Nitrogen and the North East Arabian Sea

Photo courtesy: NASA

Phytoplankton bloom in the Arabian Sea; natural colour (L); chlorophyll concentration (R).

Abstract: Nitrogen an essential macronutrient of the oceanic ecosystem, can limit the biological production if not available in a suitable form or concentration. This article looks at the role of nitrogen in the waters of the Arabian Sea.

The author  is Senior Professor and Project Director, ISRO_GBP, Geoscience Division, Physical Research Laboratory, Ahmedabad. rramesh@prl.res.in

Adapted from ‘Nitrogen sources for new production in the NE Arabian Sea’, Journal of Sea Research, Volume 65, Issue 2, February 2011, Pages 265-274.


Term Power

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Is a term used to refer to the unintentional capture of non-target species of fish, marine mammals, sea turtles, and seabirds related to fishing activities.

A coastal ecosystem that is partially enclosed, receives freshwater input from rivers or streams, is the transition zone between fresh and saline waters, and is subject to both marine influences such as tides and riverine influences such as sediment input.

Enrichment of a water body with nutrients, resulting in excessive growth of phytoplankton, seaweeds, or vascular plants, and often depletion of oxygen.

The smallest and geologically the most youthful of the three oceans. It stretches between Africa in the west, Australia in the east, Asia in the north, and Antarctic in the south. With an area of 73,440,000 sq km, it covers approximately one-seventh of the Earth’s surface.

Pelagic organisms that are free-swimming and so whose movements are independent of the tides, currents and waves. Such animals include fish, whales, squid, crabs and shrimps. The distribution of nekton is limited by temperature and nutrient supply and decreases with decreasing depth.

Refers to the plants and animals that live in the water column or in the open waters of the ocean rather than the ocean floor. Life is found throughout the pelagic zone, however it is more concentrated at shallower depths.

Microscopic, free floating, single-celled, photosynthetic algae that obtain their energy from the sun. They are the primary producers of almost all marine food webs.

A current of cold, nutrient-rich water rising to the surface. Upwellings are caused by strong seasonal winds moving surface coastal water out from the coast and leaving a space that the upwelling fills in. Many marine plants and animals live off this nutrient-rich water.