The answer could be a lot of things but for this purpose it is cyanobacteria. Along with the transition from cool spring to hot summer, we are starting to see the return of unwelcome but increasingly familiar cyanobacteria blooms. Along with providing yet another reminder that excess nutrients from poor wastewater treatment and fertilizers are degrading water quality, the prevalence of cyanobacteria blooms prompts a lot of confusion.
At high levels, certain cyanobacteria can produce neurotoxins that can sicken people and pets. Different species of cyanobacteria have different potential toxin profiles, and the dose exposure and size of the exposed body also matter.
One of the more confounding challenges of cyanobacteria is how they behave in the water column. Cyanobacteria can become buoyant, especially in the early morning and, when pushed by light morning breezes, can form a surface scum layer that is hard to ignore.
However, even when not buoyant and concentrated at the surface, the same amount of cyanobacteria can be there, more diffusely distributed through the water column. It is still present, but is harder to recognize. Wind can play a factor as well, pushing and concentrating cyanobacteria. But as we all know, the wind can change in an instant and concentrations of cyanobacteria can be redistributed around a pond over the course of a single day.
The pond I am fortunate enough to live near is in the midst of its now annual bloom cycle and my experience this past weekend was illustrative. On Friday, while the water in front of my house was clear, a friend at the downwind side of the pond sent me images of a thick cyanobacteria scum in front of her house. On Sunday this same person reported that the scum was gone. I checked my waterfront at 7:00 a.m. and saw no scum, but when I went back at 8:00 a.m., a significant scum had formed where a gentle breeze had pushed it. By 11:00 a.m. that same morning, the higher winds had cleared it out and things looked decent again.
The point here is that conditions change throughout the day and the unique characteristics of cyanobacteria behavior make it challenging to assess risk and to properly advise the public on best practices. One quick glance at a pond in one spot can give even an informed observer a deceiving sense of either comfort or fear. The take home is that once cyanobacteria start to show in quantity in a pond, the risk of exposure is heightened. Protecting ourselves requires each of us to become informed and thoughtful observers of conditions in a pond. Exercise caution in deciding if exposure to a pond during a bloom is right for you, your kids and your pets.
APCC’s cyanobacteria monitoring program and cyanobacteria webpage provide much of the information you will need to make an informed decision about your summer pond experience. APCC’s approach to monitoring and publicizing our results is to raise awareness without being alarmist and to provide people with the information needed to make good decisions in the face of uncertainty.
Over the long term, it is my fervent hope that through improvements in wastewater treatment, better stewardship of the land, the elimination of stormwater discharges to ponds, and the end of lawn fertilization we can improve pond quality and stop worrying about cyanobacteria blooms. Getting there will take a lot of work, but it’s also good to remind ourselves that the status quo is unacceptable and that we can change it.
