Alexandrium catenella

Alexandrium catenella is a species of toxic marine dinoflagellates known for causing harmful algal blooms (HABs). In the context of aquaculture management, this organism is considered a severe biological threat, as it produces potent neurotoxins that infiltrate the marine food chain and jeopardize public health.

The causative agent is a unicellular eukaryotic organism. The resulting "disease" in commercial shellfish is known as biotoxin accumulation, specifically leading to Paralytic Shellfish Poisoning (PSP) in consumers. The toxins, primarily saxitoxins, block sodium channels in nerve cells, which can have fatal consequences for humans and marine wildlife.

This organism primarily affects bivalve mollusks, such as mussels, clams, oysters, and scallops. These animals are filter feeders that ingest Alexandrium cells from the water column. The toxins do not kill the shellfish but accumulate in their tissues, turning a valuable food product into a hazardous substance.

Development and spread are triggered by environmental shifts. Ideal conditions involve high concentrations of nitrogen and phosphorus (often from agricultural runoff), optimal water temperatures, and stable stratification of the water column. The organism's cysts can remain dormant in seafloor sediments for years, serving as a reservoir for future outbreaks when conditions become favorable.

Control and prevention strategies are essential for the aquaculture industry. Management protocols involve strict water quality monitoring programs that detect the presence of Alexandrium before it reaches high densities. In addition, chemical assays of shellfish tissues are mandatory before harvesting to ensure the levels of accumulated toxins remain within safe human consumption limits defined by international regulatory standards.