ARS Algae Dichotomous Key
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<h3>Not sure?</h3>
<div>Try these quick checks under normal light:</div>
<div class="metaLine">• Spiral/coil filaments → <b>Arthrospira</b> (Spirulina)</div>
<div class="metaLine">• Many small green spheres, fairly uniform → <b>Chlorella</b></div>
<div class="actionRow">[[Back to Q6->Q6]] <span class="sep">|</span> [[Start over->Start]]</div>
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<div><b>Q2:</b> Is the organism very large (hundreds of micrometers to millimeters), single-celled, and elongated/cigar-shaped?</div>
<div class="actionRow">[[Yes->Result Pyrocystis]] <span class="sep">|</span> [[No (small, round/oval)->Q3]] <span class="sep">|</span> [[Back->Start]]</div>
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<div><b>Q3:</b> Does the organism appear reddish or pinkish under normal light?</div>
<div class="actionRow">[[Yes->Result Porphyridium]] <span class="sep">|</span> [[No (greenish or golden-brown)->Q4]] <span class="sep">|</span> [[Back->Q2]]</div>
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<div><b>Q4:</b> Are the cells very small, spherical, and green with <i>no visible flagella</i>?</div>
<div class="actionRow">[[Yes->Result Nannochloropsis]] <span class="sep">|</span> [[No (slightly larger, golden-brown; may show faint flagella)->Result Isochrysis]] <span class="sep">|</span> [[Back->Q3]]</div>
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<div><b>Q5:</b> Is the organism filamentous, forming long chains or spirals of cells?</div>
<div class="actionRow">[[Yes->Result Arthrospira]] <span class="sep">|</span> [[No (unicellular, spherical)->Q6]] <span class="sep">|</span> [[Back->Start]]</div>
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<div><b>Q6:</b> Are the cells round, green, and relatively uniform in size with no visible flagella?</div>
<div class="actionRow">[[Yes->Result Chlorella]] <span class="sep">|</span> [[No / Not sure->Not Sure Fresh]] <span class="sep">|</span> [[Back->Q5]]</div>
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<h3>Likely ID: Arthrospira platensis (Spirulina)</h3>
<img class="resultImg" src="https://upload.wikimedia.org/wikipedia/commons/2/2f/Arthrospira_platensis.jpg" alt="Arthrospira platensis micrograph (Wikimedia Commons)">
<div class="creditLine"><a href="https://upload.wikimedia.org/wikipedia/commons/2/2f/Arthrospira_platensis.jpg" target="_blank" rel="noopener"><b>Image credit:</b> Wikimedia Commons contributors, <i>Arthrospira platensis</i> (license on Commons)</a></div>
<div class="metaLine"><b>Habitat:</b> Freshwater/alkaline (not marine) <span class="sep">|</span> <b>Microscope clues:</b> Filamentous; spirals/coils (helical trichomes)</div>
<div class="actionRow">(link:"View on ARS Site")[(open-url:"https://algaeresearchsupply.com/products/spirulina-culture-arthrospira-platensis")] <span class="sep">|</span> [[Start over->Start]]</div>
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<h3>Likely ID: Chlorella vulgaris</h3>
<img class="resultImg" src="https://algaeresearchsupply.com/cdn/shop/files/IMG_0195_1.jpg?v=1708714970&width=4032" alt="Chlorella vulgaris (Algae Research Supply)">
<div class="creditLine"><a href="https://algaeresearchsupply.com/cdn/shop/files/IMG_0195_1.jpg?v=1708714970&width=4032" target="_blank" rel="noopener"><b>Image credit:</b> Algae Research Supply (product photo)</a></div>
<div class="metaLine"><b>Habitat:</b> Freshwater <span class="sep">|</span> <b>Microscope clues:</b> Small round green cells; uniform; no flagella visible</div>
<div class="actionRow">(link:"View on ARS Site")[(open-url:"https://algaeresearchsupply.com/products/algae-culture-chlorella-vulgaris")] <span class="sep">|</span> [[Start over->Start]]</div>
</div><div class="resultCard">
<h3>Likely ID: Isochrysis (Tisochrysis) lutea</h3>
