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Selected species of cyanobacteria that can form toxic blooms in temperate lakes: * Species that have posed problems in Washington lakes.
Anabaena spp. cells are attached to form unbranched filaments (like a string of beads) that may be randomly twisted and coiled, sometimes like springs, or entangled with numerous other filaments. Vegetative cells may be spherical to oblong (4 – 14 µm diameter, 6 – 12 µm long) with granular contents and conspicuous, refractive pseudovacuoles. Two types of specialized cells may be present in various numbers within a filament of vegetative cells. Akinetes are larger than vegetative cells and may appear spherical to sausage-shaped (6 – 13 µm diameter, 20 - 50 µm long). Heterocysts, which appear empty, are somewhat spherical (7 – 9 µm diameter, 6 – 10 µm long).
Aphanizomenon flos-aquae cells unite to form a straight, unbranched filament, which tapers slightly toward both ends. Filaments are usually clustered to form a bundle of parallel filaments (looking like a bundle of straw) which is free-floating. These bundles appear to the unaided eye as prominent, blue-green, “lens-shaped bodies” suspended in the water sample. Individual cells are at least twice as long as wide (5-6 µm diameter, 8-12 µm long). Each filament shows a slight tapering toward the ends, with the cells near the ends being much more elongated and empty looking. There may be one centrally-located akinete and heterocyst per filament. Akinetes are sausage-shaped (8 µm diameter, 60 – 75 µm long) and located near the center of a filament. Heterocysts are oblong to cylindrical (7 µm diameter, 12 – 20 µm long) and located in the mid-region but not adjacent to the akinete. Akinetes and/or heterocysts may be absent at times.
Cylindrospermopsis raciborskii
Cells of Cylindrospermopsis raciborskii are
very small in comparison to other algae. Filaments are typically 2 – 3
µm wide and are variable in length (10 – 120 µm long) and are either
linear or coiled and composed of rectangular cells with basal heterocysts. They often grow without a heterocyst and rarely have
akinetes. Differences in cell size are common. While
Cylindrospermopsis is primarily a tropical genus, there have been
increasing reports of its presence in temperate regions of Europe and
North America, including Oregon. C. raciborskii does not form a scum at the
water surface and is often located in bands several feet from the
surface of a lake. It produces a brown tint to the water that cannot be
easily distinguished from suspended sediment or other types of algae. A
further difficulty in observing this species in a lake or pond is that
there is no taste or odor associated with Cylindrospermopsis or
its toxins. For more information, visit the Indiana Department of
Environmental Management (pdf 941 KB).
The word Gloeotrichia comes from the Greek meaning "gelatinous hair." Gloeotrichia echinulata is found in free-floating globose colonies formed by numerous filaments radiating from a common center. Colonies can be seen easily with the unaided eye as floating “fuzz-balls” about 2 mm (or 1/16”) in diameter. Each filament tapers from a basal heterocyst into a fine hair-like tip extending beyond the mucilage, which holds the colony together. Vegetative cells near the base of each filament are spherical to barrel-shaped (8-10 µm diameter), becoming long and noticeably tapered at the opposite end. Highly refractive pseudovacuoles are present which allow colonies to be buoyant. The single, basal heterocyst is spherical (10 µm diameter). Akinetes are adjacent to heterocysts and are cylindrical (10 – 18 µm diameter, up to 50 µm long).
Lyngbya species have unbranched filaments that are straight, curved, or regularly spiraled. They usually form large, layered mats of varied thickness. Trichomes are mostly rounded or conical at the apex. A definite firm mucilage sheath is characteristic and is always present, which helps to distinguish this genus from Oscillatoria. The mucous is sometimes stratified, is thin or thick, and is colorless, slightly red, or yellow-brown. Lyngbya normally grows in dense mats at the bottom of nutrient enriched lakes; mats produce gasses during photosynthesis that can cause them to rise to the surface.
Microcystis aeruginosa forms clusters of cells (colonies), which may be spherical, lobed, or an extensive reticulate mass. Suspended colonies often appear as small blue-green “clots.” Individual cells are very small (3-5 µm diameter) with conspicuous, highly refractive pseudovacuoles that cause the colonies to be buoyant and float to the surface. A transparent, gelatinous matrix holds cells of a colony together. Akinetes and heterocysts are absent.
Nostoc cells join end-to-end to form colonies that look like a string of beads. The gelatinous colonies are composed of contorted filaments called "trichomes" and are surrounded by a thin gelatinous sheath characterized by a firm consistency. Young colonies are usually spherical and microscopic in size, remaining solid or becoming hollow as they mature. Older colonies are usually a few centimeters in size, although some species can attain a diameter of 50 cm. Heterocysts are generally solitary and the same size and shape as vegetative cells.
Nostoc
is common in both aquatic and terrestrial
habitats and readily combines in
symbiotic association with fungi or other plant life.
The genus can lie dormant for long periods of time and
then recover metabolic activity when rehydrated. Because Nostoc
can withstand freezing and thawing cycles, it is well-adapted to extreme
environments.
Oscillatoria is tolerant of organic pollutants. Oscillatoria spp. often inhabit depths of thermally stratified lakes in which gradients of physical and chemical factors occur. Common in farm ponds and lagoons where sewage is treated. O. rubescens is a red species that can form conspicuous red blooms in eutrophic lakes.
Planktothrix usually grows as straight and solitary filaments. This genus lacks a mucilaginous envelope and usually grows without a sheath. Planktothrix trichomes are slightly tapering at the ends with end cells widely rounded. Their cells are typically shorter than broad or iodiametric and their filaments exhibit gliding motility by rotation. Their cylindrical cells are slightly constricted at the cross walls, and their cell diameter ranges from 3.5 – 10µm.
Planktothrix is found with abundant gas vacuoles usually in mesotrophic or eutrophic freshwater lakes. To date, P. rubescens has always been found with microcystins in the field, and P. agardhii is highly likely to be found with microcystins in the field.
*The genus name Planktothrix has never been validly published under the Rules of the Bacteriological Code (1990 Revision). However, some Planktothrix species names have been validly published under the ICBN. Certain species are listed as Oscillatoria and elsewhere as Planktothrix. (Visit the International Journal of Systematic and Evolutionary Microbiology article "A proposal for further integration of the cyanobacteria under the Bacteriological Code).
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Akinete
Carcinogen
Colony
Cyanosis
Fasciculation
Filament
Globose
Hepatocyte
Hepatotoxin
Heptapeptide
Heterocyst Heterotrophic Obtaining food in soluble or particulate form; not photosynthetic. Hypovolumic shock Shock caused by decrease in volume of circulating blood.
Jaundice
Neurotoxin
Oblong
Photosynthetic
Pseudovacuole
Reticulate
Spherical
Toxicosis
Vegetative cell
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Last Update: Wednesday, December 26, 2007
