104-2 Pristine or Polluted? Preliminary Analytical Methods for Assessing Salmon Aquaculture Impacts in Southern Chilean Fjords

Session: A Showcase of Undergraduate Research in Hydrogeology (Posters)

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Abstract:

The fjords and channels of southern Chile form a dynamic subantarctic coastal system where glacial meltwater, estuarine mixing, and regional circulation shape unique oceanographic gradients. However, increasing industrial development, particularly salmon aquaculture, may pose growing risks to water quality and ecosystem health. This study surveyed surface water conditions in Chilean Patagonia fjords during austral autumn 2025 to assess physicochemical variability across glacial and aquaculture-influenced gradients. To assess potential chemical impacts of salmon farms on local coastal waters, we measured surface water temperature, salinity, pH, alkalinity, dissolved oxygen (DO), and pCO₂ at 15 sites surrounding the Puerto Natales region, spanning both heavily farmed and relatively pristine areas. Sites located closest to active salmon farms (within 7 km) exhibited colder (6.2–7.7 °C), more saline (29.2–35.6 PSU), and more acidic (pH 6.2–7.6) surface waters compared to more distant sites (7.5–18.3 km), which showed warmer (7.7–10.1 °C), less saline (11.2–28.6 PSU), and more alkaline (pH 7.6–8.4) conditions. Surface pCO₂ ranged from 57 to 97 ppm, with lower values observed at glacial sites farther from farms, consistent with undersaturated meltwater-influenced conditions. Alkalinity ranged from 129 to 255 ppm and tended to be higher at closer, salmon-impacted sites. DO spanned from 0.4 to 4.65 ppm. While overall DO differences were not statistically significant across sites, the lowest DO values were observed at or near farm-adjacent locations, suggesting potential localized oxygen depletion associated with aquaculture infrastructure. These results highlight distinct physicochemical patterns tied to proximity to salmon farming and glacial input. However, interpretation is limited by the lack of vertical profiles, current velocity data, and temporal resolution. This preliminary study offers a baseline for evaluating anthropogenic stress in Chilean fjords and underscores the importance of long-term, multi-depth coastal monitoring in subantarctic systems facing rapid development and climate change.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5154

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