The role of fish in the Antarctic food web in inshore and offshore waters is analysed, taking as an
example the coastal marine communities of the southern Scotia Arc (South Orkney Islands and South
Shetland Islands) and the west Antarctic Peninsula. Inshore, the ecological role of demersal fish is more
important than that of krill. There, demersal fish are major consumers of benthos and also feed on
zooplankton (mainly krill in summer). They are links between lower and upper levels of the food web and
are common prey of other fish, birds and seals. Offshore, demersal fish depend less on benthos and feed
more on zooplankton (mainly krill) and nekton, and are less accessible as prey of birds and seals. There,
pelagic fish (especially lantern fish) are more abundant than inshore and play an important role in the energy
flow from macrozooplankton to higher trophic levels (seabirds and seals). Through the higher fish predators,
energy is transferred to land in the form of fish remains, pellets (birds), regurgitation and faeces (birds and
seals). However, in the general context of the Antarctic marine ecosystem, krill (Euphausia superba) plays
the central role in the food web because it is the main food source in terms of biomass for most of the high
level predators from demersal fish up to whales. This has no obvious equivalent in other marine ecosystems.
In Antarctic offshore coastal and oceanic waters the greatest proportion of energy from the ecosystem is
transferred to land directly through krill consumers, such as flying birds, penguins, and seals. Beside krill,
the populations of fish in the Antarctic Ocean are the second most important element for higher predators, in
particular the energy-rich pelagic Myctophidae in open waters and the pelagic Antarctic silver fish
(Pleuragramma antarcticum) in the high Antarctic zone. Although the occurrence of these pelagic fish
inshore has been poorly documented, their abundance in neritic waters could be higher than previously
believed.
The seasonal cycle of ocean-atmosphere CO2flux in Ryder Bay, west Antarctic Peninsula