The increase in temperatures and decreasing water levels in bodies of water are setting the stage for an increase in algal growth within our waterways. Littoral (nearshore) algal blooms are already visible, and Cyanobacteria (blue-green) algal blooms have recently closed down beaches in Lake Champlain.
Algae, the base of the aquatic food web is important to our aquatic ecosystems. They provide food for many organisms and create oxygen and shelter. Algae remove nutrients directly from the water column. If excessive nutrients enter our waterways, the nearshore algae will respond by blooming. The more nutrients that enter, the more algal growth there will be. Generally 1 pound of phosphorus will grow 500 pounds of wet algae. Phosphorus is not the only nutrient needed, nitrogen and carbon are needed to cause a bloom.
When excessive amounts of algae cause negative impacts to other organisms, water quality, recreation or the economy, they are deemed a Harmful Algal Bloom. If a toxic condition is formed it is then classified as a Toxic Harmful Algal Bloom. Not all toxic conditions are formed by cyanobacteria; other forms of algae produce toxins too. Some forms of algae will produce toxins in response to excessive nitrogen.
An algal bloom is not only caused from the addition of excessive nutrients, but are spurred on from climate change, acid rain, removal of riparian and shoreline cover, and the addition of sodium chloride to our water ways. Anything that happens within the watershed can impact the water quality of our bodies of water and potentially feed algal growth.
The nearshore algal growth that covers rocks, docks, and available substrate, cause taste and odor issues, and clog intake pipes, while unsightly and a nuisance, does service a purpose. Without the littoral algal growth taking up the excessive nutrients, there would be a readily available food source for the phytoplankton and cyanobacteria to cause lake-wide blooms, possible toxic algal blooms can cause a greater impact on overall water quality. The nearshore algae remove the excessive nutrients, before it can impact the lake as a whole. A tipping point can be reached, when there are more nutrients available than what the algae can feed on. This is when the lake clarity starts to decrease and deep water algal blooms form. When deep water algal blooms die off, they sink to the bottom of the lake and are fed on by bacteria. During this process the bacteria use up the oxygen, creating “dead zones” where aquatic organisms can’t survive.
The nearshore algal growth has another important quality; it can be utilized as a bioindicator. Forms of algae present within a given area can indicate heavy metal concentrations, impacts from sodium chloride, nutrients, and organic pollution. Periphyton (benthic algae), monitoring of the littoral zone of lakes is a useful tool for determining anthropogenic disturbances and changes in water quality, before they can be detected in offshore monitoring efforts.
If you see an algal bloom you should be cautious. If you suspect a potential Toxic Harmful Algal Bloom, you should report it to the NYS Department of Environmental Conservation and do not recreate, or drink the water. If you are seeing a littoral algal bloom, take note of what may be causing the additional nutrients upland and work with your local watershed group to find a solution.