Abstract

This study investigates the immediate and mid-term effects of the biogeochemical variables input into the Reloncavi fjord (41 degrees 40'S; 72 degrees 23'O) as a result of the eruption of Calbuco volcano. Reloncavi is an estuarine system supporting one of the largest mussels farming production within Northern Chilean-Patagonia. Field-surveys were conducted immediately after the volcanic eruption (23-30 April 2015), one month (May 2015), and five months posterior to the event (September 2015). Water samples were collected from three stations along the fjord to determine greenhouse gases [GHG: methane (CH4), nitrous oxide (N2O)], nutrients [NO3-, NO2-, PO43-, Si(OH)(4), sulphate (SO42-)], and carbonate systems parameters [total pH (pHT), temperature, salinity, dissolved oxygen (O-2), and total alkalinity (AT)]. Additionally, the impact of physicochemical changes in the water column on juveniles of the produced Chilean blue mussel, Mytilus chilensis, was also studied. Following the eruption, a large phytoplankton bloom led to an increase in pHT, due to the uptake of dissolved-inorganic carbon in photic waters, potentially associated with the run off of continental soil covered in volcanic ash. Indeed, high surface SO42- and GHG were observed to be associatedwith river discharges. No direct evidence of the eruption was observed within the carbonate system. Notwithstanding, a vertical pattern was observed, with an undersaturation of aragonite (Omega(Ar) < 1) both in brackish surface (<3 m) and deep waters (>10 m), and saturated values in subsurface waters (3 to 7m). Simultaneously, juvenile mussel shells showed maximized length and weight at 4m depth. Results suggest a localized impact of the volcanic eruption on surface GHG, nutrients and short-term effects on the carbonate system. Optimal conditions for mussel calcification were identified within a subsurface refuge in the fjord. These specific attributes can be integrated into adaptation strategies by the mussel aquaculture industry to confront ocean acidification and changing runoff conditions. (C) 2019 Elsevier B.V. All rights reserved.