Summary 3

Aphanizomenon is a cyanobacteria genus that is commonly found in freshwater phytoplankton assemblages. In nutrient-rich lakes it can form dense blooms. Although there are more than one species of Aphanizomenon, the most common species found in toxic cyanobacteria blooms is Aphanizomenon flosaquae.

Description 4

Aphanizomenon flosaquae cells are cylindrical or barrel-shaped and tiny (3-8 μm wide; for comparison, a strand of spider silk is about 5 μm wide). 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 end of the filament may be elongated and appear partly empty (vacuolated). The cells are joined together end-to-end to form long, unbranched, straight or gently curved filaments. The filaments are usually bunched into flake-like clumps that look like tiny glass clippings.

In addition to ordinary (vegetative) cells, the filament may contain pale blue, cylindrical heterocytes (=heterocysts) and long, rod-shaped akinetes. 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

Aphanizomenon 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.

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

Because Aphanizomenon is capable of fixing dissolved nitrogen gas, it can dominate blooms where 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 Aphanizomenon blooms is complicated; blooms can develop under both low and high inorganic nitrogen concentrations.

Aphanizomenon blooms usually contain other types of Cyanobacteria, especially Dolichospermum, Gloeotrichia, Microcystis, and Woronichinia .

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.

Aphanizomenon cells may produce cylindrospermopsin (liver toxin), anatoxins (nerve toxin), saxitoxins (nerve toxin - paralytic shellfish toxin group), lipopolysaccharides (skin irritants), and BMAA (beta-Methylamino-L-alanine; nerve toxin). These toxins are released into the ambient environment when the cell wall is disrupted (cell lysis).

  • Anatoxins are rapidly degraded by sunlight and at pH levels that are slightly above neutral (neutral pH = 7.0). At low pH levels, and in the absence of light, anatoxins may persist in the aquatic environment for a few weeks. There is some evidence that anatoxins can be degraded by specialized bacteria, similar to Microcystis, but this process is not well documented.
  • BMAA can bioaccumulate in zooplankton and fish, so this nerve toxin can contribute to health risks long after the toxic bloom has died back.
  • There is not much information about environmental degradation of cylindrospermopsin and saxitoxins, but both types of toxins can persist for weeks in the aquatic environment.

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

Not all Aphanizomenon 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.
  • 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.
  • D'Anglada, L., J. Donohue, J. Strong, and B. Hawkins. 2015. Health effects support document for the cyanobacterial toxin anatoxin-A. U.S. Environmental Protection Agency, Office of Water, EAP-820R15104, June 2015.
  • 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, ww.ljlmpress.com.
  • Granéli, E. and J. T. Turner (Eds.) 2006. Ecology of Harmful Algae. Ecological Studies, Vol. 189, Springer.
  • Lage, S., H. Annadotter, U. Rasmussen, and S. Rydberg. 2015. Biotransfer of B-N-Methlamino-L-alanine (BMAA) in a eutrophicated freshwater lake. Marine Drugs 13:1185-1201.
  • Matthews, Robin A., "Freshwater Algae in Northwest Washington, Volume I, Cyanobacteria" (2016). A Collection of Open Access Books and Monographs. 6. http://cedar.wwu.edu/cedarbooks/6 (also see: http://www.wwu.edu/iws/).
  • 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

Aphanizomenon flosaquae has no commonly used synonyms.

About 5

This guide was prepared by Dr. Robin Matthews, former Director of the Institute for Watershed Studies (http://www.wwu.edu/iws/) 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 http://www.wwu.edu/iws/) and an online key to the cyanobacteria (http://www.snoringcat.net/cyanobacteria_key/index.html).

Sources and Credits

  1. (c) rmatth, some rights reserved (CC BY-NC-SA), uploaded by rmatth
  2. (c) Sonya Carlson, some rights reserved (CC BY-NC), uploaded by Sonya Carlson
  3. Adapted by rmatth from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Aphanizomenon
  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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