70E, 14N-25N) and Mixed Layer Depth (XBT,
JEDAC, USA)
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Observed and model-derived MLD for winter (Jan
Feb), and model derived Sea Surface Salinity
(SSS, psu) during Jan May for the 60E-70E,
14N-25N. Model derived fields are obtained from
the ECCO-JPL Kalman Filter Assimilation project.
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WAS
EAS
Winter mean SeaWiFS Chl a averaged over the
Eastern Arabian Sea (EAS, 66E-70E, 15N-24N)
and in the western Arabian Sea (WAS, 55E-62E,
17.5N-22.5N).
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High chlorophyll concentrations during the NEM
are being caused by blooms of dinoflagellate
Noctiluca miliaris
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CHARACTERISTICS OF ARABIAN SEA NOCTILUCA MILIARIS
BLOOMS
Noctiluca is a heterotrophic dinoflagellate
containing a green endosymbiont Pedinomonas
noctilucae
Its appearance in bloom proportions during the
NEM is unprecedented as no reports of blooms
of this organism during Int. Arabian Sea JGOFS
1992 to 1996 or from Int. Indian Ocean
Expeditions of the 1960s.
Noctiluca appears to have replaced diatoms as the
major bloom forming phytoplankton of the NEM.
It occurs in (cold) lt22oC, nutrient rich and
oxygen poor waters
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PHYTOPLANKTON BLOOM OF 2003
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Weekly SeaWiFS and MODIS/Aqua Level-3 merged Chl
a images with Sea Surface Height anomalies and
geostrophic velocity vectors from TOPEX/POSEIDON
and ERS-2
Gomes et al. (2008) Deep-Sea Research
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Precipitable water from SSM/I for June showing
particularly strong postive and pervasive trends
in the Arabian Sea (John Fasullo NCAR)
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OUTSTANDING QUESTIONS FOR THE ARABIAN SEA
Is the appearance of N. miliaris blooms the
result of climate change or natural variability?
What are the long-term impact of this possible
change in phytoplankton biodiversity and
biological productivity on

• Carbon delivery to deeper layers of the Arabian
  Sea
• Bacterial processes
• Denitrification rates
• The Oxygen Minimum Zone and
• Increased storm activity
• Coastal Fisheries

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INDIAN OCEAN CIRCULATION MODEL (John Kindle
Sergio deRada)

• 1/8-degree NCOM (Navy Coastal Ocean Model)
• 30S to 30N, 30.5 to 121.5E
• Mercator grid (13km), 40 Levels s/z
• Boundary and initial conditions from Global NCOM
• 0.5-degree NOGAPS Atmospheric forcing
• MODAS Full 3D Temperature and Salinity
  relaxation
• Initial simulation for 2007

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Carbon, Silicate, Nitrogen Ecosystem Model
(CoSiNE) Chai et al. 2002 Dugdale et al. 2002
Air-Sea Exchange
Small Phytoplankton P1
Micro- Zooplankton Z1
Biological Uptake
Total CO2 TCO2
Grazing
NO3 Uptake
NH4 Uptake
Predation
Nitrate NO3
Iron
Excretion
Ammonium NH4
N-Uptake
Meso- zooplankton Z2
Fecal Pellet
Advection Mixing
Iron
Grazing
Fecal Pellet
Diatoms P2
Lost
Iron
Detritus-N DN
Detritus-Si DSi
Si-Uptake
Sinking
Physical Model
Silicate Si(OH)4
Dissolution
Sinking
Sinking
Chai et al., 1996 2003
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30th Sept 2006
30th Sept 2006
SEAWIFS
MODEL
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Nothing in the sea falls haphazard if we cannot
predict, it is because we do not know the cause,
or how the cause works..."
Henry Bryant Bigelow
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ACKNOWLEDGEMENTS This work is being funded by
NASA Oceans and Ice NASA Biodiversity and
Ecosystem Programs. We are thankful to the
National Institute of Oceanography and the Indian
Space Research Organization for supporting ship
observations. Special thanks to Woody Turner and
Paula Bontempi for their support