Antarctic Ecosystems

Introduction

The Antarctic Large Marine Ecosystem is defined by the Antarctic Convergence (or Antarctic Polar Front), the boundary oscillating between 48 and 60 degrees of South Latitude that separates the colder Antarctic surface waters from the warmer sub-Antarctic waters to the North. The colder Antarctic surface waters sink beneath the warmer water masses. The boundary varies seasonally and as a result of winds, currents and sea conditions. The Antarctic is unique both for its geographic and climatic characteristics. Its ice cap holds 70% of the earth's fresh water. The ecological and biological characteristics of Antarctic marine species are unique from a food-chain point of view in that the food chain is peculiarly short and based almost entirely on krill, a key species crucial to the sustainability and production of all other fisheries. The inherent physical and biological variability of the Southern Ocean in some years leads to a shortage of krill in some parts, with severe detrimental effects on its seabird and seal predators.

Antarctic Fisheries

The Antarctic is classified as a low productivity ecosystem as a result of the extensive seasonal ice cover (low light penetration in winter) and extreme weather conditions. The Antarctic species most significant for fisheries have been considered in three categories: oceanic, demersal and a much smaller percentage of coastal fishes (12%). Species caught are krill, Antarctic cod, icefish, lanternfish, Antarctic squid, crabs and Patagonian toothfish. The region has often suffered from overfishing with species brought close to extinction. Catches of shelf species were remarkably reduced in the early 1990s. Today several nations are commercially extracting the krill and fish. There is concern for the Patagonian toothfish; Antarctic cod and some species of icefish are now depleted. The challenge is to understand the processes through which the marine ecosystem functions to achieve a sustainable fishery in the Southern Ocean through science-based management strategies. For more information, go to the FAO Report, Cluster 11 .

Scientific Research

The long-term objective is to describe the relationships between Antarctic krill, Euphausia superba, its predators, and key environmental variables.

Research focuses on gathering ecological and biological information to prevent overfishing of Antarctic krill, crabs and finfish and to protect seal, penguin, and pelagic seabird populations. Annual field studies in the Southern Ocean include shipboard surveys of krill and oceanographic conditions, finfish bottom trawl surveys, and studies of the reproductive and foraging behavior of land-based krill predators such as birds and marine mammals. Scientists also develop and test remote-sensing techniques to improve bio-acoustic surveys of krill abundance and distribution. Antarctic ice seals, Antarctic fur seals and seabirds are studied by many laboratories around the world. For example, Pack Ice Seals, which are thought to comprise up to 50% or more of the world's total biomass of seals are studied by the National Marine Mammal Laboratory (NMML), the British Antarctic Survey and the Australian Antarctic Division. As long-lived, top level predators in Southern Ocean ecosystems, pack ice seals are scientifically interesting because they can assist in monitoring shifts in ecosystem structure and function, especially changes that occur in sensitive polar areas in response to global climate changes.

Ecosystem Approaches to Antarctic Management

The Antarctic continent and surrounding Southern Ocean are administered under the Antarctic Treaty system which is the whole complex of arrangements made for regulating relations among states in the Antarctic. The primary purpose of the Antarctic Treaty is to ensure "in the interests of all mankind that Antarctica shall continue forever to be used exclusively for peaceful purposes and shall not become the scene or object of international discord." Many national programs, such as the Antarctic Marine Living Resources (AMLR) Program support international efforts to protect the Antarctic and its marine life through the Commission for the Conservation of Antarctic Living Marine Resources and its Scientific Committee. CCAMLR was one of the earliest international arrangements to adopt an ecosystem approach to management. Worst-case scenarios for land-based and sea-based environmental emergencies e g a ship foundering with massive fuel loss near major wildlife concentrations have been prepared to help in establishing limits on financial liability, compensation and insurability. Formal monitoring of human impacts is required under the Protocol on Environmental Protection.

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