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Immediate Report of Victoria University Of Wellington Antarctic Expedition 1987-88: VUWAE 32
Abstract
Abstract
Sea floor sediment samples were obtained from seven shore-normal transects on the southwestern Ross Sea coast from Blue Glacier to Tripp Bay, plus one transect off Cape Armitage, on Ross Island. The transects were designed to sample "near shore" sea floor sediment and biota to 100 m water depth. Samples were taken with modified Shipek grab. Current measurements were made at most of the 100 m site with an InterOcean S4 electromagnetic current meter.
- Sea floor slopes, up to 17°, for example, Tripp Island and Gregory Island, are generally devoid of sediment and bedrock is exposed at the sea floor. On low angle slopes, averaging 3°, sediment fined offshore from gravelly sand muddy sand and mud.
- Sea ice scouring and anchor ice prevents sediment accumulation on bedrock least down to 5 or 10 metres, especially at exposed coastal locations.
- Current activity which modifies or prevents sediment accumulation even moderate depths, for example Gregory Island.
- Entrapment and protection of sediment, especially by sponge mat, occurs below 50 metres, even at sites with moderate to high current regimes, such as Cape Armitage.
Current flow is approximately parallel to the southwestern Ross Sea coast and shows reversal of direction within the tidal period. Current speeds up to 25 to 30 cm/sec were measured at Gregory Island and decrease to the south at Blue Glacier where a maximum of 12 cm/sec was measured. At Cape Armitage, current speeds of up to 75 cm/sec were measured, and were accompanied by a marked directional change within the tidal period.
The macro biota from most sites have consistent substrate preference and depth zonations. Red spiny echinoids and small (up to 5 cm high) red-brown algae prefer exposed bedrock and coarse gravel generally to 20 to 30 metres depth. Pectens commonly were recovered in shallow depths less than 30 metres, usually on sandy sediment and occasionally bedrock. Sponges and sponge mat were recovered from depths greater than 50 metres on substrate from gravel to muddy sand.