Phaeodactylum

Phaeodactylum (Phaeodactylum tricornutum) is a genus of diatom algae that can become a significant nuisance in managed agricultural water systems, such as hydroponics and recirculating aquaculture systems. While generally found in marine environments, when introduced into greenhouse settings, it acts as a bio-contaminant that disrupts cultivation parameters.

The causative agent is a unicellular diatom known for its metabolic versatility. It is not a classic parasite, but rather a biological competitor. It thrives in high-nutrient solutions, stealing essential minerals from crops and creating dense biofilms on piping, roots, and growing media, which effectively starves the cultivated plants.

Target crops include all vegetables grown in hydroponic set-ups, particularly leafy greens and herbs. The presence of the algae complicates the uptake of essential nutrients by roots, leading to stunted growth, nutrient deficiency symptoms, and in severe cases, plant decay due to the buildup of toxins or oxygen deprivation caused by the algal biofilm.

Symptoms of an outbreak include a noticeable change in nutrient solution color, slippery residue on roots, and the formation of dark green or brownish films on equipment surfaces. Propagation is primarily facilitated by light exposure in nutrient tanks and poor system hygiene, where spores can survive in reservoirs and pipe bends for long periods.

To protect agricultural systems, practitioners should implement robust management techniques:

• Ensure all nutrient reservoirs and delivery lines are opaque to prevent photosynthesis.
• Utilize high-intensity UV-C sterilizers within the water circulation loop.
• Implement routine cleaning and sanitation protocols using hydrogen peroxide-based cleaners.
• Periodically replace susceptible substrates and monitor water quality parameters rigorously.