CHINSTRAP PENGUIN
Pygoscelis antarctica
ID: Black cap and a distinctive black "strap" across a white face
Measurements: 4–4.5 kg (9–10 lb)
Distribution: Southern tip of South Georgia; South Orkney, South Sandwich, and South Shetland Islands; and the northern tip of the Antarctic Peninsula
Estimated Population: ~7.5 million breeding pairs (second most abundant penguin species)
Diet: Mostly krill and fish
Diving: Usually less than 50 m (164 ft)
Temperament: Feisty
Notes: The Chinstrap Penguin is found in a variety of sub-Antarctic and Antarctic regions. It is known for its distinctive black strap across the white face and is a very energetic and feisty species. Its population is currently stable, and it is often the second most abundant penguin species after the Adélie in some areas.
ADÉLIE PENGUIN
Pygoscelis adeliae
ID: Black face; white eye-ring (bare skin) around the eye; stout body shape
Measurements: ~4 kg (9 lb)
Note: Named after French explorer Dumont d’Urville’s wife, Adélie, during his Antarctic voyage on the Zélée in 1837
Distribution: Circumpolar—mainly East Antarctica and the Ross Sea, but also found on the Antarctic Peninsula
Estimated Population: ~2.5 million breeding pairs
Diet: Krill, fish, and squid
Diving: Usually around 75 m (246 ft); can reach depths of up to 175 m (574 ft)
Temperament: Aloof, with a fixation on pebbles
Notes: The Adélie Penguin is strongly associated with the Antarctic, though it breeds on some sub-Antarctic islands. The species is highly pelagic, migrating after breeding to rich feeding grounds, sometimes reaching as far as South America. Adélies are known for their habit of resting on icebergs and molting on ice floes, a unique strategy among penguins. The species has seen a decline in numbers since 1990, largely due to the warming of temperatures around the Antarctic Peninsula and the resultant reduction in sea ice, which affects krill populations, their primary food source.
(SOUTHERN) GENTOO PENGUIN
Pygoscelis papua ellsworthii
ID: White patch above each eye, usually meeting over the top of the head; bright orange bill and feet
Measurements: ~5.5 kg (12 lb)
Distribution: Northern tip of the Antarctic Peninsula, South Shetland Islands, and South Orkney Islands
Estimated Population: ~120,000 breeding pairs
Diet: Fish, squid, and krill
Diving: Short and shallow or long and deep; usually forages within 10 km of shore, but dives can exceed 100 m (328 ft)
Temperament: Easygoing
Notes: The Gentoo Penguin comes in two forms: the northern form (P. p. papua) breeds on the Falklands and various sub-Antarctic islands, while the southern form (P. p. ellsworthii) is found only on the Antarctic Peninsula, South Shetlands, and South Orkneys. The southern form is rarer, with a population of approximately 100,000 pairs.
When French explorer J.B. Charcot visited Petermann Island in 1909, naturalist Lionel Gain made early counts of penguins breeding there. These occasional counts were followed by monitoring from the British Antarctic Survey and, more recently, by an American organization called Oceanites, which has been conducting regular monitoring since 2003. This long-running data set provides valuable insights into the changing penguin populations in the Antarctic over the last 100 years.
The population of Adélie Penguins has declined dramatically since around 1990, largely due to the warming temperatures around the Antarctic Peninsula and the decline in sea ice. This decline in sea ice impacts krill, the primary food source for Adélies. In contrast, the population of Gentoo Penguins has increased steadily, as they are less dependent on krill and feed on a wider variety of marine organisms. The Gentoo's population has grown in tandem with the decline of the Adélies, and their breeding range has extended southwards in recent years.
HUMPBACK WHALE
The humpback whale is one of the best-known and most easily recognisable of the large whales. It is famous for its frequent acrobatic behavior and its occasional tendency to approach vessels. Over the past 40 years, many thousands of humpback whales around the world have been individually identified by their natural markings—most notably the unique patterns on the ventral (underside) surface of their tail flukes. As a result, much has been learned about the biology and behavior of this species.
Humpback whales were heavily exploited by the whaling industry, but they appear to be making a strong comeback in most populations.
The humpback whale has a large, robust body. The head and lower jaw feature a variable number of rounded protuberances called tubercles. The long, narrow flippers are approximately one-third the length of the body. The dorsal fin is highly variable in shape and size—ranging from almost absent to high and falcate (sickle-shaped)—and is often scarred. It is typically located on a hump, which becomes particularly noticeable when the whale arches its back during a dive.
The blow (spout) is often lower, rounder, and more bushy than those of other rorquals (a group of baleen whales). The trailing edge of the flukes is prominently serrated.
