Antarctic food web
The foundation of the food web in the Southern Ocean is Antarctic krill—small shrimp-like crustaceans found throughout the Southern Ocean surrounding Antarctica. They can form large swarms in open ocean regions, or more scattered layers under the edges of ice packs. Krill migrate upward toward the ocean surface at night, and down into deeper water during the day. Not surprisingly, Antarctic krill populations are affected by climate variations and changes in their ocean environment. Antarctic krill consume algae that get their energy from the sun, and are the base of the marine food web for fish, birds, and marine mammals. Predators such as the Antarctic fur seal and several species of penguins all depend on Antarctic krill.
Antarctic krill is also a commercially valuable product, and is used in nutritional supplements, animal feed, and aquarium products. Other commercially valuable species in the Antarctic ecosystem include finfish, such as Patagonian toothfish and Antarctic toothfish (both marketed in the United States as Chilean seabass), as well as mackerel icefish. The United States is the largest consumer of Chilean seabass and krill products in the world.
Managing Antarctic marine living resources
Given the rich abundance of marine life in Antarctica, the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR) was established in 1982 to manage fisheries in the region with the goal of preserving species diversity and marine ecosystem stability. Each of the 25 member nations of the Convention engages in fishing or scientific research in the Southern Ocean, providing information on krill, finfish, and other marine life.
Although the aim of the Convention is to conserve marine life of the Southern Ocean, reasonable harvesting is permitted. The Convention adopted a “precautionary” approach to minimize the potential risks of unsustainable harvesting practices.
As Antarctic resources grow in economic value, the temptation to engage in illegal, unregulated, and unreported fishing has also increased, creating enforcement challenges in the Southern Ocean’s vast and harsh environment.
Following the establishment of Convention, the U.S. Antarctic Marine Living Resources Convention Act of 1984 provided the legislative authority to establish NOAA’s Antarctic Marine Living Resources Program. This program, which operates out of NOAA’s Southwest Fisheries Science Center, conducts directed research on krill-based ecosystems in the Antarctic. Ultimately it proves information to the Department of State to achieve the conservation objectives of the Convention.
NOAA Fisheries leadership role in the management of Antarctica’s marine living resources
Through AMLR, NOAA Fisheries has a long history of leadership in CCAMLR, leading working groups on ecosystem monitoring, fish stock assessments, and statistics and modeling. NOAA Fisheries scientists also hold key leadership positions at CCAMLR and have served as the Chair or Vice-Chair of the CCAMLR Scientific Committee. When new concerns about Antarctica’s unique ecosystem arise, NOAA Fisheries scientists convene workshops to address these issues, tackling topics such as vulnerable marine ecosystems and marine protected areas.
NOAA Fisheries scientific research in Antarctica
The principal mission of the U.S. AMLR program is to provide the scientific information needed to detect, monitor, and predict the effects of harvesting and associated activities on targeted species (krill and finfish) and protected species (seabirds, penguins, seals, and fur seals) and the Antarctic marine ecosystems upon which they depend. The program focuses on the area around the Antarctic Peninsula.
AMLR uses a research vessel to conduct studies about predator and prey relationships and to support research at two field stations in the South Shetland Islands. The vessel platform is used to collect environmental and oceanographic data, as well as information about the abundance and distribution of zooplankton, including Antarctic krill. Finfish surveys are conducted periodically to assess the biomass of species subject to commercial harvesting. Vessel surveys are primarily conducted in the summer months, but in recent years the program also has conducted winter surveys to provide a greater understanding of the overwinter environmental processes.
In addition to research at sea, U.S. AMLR scientists collect predator data at field stations on the South Shetlands, located at Cape Shirreff on Livingston Island (seabird and seal data) and at Copacabana at Admiralty Bay on King George Island (seabird data). Predator data are collected primarily in the spring-summer window, although some of the predators are tagged for overwinter distribution studies. In recent years, the AMLR field team has incorporated an innovative camera system to study seabird colonies throughout the year.
Protecting marine life in Antarctica
Despite its harsh remote environment, the Antarctic supports a wealth of wildlife on land and in the surrounding oceans. New Antarctic species are found and named each year. Human activities, including the harvest of fish and krill, and changing climate systems pose threats to wildlife. The U.S. AMLR Program offers a new way forward in managing complex ocean resources using an ecosystem approach. NOAA Fisheries’ scientists are international leaders in developing this management approach, linking changes in the region’s climate to the productivity of the Antarctic marine ecosystem, and promoting informed management decisions.