<img class="resultImg" src="https://image.ifremer.fr/data/00728/84015/md/37512.jpg" alt="Microscopic view of Tisochrysis lutea (IFREMER / Océanothèque)">
<div class="creditLine"><a href="https://image.ifremer.fr/data/00728/84015/md/37512.jpg" target="_blank" rel="noopener"><b>Image credit:</b> Olivier Dugornay, <i>Microalgue Tisochrysis lutea</i>, IFREMER / Océanothèque (CC BY 4.0)</a></div>
<div class="metaLine"><b>Habitat:</b> Saltwater (marine) <span class="sep">|</span> <b>Microscope clues:</b> Golden-brown tint; may show faint flagella; oval to spherical cells</div>
<div class="actionRow">(link:"View on ARS Site")[(open-url:"https://algaeresearchsupply.com/products/algae-culture-isochrysis")] <span class="sep">|</span> [[Start over->Start]]</div>
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<h3>Likely ID: Nannochloropsis oculata</h3>
<img class="resultImg" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/9d/Nannochloropsis_oculata_04.jpg/960px-Nannochloropsis_oculata_04.jpg" alt="Nannochloropsis oculata micrograph (Wikimedia Commons)">
<div class="creditLine"><a href="https://upload.wikimedia.org/wikipedia/commons/thumb/9/9d/Nannochloropsis_oculata_04.jpg/960px-Nannochloropsis_oculata_04.jpg" target="_blank" rel="noopener"><b>Image credit:</b> Nzeemin, <i>Nannochloropsis oculata</i>, Wikimedia Commons (CC BY-SA 4.0)</a></div>
<div class="metaLine"><b>Habitat:</b> Saltwater (marine) <span class="sep">|</span> <b>Microscope clues:</b> Very small spherical cells; green; no visible flagella</div>
<div class="actionRow">(link:"View on ARS Site")[(open-url:"https://algaeresearchsupply.com/products/algae-culture-nannochloropsis-1-liter")] <span class="sep">|</span> [[Start over->Start]]</div>
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<h3>Likely ID: Porphyridium (Porphyridium purpureum)</h3>
<img class="resultImg" src="https://upload.wikimedia.org/wikipedia/commons/2/25/Porphyridium_purpureum1.jpg" alt="Porphyridium purpureum micrograph (Wikimedia Commons)">
<div class="creditLine"><a href="https://upload.wikimedia.org/wikipedia/commons/2/25/Porphyridium_purpureum1.jpg" target="_blank" rel="noopener"><b>Image credit:</b> Neobodo, <i>Porphyridium purpureum</i>, Wikimedia Commons (CC BY-SA 4.0)</a></div>
<div class="metaLine"><b>Habitat:</b> Saltwater (marine) <span class="sep">|</span> <b>Microscope clues:</b> Red/pink appearance from pigments; round cells</div>
<div class="actionRow">(link:"View on ARS Site")[(open-url:"https://algaeresearchsupply.com/products/copy-of-algae-culture-porphyridium-cruentum")] <span class="sep">|</span> [[Start over->Start]]</div>
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<h3>Likely ID: Pyrocystis fusiformis</h3>
<img class="resultImg" src="https://upload.wikimedia.org/wikipedia/commons/a/aa/Pyrocystis_fusiformis.jpg" alt="Pyrocystis fusiformis micrograph (Wikimedia Commons)">
<div class="creditLine"><a href="https://upload.wikimedia.org/wikipedia/commons/a/aa/Pyrocystis_fusiformis.jpg" target="_blank" rel="noopener"><b>Image credit:</b> Wikimedia Commons contributors, <i>Pyrocystis fusiformis</i> (CC BY-SA 4.0)</a></div>
<div class="metaLine"><b>Habitat:</b> Saltwater (marine) <span class="sep">|</span> <b>Microscope clues:</b> Very large single cells; elongated or cigar-shaped</div>
<div class="actionRow">(link:"View on ARS Site")[(open-url:"https://algaeresearchsupply.com/pages/pyrocystis-fusiformis-the-firefly-of-the-sea")] <span class="sep">|</span> [[Start over->Start]]</div>
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<h3>Dichotomous Key for Algae Research Supply Algae Samples</h3>
<div><b>Q1:</b> Is the sample from a saltwater (marine) alga or a freshwater alga?</div>
<div class="actionRow">[[Saltwater / marine->Q2]] <span class="sep">|</span> [[Freshwater->Q5]]</div>
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