Abstract

Waste remediation (waste decomposition) is one of the ecosystem services (ES) salmon farming relies upon to reduce organic waste from the uneaten food and fsh faeces through the metabolism of fauna and aerobic and anaerobic microbial communities. Our objective was to infer the changes that may occur in ecosystem capacity for reducing organic matter by frstly verifying that an impact has occurred using the AZTI’s Marine Biotic Index (AMBI) and then relating that impact with changes in the ES of waste remediation reported in the literature. We relied on the combination of (i) the Driver, Activity, Pressure, change of State, Impact (Wellbeing), Response (Measure) (DAPSI(W)R(M)) approach as a causal model to establish relationships; (ii) the AMBI, as an impact indicator; and (iii) waste remediation capacity as the ES potentially affected by salmon farming. Data came from sites with different salmon farming infuence located in Los Lagos and Aysén regions, Chile. Regression analyses were used to establish causal relationships between (i) total organic matter and oxygen availability, (ii) oxygen availability and AMBI and (iii) dominance of ecological groups and oxygen availability gradient. Ecological indices were estimated for each site. DAPSI(W)R(M) allowed to determine that food provision as the driver of salmon farming activity produced an environmental pressure (organic matter), which caused a signifcant reduction in oxygen availability, indicator of state change. The main impact was due to a decrease in the oxygen availability. High representation of species of the ecological groups IV (e.g. Nassarius coppingeri) and V (e.g. Capitella capitata) in the most impacted sites suggests increased organic matter processing. The ecosystem is coping with the increase of total organic matter by changing macrofauna composition at expenses of a decrease in biological diversity and an increase in species dominance. Overall, the results indicated that salmon farming impacts could be related to the ES of waste remediation