Harmful Algae and
Bloom Producers
in Virginia Waters
and Chesapeake
Bay
Harold G. Marshall
Department of Biological Sciences
Old Dominion University
Norfolk, Virginia
Introduction
• Algae: Why are they an important and valuable natural
resource.
• Some algae are also a general nuisance, including those
that are harmful and a lethal component in our natural
waters.
•
Several of the more common bloom producing and
harmful species in Virginia waters will be presented.
Definitions
• Algae:
• Mostly microscopic single cell plants present in a variety
of water and terrestrial habitats.
• Also includes freshwater algae that form visible slender
filaments, often forming thick mats on the water’s
surface.
• Many single cell algae are motile and capable of active
movement in the water column.
• They come in different colors due to the pigments in their
cells.
Representative Algae
Single cell, colonial, filamentous, often within a
gelatinous matrix
Species Uniqueness in Size and
Morphology
Aquatic Algae
•
World wide, there are ca.
20,000 algal species.
•
About 150 of these are
known to be harmful bloom
or toxin producers.
•
We have identified over
1,400 algae in Chesapeake
Bay, and its tidal rivers.
•
These include 38 as harmful
or toxin producing species
in Virginia waters and the
Bay.
Algal Blooms
• Algae may reproduce rapidly under favorable
environmental conditions.
• Many single celled algae can double their
number 2-3 times a day.
• When concentrations are extremely high, and
they color the water, it is called an algal bloom
(e.g. “a red or green tide”).
Toxic Blooms
•
•
•
First recorded reference is in
Exodus (7:20-21), Bible’s Old
Testament, in ca. 1000 BC,
“- - - all the waters in the
river (Nile) were turned to
blood, and the fish that were
in the river died, the river
stank, - -“
Globally about 2,000 cases
of human poisoning due to
toxic blooms occur annually,
with about 15% mortality.
Common Side Effects of Blooms
•
•
•
•
Reduce oxygen levels that result in fish kill events.
Bloom cells may clog fish/shellfish gills, causing death.
Many produce noxious odors in the water, or air.
Others produce toxins harmful to fish, shellfish, or to
human health.
Diversity among Algae:
The Good, Bad and Ugly Species
The “Good” Phytoplankton:
•
Major food source for animals in
water based habitats world-wide.
•
Represents ca. 40% world’s total
annual food productivity.
•
Major world’s source of oxygen:
Produces 47 x108 tons oxygen
annually.
Diatoms
Chlorophytes
(green algae)
The “Bad” Phytoplankton:
•
Produce nuisance algal blooms mainly during
summer/fall months that result in odors, impact
recreational usage, etc.
•
Their decomposition lowers oxygen levels in the
water. A major cause of our regional fish kills.
•
Contributes to loss of oxygen in deeper basins of
Chesapeake Bay.
Cochlodinium polykrikoides
Every summer produces massive blooms
in the lower James and York rivers.
Single cells may form series of cells up to
64 in length.
Decomposing cells release strong odor
into surroundings.
Blooms reduce oxygen levels often
resulting in fish and shellfish deaths.
Cochlodinium polykrikoides Bloom
Other odor producing algae:
Cyanobacteria (blue-green algae)
• Their blooms in lakes and rivers often produce
unacceptable taste and odor levels in waters processed
for drinking, etc.
• Associated with ca. 40 species of filamentous
cyanobacteria at bloom concentrations.
• Offending products (Geosmin, 2-methylisoborneal)
produced and released from the cells.
Filamentous Odor Producing Cyanobacteria
The “Ugly”
Phytoplankton
• Toxin producers causing fish kills,
shellfish contamination, often harmful
effects to humans.
• There are at least 38 potentially
harmful algal species in Virginia
waters identified to date.
Mechanism of Toxin Infection
•
•
•
•
Eating toxin containing
shellfish, fish.
Contact with toxin released in
the water.
Exposed to toxins released to
the atmosphere as an aerosol
and inhaled.
Consume water containing
intact cells that rupture within
digestive tract.
Regional Harmful Algae
• The 5 major species of concern in Virginia are:
• Four Dinoflagellates:
• Alexandrium monilatum: Fish Killer
• Cochlodinium polykrikoides: Reduces Oxygen
• Karlodinium veneficum: Fish Killer
• Prorocentrum minimum: Reduces Oxygen
• One Cyanobacterium:
• Microcystis aeruginosa: Toxin producer, human
and animal health concerns.
Karlodinium veneficum
•
•
•
•
Single cells, small < 17 microns in
size.
Produces toxin that kills fish,
especially juveniles, and infects
shellfish.
Found U.S. east coast, Australia,
south Atlantic waters.
Considered lethal to fish at
densities greater than 10,000
cells/ml, during bloom status.
Prorocentrum minimum
• The most common bloom
producer in Virginia tidal rivers
and Chesapeake Bay.
• Blooms reduce oxygen levels in
the waters spring through
autumn.
• Often associated with fish kills.
Alexandrium monilatum
•
•
•
•
A new invasive species to Virginia rivers and Chesapeake Bay.
A toxin producer; kills fish.
First bloom event recorded in 2007 in the York River, again in 2008
In 2009, blooms appeared in the York and James rivers, plus lower
Chesapeake Bay.
• These cells form resting cysts in the sediment after a bloom; may reinoculate river at later time.
• Considered to have established itself in these waters.
Microcystis aeruginosa
•
Small cells present in gelatinous
matrix.
•
Produces toxin microcystin.
Ailments come from drinking
contaminated water.
•
In animals and humans impacts the
liver and digestive tract; may
produce skin rashes, tumors, and
neurotoxic conditions
Environmental relationships
associated with bloom development
•
•
•
•
•
•
Nutrients: Stimulates and maintains growth.
Temperatures: Faster growth with rising temperatures
(summer and fall blooms)
Light: Source of energy to maintain rapid growth.
Salinity: Either favors or inhibits bloom development
depending on species.
Current flow: Influences exposure to nutrient sources.
Prey or predator status. Prey may represent food
source and support the bloom species; or predators
may consume the bloomers.
Summary
• The microscopic plant community in Virginia’s rivers,
ponds, and lakes is an essential natural resource for its
food and oxygen production.
• Less favorable species may become more abundant with
increasing nutrient input to these waters, including odor
and toxin producing species
• Evidence for this contamination includes more frequent
and extensive algal blooms, plus fish kill events and
contaminated shellfish.
• These phytoplankton studies were supported by the:
Virginia Department of Environmental Quality and the
• Virginia Department of Health