Greenwood/Elk
California State Parks issued a Public Notice Danger Advisement regarding a harmful algae bloom in the Navarro River last month. Water samples collected from the river indicate high danger levels of Cyanotoxins (such as microcystin and nodularin) in the lagoon at the mouth of the river.
The public is advised to stay out of the Navarro River because ingestion or skin contact with contaminated water can cause serious illness to people (especially children) and death to pets. Algal blooms can sometimes create cyanotoxins that can cause abdominal pain, diarrhea, liver and kidney damage, vomiting, respiratory illness, irritation, headache and even paralysis and seizures. Fish and wildlife can also be impacted by algae blooms, resulting in fish kills, and sick and dead wildlife.
At least one person has filed an illness report with the State Water Resources Control Board, for illness resulting from swimming in the Navarro in mid-July. This young person was a guest of a family in Elk and they swam in the lagoon for about 45 minutes, remarking that the water was really warm. Within 24 hours, they reported extreme fatigue, fever, headache and eye pain. They had a COVID-19 test and the results were negative. Symptoms persisted for about a week.
harmful algae blooms have been reported in lakes for decades — however, animal deaths due to such blooms in rivers were first reported only in the last 20 years. The blooms are caused by low flows, high water temperatures, stagnant water and nutrient inputs associated with agriculture (such as nitrogen and phosphorus). All of these conditions are present in the Navarro River this summer.
On another note, algal blooms aren’t in and of themselves, negative in a river environment. Algae provide an important food source for benthic macroinvertebrates, which, in turn, are an important food source for juvenile salmon. Problems arise when algae don’t have enough grazing pressure on it, and it becomes too prolific.
Research in the Eel River has indicated that severe low summer baseflows promote conditions that cause blooms of toxic cyanobacteria to
proliferate. These problems can be exacerbated when a low flow summer follows a winter that had a big storm event because the storm event flushes out grazing stream insects which would normally keep algae suppressed. In these conditions, large algal blooms grow during the spring and early summer, and as the water warms and stagnates, the algal mats rot and can produce harmful cyanotoxins.
It is not clear if this type of winter scour-summer low flow peak algal growth scenario is occurring in the Navarro this summer, as last winter’s storms weren’t that big comparatively, but this summer’s flows are some of the lowest on record.
The Navarro Partnership between Trout Unlimited, The Mendocino
County Resource Conservation District, and The Nature Conservancy work collaboratively with landowners, businesses, and farms to improve instream flows for salmon and steelhead while increasing water supply reliability conducts research to support voluntary improvements in water management, and supports the development of flow enhancement projects. Salmon habitat restoration work within the Navarro River watershed is ongoing.
Because salmon require cool, clean water to thrive, salmon habitat restoration work typically benefits overall water quality. Often times, the goals of salmon habitat restoration work include increasing pool habitat and providing shade and cover for summer rearing of juvenile fish.
These partnerships and projects will be ever more important as we continue to see the impacts of global climate change in our own backyards.