The Antarctic Krill (Euphasia superba) is one of the approximately 80 species worldwide, of which 5 occur in the Southern Ocean. While it may not be quite at the bottom of the Antarctic food chain, it is the most important organism within it. It is also the most numerous, with possibly the greatest biomass of any species on the planet (including humans). However, it is difficult to get an accurate estimate of just how much there is, and estimates vary widely, anywhere between 60 and 300 million tonnes. It is quite possible that krill have become more numerous since whales (one of their major predators) were drastically reduced in numbers during the 20th century.
It is not only whales that eat krill; Adélie Penguins, crabeater seals, and fur seals (at least on the Antarctic Peninsula) live almost entirely upon it. Most other species of mammals and birds also feed on it at least partially. Additionally, it is harvested for human use.
Spawning takes place during the summer months, with females capable of laying several broods, each containing up to 10,000 eggs. The eggs sink to a depth of 1,000 m (3,300 ft) where they hatch. Over the next 3–5 months, they pass through several larval stages as they rise through the water column to shallower waters. Rather surprisingly for something whose sole purpose in life seems to be being eaten by anything and everything, krill can live for up to 10 years, with a fully grown adult reaching 6 cm in length (2.5 inches). Unlike most other crustaceans, size is not always a good indicator of age, as they can actually shrink when food is scarce (e.g., in winter).
Krill feed on phytoplankton and smaller zooplankton and can form hygge—densely packed swarms containing up to 30,000 individuals per cubic meter (35 cubic feet). One such swarm off Elephant Island in 1981 covered an area of 450 square km (175 square miles) and was estimated to contain around 2 million tonnes of krill. They can sometimes even be detected by satellites from space. While they may be small, and we may not always see them, krill are fascinating creatures and are vital to the ecosystem of the Southern Ocean.
('Plant' Plankton)
What are they?
Phytoplankton are the autotrophic (self-feeding) components of plankton. They account for about half of global photosynthetic activity and are a key part of ocean and freshwater ecosystems. Despite making up only about 1% of the global plant biomass, they contribute at least half of the oxygen production. The name comes from the Greek words phuton (meaning "plant") and planktos (meaning "wanderer" or "drifter").
Where are they found, and how do they produce?
Phytoplankton obtain their energy through photosynthesis, just like trees and other plants on land. This means they must have light from the sun, so they live in the well-lit surface layers (euphotic zone) of oceans and lakes. Phytoplankton form the base of marine and freshwater food webs and are key players in the global carbon cycle.
How important are they?
Phytoplankton account for about half of global photosynthetic activity and at least half of the oxygen production, despite comprising only about 1% of the global plant biomass. They are highly diverse, ranging from photosynthesising bacteria to plant-like algae to armor-plated coccolithophores. Important groups of phytoplankton include diatoms, cyanobacteria, and dinoflagellates, although many other groups are also represented.
Whale Populations in Antarctica: Recovery Since the Whaling Ban
Whale populations in Antarctica have shown varying rates of recovery since the International Whaling Commission's (IWC) moratorium on commercial whaling in 1985/86. Below is a general overview of the recovery rates for different whale species:
Blue Whales were heavily targeted during the commercial whaling era, resulting in a catastrophic decline in their population. Recovery has been slow, and the population remains much lower than pre-whaling levels. The species is still listed as endangered by the IUCN. However, estimates suggest a population of a few thousand individuals currently resides in the Southern Ocean.
Humpback Whales also suffered major declines due to whaling but have shown an impressive recovery. An IWC study indicates that the population in the Southern Ocean is about 30% of its pre-whaling number. However, the population of the Southwest Atlantic humpback whale is now estimated at around 25,000 individuals, approaching pre-whaling levels.
Fin Whales, the second-largest whale species, were another primary target for whalers due to the high reward per whale caught. It is thought that approximately 720,000 fin whales were killed in the Southern Hemisphere, reducing the population to about 13% of its original size. Their recovery has been slower compared to humpbacks, but numbers appear to be increasing. Current population estimates are limited due to sparse surveillance, though there has been a noticeable rise in sightings and fin whale aggregations in the Southern Ocean in recent years.
Minke Whales were less drastically affected by commercial whaling compared to other species. Being fast and relatively small made them less popular targets, though they still faced significant pressure. They are believed to have a stable population, with some estimates suggesting around 500,000 individuals in the Southern Hemisphere. Their populations are not as well-monitored, but they do not appear to be as threatened as other large whale species.
Southern Right Whales were heavily exploited, with a pre-whaling population estimated at around 58,000 individuals. This dropped drastically to fewer than 2,000 individuals by the 1830s. Current estimates suggest a population of around 4,742 whales, indicating that the species remains far below its pre-exploitation abundance.
Today, whale populations face additional challenges that affect recovery rates, including habitat changes and food availability due to climate change—particularly reductions in sea ice extent, which impacts the abundance of krill, a primary food source. Other ongoing threats include ship strikes and entanglement in fishing gear.
While significant progress has been made in the recovery of some Antarctic whale species since the end of commercial whaling, others are still recovering at a slower pace. Continued conservation efforts and monitoring are essential for the sustained recovery of these majestic creatures.
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