New discoveries continue to unveil the remarkable abilities of Antarctic krill.
The Southern Ocean’s dominant krill species, Euphausia superba, has shown potential in sequestering significant amounts of carbon through their waste. Recent findings indicate that these swimming crustaceans may also play a role in climate regulation by transporting their leftover food to the ocean floor.
Research published on October 7 in Biology Letters suggests that during periods of abundant food, such as phytoplankton blooms, the ejection of leftover “boluses” by krill could also contribute to carbon sequestration according to scientists.
However, the study also highlighted a concerning factor that influences bolus formation: the presence of microplastics in the water, which led krill to eject food more frequently.
Despite their small size, krill significantly impact Earth’s carbon cycle. They are essential components of the Southern Ocean ecosystem, with populations so large they can be observed from space and serving as a crucial food source for seals, whales, penguins, seabirds, and fish. Their fecal pellets, which sink rapidly to the seabed, can sequester carbon for up to a century. Scientists estimate that this biological mechanism might sequester at least 20 million metric tons of carbon annually, an amount comparable to the carbon storage capability of mangrove forests.
To feed, krill ingest seawater, filtering it for phytoplankton. They compress the phytoplankton cells into a dense mass, which they keep in their mouths while manipulating it with their mandibles and appendages to extract strands for consumption. The waste from this ingestion transforms into fecal pellets. If the bolus becomes too unwieldy, they expel it.
In laboratory settings, ecologist Anita Butterley from the University of Tasmania and her team documented this feeding mechanism, varying the types and concentrations of phytoplankton provided to the krill while observing bolus ejection rates. They discovered that increased phytoplankton concentrations correlated with a rise in boluses expelled.
However, an unintentional yet revealing aspect of their study involved microplastics. Krill subjected to microplastic contamination demonstrated a threefold increase in bolus creation compared to those in the other experimental setups.
This finding raises alarms, as it suggests microplastics may cause krill to discard food despite not being satiated. This concern becomes even more critical given the presence of microplastics already found in Antarctic krill samples. Earlier studies proposed that krill exposed to microplastics may contribute to their fragmentation, thus releasing nanoplastics.
