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Toxic Cyanobacteria in New Hampshire’s Lakes and Ponds
James F. Haney, Chairman of the Zoology Dept., UNH, and John J. Sasner,
Professor Emeritus of Zoology, UNH Responding to several incidents of toxic
algae blooms on NH lakes and ponds last summer, we asked Drs. Haney and
Sasner to update us on their research.
New Hampshire’s lakes and ponds contain many organisms that can impact
water quality. In recent years blooms of blue-green bacteria, called
cyanobacteria (formerly “blue-green algae”), have emerged as an important
factor impacting the quality of lake water used for drinking or recreation,
because these cyanobacteria produce toxic substances called biotoxins.
Anabaena and Aphanizomenon, cyanobacteria present in many NH lakes, produce
neurotoxins that disrupt nerve transmissions causing paralysis. Surprisingly,
the Aphanizomenon toxin, neosaxitoxin, is identical to the red tide toxin
responsible for closing shellfish beds in coastal waters of the Northeast
and for the deaths of marine mammals. UNH biologists, Drs. Ikawa and Sasner,
first isolated and identified this biotoxin from a toxic strain of
Aphanizomenon found in a small pond near Durham, NH.
Worldwide, there have been numerous incidents of deaths of domestic animals
and wildlife by cyanobacteria toxins in lakes and occasionally the deaths of
humans. For example, cyanobacteria nerve toxins are suspected in the 2002
death of a Wisconsin teenager who accidentally swallowed lake water while
swimming in a small golf course pond.
Also of great concern are the liver toxins, called microcystins (MC), produced
by cyanobacteria commonly found in the lakes and ponds of NH and worldwide. A
recent survey showed MC in all of the more than 80 NH lakes tested.
Fortunately, average concentrations in the water column were generally below
the World Health Organization (WHO) guideline of 1.0 microgram MC per liter for
drinking water. In reports submitted by the UNH Center for Freshwater Biology
(CFB) to the Environmental Protection Agency and the United States Geological
Survey, two cautionary points were stressed.
(1) Much of the MC appears to reside in the tiniest sized organisms in
the plankton community known as picoplankton. These are less than 2 micrometers
in diameter (more than 1000 individuals could span the head of a pin!) and
little is known about their biology. We are currently investigating the types
of toxins produced by these “invisible” lake inhabitants and plan to culture
them to determine their identity. Of special concern is the possibility for
contamination of drinking water. We need to determine whether the smallest of
these forms might pass through the filters used for treating normal drinking
water.
(2) We also discovered MC in the bottom sediments or benthos of our
lakes, 10-20 times that found in the lake water. These benthic toxins are
produced by cyanobacteria species that overwinter in the benthos, obtaining
nutrients from the phosphorus rich sediments. Models produced in our study
predict that in many NH lakes, calm and sunny weather could cause these
deep-water cells and colonies to suddenly rise up into surface waters and
accumulate as “scum” in lake embayments at concentrations that could be
dangerous if ingested by humans or domestic animals.
Cooperative efforts between the UNH Center for Freshwater Biology (CFB) and
the NH Department of Environmental Services (DES) have addressed public
health issues, and NH is among the first states to warn against swimming in
water in which cyanobacteria scum has been observed. The public is also
encouraged to send samples of suspected toxic scum to DES for analysis.
Additional information on this subject can be obtained from Internet
searches of “cyanobacteria toxins” and from the CFB (www.cfb.unh.edu.) and DES websites (www.des.state.nh.us).
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