Getting to Know Cyanobacteria: basics, blooms, toxins, and taxa

  • Getting to Know Cyanobacteria

WHAT WILL I LEARN?

Get up to speed on cyanobacteria (a.k.a. blue-green algae) including a general overview, information on conditions which lead to blooms, details regarding cyanobacterial toxins, and a rundown of the main toxin-producing groups of cyanobacteria.

Jennifer Graham from the US Geological Survey contributed greatly to this webpage

 

Getting to Know Cyanobacteria

Basics   Blooms   Toxins   Taxa  Taste/Odor

The Basics

  The Basics  

Cyanobacteria (blue-green algae) blooms have been occurring throughout the world for thousands of years. Cyanobacteria produce a number of nuisance compounds, including those that are toxic or cause severe taste-and-odor problems in drinking water supplies. Cyanobacterial toxins can make drinking water and recreational use of water unsafe. Animals die yearly as a result of cyanotoxins, and though human death is not common, many people experience symptoms indicative of cyanotoxin exposure. Very little is known about the long-term side affects of ingestion of cyanotoxins, so although there is a guideline set by WHO for safe concentrations, minimal concentrations could cause an effect over time.

 

  Conditions affecting blooms  

Nutrient Availability: Nutrients are a limiting factor for cyanobacteria populations. As long as the correct nutrients are in excess, they can grow until some other factor, often light or temperature, becomes limiting.

Competition: Ability to adapt to the environment is a big factors determining whether a bloom will form. Many blue-greens are less edible, have gas vacuoles that help them float, can sequester nutrients at the sediment water interface, or can fix dissolved nitrogen, any of which can give them a competitive advantage over other algae and lead to bloom formation.

Light Intensity: Since cyanobacteria are phytoplankton, light is important and different species thrive under different light intensities. If light is not extinguished by particles or color in the water, a bloom is more likely. Many blue-greens thrive under low light, and so may be favored unless light is nearly absent (such as in some high particulate reservoir systems).

Mixing: Mixing allows nutrients to be more evenly distributed and affects other aspects of water quality that in turn affect algal abundance and composition. Mixing can also move algae to depths with less light, limiting growth and survival. In general, blue-greens do better with less mixing (Cylindrospermopsis is one taxon that seems to do well in mixed systems, though).

Temperature: Surface water temperatures consistently above 28 degrees Celsius (82 degrees Fahrenheit) encourage blue-green blooms, although blooms may still occur in late fall (October, November) in the Northern U.S.

Species: The above factors influence different species very differently, because each species or taxon has a unique way of dealing with their environment. There are generalizations that apply to blooms and blue-green dominance, but there are exceptions in most cases. Algal bloom formation is a complicated ecological process.

Toxicity: Not all blue-greens are toxic, so while risk may be higher during a bloom, high biomass does not necessarily result in toxicity. Also, although many toxin producing algae produce taste and odor compounds, the presence or absence of geosmin or MIB is not a predictor of the presence of toxins.

 

  Cyanotoxins  

Major Classes of Toxins:

Hepatotoxins  |  microcystin  |  cylindrospermopsin

Neurotoxins   |  anatoxin  |  saxitoxin

Dermatotoxins  |   Lyngbyatoxin

BMAA   |  beta-n-methylamino-L-alanine

 

  Major Taxa  

Although there are about 50 toxigenic algal taxa, most fall into one of a handful of genera.

Microcystis

2 Microcystis_aeruginosa_108

Anabaena

3 Anabaena_circinalis_794

Aphanizomenon

4_ Aphanizomenon_flos-aqaue_836

Cylindrospermopsis

5 Cylindrospermopsis_raciborskii_straight_Culture_1715

Oscillatoria

6 Oscillatoria_agardhii_11

 

  Major Taste and Odor Compounds  

Geosmin
MIB (2-methylisoborneol)

Toxin and Taste-and-Odor Producing Cyanobacteria (list is not exhaustive)

[LYN, lyngbyatoxin-a; APL, aplysiatoxins; LPS, lipopolysaccharides; CYL, cylindrospermopsins; MC, microcystins; NOD, nodularins; ANA, anatoxins; BMAA, β-N-methylamino-L-alanine; NEO, neosaxitoxins; SAX, saxitoxins; GEOS, geosmin; MIB, 2-methylisoborneol]

 

Dermatoxins

Hepatotoxins

Neurotoxins

Tastes and Odors

LYN

APL

LPS

CYL

MC

NOD

ANA

BMAA

NEO

SAX

GEOS

MIB

Cyanobacterial Genera
Colonial/Filamentous
AnabaenaXXXXXXXX
AnabaenopsisXX
AphanizomenonXXXXXXX
AphanocapsaXX
CylindrospermopsisXXXX
FischerellaXXX
GloeotrichiaX
HaplosiphonXX
HyellaXXX
Lyngbya (Plectonema)XXXXXXXX
MicrocystisXXX
NodulariaXXX
NostocXXXXX
Oscillatoria (Planktothrix)XXXXXXXXX
PhormidiumXXXXX
PseudanabaenaXXX
RaphidiopsisXXX
SchizothrixXXX
UmezakiaXX
Unicellular
SynechococcusXXXXX
SynechocystisXXX

Table courtesy of Jennifer Graham, USGS

Other non-bluegreen freshwater toxic algae

Prymnesium parvum. A toxic Haptophyte

Pyrmnesium is primarily an issue for fisheries. It acts on exposed cells such as gill tissue and has not been linked directly with human or mammalian illness or death.

Reports, Publications, and other links

U.S. EPA

Toxicological Reviews of Cyanobacterial Toxins: Anatoxin-a, Cylindrospermopsin and Microcystins (LR, RR, YR and LA)

NOAA

NOAA Great Lakes Environmental Research Laboratory

USGS

USGS Cyanobacterial Research

World Health Organization

WHO Report: Toxic cyanobacteria in water: A guide to their public health consequences, monitoring and management

 

WATCH A STUDENT VIDEO ON CYANOS