Tracking and Managing Harmful Algae Blooms

A Presentation by Princeton Hydro Founder Dr. Stephen Souza
Available for Free Download Here

The presentation covers all things related to identifying, addressing and preventing Harmful Algae Blooms (HABs), including:

  • Understanding what defines HABs, Cyanobacteria and Cyanotoxins
  • Dispelling common misconceptions about HABs
  • Educating on the health implications associated with HABs, specifically related to drinking water and recreational water usage
  • Learning about PARETM – Princeton Hydro’s unique strategy for addressing HABs
    • (P)redict – Forecasting a bloom
    • (A)nalyze – Measuring and quantifying a bloom
    • (R)eact – Implementing measures to prevent and control a bloom
    • (E)ducate – Providing community outreach and public education

To learn more about Princeton Hydro’s Invasive Weed and Algae Management Services, visit our website or contact us!

 

Lake Management and Restoration in the Hudson River Valley

Lake Management Planning in Action
at Sleepy Hollow Lake and Truesdale Lake

The Hudson River Valley encompasses 7,228 square miles along the eastern edge of New York State. It comprises 3 million residents, 133 communities and 553 significant freshwater lakes, ponds and reservoirs. Princeton Hydro has worked with municipalities and organizations in the Hudson River Valley for over 18 years actively restoring, protecting and managing waterbodies throughout the area.

Princeton Hydro is currently implementing customized Lake Management Plans at two waterbodies in the Hudson River Valley: Sleepy Hollow Lake, a 324-acre drinking water reservoir/recreational lake located in Green County, NY and Truesdale Lake, an 83-acre lake in Northern Westchester County, NY.

Sleepy Hollow Lake

Stretching over two and a half miles long and reaching depths of approximately 70 feet, Sleepy Hollow Lake is a NYSDEC Class “A” drinking water reservoir that provides potable water for the Sleepy Hollow community. The lake is also extensively used by residents for swimming, boating and water-skiing. And, it is recognized as an outstanding large-mouth bass and white crappie (current New York State record holder) fishery!

Princeton Hydro was hired by the Association of Property Owners (APO) at Sleepy Hollow Lake to develop a comprehensive lake management plan. The first step involved an in-depth analysis of the biological, chemical and physical attributes of the lake, with the goal being to generate a database that can be used to better understand the interactions defining the Sleepy Hollow Lake ecosystem.

The data collection and investigation phase includes:

  • Watershed Investigation: an in-depth assessment of the major and minor tributaries and road network in order to identify areas of stream bank and ditch erosion; sources of both sediment and nutrient loading to the lake
  • Bathymetric Survey: the accurate mapping of water depths and the quantification of the amount of accumulated, unconsolidated sediment present in the lake
  • Fisheries & Food Web Study: the collection of fish and plankton data for the purpose of creating a comprehensive fisheries management program focused on managing the lake’s outstanding fishery, further promoting the ecological balance of the lake, and enhancing lake water quality
  • Aquatic Plant Mapping: the development of detailed maps identifying the plant species present in the lake along with their relative abundance and distribution throughout the lake, but especially within the shallower coves
  • Hydrologic & Pollutant Budget: the computation of the lake’s hydrologic budget and pollutant loading budget. The hydrologic budget represents the water balance of the lake and is an estimate of all of the inputs and losses of water. The pollutant budget represents an estimate of the amount of nitrogen and phosphorus entering the lake from various sources. These data are used to evaluate the effectiveness of lake management options, enabling us to determine the best, most ecologically sound and most cost-effective approach to protect and improve the lake’s water quality now and into the future.

Princeton Hydro is now in the process of utilizing all of the data developed during the investigation phase of the project to create a comprehensive Lake Management Plan that will be used to guide the APO’s future lake restoration and protection initiatives. The Lake Management Plan and supporting data will also be used by Princeton Hydro on behalf of the APO to seek grant funding for various lake and watershed restoration projects.

