Natural algicides

There are studies that indicate a particular mode of action as a natural algicide, without elucidating that it is a primary site. For example, Kida [140,141] reported that the Streptomyces purpeofuscus product 7-deoxy-D-glycero-D-glucoheptose inhibited chlorophyll synthesis in the green alga Scenedesmus obliquus. Yet, only chlorophyll accumulation was measured. Phytotoxins with many other sites of action could cause a similar effect. 

Efficacy Testing of Natural Algicides in Freshwater Ecosystems... 

Until recently, there has been limited research to discover natural and natural product-based algicides as alternatives to the compounds currently... 

ALGICIDE. A substance, natural or synthetic, used for destroying or controlling algae. The term is also sometimes used to describe chemicals used for contiolling aquatic vegetation, although these materials ate more properly classified as aquatic herbicides. See Herbicides. 

The unacceptable risks that synthetic herbicides pose to the environment and human health prevent their approval for use in drinking water supply systems and aquaculture ponds. The discovery of environmentally safe compounds that have a greater degree of toxic selectivity towards noxious species of cyanobacteria than copper algicides currently available would greatly benefit commercial aquaculturists and municipal drinking water suppliers and consumers. The use of natural products to selectively control cyanobacteria is desirable due to environmental safety issues and consumers negative perceptions of the use of synthetic compounds (herbicides). 

The solubility of copper in natural waters in acid media is limited by the solubility of the alkaline carbonate, malachite Cu2(0H)2C03, and in the alkaline media by the solubility of Cu(OH)2. However, it depends on the concentration of hydrogen carbonates. Depending on pH and hydrogen carbonates, only limited quantities of copper can be kept in the soluble form, this being of practical importance for the evaluation of its algicidal effects in reservoirs. 

Schrader, K.K. Natural-based algicides with potential use in catflsh aquaculture. World Aquaculture, 37(4), 35, 2006. 

---