Land-Ocean Nutrient Fluxes: Silica Cycle
Scientific
Advisory Committee
Chair: V. Ittekkot
(Germany); Members: P. Depetris (Argentina), R. Dugdale
(USA), L. Dümenil (Germany), Manuwadi
Hungspreugs (Thailand), N. Kress (Israel), J. D. Milliman (USA),
Nguyen Tac An (Vietnam), E. I.
L. Silva (Sri Lanka), F. Wulff (Sweden)
The river flux of
mineral nutrients from domestic, agricultural, deforestation and industrial
sources has undergone significant changes. Accelerated algal growth,
known as eutrophication, is one consequence and leads to deterioration
in water quality via oxygen depletion. Oxygen-deficient conditions in
turn promote the production and emission to the atmosphere of climatically-relevant
gases such as nitrous oxide and methane. Toxic algal blooms attributed
to eutrophication have a devastating effect on fisheries and on biodiversity
in general. Thus, many socio-economic and regulatory functions of water
bodies are immediately affected by changes in land-ocean nutrient fluxes.
Most current and
previous studies on land-ocean nutrient flux have concentrated on nitrogen
and phosphorus, mainly because they represent the nutrient elements
that are discharged by human activities. However, silica also plays
a crucial role in algal growth and species composition, and has source-transport-sink
characteristics distinct from N and P as related to changes in the hydrology
of rivers.
A re-examination
of the available data on land-ocean nutrient fluxes in the
light of new research on the role of silicates is warranted in order
to develop scientifically-sound strategies to reduce the risk of ecosystem
perturbation, especially in coastal waters. The project addresses aspects
of the silica cycle and their perturbation as they relate to land-ocean
interactions and the possible impact on coastal aquatic systems.
International workshops
have been held in cooperation with LOICZ in Linköping (Sweden)
in 1999, and in Nha Trang (Viet Nam) in 2000 with the IOC-WESTPAC (also
sponsored by the EU). The special issue "Land-Sea Nutrient Fluxes:
The Silica Cycle" was published through the National Centre for
Natural Science and Technology of Vietnam, Institute of Oceanography
(2002). It provides information on silica cycle compiled by participating
groups in South and Southeast Asia region. The final workshop of the
project was held in Germany in December 2003; a synthesis volume on
the Role of Silicon in Land-Sea Interaction is in preparation.
Project participants
from the South and Southeast Asia region (India, Malaysia, Sri Lanka,
Thailand, Vietnam) have joined together under the SCOPE project umbrella
and are currently establishing a network to continue the work associated
with Silica fluxes and ecosystem status.
Last up-dated 9 June 2005