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CRUCIAL CETACEAN HABITATS IN BANGLADESH
W a t e r w a y s o f t h e S u n d a r b a n M a n g r o v e
F o r e s t
Sundarban is the world's largest contiguous mangrove forest
encompassing almost 600,000 ha. About 30% of the area is composed of
a complex network of tidal waterways. The world's third largest
river system, the Ganges-Brahmaputra-Meghna (Padma-Jamuna-Meghna)
river system, passes an enormous sediment load to the delta,
supplying the physical elements for the world's largest contiguous
mangrove forest and the world's largest undersea sediment fan. The
Ganges-Brahmaputra-Meghna (Padma-Jamuna-Meghna) supplies loads of
nutrients to the Bay of Bengal - more than 1.5% of the total
riverine input to the world's oceans.
Salinity levels in Sundarban are determined primarily by freshwater
flows and tides. After construction of the Farakka Barrage (Ganges,
India) significant increases in salinity levels were documented in
Sundarban. Increased sediment deposition due to reduced river
discharges has led to the gradual drying up of distributaries that
previously drove back salinity encroachment.
C o a s t a l W a t e r s o f t h e B a y o f B e n g a l
The Bay of Bengal is a tropical ocean basin, bordered by Sri Lanka,
India, Bangladesh and Myanmar. It is largely influenced by
seasonally reversing currents and the discharge from the
Ganges-Brahmaputra-Meghna (Padma-Jamuna-Meghna) river system. These
big rivers bring enormous amounts of freshwater, nutrients and
sediment, which help create highly productive coastal waters and
supply the world's largest undersea fan.
The Bangladesh coast is dominated in the west by the Sundarban
mangrove forest and in the east by the massive freshwater input from
the Ganges-Brahmaputra-Meghna mouth. The coastal waters are
generally shallow with the 50m contour ranging from 35 to 165 km
offshore along the south facing coast. The coastline is
characterized by sandy shoals with large and small emergent islands.
T h e S w a t c h -o f- N o-G r o u n d
In the north-western part of the Bay of Bengal, a deep submarine
canyon, known as the Swatch-of-No-Ground comes up close to the
Bangladesh coast, south of the Sundarban Forest. The very deep
canyon (900+ meters) has relatively steep walls (12-15°) and is cone
shaped, ranging from about 40 km wide at its mouth in Indian waters
to about 6 km wide at its head in Bangladeshi waters. The
Swatch-of-No-Ground plays a crucial role in transporting sediments
from the continental shelf to the deep-sea fan and fish
productivity. Due to the nutrient rich waters at the edge of the
canyon, the cetacean fauna is diverse and relatively abundant.
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HABITAT_COASTAL WATERS BAY OF BENGAL