Kudremalai Point, Portugal Bay © Howard Martenstyn

Kudremalai Point - overlooking Dutch Bay

About Amazing Sri Lanka

The southern part of the Indian subcontinent, the Deccan Peninsula, stretches out into the Indian Ocean like a giant tongue, dividing it into two basins. Sri Lanka lies off the tip of this tongue, with unbroken expanses of water – the Bay of Bengal and the Arabian Sea – spread out to east and west. Southward lies the main body of the Indian Ocean.

 

This position – at the tip of a great continent, yet in the middle of an ocean – makes Sri Lanka a busy crossroads for many kinds of marine life. Just as the island itself is a birdwatcher’s paradise, drawing hundreds of migratory species from Europe and Asia, the waters surrounding it are among the best places in the world to see whales, dolphins, sharks and other long-distance travellers of the deep. Due to its strategic location and maritime properties Sri Lanka is recognised not as a small island but bigger as a valuable nation. 

 

Further away are the Chagos-Laccadive Ridge, 750km (400nm) west of Sri Lanka, whose peaks rise above sea level to form the Chagos, Laccadive (Lakshadweep) and Maldive island chains, and Ninety East Ridge, a gigantic submerged mountain range that rises 830km (450nm) east of Sri Lanka and stretches southward as far as the Horse Latitudes.

Sri Lanka India Maritime Boundary

Sri Lankan and adjacent waters in the Northern Indian Ocean (NIO)

Anatomy of an Island: Location & Topography

Sri Lanka lies within the tropical zone between latitude 5° 55’— 9° 51’N and longitude 79° 41’— 81° 53’E. It has a land area of about 65,600 sq km, bounded by a coastline some 1,800km in length.

 

The continental shelf surrounding the island and connecting it to the continent of Asia is estimated to cover between 26,000 and 30,000 sq km and supports a variety of highly productive marine ecosystems, while the littoral features a proliferation of estuaries and lagoons. Minerals and organic matter from hundreds of rivers and streams in Sri Lanka and southern India nourish these communities of coastal and marine life.

The Indian Ocean as a whole has a mean depth of 3,900m, increasing to a maximum of about 8,000m. Within the 200-nautical-mile (370km) radius of Sri Lanka’s exclusive economic zone, its maximum depth is about 6,000m. The continental shelf on which the island sits has a mean depth of 75m and forms part of the Asian continent.

 

Around Sri Lanka it is relatively narrow, rarely extending beyond 22km (12nm), pinching in off Kalpitiya Peninsula near Puttalam, and cut by submarine canyons off Dondra Head, Trincomalee, Batticaloa and several other points along the east coast. The shelf is narrowest off Trincomalee, where a giant submarine canyon makes its closest approach to land, and widest off the Jaffna peninsula at Point Pedro, where it extends outward for 60km (32nm).

 

Other important oceanographical features around Sri Lanka include Adam’s Bridge, a chain of shoals and sandbars that connects the north of the island with India; the Gulf of Mannar (part of the Laccadive Sea), which separates the two countries and is bounded by Adam’s Bridge to the north and the southern tip of India to the west; and the Bay of Bengal inlet, including Palk Bay and Palk Strait, which also separates the two countries and is bounded by Adam’s Bridge to the south.

Sri Lanka EEZ Map

Source: NHO, NARA

An Ocean Like No Other

Sri Lanka’s location, marine topography and double-monsoon weather system make it an unusually hospitable location for marine life of many species. Seven natural factors combine to produce an island ecology offering a wide variety of marine habitats, making Sri Lanka one of the best places in the world to see whales and as well as other marine species:

  • A location at the southernmost extremity of a tapering continental landmass, with expansive, unbroken stretches of deep ocean separating the island from other landmasses to the west, south and east, renders it a transit point for migrating and itinerant cetaceans.

  • A ratio of inland surface-water-to-land area of 3ha/km2 , one of the world’s highest results in an unusually large annual surface water discharge to the sea, supplying ample resources for primary production. The marine food chain in Sri Lanka’s coastal and oceanic waters thus rests on an unusually broad and rich base.

  • The oceanographic impacts of the southwest monsoon are among the greatest produced by any terrestrial weather system, and its (largely beneficial) influence on marine life is enormous. Monsoon discharges from the Western Ghats in southern India carry rich source materials for food production into waters off the northern and western coasts of Sri Lanka, while the south and south-eastern coastal waters benefit similarly due to discharges from the Wet Zone of the island itself.

  • The mass transport of nutrient-rich water from the Bay of Bengal into Sri Lankan waters during the northeast monsoon (see  ‘Monsoon Currents'), creates a second seasonal source of material for primary production, ensuring that food is abundant in these waters throughout the year.

  • A narrow continental shelf, averaging 22km (12nm) in width and often pinching in close to the shore, renders the island’s plankton-rich coastal waters easily accessible to great whales and other deepwater species and makes Sri Lanka one of the best places in the world to observe cetaceans close to shore.

  • An unusually high prevalence of submarine canyons along the island’s coast provides abundant food resources by creating movements of pelagic water that contribute to the process of ‘nutrient cycling’.

  • The warm tropical seas around Sri Lanka, along with monsoon and tidal currents, cause a vertical mixing of water layers in the multitude of channels and estuaries that line the island’s coasts – another effect believed to help create nutrient-rich conditions hospitable to marine life.

Sri Lanka is rich, not merely in the number of marine mammal species that call its waters home, but also in spectacle. The most commonly sighted whale in Sri Lankan waters is none other than the blue whale – the largest animal ever to exist on our planet. The second most commonly met great whale is the sperm whale, largest of all the toothed mammals – a gnarled, ferocious predator of the depths, though harmless to humans. Humpback whales, pilot whales, orcas, bottlenose dolphins and many other species all play their part in what may well be the greatest cetacean show on Earth. As for the marine mammal most commonly seen in Sri Lankan waters, it is the most spectacular performer of them all – the extroverted, acrobatic Sri Lankan spinner dolphin.