Tracking and Addressing Harmful Algae Blooms

Princeton Hydro’s PARE™ Program:
A Tool for Tracking and Addressing Harmful Algae Blooms (HABs)

Understanding HABs

Over the past decade we have learned more about the serious health implications associated with intense cyanobacteria (bluegreen algae) blooms. Although cyanobacteria are not truly algae, these blooms have come to be labeled Harmful Algae Blooms (HABs). Cyanobacteria have a number of evolved advantages relative to “good phytoplankton.” For example, many cyanobacteria are capable of fixing and assimilating atmospheric nitrogen, thus providing them with an unlimited source of a key growth-limiting nutrient. Most are also biologically adept at up-taking and utilizing organic phosphorus, another growth-limiting nutrient. Certain cyanobacteria can also regulate their position in the water column, thereby enabling them to capitalize on changing environmental conditions. HABsMany also are adept at effectively photosynthesizing under low light conditions. Finally, they are selectively rejected as a food source by filter feeders and zooplankton. These “life history” strategies enable cyanobacteria to rapidly out-compete phytoplankton and exploit their environment leading to a bloom.

It has been repeatedly documented that, under the correct set of conditions, HABs may generate very high concentrations of cyanotoxins. These toxins are used by cyanobacteria to achieve dominance in a lake, pond or river. Swimming in waters with even low concentrations of cyanotoxin may cause skin rashes (even for dogs and livestock), ear/throat infections and gastrointestinal distress. At high concentrations, cyanotoxins can impact the health of humans, pets and livestock. Drinking water contaminated by very high cyanotoxin concentrations can actually be lethal. Recently, increased attention is being given to possible links between cyanotoxins and neurodegenerative diseases, including Parkinson’s, ALS and Alzheimer’s.

The cyanobacteria of greatest concern include Microcystis, Planktothrix, Anabaena, Aphanizomenon, Oscillatoria, Lyngbya and Gloeotrichia. Different types of cyanotoxins are produced by these various cyanobacteria. The cyanotoxins receiving the most attention are Microcystin-LR and Cylindrospermopsin, but Anatoxin–a, Saxitoxins and Anatoxin-a(S) are also very problematic.

Regulatory agencies are still struggling to define what constitutes a “problem” and how to deal with HABs. For a number of years the World Health Organization (WHO) has used a provisional drinking water standard of 1 µg/L microcystin in drinking water. The US Environmental Protection Agency (USEPA) recently issued cyanotoxin guidance for drinking water that provides different action levels for children versus adults and for microcystin and cylindrospermopsin¹. Adding to the confusion, the majority of the States are still developing guidance and/or regulations concerning cyanotoxins in both drinking water and recreational waterbodies. As such, it is difficult to define when a bloom constitutes a problem and, more importantly, what action to implement to protect the health and welfare of the public, pets and livestock.

Cyanotoxins may be released into the environment by both living and dead cyanobacteria. However, the greatest concentrations occur as the cyanobacteria die and the cells break down –  something that is exacerbated by treating it with copper sulfate, which is the standard response to treating a bloom. Thus, “killing off” a bloom can actually make matters worse by quickly releasing large amounts of cyanotoxins into the water column. Once released into the environment, cyanotoxins are extremely stable and decompose slowly.

Common Misconceptions About HABs

There are a variety of common misconceptions about HABs, including: they occur only in the summer when water temperatures are elevated; they are unique to nutrient rich (hypereutrophic) systems; they are driven solely by elevated phosphorus concentrations; and they are most likely to occur under stable (stratified) water column conditions. The most potentially harmful misconception is that HABs can be cured by treating them with copper sulfate; because, as noted above, copper sulfate treatments can actually make things worse.

The above “typical conditions” don’t always lead to a HAB, and blooms with elevated cyanotoxin levels may occur even in nutrient-limited waters or under environmental circumstances that deviate from the “norm.” To further complicate matters, not all cyanobacteria are associated with HABs, cyanotoxin producers may not always produce cyanotoxins, and the taste and odor compounds often associated with HABs may be generated by non-HAB algae species. As such, the only definitive way to understand if a waterbody suffers from, or is in danger of suffering from, a HAB is to collect the proper data. This includes:

  • Quantification and speciation of the phytoplankton community
  • Collection and analysis of Chlorophyll a
  • In-Situ measurement of
    • Dissolved oxygen
    • Temperature
    • pH
    • Secchi disk depth
  • Collection and analysis of
    • Phosphorus (TP, SRP, DOP and DIP)
    • Nitrogen (Nitrate and Ammonia)
  • Measurement of taste and odor compounds
    • Geosmin
    • 2-methylisoborneol (aka MIB)
  • Analysis of the amount of Microcystin present in the water column.