Princeton Hydro is also overseeing the aquatic plant management program at Sleepy Hollow Lake, the focus of which is to control invasive plant species in a manner consistent with and complimentary of the lake’s overall ecological enhancement.

Truesdale Lake

At Truesdale Lake, Princeton Hydro is working with the Truesdale Lake Property Owners Association (TLPOA) to develop a comprehensive Lake Management Plan. The Plan provides a detailed project implementation roadmap for TLPOA, including recommendations for priority ranking of particular activities and restoration measures. A key element of the Plan are the short-term (1-year) and long-term (5-year) water quality and problematic algae and invasive aquatic plant control goals. Another highlight of the Plan is the review of Federal, State, County and local grants, programs and initiatives that may provide funding for identified lake and watershed projects.

During the Plan’s development, Princeton Hydro has provided the TLPOA with lake management consultation services such as community education initiatives, the coordination of NYSDEC permitting activities associated with the implementation of lake restoration measures, and the oversight and administration of an aquatic weed management program at the lake.

Earlier this year, Truesdale Lake experienced excessive aquatic weed growth, which significantly reduced the water quality, recreational use and aesthetics of the lake. Princeton Hydro utilized its Truxor, an eco-friendly, amphibious machine, to cut and remove the nuisance weed growth from the lake. This program helped reduce the negative impacts to the lake and lake users caused by the dense weed growth. Future use of the Truxor to remove invasive weeds is already part of the long-term Lake Management Plan for TLPOA. The Truxor will be used in concert with other measures to control invasive weed growth and restore a more balanced native aquatic plant community.

For more information about Princeton Hydro’s work in the Hudson River Valley or to discuss your project goals, please contact us.

Four Ways Climate Change Could Affect Your Lake

The Local Effects of Climate Change Observed Through our Community Lakes

Climate change is an enormous concept that can be hard to wrap your head around. It comes in the form of melting ice caps, stronger storms and more extreme seasonal temperatures. If you’re an avid angler, photographer, swimmer, boater or nature enthusiast, it’s likely that because of climate change you’ll bear witness to astonishing shifts in nature throughout the greater portion of your lifetime. This is especially true with respect to lakes.

2015-07-07-10-01-20Lakes are living laboratories through which we can observe the local effects of climate change in our own communities. Lake ecosystems are defined by a combination of various abiotic and biotic factors. Changes in hydrology, water chemistry, biology or physical properties of a lake can have cascading consequences that may rapidly alter the overall properties of a lake. Most of the time the results are negative and the impacts severe. Recognizing and monitoring the changes that are taking place locally brings the problems of climate change closer to home, which can help raise awareness and inspire environmentally-minded action.

Princeton Hydro has put together a list of four inter-related, climate change induced environmental impacts that can affect lakes and lake communities:

1. Higher temperatures = shifts in flora and fauna populations

The survival of many lake organisms is dependent on the existence of set temperature ranges and ample oxygen levels. The amount of dissolved oxygen (DO) present in a lake is a result of oxygen diffusion from the atmosphere and its production by algae and aquatic plants via photosynthesis. An inverse relationship exists between water temperature and DO concentrations. Due to the physical properties of water, warmer water holds less DO than cooler water.

This is not good news for many flora and fauna, such as fish that can only survive and reproduce in waters of specific temperatures and DO levels. Lower oxygen levels can reduce their ability to feed, spawn and survive. Populations of cold water fishes, such as brown trout and salmon, will be jeopardized by climate change (Kernan, 2015).

358-001-carp-from-churchvilleAlso consider the effects of changing DO levels on fishes that can tolerate these challenging conditions. They will thrive where others struggle, taking advantage of their superior fitness by expanding their area of colonization, increasing population size, and/or becoming a more dominant species in the ecosystem. A big fish in a little pond, you might say. Carp is a common example of a thermo-tolerant fish that can quickly colonize and dominate a lake’s fishery, in the process causing tremendous ecological impact (Kernan, 2010).

