Krill

Definition

Krill are small, shrimp-like crustaceans that inhabit the ocean and are key components of marine ecosystems. They play a critical role in the food web, serving as a primary food source for a variety of marine animals, including whales, seals, penguins, and fish. The abundance and reproductive capacity of krill contribute significantly to marine biodiversity and the overall health of ocean ecosystems.

5 Must Know Facts For Your Next Test

1. Krill are found in all oceans, but they are most abundant in the Southern Ocean around Antarctica, where they form massive swarms.
2. They primarily feed on phytoplankton and are known for their ability to consume large quantities, which supports both their growth and the marine animals that depend on them.
3. The lifecycle of krill is closely tied to seasonal changes in sea ice, with breeding peaks occurring when phytoplankton blooms following ice melt.
4. Krill are not only vital for marine food webs but also play a role in carbon sequestration by feeding on phytoplankton and then excreting waste that sinks to the ocean floor.
5. Overfishing and climate change pose threats to krill populations, which can disrupt marine ecosystems due to their foundational role in the food web.

Review Questions

• How do krill contribute to the marine food web, and why are they considered a keystone species?
  • Krill serve as a crucial link in the marine food web by transferring energy from phytoplankton, the primary producers, to higher trophic levels such as fish, seals, and whales. Their large populations provide an abundant food source for many species, making them a keystone species. Without healthy krill populations, the entire marine ecosystem could become unbalanced, leading to declines in predator species that rely on them for survival.
• Discuss the impact of seasonal changes on krill populations and their role in nutrient cycling within marine ecosystems.
  • Seasonal changes significantly influence krill populations as they rely on phytoplankton blooms that occur after sea ice melts during spring. This availability of food promotes krill reproduction and growth. Additionally, when krill consume phytoplankton and later excrete waste or die, they help recycle nutrients back into the ecosystem. This nutrient cycling is essential for maintaining the productivity of marine habitats and supports a diverse array of marine life.
• Evaluate the potential consequences of climate change and overfishing on krill populations and the broader implications for marine biodiversity.
  • Climate change poses significant risks to krill populations through changes in ocean temperature and salinity, which can affect their reproductive cycles and habitat availability. Overfishing of krill for use in aquaculture and dietary supplements further threatens their numbers. These pressures can lead to decreased populations of krill, which would have profound effects on marine biodiversity, disrupting food webs and leading to declines in species that depend on krill as a primary food source. Ultimately, this could destabilize entire marine ecosystems.

Related terms

Plankton: Tiny organisms that drift in ocean currents and can be divided into phytoplankton (plant-like) and zooplankton (animal-like), including krill.

Trophic Levels:

Different levels in a food chain where organisms obtain energy, with krill primarily functioning as primary consumers feeding on phytoplankton.

Ecosystem Services: The benefits that ecosystems provide to humans, including carbon cycling and oxygen production, with krill playing an important role in nutrient cycling in marine environments.