Anabaena raciborskii

Algae blooms consist of trichomes found in and below the euphotic zone, not at the surface (Saker and Griffiths 2001). Concentrations of this species in Mona and Muskegon Lakes have remained low during late summer sampling, accounting for 6% of phytoplankton count in 2002 and 2003 in the former and < 1% in 2005 in the latter, possibly due to temperature limitations (Hong et al. 2006). This species can reach very high concentrations (e.g., 176 000 units ml-1 in Newnans Lake, Florida) (Chapman and Schelske 1997).

In Constance Lake, Ontario, C. raciborskii blooms appear to be controlled by water temperature and not nutrients (Hamilton et al. 2005). This species is capable of fixing atmospheric nitrogen in its heterocytes in response to low cell nitrogen concentration, as well as taking up phosphorus at low concentrations (Shafik et al. 2001, Sprober et al. 2003). The relatively high phosphorus uptake affinity and storage capacity confer a competitive advantage upon this species both in deep lakes with nutrient stratification as well as in lakes lacking such nutrient gradation (Istvanovics et al. 2000). Moreover, this species may also compete well for light in destratified lakes (Antenucci et al. 2005) and artificially mixed reservoirs (Burford et al. 2006). Conditions that are often associated with blooms of C. raciborskii include: low flow; low water level; low nitrogen to phosphorus ratio; high water temperature; stable thermal stratification; increased retention time; high pH; high sulfate concentration; anoxia in at least some strata; high turbidity; high incident irradiation; and low macrophyte biomass (Berger et al. 2006, Bormans et al. 2004, Bouvy et al. 1999, Bouvy et al. 2006, Bowling 1994, Briand et al. 2002, Chellappa and Costa 2003, Da Silva et al. 2001, Fabbro and Duivenvoorden 1996, Hong et al. 2006, Mayer et al. 1997, McGregor and Fabbro 2000, Ramberg 1987, Saker and Neilan 2001, Tucci and Sant’Anna 2003). The optimum temperature for growth is 25–30°C, although growth can occur between 15°C and 35°C, depending on the strain. The optimum light intensity for growth is 80–121 µmol m^-2 s^-1, but growth occurs at levels as low as 22 µmol m^-2 s^-1 (Briand et al. 2004, Chonudomkul et al. 2004, Saker and Griffiths 2000, Shafik et al. 2001). The maximum salinity tolerance is 4 g L^-1 NaCl (Moisander et al. 2002).

Some strains of this species are capable of producing cylindrospermopsin, a toxic compound that affects the human liver and kidneys, as well as anatoxin-a and saxitoxin, which both act as paralytic shellfish neurotoxins (Schembri et al. 2001). Increased production of cylindrospermopsin is associated with long periods of growth in high light intensity conditions (Dyble et al. 2006), in the presence of a fixed nitrogen source (Saker and Neilan 2001), and at lower water temperatures (Saker and Griffiths 2000).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic

There is little or no evidence to support that Cylindrospermopsis raciborskii has significant environmental impacts in the Great Lakes.

Realized:
Cylindrospermopsis raciborskii is found in relatively low abundances in Lake Erie (16-1,942 trichomes/mL), Muskegon Lake (~42 trichomes/mL), and Bear Lake (~1,000 trichomes/mL) (Conroy et al. 2007, Xie et al. 2011). As a result of these low abundances, many of the negative environmental impacts seen in other locations around the world where there are higher densities are not yet occurring in the Great Lakes basin.

Potential:
Some strains of C. raciborskii produce a variety of toxins including cylindrospermopsin, anatoxin-a, and saxitoxin. These toxins have been responsible for fish kills in a reservoir in Brazil and cattle deaths in Australia (De Souza et al. 1998, Saker et al. 1999b, Thomas et al. 1998). Cylindrospermopsin has been found to bioaccumulate in certain species of mollusks, crayfish, and snails; in some cases this exposure was toxic (Kiss et al. 2002, Saker et al. 2004, Saker and Eagleshame 1999, White et al. 2006, Metcalf et al. 2002).  Anatoxin produced by some strains of C. raciborskii has been found to affect snails (Kiss et al. 2002).

At high densities (e.g., > 90% phytoplankton biomass) in more tropical climates, C. raciborskii can cause a reduction in biodiversity. This is because of its ability to fix atmospheric nitrogen, sequester phosphorous, and move throughout the water column (Borics et al. 2000, Bouvy et al. 2001, Dobberfuhl 2003, Leonarda and Paerl 2005). In the St. Johns River System, Florida, C. raciborskii appears to reduce the size and diversity of zooplankton by sequestering nutrients and making them unavailable to grazers in the water column (Leonard and Paerl 2005). Some rotifers and cladocerans exhibit reduced feeding rates, growth rates, or growth potential in the presence of C. raciborskii (Hawkins and Lampert 1989, Nogueira et al. 2004, Rothaupt 1991).  C. raciborskii may also cause phytoplankton diversity to decrease, as has been observed in Lake Jesup, Florida (Dobberfuhl 2003) and a pond in Hungary (Borics et al. 2000).

