So far, Lake Arrowhead has not had an algal bloom. Higher water temperatures plus additional development make the potential of having an algal bloom more likely, so it is important we try to head this off.
First, what is an algal bloom?
An algal bloom is due to the accumulation of algae, which harbors cyanobacteria in the water. The accumulation can be rapid and alarming. The water may look murky, green to blue-green colored water and it may have a foul odor. Scum may also appear.
 |
| Sabbatus Pond. Source: https://www.maine.gov/dep/water/lakes/reportbloom.html |
An algal bloom reduces the oxygen levels in the water, which can lead to the death of fish and other plants. Toxins also develop, making the water unsafe for humans and pets.
What causes algal blooms?
- Warm water. Lake Arrowhead is relatively shallow, and the water is warm. As our climate gets warmer, ice melts sooner and the lake freezes later. The temperature conditions are in place for Lake Arrowhead for algal blooms.
- Excess nutrients. The biggest culprit is fertilizers that are applied within the watershed, but especially on land close to the lake. Water runoff from roads, lawns and construction sites carry phosphates into the water.
Sometimes when a stratified lake turns over it can bring phosphate rich water up to the surface and into the sunlight, triggering an algal bloom.
What happens if we get an algal bloom?
The process of getting rid of a bloom is long and expensive. An application of chemicals (Alum) is applied to the lake to combat the algae. This requires funds from the community, special permitting and may need repeated applications over multiple years.
It is very much easier to prevent getting an algal bloom than fixing one.
- Do not apply fertilizers (or reduce fertilizer use) to your gardens.
- Direct rainwater from your yard, camp road and driveway, to vegetated areas.
- Keep you shorefront vegetated - bare soil allows water to run into the lake rapidly and unfiltered.
- Prevent soil erosion.
- Keep your septic system well maintained.
We are already seeing clumps of filamentous algae (cotton candy-like clouds) also called Metaphyton, and we want to prevent it going to the next step where the lake turns blue-green.
Links
Maine DEP page on Algal blooms
Lake Stewards of Maine page on Metaphyton
Lake Stewards of Maine page on Cynobacteria
Wikipedia page on Algal Blooms
Maine law on sale of fertilizer containing phosphorus
Recent dog deaths suspected to be due to toxic algal bloom