To date, cyanotoxin testing has been expensive and the data turn-around slow.

A Strategy for Tracking and Managing HABs

To help understand and monitor HABs, Princeton Hydro recently launched a multi-prong strategy called PARE™ (Predict, Analyze, React, and Educate). Princeton Hydro’s PARE™ program focuses on the importance of thoroughly understanding site conditions, properly tailoring action programs and sustaining management efforts that go far beyond simply treating a bloom. As noted above, the PARE™ program consists of four key, interrelated elements:

  • Predict – Forecast a bloom using a long-term database of keystone parameters, and/or remote sensing techniques
  • Analyze – Quantify a bloom’s severity by measuring key diagnostic parameters including Microcystin
  • React – Implement measures to prevent, control or terminate a HAB
  • Educate – Share information with and educate the community about HABs


Ideally, to successfully predict HABs, it is paramount to measure the amounts of phosphorus, nitrogen, and chlorophyll in the water column, track dissolved oxygen and water temperature profiles, and identify the types and densities of cyanoWater Quality Databacteria and phytoplankton. Overall, in order to effectively predict the onset, magnitude and duration of a HAB, it is necessary to have a good data foundation.


With an adequate database, it becomes possible to develop algorithms that account for all of the chemical, hydrologic and physical variables that may lead to HABs, including seasonal differences in weather and precipitation. In some cases it may also be possible to utilize remote sensing technology to track bloom development.

With a suitable database, it becomes possible to develop HAB thresholds based on:

  • Phytoplankton densities (cell counts)
  • Bloom indicators
    • Declining Secchi disc clarity : < 1 meter)
    • Chlorophyll a concentration: >20 µg/L)
    • MIB concentration : >10 ng/L
    • Geosmin concentration: > 10 ng/L

As part of PARE™ we also now have the ability to quickly and effectively measure the concentration of Microcystin in the water column using a combination of rapid response field test kits and accurate, quick-turnaround laboratory analyses.  The Microcystin data can then be compared to established USEPA or, when available, state guidance concentrations for cyanotoxins in drinking water and recreational water.


The data that are generated from the Predict and Analyze elements of the PARE™ program enables us to know when aChart bloom is about to occur or has developed, and quantify the severity of the bloom.  The many variables that may lead to HABs interact in a complex manner in lake and pond ecosystems. Manipulating the ecosystem to prevent or treat HABs requires extensive expertise.  

Some of the interactions that must be taken into consideration include:   

Biological linkages and interactions

  • Nitrogen fixers versus non-nitrogen fixers
  • Early blooming species potentially setting the stage for more problematic later blooming species
  • Zooplanktivory and the role of the fishery in stimulating a bloom or creating the environmental conditions supportive of a bloom
  • Nitrogen/Phosphorus ratios as well as the type, availability and sources of these primary nutrients

Through the correct understanding of these interactions it becomes possible to properly React by designing and implementing various pre-emptive controls and corrective measures such as:

  • Aeration and mixing,
  • Use of nutrient inactivators (alum, PhosLock® and alum surrogates),
  • Ozone,
  • Biomanipulation of the fish and plankton communities, and
  • Limited, properly timed algaecide applications.  

On a larger, long-term scale, the React element of the PARE™ program encompasses watershed management programs targeting nutrient load reductions that can actually reduce bloom frequency/intensity.  

Although the React element recognizes the role of algaecides as a potential part of the solution, it does not condone repeated extensive treatments with copper sulfate.  As noted above, relying solely on substantial copper sulfate treatments most often only triggers worse conditions and leads to spiraling, repetitive blooms.

Education and Outreach

Besides informing the public about health concerns related to cyanobacteria and HABs, it is important that stakeholders are also informed about measures that they can implement to help prevent blooms.  This includes “on-lot” nutrient controls such as septic management, limited application of lawn fertilizers, creation of shoreline buffers and waterfowl control. It is also necessary for stakeholders to understand the lifecycle of HABs, that ongoing monitoring and management help address HABs before they peak, and that, while seeming to be the “magic bullet,” copper sulfate is not the proper management tool.

