Literature Review of the Microalga Prymnesium parvum and its Associated Toxicity
Sean Watson, Texas Parks and Wildlife Department, August 2001
Successful and Possible Control Methods
Moshe Shilo and Miriam Shilo (1953) noted that ammonium sulphate has a lytic effect on P. parvum. They found lytic activity to be a function of temperature in the range of 2 C-30 C with lytic activity increasing as temperature increases. The authors also found that lytic activity decreases dramatically when temperatures below 10 C are reached. The authors also discovered that the lytic activity of ammonium sulphate was a function of pH in the pH range of 6.5-9.5 with activity increasing as pH increases. They suggested that this shows that free ammonia, not the ammonium ion, is responsible for lysis. The addition of ammonia to water for control of P. parvum is also effective (Glass et al. 1991). The addition of ammonium sulphate or ammonia to contaminated water controls P. parvum in the following manner: trapping and concentration of the protonated ammonia ion in the P. parvum cell due to a pH difference between the inside and outside of the cell is followed by the entry of water, swelling and lysis (Shilo and Sarig 1989).
Unslaked lime (CaO) was found to reduce the amount of ammonium sulphate or ammonia needed for complete lysis by a factor of three; unslaked lime markedly enhances the effectiveness of ammonium sulphate and ammonia because it increases the pH of water when added (Shilo and Shilo 1953). However, ammonia and ammonium sulphate are counteracted by an increase in NaCl concentrations (McLaughlin 1958). Removal of fish from contaminated water and then placing the fish in non-contaminated water was found to reverse the gill permeability effect of the toxin (Glass et al. 1991).
Shilo and Aschner (1953) found that oxygen and air decrease toxicity when bubbled through a solution of the toxin. The authors also discerned that potassium permanganate and sodium hypochloride destroy toxicity. They also noted that adsorbents such as kaolin, Norit A (acid washed), activated charcoal, calcium sulphate and pond-bottom soils have also been shown to detoxify cultures of P. parvum. In addition, the authors observed that the bacteria Proteus vulgaris and Bacillus subtilis decreased the toxicity in cultures by 50% in one hour. Paster (1973) also revealed that Proteus vulgaris and Bacillus subtilis decreased toxicity of P. parvum cultures. Simonsen and Moestrup (1997) speculated that the C. polylepsis toxin decomposition in dark may be explained by bacterial activity, and the same may be true for the P. parvum toxin.
In Palestine, a 1:100,000 of copper sulphate was used to successfully control P. parvum (Reichenbach-Klinke 1973). Introduction of acetic acid and other weak electrolytes is reported to cause P. parvum cells to lyse (Glass et al. 1991). McLaughlin (1958) noted that organic algicides or lowering the pH decreases toxicity. Glass, Linam and Ralph (1991) noted that a pH less than 6 and greater than 9 reportedly inactivates the toxin. The authors added that increasing NaCl concentrations decreases toxicity probably by replacing a cofactor (Ca++ and/or Mg++) needed to activate the toxin. They also noted that UV and strong visible light have also been found to destroy prymnesin in lab. Nygaard and Tobiesen (1993) noted that P. parvum grazes bacteria when phosphate is limited. These authors believe that P. parvum utilizes certain species of bacteria when nutrients are limited. They suggested that the presence of these bacteria could decrease toxicity. Wynne and Rhee (1988) noted that detecting the activity of phosphatase in the water could be used to determine if the environment is limited in phosphate concentrations, and that this could be used to predict toxic blooms of P. parvum.
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