The decline in penguin populations could impact the Southern Ocean’s iron cycle, and thus the ocean’s ability to capture carbon dioxide (CO2) from the atmosphere, according to a study published on Tuesday.
Iron is a crucial component of Southern Ocean ecosystems, as a source of nutrients for phytoplankton (plant plankton). The study, published in the journal Nature Communications, highlights the critical role of penguins in consuming krill, an iron-rich animal plankton, and fertilising southern waters with their droppings.
Researchers calculated the volume of droppings, or guano, from a colony of Chinstrap penguins on Deception Island, off the Antarctic Peninsula, by processing drone images using artificial intelligence. Through chemical analyses of this guano, they found a very high concentration of iron in it, around 3 milligrams per gramme.
Chinstrap penguins recycle about 521 tonnes of iron each year
Extrapolating this data to the species as a whole, the authors estimate that Chinstrap penguins, one of the most abundant penguin species, recycle about 521 tonnes of iron each year.
While this makes them one of the “major” contributors to the iron cycle, according to the authors, it is half of what they were 40 years ago, as their population has been halved since the 1980s.
The oceans capture a third of the CO2 emitted into the atmosphere each year, thanks in part to the photosynthetic activity of phytoplankton. In regions such as the Antarctic Circumpolar Current, their growth is limited by the low availability of micronutrients such as iron.
Baleen whales are known for the role they play in consuming krill and making iron available, but the similar impact of seabirds such as penguins had not yet been studied.
Decreasing populations lead to fears for the ecosystem
In contrast to whales, which pass through different ocean regions, penguins spend their lives confined to Southern Ocean ecosystems: specifically, for Chinstrap penguins, the Antarctic Peninsula and surrounding islands.
“They would therefore contribute to a more concentrated recycling of iron in these regions,” says the study’s lead author, Oleg Belyaev, a researcher at the Institute of Marine Sciences of Andalusia, ICMAN.
Because of the collapse of the population of these birds, linked to climate change, the authors are concerned about a possible imbalance in the Southern Ocean ecosystem, and its capacity to sequester CO2 from the atmosphere.
“The aim of this research is to raise awareness of the ecological importance of these seabirds,” Oleg Belyaev explained.
