Why toxic algae threats don’t just go away

The bloom of toxic blue-green algae that closed Summit Lake to people and pets is still under the close watch of Thurston County public health officers.

Tests revealing toxins were the first confirmed toxic-algae find this year in South Sound lakes. Follow-up tests last week showed high toxin levels. This means the lake remained closed over this Memorial Day weekend, which for many residents is the start of summers on the water.

The big picture on toxic algae is not encouraging. Thurston County health data shows 10 local lakes have had toxic blooms since 2010. Many lakes like Summit, west of Olympia, have had it more than once.

This situation can be serious for pets and people, especially small children. Exposure to the Anatoxin-a, which triggered the closure of Summit Lake, include lethargy, muscle aches, confusion and memory impairment.

But what turns algae blooms toxic is unclear, according to Jane Mountjoy-Venning of Thurston County Environmental Health. Scientists around the world are studying that question and answers are not clear-cut, she says.

The Summit Lake problem underscores the importance of environmental-health monitoring programs. This includes the collection and retention of public data in a way that lets authorities track trends.

Thurston County just resumed its seasonal lake monitoring. Those regular monthly tests from May through October look at water quality, including temperature, the presence of nutrients such as phosphorus, and water acidity or alkalinity, says Mountjoy-Venning.

Tight county budgets have always meant that a few lakes are not regularly tested. Tests for toxic algae are done only in response to complaints or reports of blooms.

The duration of algae blooms varies. Advisories for toxic blooms in Black Lake have lasted as long as eight weeks.

Algae naturally grows in lakes, and most blooms occur during summer and fall. These are fed by too much phosphorus and nitrogen in the water, according to the state Department of Ecology. But blooms can happen year round and not all are toxic.

Some phosphorus can be released from lake beds, but Mountjoy-Venning says other sources include failing septic systems, manure from dogs or other animals, and certain vegetable or garden fertilizers.

The lesson for lake lovers is to keep an eye out this summer and take care around any algae blooms.

The lesson for those who helped overturn the county’s $10 annual septic system fee is that problems don’t simply vanish because we quit paying attention.

Summit Lake residents have little choice now but to wait — and examine their own actions to see if they might unwittingly be feeding algae growth in the lake.

This story was originally published May 27, 2017 at 8:48 PM with the headline "Why toxic algae threats don’t just go away."