PARENT SESSION
Contributed Oral Session 83: Human Impacts on Coastal Areas
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 520 A, Level 5, Palais des congrès de Montréal
Groundwater flux and productivity bloom in coastal Arabian Sea.
Paimpillil, Joseph1, Joseph, Thresiamma2, Krishnan, Balachandran2, 1 Center for Earth Research & Environment Management, Cochin 172 National Insitute of Oceanography, Cochin 18
ABSTRACT- With the injection of nutrients in non-monsoon months when mud banks were passive, a new influence of Vembanad Lake on the coastal waters is very clear. The causative factors discussed are indicative of existence of a subterranean flow connecting Vembanad Lake to the adjacent coastal waters through the submerged porous lime shell beds. Localized phytoplankton productivity boosting in southwest coastal Arabian Sea was partially attributed to ground water discharges from a narrow strip of porous lime shell bed. Due to high environmental degradation, poor sanitary facilities and poverty, this strip was identified by IUCN as high priority area for ICZM. Forcing of ground water occurs when the water level difference between sea and lake attains a critical value to overcome the frictional resistance. Such conditions prevail during heavy fresh water discharges and on the sea level remaining at its annual low. The ground water fluxes seem to induce seasonal variability in the coastal water quality, primary productivity (three times coastal productivity) and slow changes in species diversity. A shortage of silicon, relative to the supplies of nitrogen and phosphorus seems to accelerate the growth of flagellated phytoplankton . The phytoplankton growth stimulation of Zn and Fe is of high significance as the dissolved zinc had enrichment in the lake with 116 ug/l in 1986 and with 879 ug/l in 1991. The possibility of heavy rains linked with cyclones are high with climate variability, critical conditions for ground water flow can prevail in other seasons and also at similar coastal locations. Any noticeable change of the current oligothrophic nature of the coastal region can contribute to the removal of atmospheric carbon. Attempts for reversing the eutrophication and biodiversity changes require management strategies for watersheds reaching far inland from the coastal region, restoration of wetlands and floodplains that act as nutrient traps. The control of nutrients in ground water is feasible by an improvement in the living conditions and sanitary facilities of the thickly populated coastal areas. The idea that land-use mosaic among sub-watersheds influence coastal processes may apply globally to any coastal regions hugged by wetlands and underlain with limestone deposits.
Key words: ground water flux, productivity bloom