Summary 3

Gloeotrichia is a cyanobacteria genus that is commonly found in freshwater phytoplankton assemblages. In nutrient-rich lakes it can be found in dense blooms, usually in association with other planktonic cyanobacteria. Although there are more than one species of Gloeotrichia, the most common species found in toxic cyanobacteria blooms is Gloeotrichia echinulata.

Description 4

Gloeotrichia echinulata cells are cylindrical, (5-7 μm wide; for comparison, a strand of spider silk is about 5 μm wide), with slightly constricted walls. Under magnification the cells are dark brown and may appear granular or mottled due to the presence of gas vesicles in the cells. Cells near the base of the filament are nearly equal in length and width, but cells near the end of the filament are very long and appear partly empty (vacuolated) or banded. The cells are joined together end-to-end to form long, tapered, unbranched filaments that radiate from a central location to form dense, spherical colonies.

In addition to ordinary (vegetative) cells, the filament usually contains a single, basal heterocyte (heterocyst) located near the colony center. There may also be a long, rod-shaped akinete adjacent to the heterocyte. Heterocytes are specialized cells that convert dissolved nitrogen gas into ammonium that can be used for cell growth. Akinetes are resting cells that are resistant to cold temperatures and other unfavorable environmental conditions. Akinetes are usually produced near the end of the growing cycle, and can overwinter in lake sediments.

Ecology 4

Gloeotrichia echinulata colonies are generally described as planktonic, but they may start on the bottom of a lake bottom, becoming increasingly buoyant as the colony matures.

Gloeotrichia echinulata blooms often form during warm, calm weather in lakes and ponds with relatively high nutrient concentrations (nitrogen or phosphorus) or low nitrogen to phosphorus ratios (N:P<15).

  • Recent work suggests that high total phosphorus (TP) or total nitrogen (TN) concentrations are better predictors of bloom formation than N:P ratios.
  • Gloeotrichia echinulata blooms have also been reported in unproductive (oligotrophic) lakes in northeastern regions of the USA.

The gas vesicles in Gloeotrichia cells provide a mechanism to move up and down in the water column, which increases access to nutrients and other growth factors.

Because Gloeotrichia is capable of converting dissolved nitrogen gas ammonium, it can dominate blooms when inorganic nitrogen (ammonium, nitrate, and nitrite) is limiting to other types of algae.

  • Nitrogen fixation requires a large amount of energy, so the relationship between nitrogen concentrations and Gloeotrichia blooms is complicated; blooms can develop under both low and high inorganic nitrogen concentrations.

Gloeotrichia echinulata blooms usually contain other types of Cyanobacteria, especially Aphanizomenon , Dolichospermum (aka Anabaena), Gloeotrichia, and Microcystis.

Toxicity 4

Identifying which cyanobacteria species are producing toxins is more difficult that it sounds. Historically, cyanobacteria taxa were described as "potentially" toxic based on whether they were collected in a toxic bloom. With the advancement of culturing techniques and genetic analysis, toxicity information is becoming more exact. But this is an ongoing process, so the toxicity information on these pages should be considered a work in progress.

Gloeotrichia echinulata cells may produce microcystins (liver toxin) and lipopolysaccharides (skin irritants). These toxins are released into the ambient environment when the cell wall is disrupted (cell lysis).

  • Microcystins are rapidly degraded by naturally occurring but specialized bacteria.
  • If the specialized bacteria are not present, microcystins can persist in the aquatic environment for months.

Higher water temperatures and light appear to be associated with increased toxin production.

Not all Gloeotrichia blooms result in the release of toxins.

Similar Genera 4

Information Sources 4

  • Bennett, L. 2017. Algae, cyanobacteria blooms, and climate change. Climate Institute Report, April 2017.
  • Berg, M and M. Sutula. 2015. Factors affecting the growth of cyanobacteria with special emphasis on the Sacramento-Jan Joaquin Delta. Southern California Coastal Water Research Project Technical Report 869.
  • Caldwell Eldridge, S., R. Wood, and K. Echols. 2012. Spatial and temporal dynamics of cyanotoxins and their relation to other water quality variables in Upper Klamath Lake, Oregon, 2007-09. USGS Scientific Investigations Report 2012-5069.
  • Carey, C., J. Haney, and K. Cottingham. 2007. First report of microcystin-LR in the cyanobacterium Gloeotrichia echinulata: Environ. Tox. 22:337–339.
  • Chorus, I. and J. Bartram (Eds). 1999. Toxic cyanobacteria in water: a guide to their public health consequences, monitoring and management. The World Health Organization E & FN Spon, London.
  • EPA. 2014. Cyanobacteria and Cyanotoxins: Information for Drinking Water Systems. U. S. Environmental Protection Agency, Office of Water, EPA-810F11001.
  • Graham, L. E., J. M. Graham, L. W. Wilcox, and M. E. Cook. 2016. Algae, Third Ed., ver 3.3.1 . LJLM Press,
  • Matthews, Robin A., "Freshwater Algae in Northwest Washington, Volume I, Cyanobacteria" (2016). A Collection of Open Access Books and Monographs. 6. (also see:
  • Meriluoto, J., L. Spoof, and G. Codd. 2017. Handbook of Cyanobacterial Monitoring and Cyanotoxin Analysis. John Wiley & Sons, Chichester, UK.
  • Paerl, H. W. 2014. Mitigating harmful cyanobacterial blooms in a human- and climatically-impacted world. Life 2014 4:988-1012.
  • Walsby, A. E. 1994. Gas vesicles. Microbiological Reviews 58:94-144

Synonyms 4

Gloeotrichia echinulata has no commonly used synonyms.

About 5

This guide was prepared by Dr. Robin Matthews, former Director of the Institute for Watershed Studies ( and professor emeritus at Western Washington University. In addition to this guide she has also written two ebooks (more on the way) on phytoplankton identification (see the "algae books" link on and an online key to the cyanobacteria (

Sources and Credits

  1. (c) Kyle Kerger, some rights reserved (CC BY-NC), uploaded by Kyle Kerger
  2. (c) rmatth, some rights reserved (CC BY-NC-SA), uploaded by rmatth
  3. Adapted by rmatth from a work by (c) Wikipedia, some rights reserved (CC BY-SA),
  4. (c) rmatth, some rights reserved (CC BY-NC-SA)
  5. Adapted by rmatth from a work by (c) Bryan Milstead, some rights reserved (CC BY-NC-SA)

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