During a downpour in mid-September, Katie Sweeney, outfitted in rain pants, boots and a raincoat, knelt down on a dock at the Vancouver Lake Sailing Club and started collecting water samples.
Since May, Sweeney has made this a biweekly routine as part of her graduate studies at Washington State University Vancouver while she pursues a master’s degree in environmental science. Sweeney focuses on smaller organisms in Vancouver Lake, and their interactions with cyanobacteria blooms.
It just so happens that cyanobacteria blooms have been present at and closed Vancouver Lake this year, so the public also has an interest in the same things she does.
“We always have an interest in these sort of things scientifically, but it’s always really when cool when the public starts to take notice, and become interested in the science behind it,” Sweeney said. “It’s enlightening or endearing that somebody outside is interested in what you do.”
Sweeney’s major professor for her master’s work is associate professor Gretchen Rollwagen-Bollens, who along with her husband, professor Stephen Bollens, has been studying Vancouver Lake and its cyanobacteria blooms for about 13 years. They co-direct WSUV’s aquatic ecology lab together.
Their research focuses on how certain organisms in the lake influence when the blooms occur, and how nutrients and temperature impact the blooms.
Bollens said Vancouver Lake serves as a great model to study cyanobacteria blooms for a larger purpose. The Environmental Protection agency has called harmful algae blooms, which are more than just cyanobacteria, a “major environmental problem in all 50 states.”
“This issue of big summertime blooms of cyanobacteria in Vancouver Lake, unfortunately, is not unique to Vancouver Lake,” Bollens said. “It’s becoming a global problem at mid- to high-latitude regions in North America, Europe, Asia and South America. And we’re starting to see some hint of this in the Columbia River even. We’re using Vancouver Lake as a model to help inform the global concern about these blooms.”
How blooms are born
Rollwagen-Bollens said there is a very strong association between the availability of phosphorus that’s dissolved in the lake water and when cyanobacteria levels gets high. Some of that phosphorus availability come naturally and comes from runoff from land and from local streams.
In Vancouver Lake, phosphorus attaches to particles when it enters the water and is pulled to the bottom and held to sediment. Blooms generally occur with increased phosphorus levels, but both professors explained that high phosphorus levels don’t guarantee blooms, and there are other factors at play. While cyanobacteria prefer to absorb nitrogen through water, many cyanobacteria have a special capacity to take nitrogen out of the atmosphere if needed, which puts the blooms at an advantage.
That can help cyanobacteria blooms photosynthesize and grow. In the summer, conditions for blooms to grow are great, because there’s plenty of sun, warm temperatures and periods when it gets windless. Algae can float at the surface, where light is greatest. Then when a windy day arrives it sirs up phosphorus from the bottom, and makes it more available. Once the phosphorus is added, blooms can grow quickly.
A recipe for success
Those are things that effect the birth rates and growth for cyanobacteria blooms, but predators and lacking nutrients are what effect the death rates for the blooms.
Two organisms that eat cyanobacteria are ciliates, a microscopic protozoa, and copepods, tiny crustaceans. But copepods generally only eat cyanobacteria blooms when they are low in abundance, and they don’t like to eat blooms when they are toxic. So many times before a bloom occurs, copepods eat ciliates or diatoms, another group of algae. Essentially the copepods are taking out a predator and a competitor for the cyanobacteria blooms.
The combination of available phosphorus and a lack of grazers gives the cyanobacteria blooms an opening for growth.
“High birth rates and low death rates, any population would explode,” Bollens said.
It’s difficult to predict when a bloom will arrive because it’s about predicting more than just weather and phosphorus levels, Rollwagen-Bollens explained. This summer was atypical, in particular, because of the heat experienced toward the beginning of the summer and the cool, rainy weather that came toward the end of summer.
Clark County Public Health gave Vancouver Lake its first algae caution advisory June 12, and upgraded to a warning June 27. Cautions and warning for algae stayed in place for summer, and the Row for Life dragon boat races were moved to land to avoid the water. The lake was closed for elevated levels of cyanotoxins July 24 through Aug. 8.
Times and places change
Rollwagen-Bollens said she isn’t blaming the Port of Vancouver or Vancouver Lake’s flushing channel for the blooms, but she said urban growth does affect nature. With Vancouver Lake in particular, the flushing channel isn’t a perfect replacement for flushing the lake. At one point in time, before the land reclamation and diking, the Columbia River would overwash the banks and flood into Vancouver Lake and swash everything around.
The flushing channel doesn’t have the same amount of energy, and water doesn’t get moved through the lake in the same way it might have 100 years ago, Rollwagen-Bollens said. It is part of growth, and keeping areas from flooding.
But that means there’s less renewal in the water and nutrients stick around longer now.
“Then you get the opportunity for things to build up,” she said, which drives the growth of algae.
A potential solution
The Vancouver Lake Watershed Partnership, which started in 2004 and lasted 10 years, was once dedicated to exploring the algae bloom issue. Rollwagen-Bollens and Bollens advised the group from the periphery, and it had about 21 members from various levels of government as well as citizen stakeholders. Phil Trask was project manager for the Partnership for five years before his tenure ended at the end of 2013.
Trask, who now works on environmental solutions in Portland, said the partnership “was pretty cutting edge,” and dug up old research and made sense of new research, learning about the depth of the lake, its nutrients and more.
Still, Trask said the cyanobacteria bloom problem was intractable because Vancouver Lake is a shallow, urban lake that is particularly susceptible to blooms.
“The solutions, we had some big and small, but there was no silver bullet,” Trask said. “It’s not a problem that’s easily solved.”
Bollens said these problems could continue to escalate with climate change, and in other areas across the world. Bollens can’t predict whether the frequency or length of toxic blooms will increase and cause more or longer lake closures, but he did say it’s fair to surmise that blooms will begin earlier in the year now. He thinks dedicating resources to the problem is worthwhile.
“Having a single forum for the various government agencies get together and talk about the lake and try to come up with common solutions to problems, that’s all pretty much gone now, and I think there’s a whole there,” Bollens said. “If that group could somehow be reconstituted, it would be a great thing to see that reinvigorated.”
Source: https://www.columbian.com
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