Overview
The Ross Sea is a large embayment of the Antarctic continental shelf to nearly 78° south. Seawater temperature (at McMurdo Sound) remains at around minus 2°C throughout the year and at all depths (to 800m). Ice covers all the Ross Sea during winter; the inner half of the sea has permanent shelf ice about 420m deep, the outer half is covered by pack ice 1-5m thick. In summer, around mid-December, when the water warms to minus 1.8°C, the layer of platelet ice melts and the pack ice retreats. By March, 75-80% of the pack ice has melted. Although there is little seasonal variability in temperature, there are huge fluctuations in light and associated biological productivity. Fishes and other marine life experience four months of continual darkness in winter and continual light in summer. Even during the austral summer, light is rapidly attenuated by snow, sea ice and water, so that sub-ice communities are adapted to low light levels.
Fishes are present in all habitats, forming communities together with algae, sponges, amphipods and euphausids (krill). These communities live under permanent shelf ice, under icebergs, among seasonal platelet ice, on the mud bottom, among coastal sponge reefs, and around deep seamounts. Pelagic communities, including many fishes, live throughout the water column.