The results of the research explain the ecological processes that govern the communities and suggest a model that can be used as a starting point for the study of these organisms on the white continent.

With the aim of understanding the factors that influence the assembly of microbiological communities associated with snow algae blooms, a team of researchers from the Center for Dynamic Research of High Latitude Marine Ecosystems (IDEAL) of the Austral university of Chile (UACh) published a new scientific work in the prestigious Springer Nature journal Microbiome.

The work was led by researcher Daniela Soto and included the participation of academics from the Institute of Marine and Limnological Sciences of the Faculty of Sciences of the UACh, Iván Gómez and Pirjo Huovinen, also researchers from the IDEAL Center.

Snow algae are eukaryotic microorganisms that colonize snow during the spring and summer seasons around the world. One of their functions is that they are primary producers, that is, they fix atmospheric carbon and transform it into organic carbon that serves as food for the entire community of microorganisms and possibly microinvertebrates that colonize the snow. In a region like Antarctica, their role becomes more relevant, because they influence the production of carbon at the terrestrial level and because their presence in the snow reduces a parameter called albedo, which is the amount of radiation reflected by a surface.

“In the case of white snow, it can reflect up to 90% of the radiation received. On the other hand, the presence of snow algae can reduce albedo by up to 30%. That is, instead of this energy returning to the atmosphere, it is retained on the Earth’s surface, feeding back the snow melting processes in Antarctica, which is already exacerbated due to climate change,” explains Soto.

“Despite this apparent negative property, snow algae are a reservoir of microbiological biodiversity that can host even endemic species and, as we know, the health of ecosystems also depends on biodiversity. Regarding the coloration, this is due to the fact that due to the increase in temperature and solar radiation typical of summer, snow algae proliferate until they become visible. They dye snow green because they have chlorophyll, the typical plant pigment, and they can also dye it red because, either as part of their life cycle or in response to environmental conditions, they accumulate a large amount of secondary carotenoids from russet. When this happens, even though they are still green algae, they look red due to the accumulation of these pigments,” adds the researcher.

Study results

Researchers have been able to observe how snow algae blooms in Antarctica are being less extensive in the north of the Peninsula. This is possibly due to the rapid melting of snow, which has completely eroded their habitat. In this sense, the group of scientists proposed a model that integrates the factors that influence the assembly of microbiological communities associated with snow algae. For this, a temporal analysis of the progression of the development of snow algae blooms in Antarctica was carried out, from their early stages until they were noticeably visible.

“The composition of the microbial community associated with the growth of snow algae was evaluated by massive sequencing of specific marker genes for bacteria and eukaryotes. The study lasted 35 days, where samples were collected every three or four days in four different sites around the O’Higgins base. In addition to determining the composition of the community, with molecular and environmental data we quantify the contribution of different ecological processes to the assembly of the community of bacteria and eukaryotes and how the concentration of nutrients influences the structure of the community,” explained Daniela Soto about the applied methodology.

Regarding the results, the researcher highlights that “the ecological processes that govern the composition of bacteria and eukaryotes in snow algae blooms are different. In the case of bacteria, the environmental conditions of polar ecosystems play a fundamental role by filtering out only those organisms that can tolerate them. On the other hand, in the case of eukaryotes we see that the process is more random and there are limitations in the dispersion of some species of algae. In fact, we found that some of the blooms were formed by species that are apparently endemic (e.g. Chlorominima collina,) which on the one hand challenges the conception that snow algae are capable of dispersing without major limitations around the world and, on the other hand, it highlights the role of Antarctica as a unique reservoir of biodiversity on the planet.”

At the sampling site, nutrients did not play a decisive role in the structure of the community and the researchers postulate that it is due to being in the presence of a site saturated with nutrients due to the influence of penguin colonies. “Although this does not contradict what is known about the development of snow algae, it does challenge the idea that nutrient limitation is a characteristic environmental factor of the sites where blooms develop. Finally, what we have are different scenarios and that influences both the abundance and the composition of the microbial community.”

To learn more about this research, check the publication here.