Prymnesium parvum is a species of haptophytes (= Prymnesiophyta). The species is of concern because of its ability to produce a toxin, prymnesin . It is a flagellated algae that is normally found suspended in the water column. It was first identified in North America in 1985 and was artificially (eg, invasive species or missed in previous surveys). Toxin production mainly kills fish and appears to have little effect on cattle or humans. This distinguishes it from red tide , which are algal bloom whose toxins lead to harmful effects in people. Although no harmful effects are known, it is recommended to consume dead or dying fish exposed to a P. parvumbloom. Prymnesium parvum of Haptophyta is sometimes termed a golden algae or a golden brown algae. Chrysophyceae of Heterokontophyta but the taxonomy of algae is under complex revision leading to contradictions in terms of non-scholarly texts such as those of state wildlife departments.
P. parvum grows in a salinity range of 0.5 – 30 psu (Practical salinity unit) with an optimum at 15 psu while strains collected in different places appear to have different salinity tolerances. A strain called LB 2797 (isolated from Colorado River in Texas) shows a biphasic growth pattern, that is, maximum cell densities increased to 5 to 15 psu but decreased at higher levels in laboratory culture.  The alga produces dimethylsulfoniopropionate (DMSP) and other unknown polyols , which is susceptible to adaptation to osmoregulation . The environment must be between 2 ° C (36 ° F) and 30 ° C (86 ° F) for P. parvum to live. Growth at a pHof as low as 5.8. The organism prefers highly light environments, but growth can be inhibited by excessive light ( photoinhibition ). The organism is capable of heterotrophic growth in the dark in the presence of glycerol and grazes on bacteria, especially when phosphate is limited. It has therefore been hypothesized that P. parvum satisfies its phosphate needs by. P. parvum can use a wide-range of nitrogen sources, Including ammonium , nitrate , amino acids (qui ones Apparently depends of pH), creatine, but is unable to use urea .
New evidence has shown that these toxins are produced by physiological stresses, such as nitrogen and phosphorus depletion due to competition with the environment.
- Jump up^ Rashel, Rakib H; Patiño, Reynaldo (2017). “Influence of genetic background, salinity, and inoculum size on the ichthyotoxic golden alga ( Prymnesium parvum )”. Harmful Algae . 66 : 97-104. doi : 10.1016 / j.hal.2017.05.010 . PMID 28602258 .