Background

Benthic harmful cyanobacterial blooms (HCBs) and
their toxins pose a significant environmental threat
to domestic animals, wildlife, and humans, and have
impacted drinking water treatment operations in
recent years. Specifically, dog and cattle deaths have
been attributed to exposure to benthic HCBs in
various states across the nation (and
internationally). With this in mind, state, tribal, and
local agencies have expressed a need for a greater
understanding of the role of benthic versus
planktonic blooms in cyanotoxin production and
tools for identification and quantification of HCBs.

Issue

To date, limited work has been done to review and
evaluate appropriate collection and analysis
methods for benthic HCBs. While the Interstate
Technology and Regulatory Council (ITRC) has
developed valuable draft guidance with multiple
sampling approaches, it does not specify the most
appropriate way to characterize risk quickly and
effectively during an HCB event. EPA also doesn't
currently have comprehensive guidance on
characterizing and responding to benthic HCBs to
share with states, tribes, and local agencies.

This lack of information can hinder scientists' and
decision-makers' ability to characterize risk and
quickly respond during a time-sensitive HCB event,
leading to further adverse impacts.

Methods

EPA researchers plan to conduct an estimated six
pilot studies during the summer of 2023 and 2024 at
streams and rivers across the United States that

have recently experienced benthic HCBs.

Researchers are looking to characterize locations on
wadeable streams and wadeable areas of larger
rivers where high exposure risks have the potential
to occur, such as places where children and pets
(i.e., dogs) play in water, wade, or have the potential
for direct interaction with benthic cyanobacteria;
and locations that are in the vicinity of vulnerable
drinking water systems.

Sites will be sampled up to three times a year during
the bloom season for each pilot study. Researchers
will analyze cyanobacterial composition, associated
toxins, and areal extent of benthic periphyton and
cyanobacteria mat samples. Periphyton are the
benthic algae and organic debris that cling to
surfaces and aquatic plants. They are an important
part of the aquatic community, especially in shallow
lakes, streams and rivers.

Results

The anticipated results of this study will enable EPA
to work more effectively with state, local and tribal
partners by providing sampling protocols and
analytical methods that can be employed to
efficiently assess potentially life-threatening benthic
HCB events. Results will also help state and tribal
partners develop benthic HCB plans that use
common sampling and analysis methods, with the
goal of identifying and reducing vulnerabilities for
drinking water supplies and risk of adverse impacts
to pets, wildlife, and humans recreating in and
around water.

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Related Links

Cyanobacterial Harmful Algal Blooms (CyanoHABs)
in Water Bodies: www.epa.gov/cyanohabs

EPA Newsletter and Collaboration & Outreach on
HABs: www.epa.gov/cyanohabs/epa-newsletter-
and-collaboration-and-outreach-habs#benthic

EPA HABs Contacts List:

www.epa.gov/cyanohabs/epa-office-water-and-
regions-contact-information

National Office for Harmful Algal Blooms:
hab.whoi.edu/impacts/impacts-wildlife

ITRC Strategies for Preventing and Managing
Harmful Cyanobacterial Blooms (Benthic):
itrcweb.org/itrcwebsite/teams/training/hcb

Technical Contacts for this Project

•	Tina Laidlaw

laidlaw.tina@epa.gov
Contact for EPA Region 8
www.epa.gov/aboutepa/epa-region-8-
mountains-and-plains

•	Rochelle Labiosa

labiosa.rochelle@epa.gov
Contact for EPA Region 10
www.epa.gov/aboutepa/epa-region-lQ-pacific-
northwest

•	Jim Lazorchak

lazorchak.jim@epa.gov

Contact for general study design &

implementation

•	Avery Tatters

tatters.avery@epa.gov
Contact for sampling methods

December 2022

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