Nannochloropsis

Nannochloropsis is a genus of unicellular microalgae often encountered in aquaculture and, occasionally, in hydroponic plant production. While it is not a traditional plant pathogen such as a fungus or a bacterium, it acts as a biological contaminant that can cause systemic issues in controlled environment agriculture, impacting overall crop health and system efficiency.

The nature of this issue is primarily competitive. Nannochloropsis thrives in nutrient-rich water under light exposure, effectively competing with crops for essential macro- and micronutrients. By dominating the nutrient solution, these microalgae disrupt the intended chemical balance, which is vital for optimal development of high-value greenhouse crops.

Crops most susceptible to these conditions are those cultivated via hydroponic or aeroponic techniques, such as leafy greens, herbs, and strawberries. In these systems, the presence of Nannochloropsis can quickly scale, leading to clogged irrigation emitters, fouled nutrient delivery lines, and a reduction in dissolved oxygen levels in the rhizosphere.

Symptoms of an overgrowth include a distinct green tint to the nutrient solution and the accumulation of greenish biofilm on growing media, root systems, and plumbing surfaces. Plants may show signs of chlorosis, stunted development, and reduced vigor, often exacerbated by the subsequent proliferation of anaerobic bacteria that feed on decaying algae.

Effective management and protection strategies include:

• Ensuring total light-tightness for all reservoirs and irrigation piping to prevent algal photosynthesis.
• Installing high-capacity UV sterilizers in the recirculation lines.
• Performing routine cleaning and disinfection of the system between production cycles.
• Monitoring nutrient solution parameters to ensure they remain optimized for the plants rather than the microalgae.