Be an Algae Watcher


General Information

Algae are a normal part of a healthy aquatic ecosystem but in excess they can put stress on other organisms in our lakes and rivers. Many local recreational water users have noted an increase in algae and aquatic plant growth, despite little observed change in nutrient concentrations which are often the cause of algal blooms and excessive aquatic plant growth.

Algae are naturally occurring aquatic organisms, similar to plants, which contain chlorophyll and produce their own food through photosynthesis.  Algae are present naturally in all lakes; however, they are often found at low enough concentrations that they are not noticeable to most people.  These organisms form a significant component of the base of the aquatic food chain.

There are many varieties of algae and a microscope or other laboratory techniques are often required to properly identify species.  Algae can generally be grouped into two easily identifiable forms:  filamentous, and planktonic. Filamentous algae is very fibrous and when removed from the water resembles long stringy masses.  It can look like green cotton, smell like a pigpen, feel slippery or silky, or leave masses of “algae paper” on shore where it has dried out (Huynh and Serediak, 2006).  Planktonic algae has no fibrous structure and flows freely with the water.  The algae can stick to an item dipped in the water.  It can look like pea-soup, be globular, have a grassy odour, be a deep green or a green-black colour, or look like bright green foam (Huynh and Serediak, 2006).  Algae can also be classified under a variety of other categories including green algae, diatoms, flagellates, and blue-green algae.

An algae bloom may occur when the right conditions combine to allow an existing population of algae to grow rapidly into a very large noticeable colony.  Keep in mind that due to the variety of algae species that may be present in a lake, algae blooms can appear in many colours including blue, red, brown or yellow, and in many forms and intensities.

Algae blooms are caused by a number of environmental factors aligning to create ideal growing conditions.  These factors include calm water, warm sunny conditions, shallow warm water and, usually, high nutrient levels (although in some cases this does not seem to be necessary).  Conditions ideal for a bloom usually occur in late summer and early fall; however, due to the effects of climate change this window may be shifting.

Blue-Green Algae

Blue-green algae (scientifically referred to as Cyanobacteria) is actually a type of bacteria that contains chlorophyll.  Blue-green algae may produce a variety of toxins called microsystins, two of which are neurotoxins, and this is why blooms need to be reported and assessed.

A blue-green algae bloom can typically be identified because the water looks bluish-green, like green pea soup, or turquoise paint (see photos).  When the blooms are very dense, they may form solid-looking clumps. Fresh blooms often smell like newly mowed grass; older blooms may smell like rotting garbage (Ontario Ministry of the Environment and Climate Change website, 2014).

When certain blue-green algae species die or are damaged, their cells break down and toxins can be released into the water. This is why boiling your water is not an effective treatment during a bloom.  Laboratory analysis of water samples is the only way to identify whether a particular algae is the type that produces toxins, if toxins are present in the water and whether their concentration is cause for health concern.  However it is difficult to sample all parts of an algae bloom so if a blue-green bloom occurs a precautionary approach to water use is best.

Reporting a Bloom

If you are concerned your lake or river is experiencing an algae bloom you should report it to the Ministry of Environment and Climate Change (MOECC) by calling their Spills Action Hotline 1-800-268-6060. The more people that report a bloom the better understanding of size and duration the MOECC will have.

The MOECC is responsible for sampling blooms to identify if it is a blue-green algae bloom and if it contains amounts of the toxin microsystins. They share their results with the local health unit who is responsible for determining if there should be a drinking water advisory or not.

Health Units within the MVCA

City of Ottawa:

Lanark County:

Frontenac County:

Tracking a Bloom

Whether you are an angler, boater, paddler, swimmer or any sort of water enthusiast, we are asking you to report what you are seeing on the water that you use. Information about when, where and how often algal blooms and excessive aquatic plant growth are occurring will help develop future research on the causes of green algal blooms and excessive aquatic plant growth in local lakes and rivers. This information will also help us gain a greater understanding about the algae and aquatic plant growth in the waters that we cherish. MVCA is partnering with to help us track bloom observations as well as other data in an open and easily accessible format.

The MOECC Hotline is the first priority for reporting our tracking system will be used for other purposes.

For more information about this project contact Kelly Stiles at 613.253.0006 ex 234 or

More Information


Algae bloom 2016 Photo: Ed Carew