The open again, closed again life of Vancouver Lake will most likely continue this summer and deeper into the future.
So far, the lake has been closed twice, once for elevated levels of E. coli bacteria, and once for elevated levels of cyanotoxins, which are caused by blooms of cyanobacteria, also known as blue-green algae. The latest cyanotoxin closure began on July 24, after Clark County Public Health received laboratory analysis that discovered toxin levels above the state Department of Health’s threshold levels.
That closure remains in place, and was preceded by another closure on July 16 for elevated levels of E. coli bacteria, which can live in human and animal intestines. While advisory levels have fluctuated, Vancouver Lake has been under some kind of Public Health advisory since June 12.
Public Health conducted testing at Vancouver Lake on Monday. Test results could return as soon as today. Public Health conducts its testing around 1 p.m. because that’s generally when the water is the scummiest, and it’s also a peak time for people to recreate in the lake, said Alyssa Payne, an environmental health specialist with Clark County Public Health. The Washington State Department of Ecology pays for the testing, and samples are collected and shipped overnight to King County Environmental Lab.
Payne explained that Vancouver Lake has struggled with cyanotoxins in part because of how shallow it is. The lake water also carries many nutrients that help cyanobacteria develop, along with lots of sunlight and warm weather.
Clark County has had weather above 80 degrees for the past week, with three days registering at 89 degrees or higher. Clark County Public Health Officer Dr. Alan Melnick said it’s likely that Clark County will start seeing more algae blooms earlier and later in the year as the Pacific Northwest continues to register hotter, sunnier weather.
Public Health issued its first blue-green algae advisory this year on June 12, before the summer solstice. But weather that week included consecutive 90-degree days and one day that peaked at 96 degrees.
“Whenever you have a body of water that is fairly shallow, with lot of nutrients in it and sunlight, it is a recipes for algae,” Melnick said.
Melnick said the Eurasian milfoil at Vancouver Lake did not factor into the problems with blue-green algae, which has caused some confusion for residents.
“That’s another situation altogether,” he said.
Payne said the U.S. Geological Survey and U.S. Department of Interior have studied Vancouver Lake before and examined its nutrient budgets.
“There’s a lot of nutrients going into the lake and there’s not really a lot of outlets. There’s not a lot of freshwater sources,” Payne said. “That’s why rainfall has kind of made the bloom a little bit better; but throughout the summer months, it resorts back to this state.”
E. coli closed the lake on July 16 and 17, and there were elevated levels of E. coli present on July 30. Payne said that more geese seem to have been present at the lake this year than in years past, although that’s an anecdotal observation. If you walk around Vancouver Lake Regional Park, you’ll see the grass area near the water is littered with goose droppings.
“At the swim beach, there’s a lot of bird wildlife and a lot of geese poop in the grass,” Payne said. “What we’ve seen in previous weeks is there are a lot of geese hanging out at the lake that haven’t been there in previous years. That’s what our anecdotal observation has been. We have a larger presence of geese. E. coli could be pollution or bather load, but those don’t seem like likely causes because if they were they wouldn’t have been problems in the past.”
Melnick expressed he can never guarantee safety in natural bodies of water, but did say that if Vancouver Lake isn’t under an advisory or closure, swimming in it shouldn’t present a great risk. In other words, it’s a fairly safe watering hole when it doesn’t have elevated toxin levels or E. coli bacteria present.
Melnick said he wants people to be able to enjoy swimming in Vancouver Lake, but stressed that people should pay attention to advisories, warnings and closures issued by Public Health.
“People need to pay attention to the signs and the press releases,” he said.
Source: https://www.columbian.com
Be First to Comment