The ecosystems in deep eastern South Pacific (ESP) waters are almost unknown. That is why the exploration of mesopelagic (>500 m) and abyssopelagic (>3000 m) communities represents a unique opportunity for science to discover new lifeforms, species, and genes, while also posing a major challenge for oceanography in the South Pacific Basin.

At the Millennium Institute of Oceanography we have decided to take on this challenge, and our project will allow us to reveal the mechanisms through which communities spread widely, colonizing unique habitats such as the Atacama Trench and the Nazca, Salas & Gómez, and Juan Fernández ridges. Our hypothesis is that these ranges significantly contribute to the dispersion of species and the gene flow in the coast-ocean direction, produced by the circulation of water masses and the water mixture associated with meso and large-scale physical dynamics.

To test our hypothesis we will collect deep water samples by means of a MOCNESS net (maximum depth: 6,500m) with an underwater video profiler (UVP), conductivity, temperature and fluorescence sensors, and stratified sampling nets. The UVP will provide particle-size distribution profiles, while the net samples will be divided for examination of live animals, DNA analysis and taxonomic studies. Water samples for molecular and genomic analyses of microbial communities (ranging from viruses to protists) will also be taken and in-situ incubation systems will be developed to calculate activity/ (micro) biological rates. We will also undertake quantitative and qualitative assessments of fish parasites and plankton as biomarkers for parasite host dispersion and habitat colonization.  Individual and biogeochemical models will be used to analyze the mechanisms that contribute to preserving endemic communities and the connectivity among different islands, seamounts and other oceanic regions.

The expeditions will be organized in cooperation with international partners. The molecular analyses of selected plankton will focus on DNA microsatellites and mitochondrial DNA in order to relate sampled populations and species both in the coast-ocean direction and in the vertical dimension. Additionally, the biogeochemical conditions of the deep ocean will be defined through measurements of carbon and pH/pCO2 reserves, along with saturation states of calcite and aragonite (Ω). We will also perform measurements of inorganic carbon isotopes (12C, 13C, and 14C) and dissolved organic carbon as well as age determination (DO14C) to learn about biogeochemical rates and the mixture of water masses in deep water ecosystems.

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