The Government of the Northwest Territories Department of Environment and Climate Change (ECC) conducts and supports water monitoring initiatives throughout the Northwest Territories. One such initiative includes water monitoring on the Tsiigehnjik (Arctic Red River), designated as one of Canada’s Heritage Rivers in 1993. This designation highlights the river's significance, particularly in the context of the Gwich’in Land Use Plan, highlighting its value to the Gwichya Gwich’in.
In recent years, rusty-brown flocs, which are loosely clumped masses of particles, have been observed in the Tsiigehnjik, Teetł'it Gwinjik (Peel River), and Deh Cho (Mackenzie River)—a phenomenon not previously recorded. These flocs typically appear along the shoreline from mid-July to late August (Photo 1). In 2020, the flocs were also observed in the mainstem of the Peel River (Photo 2). Since then, community-based monitors in Tsiigehtchic, Fort McPherson, and Aklavik have been prepared to collect samples should they appear. In sampling conducted so far, the substance has been identified as iron-oxidizing bacteria (iron bacteria).
Iron bacteria are long, thread-like bacteria that “feed” on iron. Unlike most bacteria, which feed on organic matter, iron bacteria feed by oxidizing ferrous iron into ferric iron. This process converts dissolved ferrous iron into insoluble ferric iron, resulting in the rusty-brown sheen on the water’s surface. As iron bacteria die and decompose, they release a rusty-brown deposit onto the surface water. These flocs are often mistaken for petroleum sheens, but unlike petroleum, which remains intact, iron bacteria sheens break apart when disturbed, resembling shattered glass.
Iron bacteria can generally thrive wherever oxygen and iron-rich rocks or soils are present near surface water. Their growth varies from year to year, depending on weather conditions and temperature. The increased presence of these flocs in recent years may be linked to regional permafrost disturbances (thaw slumps). These slumps, which have eroded large volumes of previously frozen soil, release more metals, including iron, into the aquatic environment.
Iron bacteria pose no risk to human, pet or ecosystem health. They are found naturally in soils and water in low numbers and will thrive as more iron becomes available. However, the orange slime in the water or leaching from the shore is often considered to be an aesthetic problem and can make water taste bad. In the Northwest Territories, water treatment plants are capable of removing iron bacteria before it reaches resident’s taps.
ECC will continue working with community monitors during the summer of 2025 to confirm these findings. In addition, we are partnering with researchers from the University of Alberta to analyze weather patterns, flow trends, and water quality to help understand the year-to-year variations in floc occurrences.
Photo 1: Peel Channel at Aklavik (Billie Archie, Aklavik; August 2017)
Photo 2: Peel River at 8 Mile (Andrea Czarnecki, GNWT; July 2020)