Is the krill decline impacting their natural predators?

A decline in krill population

Krill are generally known as tiny creatures that whales eat in huge amounts by non-oceanographers, which is just about all I knew of them before college. This isn’t an incorrect description, but krill are so much more than that and are a vital part of the ecosystem in the SW Atlantic sector of the Southern Ocean where their populations have been steadily declining for years. This is a result of the oceans warming from climate change and making the krill’s natural habitats unsatisfactory for a lot of phytoplankton and subsequently, the krill.

Krill habitation is tied to the presence of abundant food sources and sea ice, both of which are decreasing in the SW Atlantic sector of the Southern Ocean. The phenomenon has led to a smaller total area of the ocean being inhabited by the tiny creature depicted below.

Effects of the decline

The decrease in krill density in the Southern Ocean has already been shown to have impacts on the larger ecosystem by Angus Atkinson in a 2004 study where he — along with fellow oceanographers — tied an increase in salps in the same sector of the Southern Ocean to the decline in krill. The creatures historically resided in separate areas of the Southern Ocean but as the krill move out the salps are free to move in to the newly warmer, less nutrient rich, and less competitive waters. The question at hand is whether this migration of krill will have a significant effect on the population of the krill’s numerous predators.

Larger impacts

As you can see from the diagram above, krill are a food source for several different aquatic predators. With krill moving out of warming areas of the Southern Ocean these predators that use krill as a food source might struggle to survive in the same ecosystems that they used to thrive in. It is reasonable to believe that having a major source of food removed from their environment would have a significant impact on some of these organisms, especially those like baleen whales where it makes up most of their diet. The effects of climate change may echo throughout every level of our ocean ecosystems.

If these organisms that prey on krill see decreases in their own populations then there is likely to be an increase in the price of certain products worldwide. Fishing and harvesting in the Southern Ocean would be negatively effected by this population decline and products such as furs, seafood, oil, and many more would see the effects of this price increase as they become less abundant.