Krill – March 11, 2020
It’s Science Wednesday! Today’s topic is pretty small – centimeters long in fact. We’re talking about krill, small crustaceans that form a crucial part of the food web in Antarctic waters. But the problem we’re talking about is big: krill populations have declined 70-80% since the 1970s! A combination of climate change and industrial-scale fishing has wreaked havoc on krill populations, which is affecting the whales, penguins and seals that feed and depend on it.
Krill are quite sensitive to conditions in the water: the females lay their eggs in the upper ocean during the summer. Those eggs then sink to where an ideal water temperature range allows them to hatch. Once they hatch, the larvae swim up to the surface to find food in the form of phytoplankton – microscopic marine algae. The baby krill must then eat enough through the fall, in order to survive the winter, when the sunlight disappears and the sea ice forms. It’s not merely the presence of sea ice – it’s the timing that is so important for krill survival, as this ice provides not only shelter but a food source as well, given algae can be found congregating at the bottom and in the cracks of the ice.
While warmer ocean temperatures help krill hatch faster, decline in sea ice area and delays in sea ice formation, due to warmer temperatures, affect the phytoplankton, which then affect the krill’s ability to survive as well. To understand better the future impacts, more studies need to be undertaken – especially on observations of krill during the winter, when they’re sheltering under the sea ice.
Photos taken on Deception Island, Antarctica.