2. Less water availability = increased salinity

Just as fish and other aquatic organisms require specific ranges of temperature and dissolved oxygen to exist, they must also live in waters of specific salinity. Droughts are occurring worldwide in greater frequency and intensity. The lack of rain reduces inflow and higher temperatures promote increased evaporation. Diminishing inflow and dropping lake levels are affecting some lakes by concentrating dissolved minerals and increasing their salinity.

Studies of zooplankton, crustaceans and benthic insects have provided evidence of the consequences of elevated salinity levels on organismal health, reproduction and mortality (Hall and Burns, 2002; Herbst, 2013; Schallenberg et al., 2003). While salinity is not directly related to the fitness or survival rate of all aquatic organisms, an increase in salinity does tend to be stressful for many.

3. Nutrient concentrations = increased frequency of harmful algal blooms

Phosphorus is a major nutrient in determining lake health. Too little phosphorus can restrict biological growth, whereas an excess can promote unbounded proliferation of algae and aquatic plants.

before_strawbridgelake2If lake or pond water becomes anoxic at the sediment-water interface (meaning the water has very low or completely zero DO), phosphorus will be released from the sediment. Also some invasive plant species can actually “pump” phosphorus from the sediments and release this excess into the water column (termed luxurious uptake). This internally released and recycled sedimentary phosphorus can greatly influence lake productivity and increase the frequency, magnitude and duration of algae blooms. Rising water temperatures, declining DO and the proliferation of invasive plants are all outcomes of climate change and can lead to increases in a lake’s phosphorus concentrations and the subsequent growth and development of algae and aquatic plants.

Rising water temperatures significantly facilitate and support the development of cyanobacteria (bluegreen algae) blooms. These blooms are also fueled by increasing internal and external phosphorus loading. At very high densities, cyanobacteria may attain harmful algae bloom (HAB) proportions. Elevated concentrations of cyanotoxins may then be produced, and these compounds seriously impact the health of humans, pets and livestock.

rain-garden-imagePhosphorus loading in our local waterways also comes from nonpoint sources, especially stormwater runoff. Climate change is recognized to increase the frequency and magnitude of storm events. Larger storms intensify the mobilization and transport of pollutants from the watershed’s surrounding lakes, thus leading to an increase in nonpoint source loading. Additionally, larger storms cause erosion and instability of streams, again adding to the influx of more phosphorus to our lakes. Shifts in our regular behaviors with regards to fertilizer usage, gardening practices and community clean-ups, as well as the implementation of green-infrastructure stormwater management measures can help decrease storm-related phosphorus loading and lessen the occurrence of HABs.

4. Cumulative effects = invasive species

A lake ecosystem stressed by agents such as disturbance or eutrophication can be even more susceptible to invasive species colonization, a concept coined “invasibility” (Kernan, 2015).

For example, imagine that cold water fish species A has experienced a 50% population decrease as a result of warming water temperatures over ten years. Consequently, the fish’s main prey, species B, has also undergone rapid changes in its population structure. Inversely, it has boomed without its major predator to keep it in check. Following this pattern, the next species level down – species B’s prey, species C – has decreased in population due to intense predation by species B, and so on. Although the ecosystem can potentially achieve equilibrium, it remains in a very unstable and ecologically stressful state for a prolonged period of time. This leads to major changes in the biotic assemblage of the lake and trickle-down changes that affect its recreational use, water quality and aesthetics.

• • •

Although your favorite lake may not experience all or some of these challenges, it is crucial to be aware of the many ways that climate change impacts the Earth. We can’t foresee exactly how much will change, but we can prepare ourselves to adapt to and aid our planet. How to start? Get directly involved in the management of your lake and pond. Decrease nutrient loading and conserve water. Act locally, but think globally. Get out and spread enthusiasm for appreciating and protecting lake ecosystems. Also, check out these tips for improving your lake’s water quality.


