Chaetoceros tetrachaeta

Chaetoceros tetrachaeta is a species of marine diatom that acts as a significant hazard in aquaculture systems. While not a conventional plant disease, its presence in high densities poses a severe biological threat to farmed fish populations by causing extensive physical damage to their respiratory organs.

The primary mechanism of harm is mechanical. These diatoms possess long, sharp spines that become lodged in the gill filaments of fish as they respire. This penetration causes acute irritation, inflammation, and cellular destruction, leaving the gills vulnerable to secondary opportunistic pathogens and severely impairing the fish's oxygen exchange capacity.

This biological hazard affects various species cultivated in marine or brackish water environments. The susceptibility is highest in high-density farming operations where fish cannot escape the bloom areas. Salmonids and other marine finfish are particularly prone to these injuries, often resulting in high mortality rates during bloom events.

Development and spread are heavily dependent on environmental conditions, particularly nutrient enrichment (eutrophication) and rising water temperatures. Under favorable conditions, this diatom can undergo rapid proliferation, turning the water into an abrasive suspension that is lethal to fish stocks within a matter of days.

Effective management and prevention strategies are essential for maintaining farm profitability:

• Implement proactive phytoplankton monitoring programs to detect early signs of a bloom.
• Utilize deep-water pumping systems to bypass surface-level bloom concentrations.
• Reduce stocking density and stop feeding during intense bloom events to minimize metabolic stress.
• Establish contingency plans for emergency harvesting or relocating cages to cleaner water zones.