Prymnesium parvum toxic blooms: toxin use in allelopathy and predation and how conservation can help aquatic populations

Golden alga, Prymnesium parvum, has become a rising concern in terms of conservation. This is due to the toxic blooms they create that kill populations of fish and phytoplankton. P. parvum produce prymnesin toxins, which cause the blooms to be so dangerous. Previous research has claimed that prymnesins lyse cells and toxify other cells, neurons and fish. Specifically, the toxins have been shown to cause ion leakage due to the damage done to cell membranes. Further investigation has provided understanding into the correlation P. parvum toxin has with the acclimation of inorganic phosphorus and nitrogen at the genomic level. Of the 23 genes already identified in P. parvum, three genes associated with phosphorus transport indicate phosphorus deficiencies. Nutrient limitations have aided in the characterization of compounds within P. parvum toxins. Specifically, seven fatty acids in addition to a hydroxamic acid have been identified among all the toxic compounds that are ichthytoxic and cytotoxic. Further research has delved deeper into the types of prymnesin toxins. Specifically, polyketides prymnesin-1 and prymnesin-2 were identified via liquid chromatography and mass spectrometry. P. parvum toxins have been identified to play a role in micro-predation that is different from allelopathy. Factors that alter the levels of toxicity in P. parvum have been under study as well. Sunlight has proven to reduce the levels of toxicity in cells with increased exposure in terms of time and magnitude. This leads to the idea that fish population survival depends on where the toxic blooms occur. Fish populations in the Colorado River and the Brazos River in Texas have shown evidence of fish population decline due to toxic P. parvum blooms. However, the location of the river correlates with aquatic life survival. Specific conservation acts have used ammonium successfully to reduce toxic P. parvum blooms. Others have attempted to add inorganic nitrogen and phosphorus plus cornseed meal to the blooms, but this attempt caused the increase in pH levels. Thus far, research has made great strides in understanding P. parvum and prymnesins at [email protected] 2 the genomic, molecular, and organism level, which in turn has aided in understanding of how to control the toxic blooms. Introduction Prymnesium parvum is an alga species belonging to the division Haptophyta, which is in the class Prymnesiophycea (Graneli et al. 260). This alga is unicellular and is primarily immobile (Graneli et al. 261). P. parvum has two flagella used for movement and a haptonema used to attach to surfaces (Graneli et al. 261). The haptonema has also been thought to secrete chemicals (“Prymnesins: Toxic” 679). P. parvum live all over the world with the exception of Antarctica (Graneli et al. 260). They are mixotrophic and release chemicals into the surrounding waters, which produces a slew of toxic events (Graneli et al. 260) Internal concentrations of inorganic nutrients nitrogen, phosphorus, and carbon vary depending on if the surrounding environment is nutrient replete or deficient (Graneli et al. 261). It is typically observed that under nutrient deficient conditions, toxic algal blooms that appear golden and result in massive fish and gilledorganism mortalities occur (Graneli et al. 260). These toxic blooms are caused by chemicals that are “hemolytic to other organisms” and “inhibit growth or kill competing phytoplankton species” (Graneli et al. 261). Harmful algal blooms occur most frequently in “cooler waters located in the subtropical and temperate zones”, although events have occurred in “mainland fresh water reservoirs” (Manning and Claire 679). The blooms generally occur 5 m from the surface (VanLandeghem 582) and an average toxic bloom produced by P. parvum is about 1000000 cells/mL water (Remmel and Hambright 126). In addition to organism mortalities, these blooms are creating eutrophication and excessive demands on the supply of freshwater (VanLandeghem