Common name: Nannochloropsis oculata

General Information

Nannochloropsis oculata is a microalgae belonging to the class Eustigmatophyceae. This species is a popular choice among aquarists and marine biologists due to its high nutritional value and ease of cultivation. It is often used in aquaculture as a food source for rotifers and other small marine organisms, making it an essential component in the rearing of fish larvae and invertebrates.

Despite its microscopic size, Nannochloropsis oculata plays a significant role in hobbyist and commercial aquaculture settings. It is renowned for its high lipid content, especially omega-3 fatty acids, which are beneficial for the growth and development of marine species. Its ability to thrive in various environmental conditions makes it a versatile and reliable food source.

Care

Caring for Nannochloropsis oculata involves maintaining optimal growth conditions in terms of light, nutrients, and water quality. It thrives under moderate to high light conditions and requires a nutrient-rich environment to maximize its growth rate. Regular monitoring of water parameters ensures a healthy culture, which in turn supports the nutritional quality of the algae.

This microalgae is often cultured in dedicated tanks or reactors where conditions such as pH, salinity, and temperature are carefully controlled. An ideal setup includes a nutrient medium rich in nitrogen and phosphorus, along with a consistent light source to promote photosynthesis.

Behavior and Compatibility

Nannochloropsis oculata is non-toxic and poses no threat to other marine life, making it an ideal addition to aquaculture systems. It is compatible with a wide range of marine organisms, particularly those that feed on phytoplankton. This species is non-motile, meaning it relies on water movement for distribution rather than active movement.

Cultivation

Cultivating Nannochloropsis oculata involves creating the ideal conditions for its growth, which requires careful attention to various environmental parameters. The following steps provide a detailed guide to cultivating this microalgae successfully.

Nannochloropsis oculata thrives under moderate to high light conditions, ideally between 2000 to 5000 lux, for 16-18 hours per day. Consistent lighting and nutrient availability are critical to support healthy growth and photosynthesis. The optimal temperature for cultivating this species is between 20-24°C, or around room temperature.

The ideal salinity for Nannochloropsis oculata is between 25-35 ppt, which mimics its natural marine environment. The pH should be maintained between 7.5 and 8.5. Regular monitoring of salinity and pH levels helps ensure that the culture remains within the optimal range for growth.

Aeration is vital for keeping the algae suspended and ensuring that nutrients and carbon dioxide are evenly distributed throughout the culture. Continuous aeration using an air pump is recommended to prevent settling and promote gas exchange, which maintains consistent oxygen levels. While CO2 injection can support better growth, it is not required in a typical home setup.

Under optimal conditions, Nannochloropsis oculata has a rapid growth rate and can double its population within 1-2 days. Harvesting can begin once the culture reaches a dense, dark green color, indicating a high concentration of cells. Typically, harvesting is done by removing a portion of the culture while leaving enough algae to continue growing. The removed portion can be used as feed or stored for later use.

Cultures of Nannochloropsis oculata can be refrigerated to extend their viability when not in active use, which helps to maintain a backup culture in case of contamination or other issues.

Maintaining a pure monoculture is one of the most challenging aspects of cultivating Nannochloropsis oculata, especially in non-laboratory environments. To prevent cross contamination, use sterile equipment, regularly clean cultivation tanks, and minimize exposure to open air. Filtering incoming water and sterilizing all tools before use can also reduce the risk of contamination by other microorganisms.

To measure culture density, a Secchi stick, which features a visible target at the end that is submerged into the culture, can be used. This simple tool helps to determine the density based on how far it can be submerged while remaining visible.

Cultivators can enhance growth rates by providing sufficient light, nutrients, and carbon dioxide. Regular monitoring and maintaining stable conditions are key to ensuring a successful and productive culture. Fertilizers like Guillard's F/2 are commonly used to provide essential nutrients, including nitrogen and phosphorus, to support healthy growth. Cultivators can enhance growth rates by ensuring the algae have access to sufficient light and nutrients.

Common Issues

While Nannochloropsis oculata is generally resilient, it can be susceptible to contamination by other microorganisms, which may outcompete it for resources. Maintaining a sterile monoculture environment and monitoring for signs of contamination are crucial steps in preventing such issues. It can be particularly challenging to maintain a monoculture in non-laboratory environments, where external factors are harder to control.

Habitat

In the wild, Nannochloropsis oculata is found in marine and brackish environments. It thrives in nutrient-rich waters where it can form dense blooms. Its natural habitat includes coastal waters and estuaries where it contributes to the marine food web.