Work

Environmental impact of exposed salmon farms: transect reveals matching gradients in seafloor ecosystem structural and functional proxies

Year: 2025

Type: article

Abstract: Exposure of fish pens to strong currents in the open ocean facilitates the dispersion of farm-derived organic-rich solid wastes (faeces, uneaten feed) and thus lessens the effect of waste deposition on the seafloor ecosystem. Quantifying this effect requires tools that can detect deviations in seafloor ecosystem functioning, including trends that, if left unattended, accumulate to cause adverse effects. Here, we demonstrate a spatial gradient in the seafloor O 2 demand, maintained by local deposition of farm-derived organic waste, that could be used as such a tool. To detect this gradient, we measured the in situ sediment-seawater O 2 flux with 2 seafloor landers, a benthic chamber lander and an aquatic eddy covariance lander, deployed at 19 sites along a 3000 m transect heading towards a salmon farm in the D’Entrecasteaux Channel, Tasmania, Australia. We found that the seafloor O 2 demand gradually increased within approximately 500 m of the farm from a background level of 220-560 to 1922 µmol m -2 h -1 . The observed gradient was consistent with a gradient in the biological structure of the seafloor, demonstrated by traditional analyses of benthic macrofaunal assemblages. We discuss how regular monitoring of the seafloor O 2 demand with autonomous benthic landers can support proactive ecosystem-based management of open-ocean fish farms.

Source: Aquaculture Environment Interactions

DOI: 10.3354/aei00509

Authors: Kay Vopel, David R. Plew, Michelle N. Simone, Adam Davey, D. Jeff Ross

Language: English

Topic: Marine Bivalve and Aquaculture Studies

Subfield: Global and Planetary Change

Field: Environmental Science

Domain: Physical Sciences

SDG: Life below water

Open Access status: gold

Estimated APC paid: $2,157

Funders: Seafood Innovations, Australian Government, University of Tasmania