Increased risk of harmful algal blooms is linked to open-pen salmon farming

Toxic algal bloom surrounding a salmon farm in Chile

Scientific research links open-pen salmon farming to an increased risk of harmful algal blooms

  • “This increase in nutrient levels triggers eutrophication, leading to hypoxic conditions and the proliferation of algae (algal blooms) that threaten marine ecosystems by causing species declines and habitat destruction (Dai et al., 2023).”

    5 May 2026

  • “Salmon farming and human sewage treatment both produce nitrogen, which is an important factor in the health of waterways. Too much nitrogen can cause algal blooms that lead to serious impacts on aquatic animals and plants.”

    20 March 2025

  • “One of the significant environmental concerns associated with aquaculture is nutrient loading, which can lead to harmful algal blooms and other negative impacts on marine ecosystems.”  21 October 2024

  • “There is a strong correlation between the occurrence of toxic algal blooms and the [sic] aquaculture across the globe (Hallegraeff et al., 2021).”

    “Conditions that favour algal blooms can arise from higher water temperatures […] and studies have shown that blooms can spread due to abrupt rise in nutrients like phosphorus and nitrogen, […] (Cressey, 2017).”  January 2024

  • “TISC’s [the Tasmanian Independent Science Council] leading water quality expert Christine Coughanowr said Tasmania boasts some of the largest salmon cages in the world but the untreated pollution from a typical farm’s 20 cages is contributing to the algal blooms and oxygen crashes that will also be exacerbated by climate change.”  20 July 2023

  • “Eutrophication, human-mediated introduction of alien harmful species, climatic variability, and aquaculture have all been mentioned as possible causes of HAB [harmful algal bloom] trends at various spatial and temporal scales.”  8 February 2021

Harmful algal blooms kill marine life

UNESCO’s Intergovernmental Oceanographic Commission states:

 “These [harmful algal] blooms can kill marine life and even cause death in humans.”