Chaetoceros tetrachaeta

The primary external sign of a high concentration of this species is a change in water clarity, which takes on a turbid, yellowish-brown, or greenish-brown hue.

In fish farms, the infestation manifests as atypical fish behavior: they begin to surface, showing signs of asphyxia despite sufficient dissolved oxygen levels.

Microscopic examination of water samples reveals characteristic chains of algae with sharp, rigid projections that are easily identified by their morphological structure.

Affected individuals exhibit increased mucus production in the gill filaments, which is a defensive response to mechanical irritation.

Visually, during mass development, the formation of dense flocs or mucous aggregates is observed, which settle on cage nets and filtration systems, impeding water exchange.

Chaetoceros tetrachaeta is a species of microscopic marine diatom algae belonging to the class Bacillariophyceae. This organism is unicellular but is capable of forming characteristic chains connected by thin, silicified projections known as setae.

This species is classified as a planktonic marine organism that plays a significant role in ocean ecosystems; however, in artificial water bodies or coastal farms, its excessive proliferation leads to pathological conditions.

Biologically, this pathogen is distinguished from other diatoms by the presence of four specific setae, which give it a unique morphology and allow it to remain effectively suspended in the water column.

Reproduction occurs primarily through cell division, which, under favorable conditions, leads to a rapid increase in population density within the water area.

Although Chaetoceros is not a parasite in the traditional sense, the mechanical impact of its silica shells on the gills of hydrobionts classifies it as a harmful agent in industrial fish farming.

The development of Chaetoceros tetrachaeta is directly dependent on water temperature, with an optimal range for outbreaks between 15 and 22 degrees Celsius.

A key factor in its spread is the excessive content of biogenic elements, such as phosphates and nitrogen compounds, resulting from uneaten food residues.

High solar radiation intensity significantly accelerates the algae's metabolism, promoting a rapid transition to the algal bloom stage.

Disruption of hydrodynamics and stagnant conditions in coastal zones or closed-loop water supply systems create an ideal environment for the localization and accumulation of this species' biomass.

Seasonal upwellings also play an important role, bringing nutrients from the depths to the surface and stimulating a sharp increase in the diatom population.

The primary harm consists of mechanical injury to the fish's gill apparatus by the sharp, rigid setae of the diatom shells, which leads to secondary bacterial infections.

Mass accumulations of algae physically block the gill slits, causing respiratory distress and subsequent mortality of young fish due to the inability to perform normal gas exchange.

During their lifecycle and subsequent decomposition, the algae release specific metabolites that negatively affect the appetite and general physiological state of the hydrobionts.

Disruption of technical filtration systems leads to economic losses associated with the need for urgent equipment maintenance and potential culling of part of the population.

In severe cases, the bloom triggers sharp fluctuations in water pH, which further stresses the cultured organisms and reduces their immunity against other diseases.

To prevent critical population growth, it is necessary to conduct regular monitoring of the phytoplankton composition and control nutrient levels in the water.

Optimizing feeding rations helps reduce the organic load, which limits the food supply for diatom development in cages.

• Installation of metered aeration systems to eliminate stagnant zones.
• Regular cleaning of netting from accumulated algae.
• Use of ultraviolet sterilizers in closed-loop water supply systems.
• Control of light intensity during peak solar activity periods.

The use of algicides is permissible only in extreme cases and with strict adherence to dosages to avoid harming the fish stock.

An important element of prevention is maintaining proper stocking density, as overcrowding contributes to the accumulation of metabolic products that nourish the algae.