These toxins aren’t readily broken down
after they are ingested by an organism. As a
result, they can pass through the food chain
of animals living in and around a body of
water as one animal preys on another, which
causes harm across the ecosystem. At each
level of the food chain, toxins become more
concentrated. An individual fish may only have
a little microcystin in its body, but a bird that
eats a lot of fish will build up a greater amount
as a result—a phenomenon known as bio-magnification.
The algae had spread in huge numbers,
coating parts of the lake in thick, green goo.
It looked like an enormous experiment gone
Fortunately, in the United States incidents
like the Toledo water emergency don’t happen
often. But algal blooms are occurring on an
unprecedented scale in lakes, bays, gulfs, and
ocean coastlines throughout the world.
The algae that caused Toledo’s woes more
than three years ago are called Microcystis
aeruginosa. Because they depend on warm
temperatures for reproduction, these algae
grow rapidly in the summer.
These blooms can have harmful
consequences for the people who live
nearby. Even if the algae don’t
contaminate tap water, their
uncontrolled growth can cause
a variety of health problems
through direct contact with skin
or when people inhale airborne
toxins—and some research suggests that algal blooms could be
on the rise.
“They require temperatures between 75 °F
and 80 °F to bloom; they can also grow at
colder temperatures, but they don’t grow as
fast,” says Laura Johnson, director of the
National Center for Water Quality Research at
These little guys, Microcystis aeruginosa,
release a nasty toxin.
10 Western Lake Erie Bloom severity
signi cant mild
Algae: helpful or harmful?
The term algae refers to a variety of organisms—many of which are microscopic—that
live in water and produce energy from sunlight. They are a natural part of marine and
aquatic ecosystems. Algae produce about half
of the oxygen in the Earth’s atmosphere. They
are also the basis of many food webs and
provide food for other organisms—including
2003 2005 2007 2009 2011 2013 2015 2017
Several types of pollution can contribute to
algal blooms. Sewage
released into water is
one source. It is called
because it flows into
the water from a single
source, such as a pipe.
Between 2002 and 2017, algal blooms in western Lake Erie have been on
the rise, according to this severity index. The index is based on a bloom’s
biomass over 30 days.
Usually, this type of
pollution can be fixed.
Clean up the source,
and the problem is
A few types of algae, however, can cause
serious problems when they gather in large
concentrations. Some produce toxins called
microcystins. When these compounds enter
the body, they travel to the liver and covalently bind to and inhibit protein phosphatase
enzymes. These important enzymes remove
phosphate groups from proteins involved in
DNA repair and apoptosis, a natural process
of cell death that can lead to disease when it
gets out of balance. Microcystins jam these
critical systems, destroying liver cells.
Heidelberg University in Tiffin, Ohio. “Blooms
in Lake Erie start when it gets warm enough,
usually from mid-July to early August, and
don’t end until September or October, when
it starts to get cold and the day length is
Even when they begin to die off in the
fall, algae can still cause trouble. The dead
algae sink to the bottom of Lake Erie and are
decomposed by bacteria, an aerobic process
that consumes the water’s oxygen that other
animals need to survive.
Trickier to control is
“nonpoint” pollution, such as fertilizer runoff
from agricultural operations. The rain flushes
whatever fertilizer is not absorbed by plants
in farm fields and, eventually, into rivers and
lakes. But this only happens on some occa-
sions, which makes it different from point-
“[The Lake Erie] blooms were closely associated with point sources of pollution, primarily from wastewater treatment plants. All of
the sewage that was making it into the water
was being treated for bacteria, but phosphorus and nitrogen weren’t being removed,”
BARRY H. ROSEN, USGS; RS GRAPHX,INC.
SHELLE Y RUSSEL, ADAP TED FROM EPA; NASA; WIKIPEDIA
16 ChemMatters | APRIL/MAY 2018