Eutrophication is a process of proliferation of unusual algae extensively in presence of excess water soluble nutrients mainly nitrogen (N) and phosphorous (P) in aquatic systems. In high rainfall zone, the extent of runoff from agricultural, urban or rural is obviously higher and this runoff may contain considerable amount of nutrients that may be trapped in static aquatic ecosystems like ponds, lakes, reservoirs etc and might cause eutrophication, one type of water pollution. Besides, the mobile aquatic systems are also affected by the enrichment of these nutrients resulting in eutrophication.

Due to enrichment of nutrients, heavy growth of algae and other aquatic plants occurs. The increased production of phytoplankton increases total biological productivity of the aquatic ecosystem. The phytoplankton becomes concentrated in the upper layers of the water, giving it a musky green cast. The turbidity reduces light penetration and affects the primary production.

The dissolved oxygen concentrations becomes high during the day time due to high photosynthetic activity, but during the midnight the oxygen level drastically reduces as the gas is consumed by the aquatic lives (including the heavily grown floral population) thriving in the waterbody.

I think that the process gets accelerated during monsoonal runoff as it brings nutrients from the adjacent landmasses. However Begun babu of Marine Science Dept has experion this.

Sincere thanks resp.Dr. Ghosh and Dr. Mitra for valuable remarks