About eight million farmed salmon have died in northern Norway due to a persistent algae bloom, causing significant economic impact on one of the country's key industries. The Norwegian Directorate of Fisheries estimated the loss at 11,600 metric tons of salmon, worth more than $82 million, although the Norwegian Seafood Council suggests the total could be much higher. Nine salmon companies in the regions of Troms and Nordland have been affected, with some losing up to 90% of their salmon for this and next year's production. While algae blooms are natural, their lethal concentration this year is rare and possibly exacerbated by climate change, according to experts.

Algae blooms occur when water conditions, such as slow currents and warmer temperatures, cause the population of microscopic plant-like organisms to explode. These blooms are particularly dangerous for farmed salmon, which unlike their wild counterparts, can't swim away. The algae affect the fish's gills, effectively suffocating them. Although similar blooms have occurred in the past, the scale and impact of this year's event have raised concerns. Peter Jones from University College London noted that the mortalities in Norway in just the last few days have been almost as great as an entire year's worth in Scotland.

Lars-Johan Naustvoll, a biologist at Norway’s Institute of Marine Research, was hesitant to directly blame climate change but acknowledged that warmer temperatures extend the phytoplankton's growing season. The bloom may not be over, warn Norwegian authorities, emphasizing the need for vigilance as the algae could spread further north. Under Norwegian regulations, the suffocated fish cannot be sent to markets and are likely to be incinerated or sent to landfill.

While it's difficult to stop algae blooms, the event serves as another warning of the myriad impacts of climate change, says Peter Jones. The incident highlights the vulnerabilities in the salmon farming industry, which is particularly susceptible to environmental changes. As the seas, especially in the Arctic, continue to warm, the industry may need to brace for more such events in the future.