Implementing PARE™

Begin PARE™ early, with the sampling of the above-noted key water quality Sampling Kitparameters and bloom initiated in early spring.  Then sample on a regular basis over the entire course of the growing season, especially in the summer when cyanobacteria problems emerge and peak. This information will become the foundation of the comprehensive database used to make timely management decisions.  The key is to be in a position to predict the onset of a bloom so that management actions can be implemented in a proactive, as opposed to reactive, manner.  Microcystin sampling can be focused on beach areas or around water intakes.  Begin with the simple, test-strip rapid response, in-field testing and, when necessary, use the laboratory analyses to confirm or further quantify whether a bloom has triggered a cyanotoxin problem.  If there is early evidence of a cyanobacteria bloom, implement the proper measures needed to control the bloom.  While bloom control measures are being implemented, continue to collect and analyze the microcystin data to confirm that the implemented measures have improved water quality and that conditions are safe for the ingestion of the water or the recreational use of the lake. After achieving specific water quality and HAB control goals, continue to implement the measures needed to track conditions and prevent/react to future blooms.  This will further facilitate the ability to respond to and control cyanobacteria blooms.

For more information about HABs and PARE™ come see us at the upcoming Pennsylvania Lake Management Society (PALMS) Conference. Click for details.

¹0.3 µg/L for microcystin and 0.7 µg/L for cylindrospermopsin children < than school age. For all others 1.6 µg/L for microcystin and 3.0 µg/L for cylindrospermopsin.

Natural VS. Artificial Lakes

In addition to deep versus shallow, waterbodies can also be compared and contrasted as naturally occurring or as the result of an artificial impoundment or reservoir. While there are a wide variety of natural lakes -from the glacial lakes of northern regions, to oxbow lakes adjacent to rivers, to coastal lakes that can be connected to the ocean – most of these natural systems have a number of common characteristics. Some of these include variable nutrient and sediment loading (from low to high, depending on the nature of the watershed) and low to moderate watershed-to-lake area ratios. In addition, natural waterbodies tend to have distinct and sometimes extensive littoral zone fringe habitat along the shoreline. Littoral habitat is the interface between the land and the open waters of a lake. Typically, rooted aquatic macrophytes (plants and mat algae) are found in the littoral zone, along with a number of aquatic organisms that use this habitat for food and/or cover. Thus, the littoral zone of lake is frequently the most productive areas of this ecosystem.

Graphic adapted from

Graphic adapted from

In contrast, large artificial impoundments, frequently called reservoirs, are waterbodies typically created by placing a dam across a stream or river (see below). This often results in the triangular shape of a reservoir; the deepest portion is located just behind the dam. Unlike many natural lakes that have a number of small inlet or inflow streams, a reservoir typically has one main inflow, which is essentially the river or stream that was originally dammed. Traveling upgradient from the dam towards the main inlet, water depth will decline. Additionally, many reservoirs are a type of hybrid of natural lakes and rivers. The upgradient/inflow part of the reservoir functions more like a riverine system, while the main body of the reservoir near the dam functions more like a lake (see below).

Graphic adapted from Reservoir Limnology: Ecological Perspectives, edited by K.W. Thornton, B.L. Kimmel and F.E. Payne, 1990

Graphic adapted from Reservoir Limnology: Ecological Perspectives, edited by K.W. Thornton, B.L. Kimmel and F.E. Payne, 1990

Since reservoirs are essentially dammed rivers, they tend to have very large watershed-to -lake area ratios, which means they tend to experience substantially higher nutrient and sediment loads compared to natural lakes. Thus, the level of productivity (algae growth) in the open waters of a reservoir is substantially higher than those of a natural lake. This means reservoirs have the tendency to experience larger and more frequent algal blooms. High rates of sediment loads also means rates of sedimentation will be higher in reservoirs compared to natural lakes. Finally, since the water level of reservoirs are highly dependent on inflow from the main riverine source, as well as water withdrawals in the case in drinking water supplies, the establishment of a littoral zone in reservoirs tends to be very limited.

In summary, a reservoir of comparable size to a natural lake will typically have a higher level of algal productivity, higher rates of sedimentation, and a smaller amount of biological diversity (with the general absence of a littoral zone). Thus, water quality problems can be larger and more frequent in reservoirs when compared to many natural lakes. Since many reservoirs are vital sources of potable water for millions of people throughout the United States, the general management activities for a reservoir tends to be higher relative to many natural lakes.

Join us next time, when we will discuss lake and pond productivity, the role the watershed plays in productivity, and how this impacts their recreational, potable and ecological value.