Water Quality Monitoring Blue-Green Algae

blue-green algae cyanobacteria measurement in water

What is blue-green algae?

Blue-green algae, also known as cyanobacteria, are microscopic photosynthetic organisms that naturally occur in aquatic ecosystems. Dense growth of this bacteria can result in a range of colors, including blue, green, red, and black. Cyanobacteria can remove nitrogen and carbon from water, but overabundance can result in harmful algal blooms (HABs), especially in warm, nutrient-rich waters, particularly those with elevated levels of nitrogen and phosphorus from sources such as agricultural runoff and wastewater. This nutrient overload can lead to eutrophication, which can negatively impact human health and the environment.

blue green algae bloom warning water quality measurement and monitoring

Why measure blue-green algae?

Monitoring blue-green algae is important because they can pose a serious threat to water quality, aquatic ecosystems, drinking water safety, recreation, and public health through both toxin production and the large biomass generated from algal blooms.

algae water quality monitoring sampling measurement

Cyanobacteria can produce a range of algal toxins, or cyanotoxins, that can negatively affect the health of humans, pets, wildlife, and livestock when contacted or ingested. The most common cyanotoxins include microcystins, cylindrospermopsins, and anatoxins, which can affect the liver (hepatotoxin), damage the nervous system (neurotoxin), bioaccumulate in tissues, and even cause death.

In addition, rapidly growing blooms can cause hypoxia as large amounts of biomass decompose. This creates oxygen-poor environments indicated by a sharp decrease in dissolved oxygen. Hypoxia can lead to fish kills, harm sensitive species, and trigger cascading effects throughout aquatic communities.

These threats result in devastating impacts on the environment, public health, and the availability of safe drinking water. Removing cyanotoxins can be especially challenging for drinking water treatment systems, and large HAB events can overwhelm treatment capacity.

How is blue-green algae measured?

YSI measures algal pigments related to blue-green algae in real-time through the in vivo fluorometry technique with the Total Algae (TAL) sensor for the EXO Sonde and ProDSS. This method uses LEDs to directly detect the fluorescence of phycocyanin (PC) or phycoerythrin (PE) pigments in the water column at specific wavelengths. The raw fluorescence values can be correlated to the relative algal biomass using internal calculations and site-specific studies.

algae water quality sensor diagram in vivo fluorometry

The Total Algae sensor also measures chlorophyll with a separate LED channel. Since it measures at a specific wavelength, the phycocyanin/phycoerythrin channel does not receive interference from chlorophyll or turbidity.

Generally we recommend the EXO TAL-PC sensor for freshwater monitoring and the EXO TAL-PE sensor for saltwater environments. These sensors are a valuable tool for early detection because they are placed right in the water, eliminating the need for sample collection, extraction, or lab processing and delivering real-time readings.

algae water quality sensors fluorescence phycocyanin phycoerythrin