Massachusetts waterbodies have a range of water quality conditions, which is what makes them unique. Cyanobacteria are naturally occurring and can sometimes cause harmful algal blooms (HABs). To learn more about water quality and cyanobacteria, explore the resources provided on these pages.
What is water quality?
Water quality in a lake or pond refers to its biological, chemical and physical characteristics. These characteristics determine the waterbody’s suitability for uses such as, but not limited to, supporting aquatic and other wildlife, recreational purposes, and/or drinking water. Water quality can be assessed in various ways to understand which parameters may be within an appropriate range to support its uses or not. Common parameters that are often measured and documented are temperature, dissolved oxygen, pH, turbidity, and phosphorus. Additionally, presence of aquatic plants and/or algae can also be informative in understanding the waterbody better. For more information on water quality, please visit our water quality webpage.
What is/are cyanobacteria?
Cyanobacteria, sometimes referred to as blue-green algae or harmful algal blooms (HABs), are actually bacteria that are able to photosynthesize similar to plants and algae. Cyanobacteria are estimated to be 2-3 billion years old based on some fossil records. They are found in all waterbodies and are considered a natural part of the ecosystem. However, an abundance of cyanobacteria growth, or a cyanobacteria bloom, causes their presence to be visible on a waterbody’s surface (a scum look) or throughout the water column (murky water), both of which are typically a shade of green, though they can vary. It is important to know that some cyanobacteria are capable of producing toxins, referred to as cyanotoxins, that can be harmful or dangerous to humans and animals. For more information on cyanobacteria, please visit our cyanobacteria webpage.
Primary Measuring Tool – the Secchi Disk
Tools that measure cyanobacteria and/or water quality parameters vary in what each tool is capable of, what data is gained from measuring, and how that data can be used to understand what it is telling you. However, one of the most basic lake management tools that can be utilized in understanding both cyanobacteria and some water quality parameters is the Secchi disk.
A Secchi (pronounced SECK-ee) disk is an 8-inch disk with alternating white and black quarters. The disk is attached to a rope (though we recommend using a surveyor’s tape measure on a reel for convenience) which is then lowered into the water of a lake or pond until it can no longer be seen by the observer. The depth at which the disk disappears, often referred to as the Secchi depth, is the measure of the transparency of the water.
Transparency is often and easily affected by the presence of algae and/or cyanobacteria, natural color of the water, and suspended sediments. As all of these factors increase, the transparency of the water will decrease. Transparency is an easy to measure indicator that can be measures through most of the year and can continue from year to year, which allows for trends to be identified over time. Depending on the direction of the trend, these measurements can sometimes serve as an early warning system for both acute and chronic issues within a waterbody.
Additional information about measuring other water quality parameters and cyanobacteria presence is provided on their respective pages.