Prymnesium parvum f. patelliferum, Prymnesium parvum f. parvum (J.C. Green, D.J. Hibberd & R.N. Pienaar)

Yellow-copper or copper-brown colored water may be indicative of a P. parvum bloom. Blooms have also been reported to produce white foam on the water’s surface.

P. parvum has a sexual haploid-diploid life cycle with four forms, 3 motile and one resting cyst form that may serve as a way to reseed populations following unfavorable conditions (Garcés et al. 2001; Granéli et al. 2012). It’s maximum growth rate ranges from 0.3 to at least 1.15 cell division per day via mitosis, increasing as environmental conditions become more favorable (e.g. moderate salinity and temperatures) (Larsen et al. 1998).

It is mixotrophic, supporting its growth with autotrophy (photosynthesis) or heterotrophy if nutrients are scarce (typically during a bloom event) (Fistarol et al. 2003; Tillmann 2003; Granéli and Johansson, 2003a). During a P. parvum bloom when toxin concentrations are high enough to lyse the cells of zooplankton and other phytoplankton, P. parvum can consume them by phagotrophy and absorb the recently released dissolved organic material by saprophy, effectively resisting potential inorganic nutrient limitation from their rapid growth (Granéli et al. 2012; Roelke et al. 2016). As competition is reduced, P. parvum blooms can grow and begin to produce toxin concentrations capable of killing larger organisms, including fish and invertebrates (Ultizer and Shilo 1966; Ulitzer 1973;  Granéli et al. 2012; Svendsen et al. 2018). A few grazers, including some ciliates, rotifers, and dinoflagellates, do consume P. parvum but only when it is not in bloom or producing toxins (Tillman 2003; Rosetta and McManus 2003; Schwierzke et al. 2010).

A genetic analysis of U.S. P. parvum strains from northern and southern states revealed that their DNA sequences were more similar to various European strains than to each other, indicating that invasions may have been independent and relatively recent (Lutz-Carrillo et al. 2010).  These transoceanic, long-distance invasions are hypothesized to be facilitated by air and ocean currents and by ballast water and global trade of aquaculture (Hallegraeff and Gollasch 2006).  Local dispersal is attributed to transportation by birds, wind, and anthropogenic movement (drilling equipment, water tankers, and recreational boats) (Kristiansen 1996; Renner 2009).

Potential pathway(s) of introduction: Dispersed wind, Hitch hiker on waterfowl, Shipping ballast water.

Prymnesium parvum has a moderate probability of establishment if introduced to the Great Lakes (Confidence level: High).

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

Environmental	Socioeconomic	Beneficial

Blooms of P. parvum are capable of producing concentrations of chemicals that can suppress the growth or kill competing phytoplankton and predatory zooplankton (e.g. Harpacticus sp. and Daphnia magna) (Fistarol et al. 2003, 2005; Granéli and Johansson 2003a; Roelke et al. 2007; Errera et al, 2008; Brooks et al. 2010). Zooplankton abundance was decreased within 48 hours of exposure to P. parvum and community composition was shifted to be copepod dominated which may have substantial food web consequences (Witt et al. 2019). Presence of P. parvum increases carbon transfer through the microbial loop which boosts dissolved organic carbon and bacterial biomass - which are food sources for P. parvum (Uronen et al. 2007). P. parvum also produces a wide range of ichthyotoxic compounds, including prynmnesens (Igarashi et al. 1996, 1999; Rasumussen et al. 2016), fatty acids (Henrikson et al. 2010), and fatty acid amides (Bertin et al. 2012a,b), which damage gill membranes in fish, tadpoles, bivalves, and crayfish (Ultizer and Shilo 1966; Ulitzer 1973;  Granéli et al. 2012; Svendsen et al. 2018) and have hemolytic and anticoagulant effects (Binford et al. 1973; Doig and Martin 1973; Schug et al. 2010; Skingel et al. 2010). Mortality likely occurs once sufficient gill tissue is destroyed (Ulitzur and Shilo 1966; Remmel and Hambright 2012). At least 153 fish kill events impacting eight native species due to P. parvum have been recorded in Texas between 1981-2008 (Southard et al. 2010). Dunkard Creek in Pennsylvania also experienced a major fish kill following a spike in salinity from the release of mining waste, with P. parvum wiping out 18 fish and 14 freshwater mussel species (Renner 2009). Sustained declines of the relative size and/or abundance of nine fish species in recently depleted reservoirs of the Upper Colorado and Brazos Rivers were attributed to toxic P. parvum blooms in 2001 (VanLandeghem et al. 2013). Both the Dunkard Creek and Colorado and Brazos River P. parvum blooms occurred in typically freshwater systems that would not support toxin production, however, its cysts can lie dormant and bloom without warning once favorable conditions occur (e.g. salinity levels) (Genitsaris et al. 2009).

Presence of P. parvum compounds the mortality effects of viral hemorrhagic septicemia virus by 50% in Oncorhynchus mykiss (Rainbow Trout) when compared to the virus alone (Andersen et al. 2016).

Prymnesium parvum has the potential for high socioeconomic impact if introduced to the Great Lakes.

Fish kills from P. parvum toxicity is a major source of economic impact. As of 2010, P. parvum was responsible for the death of over 34 million fish in 33 waterbodies in Texas with an estimated value of US$13 million. Numerous Texas sport fisheries have also been severely affected, and economic losses in three counties surrounding an infested lake over two years were estimated at US$3.9 million (Southard et al., 2010). Further, infested lakes are unsightly and can be toxic to humans and can reduce recreation, tourism, and fishing (Glass 2003). Management and control are also very costly, especially in large water bodies (Roelke et al. 2016).

