Omega-3 Rich Phytoplankton: Feeding Zooplankton While Removing Nitrogen and Phosphate

At Hydralife Solutions, we grow the microscopic organisms that form the foundation of healthy aquatic ecosystems. This article covers one of the species in our blend, a freshwater green microalga that does two jobs at once: it strips excess nutrients out of the water column, and it feeds the zooplankton that carry that energy up the food web.

One of the green microalgae species in our blend.

A Biological Filter: Nutrient Uptake Capabilities

In bioremediation terms, this species functions as a highly efficient biological filter, actively removing excess nutrients from the water column and reducing what remains available to cyanobacteria and nuisance algae. That makes it valuable both for managing water quality and for slowing eutrophication.

Nitrogen Consumption

This species takes up all three major inorganic nitrogen forms:

Ammonia (NH₃/NH₄⁺): This is the preferred nitrogen source, because assimilating it costs the cell the least energy. Published work on comparable freshwater green microalgae shows uptake rates of 0.05 to 0.15 grams of ammonia per gram of biomass per day under optimal conditions. The cell absorbs ammonia straight out of the water column and routes it into amino acids and proteins.

Nitrite (NO₂⁻): Nitrite is less commonly available in healthy systems, but this species will use it, at lower rates than ammonia. That matters in water bodies where nitrification is actively underway, such as golf course irrigation ponds fed by effluent.

Nitrate (NO₃⁻): As the most oxidized form of inorganic nitrogen, nitrate costs more cellular energy to assimilate, but this species uses it readily when it is there. Uptake rates for comparable freshwater green microalgae typically run 0.03 to 0.10 grams of nitrate per gram of biomass per day, depending on light, temperature, and other conditions.

Total nitrogen removal can be substantial. Under ideal growth conditions a healthy population removes 20 to 40 milligrams of total nitrogen per liter of culture per day, which is what makes this species a strong bioremediation candidate.

Phosphorus Uptake

Phosphorus, mostly as orthophosphate (PO₄³⁻), is the other nutrient this species pulls efficiently out of the water:

Uptake Rates: Species of this type typically show phosphorus uptake rates of 0.01 to 0.03 grams per gram of biomass per day. That looks modest next to nitrogen, but algae need far less phosphorus; typical N:P ratios sit around 16:1 (the Redfield ratio).

Luxury Uptake: This species performs luxury consumption of phosphorus, storing excess phosphate internally as polyphosphate granules when concentrations are high. That stored phosphorus then supports growth after the water column runs short, which is exactly the window in which cyanobacteria would otherwise take over.

Water Quality Impact: Even modest populations bring phosphate down from problematic levels (above 0.05 mg/L) to levels that limit harmful algae blooms, cyanobacteria in particular.

A Nutritional Goldmine for Zooplankton

This species is more than another green alga in the water column. It is an exceptional food source for zooplankton, the small animals that link primary producers to everything above them in the food web.

What makes it so nutritionally valuable is cellular composition, which is rich in exactly the compounds zooplankton need:

Protein Content: This species carries 40 to 50 percent protein by dry weight, supplying the essential amino acids that support zooplankton growth and reproduction.

Lipid Profile: Most important, this species carries high levels of polyunsaturated fatty acids, including the omega-3 eicosapentaenoic acid (EPA). Those long-chain fatty acids drive zooplankton development and reproduction, and most zooplankton cannot synthesize them; they have to eat them.

Vitamins and Minerals: The cells also supply essential vitamins and trace minerals that support metabolic function in the animals grazing on them.

Digestibility: Small cells and a relatively thin cell wall mean a wide range of grazers can eat and digest this species, from rotifers to copepods.

The Bottom Line

This species is a good example of how efficient natural systems already are. One organism handles two problems at once: it delivers high-value nutrition at the base of the food web, and it works as a biological filter on the excess nutrients that would otherwise feed a bloom. Selecting and growing species with that combination of traits is the whole basis of our approach to water quality management.

At Hydralife Solutions, we work with the organisms already present in freshwater rather than against them. This species is one example of how microscopic organisms produce macroscopic changes in water quality and ecosystem health.

For more on the species in our blend and how they work, visit www.hydralife.org.