Euxinic conditions and altered biogeochemical cycles in a Patagonian fjord influenced by volcanic activity
Year: 2026
Type: article
Abstract: Fjords in Chilean Patagonia are highly dynamic systems shaped by land-derived inputs, oceanic exchange, and tectonic activity. Prior to the elaboration of the present article, no in-depth investigation had been undertaken into the anoxic or euxinic conditions of fjords in this region. Consequently, the present research represents an interdisciplinary oceanographic approach to studying Quitralco Fjord (45.6° S, 73.1° W; 2022–2025) and provides the first evidence of a volcanically influenced euxinic fjord in Chilean Patagonia. A subsurface anoxic layer, beginning between 90 and 120 m and extending to the basin floor (~ 160 m), was shown to exhibit elevated temperatures and high concentrations of H 2 S, consistent with inputs of volcanically derived fluids. A bubble-like acoustic scattering and the detection of CH 4 within this layer suggest an external input of the gas into the water column. Although largely stagnant, this layer shifted vertically over time, likely driven by interannual deep-water renewal. Within the euxinic layer, nitrate was completely depleted, while high phosphate (20 µM) and ammonium (25 µM) concentrations indicated an active sulfur cycle. A pronounced deep fluorescence maximum was also detected in the dark, anoxic basin, attributed to fluorescent dissolved organic matter (fDOM) dominated by two humic-like components (C1 245(350)-440 and C3 270(400)-505 ) with high aromaticity. Microbial community composition changed markedly across the redox gradient, while geochemical and microbiological fingerprints exhibited shifts in metabolic potential through the water column. The geological emissions of H 2 S from the seabed likely enhance and sustain the euxinic conditions, thereby strongly influencing the biogeochemical cycles of the basin. Overall, the present study reveals a previously unrecognized link between volcanic activity and fjord biogeochemistry, documenting for the first time the development of euxinic conditions in a Patagonian fjord in Chile.
Source: Scientific Reports
Authors: Iván Pérez-Santos, Paulina Montero, Marcelo H. Gutiérrez, Gerdhard L. Jessen, Alexander Galán, Laura Farías, Leonardo Castro, Camilo Rodriguéz-Villegas, Patricio A. Díaz, Claudia Aracena, Elías Pinilla, Karen Sanzana, Aranza L. Pérez, Karina Fuentes, Constanza Asmut, Guido Mancilla-Gutiérrez, Gabriel Soto, Cynthia Urrutia, Claudio Navarro, Matías Castro, David Silva, Salma Espinoza, Laura A. Bristow, Morten Larsen, Osvaldo Ulloa
Institutions: University of Concepción, Universidad de Los Lagos, Patagonian Ecosystems Investigation Research Center, Austral University of Chile, Catholic University of the Maule, Universidad Católica de la Santísima Concepción, Center for Climate and Resilience Research, Interdisciplinary Center for Aquaculture Research, Universidad Bernardo O'Higgins, Instituto de Fomento Pesquero, University of Maine, Universidad de La Frontera, Millennium Institute of Oceanography, University of Gothenburg, University of Southern Denmark
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,690
Awards: CENTER FOR OCEANOGRAPHIC RESEARCH IN THE EASTERN SOUTH PACIFIC (COPAS), G2353769666, BACTERIOPLANKTON RESPONSES TO ALLOCHTHONOUS DISSOLVED ORGANIC MATTER (DOM) IN A NORTHERN PATAGONIAN FJORD LINK BETWEEN DOM COMPOSITION AQUATIC TROPHIC STATUS AND HYPOXIA, RESEARCH PROGRAM FOR CLIMATE ACTION PLANNING, G2945545320, G3031716883, G3253050093, RECENT DEOXYGENATION TREND IN THE NORTHERN PATAGONIAN FJORD LOCAL DRIVERS AND CONNECTION TO CLIMATE MODES., DIATOM AND MICROBIAL COMMUNITY RESPONSE TO FRESHWATER PULSES IN A NORTHERN PATAGONIAN FJORD IMPACTS ON CYCLING OF SILICIC ACID AND SILICON ISOTOPES., ON THE INFLUENCE OF LOCAL AND REMOTE OCEANOGRAPHIC PROCESSES ON DEOXYGENATION, HYPOXIA, AND ANOXIA IN PATAGONIAN FJORDS., GEOMICROBIOLOGICAL LANDSCAPE ACROSS THE ANDEAN CONVERGENT BOUNDARY AND BEYOND, G6748843832, CENTER FOR CLIMATE AND RESILIENCE RESEARCH, G7446527141, G7591323743, G7896524835, "SPATIOTEMPORAL DYNAMICS OF METHANE IN (CH4) THE COASTAL-CONTINENTAL SHELF TRANSITION ZONE OF CENTRAL CHILE: SHORT-TERM PERSPECTIVES ON SOURCES AND DRIVERS", G8228512024, G8707107318, G953747012
OpenAlex ID: W7165125918