Conducting research in Antarctica
Dr. Douglas Krause, an ecologist in NOAA’s Southwest Fisheries Science Center describes the highlights and challenges of working in Antarctica:
“Ecologists, I think, tend to wonder how natural systems might have worked in the absence of the large perturbations created by humans. The Antarctic may be the closest that we can get to observing that in the modern world, and it is exciting. However, while working in remote locations like the Antarctic have many professional upsides, practically it is a difficult place to reach. The end result of that difficulty is that we need to deploy to these locations for long time periods, typically months at a time. This can mean long separations from friends and loved ones often during holidays and major life events.”
Conducting research in the Antarctic requires a dedicated team of scientists willing to work in challenging conditions far from home. Year after year, the U.S. AMLR Program has successfully assembled field teams that have collected and produced a valuable database of Antarctic ecosystem information, ultimately used to guide management decisions in CCAMLR.
Learn more about the ongoing field research in Antarctica.
Antarctica in a changing climate
Climate change is altering Antarctica’s land and ocean environments. Over the past 50 years, the annual average air temperature in this region has increased by about 5 degrees Fahrenheit. The changes in air temperature and corresponding surface temperature have caused what were once “permanent” ice shelves—some the size of Rhode Island—to crumble into the sea, permanently modifying the Antarctic landscape and the Southern Ocean.
One of the most dramatic effects of oceanic and atmospheric warming in this region is the decline in the extent and duration of annual sea ice critical to species such as krill, penguins, seals, and whales. Over the past 20 years, NOAA Fisheries scientists observed that the decrease in sea ice extent and duration resulted in a decline in krill, and also in a fundamental change in the mechanisms governing the environment around the South Shetland Islands. With ice less prevalent each decade, the productivity of the ecosystem becomes controlled by other atmospheric forces, which affects everything from the temperature and currents to the amount of nutrients in the water.
El Niño and the Antarctic environment
A principal driver of climate in the Antarctic is the El Niño-Southern Oscillation (ENSO), which is traditionally known to affect the mid-latitudes. In Antarctica’s South Shetland Islands, ENSO can cause the productivity of the marine environment to vary greatly within and among years. ENSO interacts with the local atmospheric and marine climate to create complicated patterns that scientists are just beginning to unravel.
The effects of climate change and ENSO can be tracked as they ripple up the food chain, causing predators at every level to alter their behavior, feeding, or reproductive strategy. As ocean temperatures and nutrients change, NOAA Fisheries scientists monitor the effects on all components of the ecosystem, including changes in water density and current patterns, abundance of Antarctic krill and other zooplankton, and predator populations.
Adapting to a rapidly changing environment
NOAA Fisheries scientist Dr. Christian Reiss, working with scientists at the Scripps Institution of Oceanography (University of California, San Diego) has shown that yearly variability in phytoplankton production (the principal food for krill) is associated with the rising and falling water temperatures caused by ENSO. This fundamental connection between global atmospheric climate patterns and the base of the Antarctic food web shows that global climate changes directly affect the Antarctic marine life that the United States and CCAMLR member nations are tasked with managing.
For instance, NOAA Fisheries scientist Dr. Jefferson Hinke studies three species of penguins on the South Shetland Islands facing changing environmental conditions. He has found that gentoo penguins, a generalist species that are able to quickly adapt to changes, show increasing population sizes. At the same time, chinstrap and Adélie penguins, which are considered specialist species in either food or nesting habitat selection, are declining in number at study sites.
Antarctic fur seals also show adaptations to changes in prey availability based on a changing climate. NOAA Fisheries scientist Dr. Mike Goebel has shown that after three decades of population growth following re-colonization of the South Shetlands in the early 1960s, the fur seal population stabilized and has not increased in the past decade. Krill is the primary prey of fur seals during the summer. However, fur seals appear to have more flexibility in diet and will consume fish and squid if krill is not available. Their ability to eat other non-krill prey may help them adapt to fluctuating krill availability.
Because NOAA Fisheries scientists in Antarctica have conducted annual surveys for more than 30 years, researchers are able to detect changes in the environment and study the complex relationships between populations and changing ocean conditions in the short and long terms. This research helps manage living marine resources sustainably.
Ross Sea Designated as World’s Largest Marine Protected Area
In 2016, CCAMLR made history by declaring the largest marine protected area on the planet in Antarctica’s Ross Sea. U.S. AMLR researchers led the U.S. scientific delegation to CCAMLR, providing the scientific basis for the negotiations led by the U.S. Department of State. This designation marks the first time that CCAMLR’s 25 member nations reached consensus to protect this huge area of the Southern Ocean. The 598-square-mile marine protected area (MPA) will provide critical habitat, including breeding and foraging grounds, for penguins, seals, krill, whales, and other species. The Ross Sea MPA is designed to provide representative protection of different habitats and bioregions, to mitigate or eliminate a number of specifically identified potential ecosystem threats from fishing, and to support existing and future scientific research and monitoring.