Cylindrospermopsis raciborskii has a moderate socio-economic impact in the Great Lakes.
Realized:
Cylindrospermopsis raciborskii is found in relatively low abundances throughout the Great Lakes and as a result these populations do not yet exhibit the negative socio-economic impacts seen in other locations around the world with larger populations of C. raciborskii.

Potential:
A history of human health and water quality impacts elsewhere in the world under conditions similar to those found in the Great Lakes warrants significant concern, resulting in the assessment of this species as likely to have moderate socioeconomic impact.

Cylindrospermopsin from toxic C. raciborskii strains has caused liver damage and even death in humans, when the species occurs in water supply systems (Bernard et al. 2003; Falconer and Humpage 2006; Hawkins et al. 1985). Cylindrospermopsin also has the potential to be genotoxic or carcinogenic in humans and to cause acute skin reactions in people on contact (Falconer and Humpage 2001; Falconer and Humpage 2006; Humpage et al. 2000; Shen et al. 2002; Stewart et al. 2006).

Strains of C. raciborskii that produce toxins can severely impact water quality both in drinking water for humans and as a result of bioaccumulation in aquatic organisms (Bernard et al. 2003, Bouke et al. 1983, Hawkins et al. 1985, Kiss et al. 2002, Saker et al. 2004, Saker and Eagleshame 1999, White et al. 2006).

Cylindrospermopsin is a potent inhibitor of protein synthesis, an irritant, and causes cutaneous sensitizing that could be harmful to recreational users of impacted water bodies; to date, however, populations in the Great Lakes basin have not been known to produce cylindrospermopsin (Conroy et al. 2007, Stewart et al. 2006, Xie et al. 2011). Treatment of a C. raciborskii bloom with copper sulfate resulted in contamination of a reservoir on Palm Island, Australia with cylindrospermopsin. After drinking the contaminated water, 141 people were hospitalized with hepatoenteritis and other symptoms affecting kidneys, adrenal glands, small intestine, lungs, thymus, and heart (Bernard et al. 2003, Bouke et al. 1983, Hawkins et al. 1985). There is also accumulating evidence that cylindrospermopsin is carcinogenic (Falconer and Humpage 2001).

There are multiple reports of toxic C. raciborskii blooms occurring in aquaculture ponds in Australia and other tropic regions. This often results in bioaccumulation of cylindrospermopsin within the organisms intended for harvest and the economic loss of infected organisms. Such blooms also create a risk of the toxin getting into the human food market if not detected soon enough (Saker and Eaglesham 1999).

Furthermore, in areas outside of the Great Lakes, the overwhelming biomass of C. raciborskii blooms in association with the changes to the biodiversity of the system can negatively impact the natural value of the area (Leonard and Paerl 2005).

There is little or no evidence to support that Cylindrospermopsis raciborskii has significant beneficial effects in the Great Lakes.

Regulations (pertaining to the Great Lakes region)
There are no known regulations for this species.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control
Biological
There are no known organisms that can degrade cylindrospermopsin. However, several studies have found that a variety of unidentified bacteria degraded 100% of saxitoxin, another toxin produced by C. raciborskii (Donovan et al. 2008, Ho et al. 2012).

Physical
Cylindrospermopsis raciborskii blooms are often associated with a stratified water column, which is one of the reasons they are so prevalent in shallow water bodies with a long turnover period. A mechanical system can be used to create artificial destratification to increase vertical mixing, introduce oxygen, and reduce internal nutrient loading. The installation of a destratification mechanism was attempted in a reservoir in Australia. While there was a reduction in internal nutrient loading, the increased turbidity of the water yielded a competitive advantage for C. raciborskii, which can move throughout the water column to compete for light (Atenucci et al. 2005).

Cylindrospermopsin can be absorbed by activated carbon with high mesopor capacity, and nanofiltration may be another viable option, but not enough research has been done to be conclusive about the efficacy of either technique. Saxitoxins can be absorbed by activated carbons that have a large fraction of the pores that are smaller than 1 nm (Westrick 2010).

Chemical
Cylindrospermopsin can be inactivated by chlorine, ozone, and hydroxyl radical treatments. Saxitoxin can be inactivated by chlorine (Westrick 2010). However, the use of copper-based algicides may inhibit the degradation of cylindrospermopsin (Smith et al. 2008).

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.

Genetic similarities exist between strains of C. raciborskii from Australia and Europe, Africa and Australia, and North and South America (Dyble et al. 2002, Gugger et al. 2005). The relatively recent colonization of northerly latitudes in North America, including the Great Lakes, probably involves populations originally from South America (Gugger et al. 2005).