Antarctic Krill: study finds krill releases iron, a part of the CO2 absorption process

Krill is one of the primary foundations in the ocean's food chain. And iron is an important component of sea water, involved in the complicated process of absorption of carbon dioxide (CO2) by microscopic plants. These two elements, krill and iron, were brought together in a press release released today from the British Antarctic Survey:

"A new discovery reveals that the shrimp-like creature at the heart of the Antarctic food chain could play a key role in fertilizing the Southern Ocean with iron – stimulating the growth of phytoplankton (microscopic plant-like organisms). This process enhances the ocean's capacity for natural storage of carbon dioxide.

Reporting this month in the journal Limnology and Oceanography, an international team of researchers describe how Antarctic krill (Euphausia superba), once thought to live mostly in surface waters, regularly feed on iron-rich fragments of decaying organisms on the sea floor. They swim back to the surface with stomachs full of iron, releasing it into the water.

Antarctic krill is the staple diet for fish, penguins, seals and whales; and is harvested by commercial fisheries for human consumption.

Lead author from British Antarctic Survey, Dr Katrin Schmidt says, 'We are really excited to make this discovery because the textbooks state krill live mainly in surface waters. We knew they make occasional visits to the sea floor but these were always thought as exceptional. What surprises us is how common these visits are – up to 20% of the population can be migrating up and down the water column at any one time.'

The scientists painstakingly examined the stomach contents of over 1000 krill collected from 10 Antarctic research expeditions. They found that the krill, caught near the surface, had stomachs full of iron-rich material from the seabed. The team also studied photographs of krill on the sea floor, acoustic data and net samples. All these provided strong evidence that these animals frequently feed on the sea floor.

This finding has implications for managing commercial krill fisheries and will lead to a better understanding of the natural carbon cycle in the Southern Ocean."

Iron is known to enter the seas through the upwellings of deep sediments, run-off and wind-blown dust from land, and melting icebergs. Iron stimulates plankton growth which, in turn, takes in CO2. Dying plankton settle on the bottom thereby capturing and holding the CO2 - and the iron. This new study indicates that krill may also be a vital component in the recycling of iron, thereby stimulating plankton growth, and the CO2 absorption cycle is further stimulated.

The need for managing commercial krill fisheries to ensure a healthy food cycle for a variety of sealife in the Southern Ocean is now given extra importance based on what disruptions could occur to the carbon cycle should krill be over-harvested.

Read the press release from the British Antarctic Survey.

Southwest Fisheries Science Center: 25 years studying the Antarctic seas

Twenty-five years ago the Southwest Fisheries Science Center was formed in La Jolla, California. And since that time, federal researchers have been plying the Antarctic seas, monitoring the health and biodiversity of that chilly region to the south.

Their studies have resulted in the declaration of as many as 30 biological hotspots that need protection from overfishing and destructive bottom-harvesting techniques. In addition, the researchers continue to monitor the impact of commercial fishing on species such as Chilean sea bass (renamed from Antarctic or Patagonian toothfish) and the overall population of krill, currently being harvested for vitamins and fish meal.

A popular commercial fish, Chilean sea bass numbers have plummeted by as much as 80 to 90% and more, according to some experts. But even with conservation efforts in place and many chefs and restaurants choosing not to carry the tasty fish on their menus, their numbers remain drastically low.

“That is one of the key things we want to unravel,” said George Watters, director of the Antarctic Ecosystem Research Division at the fisheries center. “Why haven’t these things recovered? We want to know that so that in the future we can prevent that kind of thing from happening again.”

The work undertaken by the Southwest Fisheries Science Center is by no means easy. Two month-long expeditions take place every January and February when sea conditions in the Southern Ocean are most favorable. But at best, it's bone-chilling work as the researchers monitor seal and sea birds movements, take video and samples from the sea floor, and basically spend time in one of the most inhospitable places on the planet for the purpose of gauging the overall health of an ecosystem that, as remote as it is, is closely tied to all of us.

“The real challenge with our work is to sort out the causes of the different trends we see,” said Mike Goebel, a wildlife biologist with the program. “Sometimes it can make sense and other times it doesn’t make sense, so you are always searching for the best possible explanation of what we observe.”

Of particular interest to the researchers, has been the study of krill populations and the impact of commercial harvesting on this fundamental ocean food source. If you have sprinkled fish meal on your plants or popped an Omega-3 vitamin supplement in the morning, there's a good chance that it consists of krill. Since krill is the principal food source for many ocean species, a decline in krill populations can have tremendous adverse effects on other species. And there are indications that krill populations have declined by as much as 80% in some areas.

One of the many challenges facing the seas of the Antarctic is a confusion or outright lack of unifying international regulations and management to protect the Southern Ocean. Many interested nations are looking to solve the situation and avoid a disastrous exploitation of the region from legal or illegal harvesting activities.

“There is a huge emphasis globally on maintaining the uniqueness and special character of Antarctica,” director Watters said. “Decision-making is supposed to be made on the basis of the best available scientific evidence. That is where we come in.”

Read more about the center's studies in the San Diego Union-Tribune.