Benthic marine algae from South Shetland Islands (Antarctica): biodiversity and evolutionary patterns

Abstract

The present work focuses on different aspects related to the Antarctic seaweed. As the main primary producers of the coastal areas of Antarctica, this group of organisms play a key role in shaping the biological communities and the ecological dynamics of Antarctic shores. However, compared to other groups of Antarctic organisms or the seaweed communities of other regions of the world, Antarctic macroalgae remain less studied. This is especially true in several areas of knowledge as their actual biodiversity, their evolutionary history and patterns, some aspects of their ecology or the total extent of their relations with other Antarctic organisms and their environment. Aiming to address the lack of knowledge of these areas, we aimed to extend it by focusing our work in several key aspects of Antarctic seaweed biology. As so, we tried to respond several specific questions regarding the topics above mentioned. In this context, we studied biodiversity of seaweed communities that are present in the South Shetland Islands. For that, we tried to identify the composition and influencing factors of the seaweed assemblages present in Deception Island. We also studied how seaweed biodiversity affects Antarctic epiphytic diatoms richness, studying the composition of them, both from Deception and Livingston islands. Moreover, we tried to expand the data with evolutionary relevance by analysing the nuclear DNA content and ploidy levels (C values), as well as the nuclear developmental patterning of some common Antarctic seaweed species with no previous data for those characters. This was achieved by using a fluorimetry technique that sets a reference for comparison for future studies on those parameters. Additionally, we condensed the latest knowledge on the chemical ecology of seaweeds and other organisms from Antarctica, and tried to expand it by investigating the potential antimicrobial activity of these seaweeds. For this, we tested their natural extracts against several Antarctic microorganisms and identified several species that were active chemically. Also, we tested the same extracts for antimicrobial action against several microorganisms that are common human pathogenic surrogates and identified potential human interest in these seaweeds on the search for new sources of antibiotics. Finally, we reported our findings on the role seaweed have in the context of climate change in the Antarctic region. Those findings include the identification of non-native kelp rafts that arrived to the maritime Antarctica, and presented several passenger species that have potential invasiveness in the Antarctic. Regarding that, we classified and explored the possible roles that the rafts themselves and the species travelling with them may play in futures scenarios of climate change in Antarctica.