Phytoplankton vs Spirulina

These two sit next to each other on health shop shelves so often that people assume they are variations on the same thing. They are not even in the same biological kingdom. Marine phytoplankton (specifically Nannochloropsis) is a true eukaryotic microalga. Spirulina (Arthrospira platensis) is a prokaryotic cyanobacterium. Calling them both "algae" is taxonomically sloppy, and it leads people to assume they do the same job. They do not.

They Are Not Even in the Same Biological Kingdom

Nannochloropsis is a eukaryotic microalga: a true algae with a nucleus, chloroplasts, and a cell membrane. Spirulina (Arthrospira platensis) is a prokaryotic cyanobacterium: it photosynthesises but has no nucleus and is structurally closer to bacteria than to plants. The supplement industry groups them together under "algae" for convenience, but the biology, the nutrient profiles, and the cultivation requirements are different.

This matters because the differences are not minor variations within a category. They are fundamental distinctions that determine what each organism can and cannot provide nutritionally.

The Omega-3 Divide Between Phytoplankton and Spirulina

This is the difference that should drive your decision if omega-3 matters to you. Nannochloropsis produces EPA at concentrations that make it one of the richest plant-based sources of this fatty acid. We chose it for ULTANA specifically for this reason.

Spirulina produces essentially none: no EPA, no DHA, and negligible ALA. If you are taking spirulina hoping it covers your omega-3 needs, it does not, and no amount of marketing language about "complete nutrition" changes that. Spirulina has many genuine strengths, but omega-3 is not among them.

Where Spirulina Genuinely Wins Over Phytoplankton

Protein density is spirulina's standout advantage, at 55 to 70 per cent protein by dry weight compared to Nannochloropsis at 30 to 45 per cent. At supplement doses of 3 to 5 grams, neither delivers a meaningful absolute protein hit, but spirulina's amino acid density per gram is legitimately impressive.

Phycocyanin is a blue-green pigment unique to cyanobacteria with documented antioxidant properties. It is the reason spirulina has its distinctive colour. Neither phytoplankton nor chlorella contains it. If phycocyanin specifically interests you, spirulina is the only option.

Digestibility also favours spirulina. It lacks the tough cellulose cell wall that makes chlorella hard to digest without processing. Its cell membrane is more easily broken down by your digestive system, meaning the nutrients are accessible without additional processing steps.

Where Phytoplankton Genuinely Wins Over Spirulina

EPA omega-3 is the clearest advantage, with no contest between the two. Nannochloropsis delivers it and spirulina does not.

Carotenoid diversity is another area where phytoplankton excels. Nannochloropsis produces violaxanthin, vaucheriaxanthin, and beta-carotene, carotenoids less commonly found in terrestrial foods that provide a different antioxidant profile from spirulina's phycocyanin.

Cultivation purity tends to favour phytoplankton products grown in closed photobioreactors. Most commercial spirulina is grown in open-pond systems, which introduces environmental exposure risks. This is not a universal rule, but it is a common enough pattern to check for. We covered the contamination question in our heavy metals guide.

What Neither Spirulina Nor Phytoplankton Does

Neither spirulina nor phytoplankton has EFSA-authorised health claims for immune support, detoxification, anti-ageing, or energy enhancement. Both are marketed with these claims routinely, and both sets of claims are unsupported at the regulatory level. We do not make any of these claims for our own products.

The EFSA-authorised claims that do apply to phytoplankton relate to its EPA content: EPA and DHA contribute to the normal function of the heart at 250mg combined daily (Commission Regulation EU No 432/2012). Spirulina has no equivalent EFSA-authorised health claims at standard supplement doses.

Phytoplankton vs Spirulina FAQs

Does spirulina contain omega-3?

Not in any meaningful amount. Published fatty acid analyses show negligible EPA, DHA, and ALA in Arthrospira platensis. If you need plant-based omega-3, spirulina cannot provide it. Phytoplankton from Nannochloropsis is the direct source for EPA.

Is spirulina or phytoplankton better for protein?

Spirulina is denser at 55 to 70 per cent protein by dry weight versus 30 to 45 per cent for Nannochloropsis. At typical supplement doses of 3 to 5 grams, neither provides a large absolute protein contribution, but spirulina delivers more per gram.

Are spirulina and phytoplankton the same thing?

No. They are not even in the same biological kingdom. Spirulina is a prokaryotic cyanobacterium. Phytoplankton (Nannochloropsis) is a eukaryotic microalga. They are grouped under "algae" for retail convenience, but their biology, nutrient profiles, and production methods differ substantially.

Can I take both spirulina and phytoplankton together?

Yes. Their nutrient profiles complement rather than duplicate each other. Phytoplankton provides EPA and distinctive carotenoids. Spirulina provides higher protein density and phycocyanin. Taking both covers a broader range of nutrients than either alone.

Why does Phytality sell phytoplankton but not spirulina?

We specialise in organisms we grow ourselves in controlled environments. Our expertise is in Nannochloropsis cultivation in closed photobioreactors. Spirulina is a valuable organism, but it is not one we currently cultivate, and we prefer to sell products from supply chains we control directly.

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Consult your GP or a qualified healthcare professional before starting any supplement.

Methodology and Disclosure

Nannochloropsis composition cites Zanella and Vianello 2020 (J Funct Foods). Spirulina biology and cultivation cites Furmaniak et al. 2017 (Front Microbiol). EFSA health claims cite Commission Regulation (EU) No 432/2012. Protein and fatty acid comparisons reflect published compositional data for both species.

Vendor disclosure: Phytality manufactures phytoplankton (ULTANA) supplements and does not currently sell a standalone spirulina product. This commercial position has been declared. Spirulina's genuine advantages (protein density, phycocyanin, digestibility) have been stated directly.