Algae Bloom In Ross Island Lagoon

Algae Bloom Information

The Oregon Health Authority issued a recreational use health advisory today for the Ross Island Lagoon, located about a mile south of downtown Portland in Multnomah County.

The advisory is being issued due to visual confirmation of a cyanobacteria bloom (harmful algae) in the lagoon. Water samples have been taken to confirm the type of cyanobacteria and level of potential toxins that may be produced, but results from analysis of the sample won’t be available until next week. At that time, depending on the level of toxins found in the sample, OHA Public Health Division officials will determine if the advisory can be lifted or kept in place until the bloom is gone.

Because sample analysis is needed to determine if a bloom is producing toxins, OHA is issuing an advisory based on visual observations to protect the public health until data is available. If toxins are being produced by the bloom, they can be harmful to humans and animals.

Drinking water directly from the river where a bloom is identified is especially dangerous since any toxins produced cannot be removed by boiling, filtering or treating the water with camping-style filters. People who may draw water directly out of this area for drinking or cooking are advised to use an alternate water source. No public drinking or potable water systems are affected.

Although the advisory is confined to the Ross Island Lagoon and its mouth, the lagoon is influenced by the dynamics of the river, which can cause bloom creep as the water in the lagoon rises and recedes. People should always be aware that blooms can develop on any water body under the right environmental conditions. The Willamette River is a big river and blooms can develop in areas along its course where low flow and slow-moving water can be found, officials say.

People should avoid swimming and high-speed water activities, such as water skiing or power boating, in areas where blooms are identified. Although toxins are not absorbed through the skin, people who have skin sensitivities may experience a puffy red rash at the affected area.

OHA public health officials recommend that those who choose to eat fish from waters where cyanobacteria blooms are present remove all fat, skin and organs before cooking, as toxins are more likely to collect in these tissues. Fillets should also be rinsed with clean water. Public health officials also advise people to not eat freshwater clams or mussels from the lagoon and that Oregon Department of Fish and Wildlife regulations do not allow the harvest of these shellfish from freshwater sources. Crayfish muscle can be eaten, but internal organs and liquid fat should be discarded.

Exposure to toxins can produce a variety of symptoms including numbness, tingling and dizziness that can lead to difficulty breathing or heart problems, and require immediate medical attention. Symptoms of skin irritation, weakness, diarrhea, nausea, cramps and fainting should also receive medical attention if they persist or worsen. Children and pets are at increased risk for exposure because of their size and level of activity. People who bring their pets to the Ross Island Lagoon for recreation activities should take special precautions to keep them from drinking from or swimming in the water body.

It’s possible cyanotoxins can still exist in clear water. Sometimes, cyanobacteria can move into another area, making water that once looked foamy, scummy or discolored now look clear. However, when a bloom dies elsewhere in the water body, it can release toxins that may reach into the clear water. There also are species of cyanobacteria that anchor themselves at the bottom of a water body, live in the sediment, or can grow on aquatic plants and release toxins into clear water near the surface. To lift an advisory, OHA relies on laboratory tests of water samples to determine when levels of cyanotoxins are no longer a public health issue.

With proper precautions to avoid exposure to affected water in the lagoon, people are encouraged to enjoy activities such as swimming, fishing, camping, hiking, biking, picnicking, and bird watching in other areas of the Willamette River.


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