References

  1. Hall, Catherine J., and Carolyn W. Burns. “Mortality and Growth Responses of Daphnia Carinata to Increases in Temperature and Salinity.” Freshwater Biology 47.3 (2002): 451-58. Wiley. Web. 17 Oct. 2016.
  1. Herbst, David B. “Defining Salinity Limits on the Survival and Growth of Benthic Insects for the Conservation Management of Saline Walker Lake, Nevada, USA.” Journal of Insect Conservation 17.5 (2013): 877-83. 23 Apr. 2013. Web. 17 Oct. 2016.
  1. Kernan, M. “Climate Change and the Impact of Invasive Species on Aquatic Ecosystems.” Aquatic Ecosystem Health & Management (2015): 321-33. Taylor & Francis Online. Web. 17 Oct. 2016.
  1. Kernan, M. R., R. W. Battarbee, and Brian Moss. “Interaction of Climate Change and Eutrophication.” Climate Change Impacts on Freshwater Ecosystems. 1st ed. Chichester, West Sussex, UK: Wiley-Blackwell, 2010. 119-51. ResearchGate. Web. 17 Oct. 2016.
  1. Schallenberg, Marc, Catherine J. Hall, and Carolyn W. Burns. “Consequences of Climate-induced Salinity Increases on Zooplankton Abundance and Diversity in Coastal Lakes”Marine Ecology Progress Series 251 (2003): 181-89. Inter-Research Science Center. Inter-Research. Web. 17

Invasive Species in Watershed Management

A Presentation by Princeton Hydro Director of Aquatic Programs Dr. Fred Lubnow

Available for Free Download Here

Dr. Fred Lubnow, Director of Aquatic Programs for Princeton Hydro, recently held an information session about Hydrilla, the Godzilla of Invasive Species. Hosted by the Lake Hopatcong Commission, the presentation covered how to identify Hydrilla and how to prevent its proliferation.

Many recreational lake users can identify Water Chestnut, but Hydrilla is much more difficult to differentiate from another species, Elodea, which is native to Lake Hopatcong.  Dr. Lubnow’s presentation illustrates how to easily compare Elodea to Hydrilla. Armed with this information, lake users will be able to spread the word and be on the look-out for Hydrilla and other invasives.

To learn more about Princeton Hydro’s Invasive Species Management Services, visit our website or contact us!

Dr. Lubnow Invasive Species Presentation

Visit Princeton Hydro at PALMS Conference: February 24 & 25

The Pennsylvania Lake Management Society (PALMS) is hosting its 26th annual conference on February 24 & 25 at the Ramada Hotel and Conference Center in State College, PA. Lake professionals, students, recreation enthusiasts, lakeside residents and community members are all invited to come together to explore a variety of topics related to managing lakes and reservoirs. 

The conference offers a collection of professional presentations, workshops and panel discussions. Attendees are also invited to the exhibit hall to discover the latest lake management tools and technologies, exchange information with a diverse group of vendors and network with peers. Be sure to visit the Princeton Hydro Booth to talk with them about the latest advancements in pond, lake and watershed management.

On February 24, Princeton Hydro President, Stephen Souza, invites you to attend his presentation on tracking and controlling cyanobacteria (blue-green algae) blooms using the firm’s unique PARE™ program. The presentation is at 11:10am followed by a panel discussion on cyanobacteria related lake and pond issues at 11:50am.

During the second day of the conference, Princeton Hydro Director of Aquatic Programs, Fred Lubnow, encourages you to join him for a lecture and discussion on the ecology and management of shallow lakes at 11:30am. 

Click here for the complete 2016 PALMS Conference Schedule. The Princeton Hydro team hopes to see you there! 

In advance of the conference, if you’d like to learn more about the problems associated with cyanobacteria (blue-green algae) blooms and how to implement PARE™, a comprehensive program for tracking and quantifying harmful algae blooms, you can read the “Emerging Issues” white paper by clicking here.

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

Predict

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.

Analyze

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.

React

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.