Isochrysis galbana - Essential DHA-Producing Marine Microalgae

Scientific Classification

Kingdom: Chromista | Phylum: Haptophyta | Class: Prymnesiophyceae | Order: Isochrysidales | Family: Isochrysidaceae | Genus: Isochrysis | Species: I. galbana

Isochrysis galbana Species Profile

Isochrysis galbana represents one of the most nutritionally valuable marine phytoplankton species in commercial aquaculture, measuring 4-6 micrometers in diameter. This golden-brown flagellated microalgae features two flagella for motility and distinctive chloroplast pigmentation. The species name "galbana" derives from the golden color imparted by high fucoxanthin pigment concentrations. This species stands virtually alone among easily cultured microalgae for producing substantial docosahexaenoic acid (DHA) content.

Nutritional Characteristics

Protein Content: 30-40% dry weight with complete amino acid profile.

Lipid Content: 20-30% dry weight with exceptional omega-3 profile:

• DHA Content: 8-15% of total fatty acids - EXCEPTIONAL among microalgae
• EPA Content: 1-3% of total fatty acids
• Fucoxanthin: Significant carotenoid content providing golden coloration
• Sterols: Rich in fucosterol and other marine sterols

Why DHA is Critical: DHA represents the most critical omega-3 fatty acid for neural development, vision formation, and immune function in marine fish larvae. Most easily cultured phytoplankton produce primarily EPA with minimal DHA, but Isochrysis galbana provides substantial DHA making it indispensable in commercial fish hatcheries. Fish larvae cannot synthesize DHA de novo and must obtain it through dietary sources.

Critical Aquaculture Applications

Bivalve Mollusk Hatchery Standard: Oyster larvae, clam spat, scallop veligers, and mussel larvae achieve maximum growth rates, highest survival percentages, and fastest settlement times when fed Isochrysis galbana. The biochemical composition matches nutritional requirements of filter-feeding bivalve larvae better than most alternatives. Isochrysis has become the global standard for shellfish hatcheries.

Copepod Enrichment Programs: Marine copepods enriched on Isochrysis diets transfer DHA through the food chain to fish larvae, providing this essential fatty acid fish cannot synthesize. This enrichment strategy dramatically improves survival rates in marine finfish larviculture. Studies show 200-350% improvements in fish larvae survival when fed DHA-enriched versus DHA-deficient copepods.

Marine Fish Hatchery Essential: High-value species including grouper, snapper, yellowtail amberjack, cobia, and barramundi benefit tremendously from Isochrysis in live food chains. Whether fed directly to fish larvae or used to enrich rotifers and copepods, the DHA transfer supports proper neural development and reduces jaw deformities common in DHA-deficient larvae.

Reef Aquarium Applications

Premium SPS Coral Nutrition: Acropora, Montipora, Stylophora, and Pocillopora species benefit significantly from Isochrysis supplementation. The DHA content supports coral tissue regeneration, skeletal growth, and stress resistance in reef environments.

Tridacnid Clam Food: Giant clams (Tridacna maxima, crocea, derasa, gigas, squamosa) filter-feed actively on Isochrysis, supplementing zooxanthellae-derived nutrition with essential fatty acids and amino acids.

Filter-Feeder Nutrition: Feather duster worms, Christmas tree worms, and non-photosynthetic invertebrates thrive on regular Isochrysis feedings, displaying enhanced feeding responses and improved crown/tissue regeneration.

Cultivation Parameters

Optimal Culture Conditions:

• Salinity: 25-35 ppt, optimal 30-33 ppt
• Temperature: 18-28°C, optimal 22-26°C (64-82°F)
• pH: 7.8-8.8, optimal 8.0-8.5
• Light: 100-200 μmol photons m⁻² s⁻¹
• CO2 Enrichment: Beneficial for enhanced growth rates
• Growth Rate: Doubling time 20-36 hours

Culture Medium: Responds well to standard marine aquaculture media including F/2, Conway medium, and Guillard's formulations. Tolerates slightly lower nitrogen concentrations than many species, suitable for continuous culture systems. Commercial phytoplankton fertilizers work well for hobbyist-scale production.

