The physical environment

- Physical Environment-

The continental shelf off the east African coast from Somalia to South Africa and Madagascar

is incised by deep canyons and gullies. Some of these features can be seen in the

Tanzanian study area, in the higher resolution bathymetry, in the map on page 10. Such

data, gathered as part of hydrocarbon industry operations, are of great importance to

understand the deep-sea ecosystems of the western Indian Ocean. Submarine canyons

have received significant research attention globally and are considered important hotspots

for biodiversity because of the habitat heterogeneity associated with them. Their

role as conduits of nutrients and other material to deeper water is also important. South

of the Tanzania study area the canyons of the KwaZulu-Natal shelf edge off South Africa

are the subject of increasing geological study owing to their importance as habitat for


The observations presented in this guide covered a depth range of nearly 2000 m from

660 m (Mozambique) to 2580 m off Tanzania.

Water temperature decreased with depth from

around 28⁰C at the surface to 2.5⁰C at the seabed

at the deepest site. None of the observations were

made in submarine canyons but there was variation

in the seabed slope across the sites. The seabed

was almost flat at Kamba-1 whereas at Mzia-

3, closest to a canyon, there was a 7° slope over the

Above: Rocks on the seabed at 1380 m

area studied. At most sites the seabed sediment

was soft deep-sea mud with burrows, tracks, deposits

and other traces of animals living in or on

the sediment (below).

There was some variation in the grain size; particles

were generally smaller in size with increasing

depth. The Ngisi-1 site, at around 1330 m to

the north of the study area, was something of an Above: Bedform at 1320 m


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