Krill

Definition

Krill are small, shrimp-like crustaceans that play a crucial role in marine ecosystems, especially in polar and temperate regions. They serve as a primary food source for a variety of marine animals, including whales, seals, and penguins, making them vital for maintaining the balance within these ecosystems. Their presence indicates healthy ocean environments and they are also essential for the nutrient cycling in these marine systems.

5 Must Know Facts For Your Next Test

1. Krill are primarily found in cold ocean waters, especially around Antarctica and in the North Atlantic, where they thrive in nutrient-rich environments.
2. They reproduce rapidly, with females capable of producing thousands of eggs at a time, leading to population booms that can support large marine predators.
3. Krill play a significant role in carbon cycling by feeding on phytoplankton and transporting carbon to deeper ocean layers when they die and sink.
4. Commercial fisheries target krill for use in aquaculture and dietary supplements due to their high omega-3 fatty acid content.
5. Changes in sea ice cover due to climate change can impact krill populations, which may have cascading effects on the entire marine food web.

Review Questions

• How do krill contribute to the marine food web and what would happen if their populations decline?
  • Krill serve as a foundational food source for many larger marine animals such as whales, seals, and seabirds. If krill populations were to decline due to environmental changes or overfishing, it would disrupt the food web significantly, leading to starvation and declines in populations of these predators. This would also affect species that rely indirectly on krill through predation on their predators, showcasing how interconnected marine ecosystems are.
• Analyze the ecological significance of krill in polar marine ecosystems and how they interact with other species.
  • Krill are ecologically significant because they form a crucial link between primary producers like phytoplankton and higher trophic levels including fish, seabirds, and marine mammals. Their feeding habits help control phytoplankton populations while simultaneously supporting the diets of numerous predators. Additionally, they play a role in nutrient cycling as they consume organic matter from the water column and contribute to carbon export when they sink to deeper waters after death.
• Evaluate the potential impacts of climate change on krill populations and the broader implications for polar ecosystems.
  • Climate change poses significant threats to krill populations through alterations in sea ice extent, water temperature changes, and shifts in phytoplankton availability. Since krill depend on sea ice for breeding and shelter during their life cycle, any reduction could lead to diminished reproduction rates. This decline could cascade throughout polar ecosystems by affecting predator populations reliant on krill as a food source, thereby disrupting ecological balance and potentially leading to shifts in species distributions and biodiversity loss in these sensitive habitats.

Related terms

Phytoplankton: Microscopic plants that form the base of the marine food web, serving as the primary producers that convert sunlight into energy.

Zooplankton: Small drifting animals, including krill, that feed on phytoplankton and are a key link in the food chain between primary producers and larger predators.

Antarctic Circumpolar Current: A strong ocean current that flows around Antarctica, influencing nutrient distribution and supporting rich marine biodiversity, including vast populations of krill.