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Tisochrysis lutea - Premium DHA Strain (formerly Isochrysis T-ISO)

Scientific Classification

Kingdom: Chromista | Phylum: Haptophyta | Class: Prymnesiophyceae | Order: Isochrysidales | Family: Isochrysidaceae | Genus: Tisochrysis | Species: T. lutea

Tisochrysis lutea Species Profile

Tisochrysis lutea represents the taxonomically corrected name for the strain previously known as Isochrysis galbana T-ISO (Tahitian Isochrysis strain). This premium marine phytoplankton species measures 4-6 micrometers and produces the HIGHEST DHA concentrations among commonly cultured microalgae species. Tisochrysis lutea has become the gold standard phytoplankton in commercial shellfish hatcheries worldwide, surpassing even the original Isochrysis galbana in nutritional quality.

Biochemical Analysis

Protein Content: 35-45% dry weight - Higher than standard Isochrysis galbana

Total Lipids: 22-32% dry weight with exceptional omega-3 profile:

• DHA Content: 12-18% of total fatty acids - HIGHEST among microalgae
• EPA Content: 2-4% of total fatty acids
• Combined Omega-3: Provides both essential long-chain PUFAs
• Digestibility: Excellent cell wall digestibility maximizing nutrient transfer

Commercial Importance

Shellfish Aquaculture Industry Standard: Tisochrysis lutea serves as THE primary phytoplankton species in oyster hatcheries (Pacific oysters, Eastern oysters, European flat oysters), clam hatcheries (Manila clams, hard clams, soft-shell clams), and scallop production facilities globally. The exceptional DHA content supports optimal larval development, producing stronger juveniles with higher survival rates during nursery phases. Commercial hatcheries report 15-30% improvements in bivalve larvae survival using Tisochrysis lutea versus standard Isochrysis galbana.

Marine Fish Larviculture: High-value species including grouper, red snapper, yellowtail amberjack, cobia, and barramundi benefit tremendously from Tisochrysis in live food chains. The DHA transfer supports proper neural development and reduces jaw deformities that plague fish larvae fed DHA-deficient diets. Studies document 40-60% reductions in larval deformities with Tisochrysis-enriched feeds.

Ornamental Fish Breeding: Captive breeding programs for angelfish, butterflyfish, anthias, dottybacks, and clownfish achieve higher larval survival rates incorporating Tisochrysis into phytoplankton rotations. This species has become critical for reducing collection pressure on wild reef fish populations through successful captive breeding.

Reef Aquarium Copepod Applications

Optimized Copepod Reproduction: Marine copepods (Parvocalanus crassirostris, Pseudodiaptomus pelagicus, Acartia tonsa, Tisbe biminiensis) achieve maximum egg production rates on Tisochrysis diets. The DHA-rich fatty acid profile transfers to copepod tissues, producing more nutritious live food for reef fish. Research shows copepods fed Tisochrysis contain 150-250% higher DHA levels than those fed DHA-poor diets.

Enhanced Copepod Nauplii Quality: Copepod nauplii hatched from Tisochrysis-fed females contain significantly higher DHA levels, making them more valuable as live food for marine fish larvae and finicky reef fish species like mandarins, anthias, and dartfish.

Sustainable Production: The nutritional completeness supports long-term copepod culture sustainability without population crashes or declining reproduction common with nutritionally inferior diets.

Cultivation Parameters

Optimal Growth Conditions:

• Salinity: 25-35 ppt, optimal 30-35 ppt
• Temperature: 22-28°C, optimal 25°C (72-82°F)
• pH: 7.8-8.8, optimal 8.2-8.6
• Light: 100-250 μmol photons m⁻² s⁻¹
• Photoperiod: Continuous light or 16:8 light:dark
• Aeration: Gentle continuous with CO2 enrichment
• Growth Rate: Doubling time 24-40 hours

Culture Medium: Thrives in standard marine media with slightly elevated nitrogen. F/2 medium, Walne's medium, and commercial fertilizers all support healthy growth. Benefits from CO2 enrichment when available.

Direct Coral Applications

Small Polyp Stony Corals: Acropora, Montipora, Seriatopora, and Stylophora all benefit from regular Tisochrysis supplementation. The high DHA content supports coral growth, coloration, and recovery from stress events including shipping, handling, fragmentation, or environmental parameter fluctuations.

Large Polyp Stony Corals: Euphyllia, Favia, Favites, and other LPS species consume Tisochrysis readily, benefiting from the exceptional nutritional profile for tissue development and skeletal growth.