Read more from Dr. Alexander Hayward, a climate scientist at the National Center for Climate Research, who was recently the lead on a study showing drastic shifts in Antarctic phytoplankton communities. These modifications may have long-lasting effects on the Southern Ocean’s food web. The study, published in Nature Climate Change, is based on almost 30 years of data. It captures the radical changes happening to key microorganisms that are at the base of the marine food web.
Dr. Pat Wongpan, a sea-ice scientist with the Australian Antarctic Program Partnership and Dr. Simon Wright, a marine biologist at the University of Tasmania, co-authored the study. First, it illustrates the impact of environmental change on the distribution of phytoplankton species composition between 1997 and 2023. Over this time, surface waters saw a major decline in surface waters’ iron content. Simultaneously, temperatures increased, which is harmful to iron-demanding diatoms that play an essential role in carbon sequestration.
These findings aren’t only a blessing to those of us who love transportation research. They carry profound implications. They signal a deeper ecological change that could upend the whole Antarctic food web.
Study Overview and Methodology
Our research team painstakingly pieced together the contributions of phytoplankton communities going back almost 30 years. Based on a nationwide dataset of 14,824 field samples, with most of these samples collected in the peak summer months. As these DNA samples were collected from the Southern Ocean that surrounds the continent of Antarctica, this region has enabled marine researchers to monitor major shifts in species relocation.
Dr. Wongpan noted that “our analysis showed that from 1997 to 2016, there were major reductions in populations of diatoms as sea ice increased.” To me, the decline in diatoms is really alarming. It has resulted in a community shift towards haptophytes and cryptophytes, classes of phytoplankton that are less capable of sequestering carbon than diatoms.
“Diatoms were replaced by haptophytes and cryptophytes that are more effectively grazed by jelly-like salps, which are poor food for fauna and less efficient in carbon transport,” – Dr. Pat Wongpan
The study emphasizes the importance of routine field sampling. Dr. Wright remarked on its significance: “Over time it yields a valuable database.” These long-term observations are key to detecting these shifts in marine ecosystems, and especially knowing how they’re changing due to climate change.
Environmental Shifts and Their Consequences
The nature of shifts in phytoplankton communities beginning in 2016. This shift occurred at the same time that sea-ice extent around Antarctica plummeted. The dramatic loss of sea ice, essential habitat for this species, played a significant role. It alters nutrient dynamics and species interactions throughout the ecosystem.
Dr. Hayward explained the broader implications: “Our research documents an ecological system change in the southern polar ocean caused by climate change, which could itself influence the climate through a feedback mechanism.” He further elaborated that “the carbon dioxide that would otherwise be stored in the deep ocean could now be released back into the atmosphere.”
The replacement of diatom-dominated communities with those primarily consisting of haptophytes and cryptophytes has drastic implications for krill survival. These krill rely on diatoms, a type of phytoplankton, as their main food source. A sharp decline in krill availability would have devastating ripple effects felt across a multitude of species. Penguins, seals, and baleen whales can all include krill as a part of their diet.
Broader Ecological Implications
These results highlight not only the remarkable sensitivity of the Antarctic marine ecosystem to ongoing climate change. The relationship we found between shifts in phytoplankton communities and patterns of decreasing trends in sea-ice coverage reinforces this sensitivity even more.
“The tiny algae at the base of the Antarctic food web are changing in ways that could ripple through the entire ecosystem—from krill to whales—and alter how the ocean helps regulate our climate,” – Dr. Alexander Hayward
As these basic, nature-altering changes take shape among our marine friends, the impact goes further than just affecting local habitats. Changes to phytoplankton dynamics can have outsized impacts on global carbon cycling. This, in turn, could dramatically affect state climate regulation on an even broader national scale.