Coscinodiscus wailesii

Coscinodiscus wailesii is a large marine centric diatom species that is recognized as a significant agent in causing harmful algal blooms within marine environments. While not a disease of land plants, it is considered a biological hazard in aquaculture, where its excessive growth disrupts ecosystem stability.

The causative agent is a single-celled organism known for its large size and capacity to rapidly sequester nutrients. Its presence is most problematic due to the heavy secretion of extracellular mucus, which can coat surfaces and biological tissues, interfering with the physiological functions of marine animals.

This species affects marine aquaculture sites, particularly those involved in shellfish and fish farming. The accumulation of its biomass and the resulting mucus production can physically clog filtration systems and the gills of aquatic organisms, leading to reduced growth rates and increased mortality.

Symptoms of an infestation include a visible decrease in water clarity and the formation of a dense, gelatinous film on nets, cages, and substrates. A secondary effect is the potential for local hypoxia, which occurs when the massive bloom collapses and the bacterial decomposition consumes the available oxygen.

Development is driven by nutrient enrichment in coastal waters and specific water temperature regimes. Protection and prevention strategies include regular water quality monitoring, reducing nutrient discharge into farming areas, and frequent cleaning of aquaculture infrastructure to manage the build-up of the diatom's mucus.