Today on the SUFB podcast, we put the spotlight on krill. Though they aren’t a single species, we decided to highlight krill today because these little guys and gals make up an incredibly large component of marine food webs. Krill are essentially the corn of the ocean, in that they represent the primary food source for a wide variety of marine predators. Not only are they rich in nutrients, they are also extremely abundant. In 2009, a study focusing on a single species of krill (Euphausia superba) estimated its biomass in the southern ocean at 379 million tons and its abundance at 800,000,000,000,000 (eight hundred trillion) adult individuals.
Krill are found in all the worlds oceans, mostly in depths up to 500 meters. However, a species known as ice krill (Euphausia crystallorophias) can be found in the Southern Ocean at depths of 4,000 meters. Like many other zooplankton, krill exhibit diurnal migrations throughout the day. This means that during the day, they typically remain in deeper waters to avoid predation. However, at night they vertically migrate to the sea surface to feed on phytoplankton and other zooplankton.
Certain types of krill can live anywhere from six months to six years, depending on the species and their environmental conditions. Females can carry thousands of eggs in each brood, and can contribute multiple broods per breeding season. Juvenile krill go through a variety of larval stages, throughout which they repeatedly molt and shed their exoskeleton and develop adult morphologies.
This is the part of the post where I typically throw in the threats facing our highlighted species and what you can do to help protect it. However, krill are actually doing (relatively) ok. Since krill are actually a grouping of multiple species, the IUCN doesn’t have a specific listing just for this group. There is some industrial krill fishing in the Antarctic (mostly as a food source for livestock and aquarium fish), but currently its not a heavily exploited stock. The most pressing threat facing krill at this point is climate change; these small crustaceans can be susceptible to slight changes in ocean chemistry or water temperature. If ocean acidification or sea surface warming either shifts krill distributions or increases krill mortality, we could expect to see substantial impacts on higher trophic-level animals like seals and whales.
Enjoy the Podcast!