Download Methodology Study area Results Introduction Conclusion Abstract

Influence of physical and biological processes on the
seasonal cycle of biogenic flux in the Equatorial Indian
Ocean
P.J. Vidya1, S. Prasanna Kumar1*, Mangesh Gauns1, Arati Verenkar1, Daniela Unger2 , V.Ramaswamy1
1National
Institute of Oceanography, Dona Paula, Goa-403 004, India.
2Centre for tropical Marine Ecology GmbH, Fahrenheitstrabße 6, D-28359 Bremen, Germany.
Email: [email protected], [email protected]
Abstract
Seasonal cycle of biogenic fluxes obtained from sediment trap at two locations, 5°24’N, 86°46’E (SBBT) and
3°34’N, 77°46’E (EIOT), within the equatorial Indian Ocean (EIO) were examined to understand the factors that
control them. The enhanced biogenic flux at SBBT during summer monsoon could be explained with the help of
bottom-up control wherein the physical processes controlled chlorophyll biomass through nutrient supply. The
mismatch between the lack of seasonality of biogenic flux at EIOT and seasonality in the chlorophyll biomass can
be explained by top-down control.
Study area
Introduction
The Equatorial Indian Ocean (EIO) behaves uniquely
compared to the other equatorial regions of the world ocean
primarily due to the seasonal reversal of the winds between
winter (December-March) and summer (June-September)
[Hastenrath and Greishar, 1989]. The intense air-sea
interaction makes this region important in earth’s climate.
Hence, the quantitative study of the biogenic flux help us to
understand the carbon cycle and related changes in the
climate.
Methodology
Results
Static stability
Data
Source
Biogenic flux
PARAFLUX Mark Vl series
Sediment trap
Chlorophyll-a
& PAR
SeaWiFS
SSHA
Topex- Poseidon/Jason-1
Wind speed
QuickSCAT
Temp. & Sal.
World Ocean Atlas 2005
Nitrate, chl-a
PP, phyto. Cellno.
& MesoZ
SK -227 Cruise, Sagar
Kanya in August 2006
Ekman pumping
m/day
Advection
SBBT
EIOT
Conclusion
Sediment trap data gives insight into the processes that link the primary
production to the sinking organic carbon in which physical and
biological processes are intimately coupled. Though SBBT and EIOT
are within the same geographical entity, the processes that control the
primary production in the euphotic zone and the biogenic flux to the
deep ocean are very different.
Diatoms
Larger size
Classical food chain
Pico-autotrophs
smaller size
Microbial loop
Acknowledgement
Authors thank the Director, National Institute
of Oceanography (NIO), Goa, and Council of
Scientific and Industrial Research (CSIR),
New Delhi for the facilities provided. First
author thank INSA for providing the travel
support.
Indian National Science Academy
Reference: Hastenrath, S., and Greischar, L (1989), The monsoonal heat budget of the hydrosphereatmosphere system in the Indian Ocean sector, J. Geophys Res., 98, 6869–6881.