Krill

Definition

Krill are small, shrimp-like crustaceans that play a vital role in the marine food web, primarily found in the oceanic waters of the Southern Hemisphere. They are a key food source for many marine animals, including whales, seals, and fish, and their abundance impacts the biodiversity of various marine habitats, especially in the Southern Ocean.

5 Must Know Facts For Your Next Test

1. Krill are primarily found in cold waters, with the largest populations located in the Southern Ocean surrounding Antarctica.
2. There are several species of krill, but Antarctic krill (Euphausia superba) is the most studied and commercially important due to its role in the ecosystem.
3. Krill populations can fluctuate dramatically based on environmental factors such as sea ice coverage and water temperature, which can influence their availability as a food source.
4. These crustaceans can form massive swarms that can be visible from space, showcasing their abundance and importance in marine ecosystems.
5. Krill play a significant role in carbon cycling by consuming phytoplankton and releasing carbon compounds back into the water column, affecting global climate processes.

Review Questions

• How do krill contribute to the marine food web, and what impact does their population have on larger marine animals?
  • Krill serve as a crucial food source for many larger marine animals such as whales, seals, and various fish species. Their position at the base of the food web means that fluctuations in krill populations can directly affect these predators. If krill populations decline due to environmental changes or overfishing, it could lead to a reduction in the populations of these larger animals that depend on them for sustenance.
• Discuss the relationship between krill and phytoplankton within marine ecosystems, emphasizing their interdependence.
  • Krill rely on phytoplankton as their primary food source, forming a direct link between primary producers and higher trophic levels in marine ecosystems. Phytoplankton produce energy through photosynthesis, which supports krill populations. This interdependence means that any changes in phytoplankton abundance due to climate change or pollution can significantly impact krill populations and consequently affect the entire marine food web.
• Evaluate the implications of declining krill populations on global climate processes and marine biodiversity.
  • Declining krill populations could have profound implications for both global climate processes and marine biodiversity. Since krill are integral to carbon cycling by consuming phytoplankton and releasing carbon back into the ocean, a decrease in their numbers may disrupt this balance, potentially exacerbating climate change. Additionally, with fewer krill available as a food source, marine animals that depend on them could face population declines, leading to reduced biodiversity and altered ecosystem dynamics in marine habitats.

Related terms

Phytoplankton:

Microscopic plant-like organisms that form the base of the marine food web, producing energy through photosynthesis and serving as the primary food source for krill.

Zooplankton:

A diverse group of drifting animals in the ocean, including krill, that feed on phytoplankton and serve as a crucial link in transferring energy from primary producers to higher trophic levels.

Biodiversity:

The variety of life in a particular habitat or ecosystem, which can be significantly affected by the presence and population dynamics of krill and other keystone species.