Unraveling the microbiomes from Antarctic Krill in South Orkney and South Georgia Islands

X Simposio de Estudios Polares, 15-17 May 2024, Salamanca

The Antarctic krill (Euphausia superba) biomass is estimated between 300 and 500 million tons. Because of its large biomass and central position in the marine food web, krill is considered a key species that shapes the functional diversity, productivity, and carbon sequestration of the Southern Ocean. Krill populations are declining while salps abundances are increasing, potentially altering Southern Ocean food webs and future carbon sequestration. This study analyzes the krill microbiome obtained from 70 individuals, in different body parts (exoskeleton, molt, stomach, hepatopancreas and fecal pellets), and in two distant geographical locations (South Orkney and South Georgia Islands). Diversity analyses revealed that the number and composition of species were different among krill body parts and geographical locations. Yet, certain taxa predominate in almost all samples: the prokaryotic Class Gammaproteobacteria, and the eukaryotic Classes Gregarinomorphea and Phyllopharyngea. We also observed that microbial communities changed gradually between geographic locations and between biologically related body parts (i.e., between exoskeleton and molt, and between different parts of the digestive system). In each krill body part, we identified indicator species, that included both pathogenic (e.g., the prokaryotic Order Thiotrichales) and symbiont (e.g., the eukaryotic Order Eugregarinorida) microorganisms. Indeed, we found a major abundance of krill pathogens in the samples from South Georgia, the studied area with higher temperatures recorded in the water column. These findings reveal the importance of knowing more about the Antarctic krill microbiome and its links to biogeography and Climate Change. In future steps, we will increase the number of samples (>500 samples) and the geographic range (>3 areas). The complete dataset (that will include metagenomes and the microbiome of salps and seawater) will allow us to describe the similarities and connections among krill and salps microbiomes, and also unveil their functionality

Peer reviewed