There is little or no evidence to support that Prymnesium parvum has the potential for significant beneficial impacts if introduced to the Great Lakes.

P. parvum cells have a high lipid content and may be useful in the production of biofuel (Ng et al. 2015).

Prohibited in Wisconsin under is. Admin. Code § NR 40. In New York,  P. parvum is prohibited and cannot be knowingly possessed, sold, imported, purchased, introduced, or propagated under 6 NYCRR Part 575. Explicit regulations are not defined for P. parvum in Michigan, Minnesota, Illinois, Indiana, Ohio, Pennsylvania, or Ontario.
Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control

Biological
Nonindigenous Arundo donax (giant reed) contains growth-suppressing and algicidal compounds that reduced the exponential growth rate of P. parvum (Patino et al. 2018). P. parvum blooms are suppressed by cyanobacteria presence (Roelke et al. 2010a, 2012) and the cyanotoxins microcystin and nodularin inhibit P. parvum growth (Pflugmacher 2002; Legrand et al. 2003; James et al. 2011)

Physical
Aquaculture facilities that experience P. parvum blooms have used flocculation with various mediums, including soil, sand, and clay mixtures to directly settle P. parvum cells (Sengco and Anderson 2004; Padilla et al. 2010), bind phosphate ions to reduce nutrient loads and P. parvum bloom potential (Chen and Pan 2012; Seger et al. 2015), and to remove algal toxins from the water (Prochazka et al. 2010; Seger et al. 2015). Most clays could efficiently remove >80% of P. parvum cells, however, only bentonite clays and a lanthanum based bentonite clay reduced toxin availability and ichthyotoxicity (Seger et al. 2015).  A commerical oil absorbant sponge, typically used to remove petroleum hydrocarbons from stormwater, successfully removed 87-100% of P. parvum cells. However, algal toxins were released during filtration with the lanthanum based clay but were mediated by the addition of a charcoal filter (Armstead et al. 2017). Physical control via flocculation is successful in aquaculture but may have limited effects in natural environments depending on treatment and bloom specific conditions (Sengco et al. 2005).

Allelopathic chemicals produced by P. parvum were degraded in a few hours with light as low as 100 μE m2 s1 (Granéli and Salomon 2010) and two hours of exposure to UV light was shown to deteriorate toxins enough to prevent acute ichthyotoxicity (James et al. 2011). While effective, light treatment may be a useful control strategy in site-specific conditions but is costly on a large scale.

High flow events and intentional dilutions of bloom-containing waters can cause unfavorable bloom conditions for P. parvum by reducing salinity and ambient toxin concentrations, altering nutrient concentrations, and hydraulic displacement (Roelke et al. 2007, 2016; Errera et al. 2008; Hambright et al. 2010). Flooding infested waters with a hydraulic dilution reduced toxin production and increased zooplankton biomass by 225 times whose grazing reduced P. parvum’s reproduction and density by 52% (Schwierzke-Wade et al. 2011). Further, a large inflow event in Lake Granbury, Texas reduced P. parvum densities by 89% and completely negated any ichthyotoxicity (Roelke et al. 2010b). While hydraulic dilutions and flood events can effectively control harmful blooms after they’ve started, they are difficult to manipulate on a whole-lake scale.

Chemical
In aquaculture, ammonium sulfate and copper-based algaecides lysed P. parvum cells and potassium permanganate lowered toxicity (Barkoh et al. 2003, 2010, Rodgers et al. 2010; Umphres IV et. al 2012; Grover et al. 2013). However, these chemicals are broad-spectrum, and can harm or kill non-target organisms and can have unintended side-effects (e.g. ammonium additions may raise ammonia concentrations to harmful levels for fish) (Barkoh et al. 2003; Rodgers et al. 2010). A commercial peroxidizing aquatic herbicide suppressed P. parvum bloom formation but did not negatively impact Lepomis macrochirus (bluegill sunfish), making it a potentially safe and effective chemical control alternative (Umphres IV et al. 2012, 2013). Alternatively, P. parvum has demonstrated resistance to commercial peroxidzing agricultural herbicides and their use may give it a competitive advantage over other phytoplankton (Yates and Rogers 2011, Flood and Burkholder 2018). Glyphosate-based herbicides can also stimulate P. parvum growth in environmentally relevant concentrations, giving it a potential competitive advantage in water bodies surrounded by agriculture (Dabney and Patino 2018).

Nutrient additions (phosphorus and nitrogen) can also suppress P. parvum toxin production and growth and promote the dominance of native phytoplankton (Kurten et al. 2011).  Both nitrogen (ammonia or nitrate) and phosphorus need to be added to achieve P. parvum suppression, as fertilization with only one has no effect and adding phosphorus alone can even increase P. parvum growth and toxicity (Kurten et al. 2010). However, excess nutrients can cause pH and dissolved oxygen problems and nitrogen additions using ammonia can lead to harmful concentrations and unhealthy pH levels (Barkoh et al. 2003; Kurten et al. 2007, 2011). Recommended fertilization rates for systems where high pH is a concern is 117 μg NO3-N ⁄l plus 16 μg PO4-P ⁄l applied three times weekly (Kurten et al. 2010).

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