Spirulina subsalsa

Spirulina subsalsa is a filamentous cyanobacterium that is often categorized as a biological nuisance in agricultural water management systems. Unlike common fungal or viral pathogens, this organism functions as an opportunistic photoautotroph that thrives in aquatic environments rich in mineral nutrients.

The primary agricultural targets for this organism are rice paddies and irrigation infrastructure. While not a direct parasitic pathogen, its uncontrolled proliferation creates significant competition for light and nutrients, ultimately hindering the development of crop seedlings by covering the water surface with dense biological mats.

Symptoms of an infestation involve the visible appearance of dark green, slimy crusts or biofilms on the surface of flooded areas or moist soil. As the biomass decomposes, it can generate unpleasant odors and significantly decrease the dissolved oxygen levels, which is detrimental to the healthy root respiration of the plants.

The development of Spirulina subsalsa is driven by high solar radiation, warm water temperatures, and elevated levels of nitrogen and phosphorus (eutrophication). These conditions allow the cyanobacteria to rapidly multiply, creating extensive colonies that spread throughout the irrigation networks if not managed properly.

The economic impact involves reduced crop productivity and increased maintenance costs for irrigation systems. Effective protection and management practices include:

• improving water circulation to prevent stagnation;
• monitoring fertilizer application rates to limit nutrient runoff;
• applying approved algicides when infestation density exceeds threshold levels;
• periodic mechanical cleaning of distribution canals.