Discovery of deep-sea cold seeps from Argentina host singular trophic linkages and biodiversity

BRAVO, MARIA EMILIA; PRINCIPI, SEBASTIAN; LEVIN, LISA ANN; ORMAZABAL, JUAN PABLO; FERRONATO, CAROLA; PALMA, FERMIN; ISOLA, JOSE; TASSONE, ALEJANDRO ALBERTO

Otro; Deep-Sea Research Part I; 2023

Chemosynthetic ecosystems host unique geological, biogeochemical, microbial andfaunistic settings which provide key ecosystem services for human wellbeing. In theArgentine continental margin, the existence of chemosynthetic ecosystems is stillunknown. We present the first finding of chemosynthetic ecosystems in the Argentinedeep sea. We asses and compare biological and geological settings for both coldseeps and both against a control site (no gas). We found two cold seeps with craterlike geomorphic features (pockmarks) of 500 m and 1000 m diameter at depths 500 m.Both cold seeps exhibited methane gas bubbles trapped at the surface of the seafloor,one evidenced seepage to the water column. Cold seeps hosted dense benthicmacroinvertebrates (≥ 350 µm) assembles consisting mainly of polychaetes, peracaridcrustaceans and mollusks. The fauna from Argentinean seeps exhibited δ13C andδ15N stable isotope signatures indicative of multiple trophic levels, supported by bothchemosynthetic and photosynthetic sources of energy. The difference in bubbling towater column was not related with different trophic input of chemosynthetically-derivedsources of energy, suggesting that gas input is mediated by the bubbles trapped in theseafloor sediments. The presence of gas bubbles trapped in the surface sediments ofthe ocean floor allowed the detection of ecological and trophic characteristics of activechemosynthetic ecosystems. The integration of the sub-bottom dimension can helpimprove our understanding on the interactions of chemosynthetic ecosystems withseafloor fluid flow in a more reliable manner than the gas plumes. These cold seepsare significant areas for the preservation of biodiversity and functions of the deepocean that are currently lacking conservation efforts and fall within areas tendered foroil and gas industry development. Information provided here can inform effectiveconservation actions and improve our understanding of the distribution ofchemosynthetic ecosystems worldwide.