Blooms are not always flowers. Algal blooms refer to events in freshwater or oceans when microscopic algae reproduce so rapidly that they become visible using just our eyes. The news has been rife with reports about Lake Erie, Lake Champlain and in Maine such places as Lake Auburn, China Lake, and the Belgrade lakes where agencies are keeping a close watch on toxic algal blooms. Freshwater, blooms are mostly caused by cyanobacteria, previously called blue-green algae. Those blooms often form surface scum layers which make the water look very green and often result in odor or taste problems. They can also be toxic, having caused death to pets and livestock, and are implicated in human health threats.
The Norway lakes have been spared severe algal blooms – so far. However, if you have been on water the in the past few years, you may have noticed some unusual sights: those billowing green or yellowish clouds just below the surface or attached to aquatic plants are becoming more common. Called “metaphyton”, they are large accumulations of long filaments (strings) of several different algal species, including cyanobacteria. The clouds often start as mats of algae on shallow bottoms, which rise upward due to gas bubbles.
Another recent observation in our lakes is that of little fuzzy whitish-green balls about the size of a rice grain. These little clusters of algae, Gloeotrichia, or Gleo for short, are visible to the naked eye. Each ball is actually a colony of cyanobacteria, which is common in many lakes in Maine. This species uses “resting” cells which settle on the bottom to survive the winter. The bottom sediments are also where nutrients like phosphorus are regenerated from decomposing plants, algae and animals. In the spring these cells are pumped up with nutrients, ready to create many daughter colonies.
The possible human impacts of the various types of algae that can grow in our lakes runs from skin irritation to severe health issues.
What causes algae growth? Well, a study published in the April 2015 issue of Ecology Letters states that cyanobacteria have 1) increased significantly since 1800, 2) have increased more than other kinds of algae, and 3) have increased more rapidly since 1945. These increases were best explained by nutrient increases (phosphorus and nitrogen), getting into the water from the surrounding watershed via snowmelt, storm water runoff, and land development that reduced natural filtration.
These alarming observations are warnings that we need to address runoff that hurts our lakes and ponds in order to stop potential toxic algal blooms. These are problems that can occur relatively quickly, perhaps from a sudden release of nutrients into a lake, or over time from gradual runoff. Unfortunately, they always take many years to fix. All of us can play a role in maintaining the health of our lakes by paying attention to what we allow to pass into our lakes, from limiting use of products containing phosphates, such as fertilizers, to the way that water runs off our properties. The Lakes Association of Norway is developing a plan to conduct watershed surveys to protect the lakes by looking at how nutrient flow could be reduced. Future columns will highlight this crucial project. We have the ability to reduce these nutrient influxes to our lakes. If we don’t, the lakes may die in the not too-distant future.
By Stephan Zeeman, Ph.D.