Science Centres: Aquatic Biodiversity and Biosecurity, Fisheries, Oceans

The ecosystem of the Ross Sea is sustained by a diverse, interconnected food web.

Ecosystem

Environmental setting: The Ross Sea is covered by sea ice for most of the year. The ice expands from late February onwards, and retreats from late October. The advance and retreat processes start near the front of the Ross Ice Shelf. Areas of open water surrounded by sea ice (polynyas) form in the inner Ross Sea.

Phytoplankton and Primary Production: Growth of phytoplankton makes up the largest contribution to primary production in the Ross Sea. Sea-ice algae also contribute to primary production. Bursts of growth occur in the spring and summer along the coast, in polynyas, and in the waters left as the sea ice melts.

Zooplankton: Primary production is channelled through copepods, the most common type of zooplankton, and a number of smaller species of zooplankton such as flagellates and ciliates. Larger zooplankton include krill, amphipods and salps. Two species of krill are found in the Ross Sea: the larger Antarctic krill in the north, and smaller crystal krill in waters over the continental shelf to the south.

Detritus and Bacteria: Algae, dead organisms and excreted products can fall to the sea-floor, often in large amounts. Detritus can be decomposed in the water column and on the sea bed by bacterial action.

Benthos: Falling detritus, and the growth of coralline macroalgae in coastal regions, provide nutrition for the benthic (bottom-dwelling) invertebrates. These benthic organisms have varied feeding strategies and include grazers, such as urchins, sea cucumbers, and snails; predators, such as the Antarctic whelk and seastars; filter-feeders, such as Antarctic scallops, bivalves, anemones, soft corals, and sponges; and scavengers, such as large worms.

Fish: Antarctic toothfish, ‘cryopelagic’ (freezing, open water) fish that live on the underside of sea ice, grow up to 2 m long. Silverfish, found through the Ross Sea, grow to a length of about 30 cm and comprise the diet of almost all large predators in the area. Other fish include grenadiers (or rat-tails), skates, deep-sea and moray cods, dragonfish and ice-fish.

Cephalopods: A number of species of squid and octopus live in the Ross Sea, including the colossal squid that can grow to more than 4 m in length.

Birds: There are large numbers of breeding emperor penguins and Adélie penguins in the Ross Sea. Several other species of birds breed in the region, including Antarctic petrels, snow petrels, and the south-polar skua. Many other birds visit in summer, including two species of albatross.

Seals: Seals are the most common marine mammals in the Ross Sea, with crabeater seals, Weddell seals, leopard seals and Ross seals.

Cetaceans: Baleen whales in the region include dwarf minke whales, Antarctic minke whales and smaller numbers of fin, humpback, sei and blue whales. Toothed whales sighted in the Ross Sea include orca, sperm whales, southern bottlenose whales and Arnoux’s beaked whale.

Ross Sea Trophic Model

Below is a simplified food-web model of the Ross Sea (a more detailed model was developed in this research project). Detailed information on each of the groups in the model is available on the Publications and Documents page.