Coral-Safe Testing for Cosmetics and SPF Ingredients
Coral-safe testing is empirical coral ecotoxicology: exposing live reef-building corals, or their larvae and primary cells, to a finished formulation or ingredient at environmentally realistic concentrations, then measuring defined biological endpoints such as bleaching, tissue loss, deformity, and mortality. Unlike an ingredient-list check, it characterises the actual coral-exposure risk of the product as sold. ReefTox runs it in a closed-loop coral ecotoxicology laboratory in Brittany, combining a free predictive pre-evaluation with live-coral bioassays on up to 50 coral species across 30 genera.
Reviewed 12 June 2026
Reviewed by Vincent Bourgeteau, President
Vincent Bourgeteau is a biologist and President of ReefTox (EcoSeaStems SAS), a closed-loop coral ecotoxicology laboratory in Brittany, France.
Closed-loop lab, Brittany
What is sunscreen testing for coral safety?
Sunscreen testing for coral safety is separate from SPF efficacy testing. SPF testing measures whether a product delivers its labelled sun protection; coral-safety testing measures whether the same product harms reef-building corals when it washes off into the sea, a sunscreen can pass SPF testing and still be untested for coral impact. The two are not substitutes.
Coral-safety testing works in two layers. First, the formulation is screened against reef-protection ingredient bans (Hawaii Act 104, US Virgin Islands Act 8185, Palau), the necessary floor. Then the finished product is exposed to live coral at environmentally realistic concentrations and scored on defined endpoints, bleaching, deformity, DNA damage, mortality, to produce an actual dose-response, the ceiling that characterises the product as sold. At ReefTox every engagement begins with a free predictive pre-evaluation (six formulation pillars + ICP-OES water analysis + ingredient screening) before any coral is exposed.
What does coral-safe testing measure?
A coral bioassay exposes the test material to live coral and scores defined endpoints. Acute endpoints are EC50, LOEC and NOEC; the chronic phase adds EC10 and EC50.
- • Bleaching (computer-assisted), tissue loss, and mortality.
- • Morphological and behavioural anomalies: polyp retraction, mesenteric filament ejection.
- • Before/after photography across the exposure and recovery windows.
- • Three bioassay platforms by life stage: coral planula (larval, most sensitive), coral nubbin (adult fragment), in-vitro primary coral cell.
How does ReefTox test a formulation for coral safety?
Every engagement starts with a free predictive pre-evaluation before any coral is exposed, then runs live-coral bioassays documented in a defensible coral ecotox report.
The free predictive pre-evaluation
Six formulation pillars + ICP-OES water analysis + ingredient screening against Hawaii Act 104 and US Virgin Islands Act 8185 classify the risk and route the formulation to a compatible coral panel, before any coral is exposed. It is free and included with every engagement.
The live-coral bioassay
Acute testing is 96 hours of exposure, with 6 replicates and 6 blanks, producing EC50, LOEC and NOEC.
Chronic phase, the deeper program
The 3-month exposure + 1-month recovery chronic phase (EC10, EC50) is an optional 3-month chronic program for continuous-exposure chemistries. The outcome is documented in a defensible coral ecotox report.
The free pre-evaluation is distinct from ReeFilter, the live-coral acute test on SPF ingredients.
How is harm attributed to my product and not a heatwave?
Coral stress is etiologically non-specific, bleaching is a final common pathway reached by thermal, photo-oxidative, viral, and direct-chemical routes alike, so field observation cannot attribute cause. A controlled bioassay holds genotype, light, and carrier constant and varies one substance, manufacturing the counterfactual the reef cannot supply.
The asymmetry is worth stating plainly: controlled testing demonstrates that a defined formulation causes measurable harm under defined conditions; it does not prove absolute field "reef-safety". That is why the permitted wording is "Reef Safer", anchored to the documented test result, not to absolute safety.
Why does test design decide what you see?
The coral life stage exposed decides whether harm is visible: planula deformity can fire orders of magnitude below an adult-fragment finished-formulation NOEC for the same chemistry. Sub-lethal endpoints fire well below mortality, so a test that scores only survival can read "no effect" on a chemical that is in fact harming the coral. ReefTox designs assays around the most sensitive relevant life stage.
How many coral species are tested?
ReefTox maintains up to 50 coral species across 30 genera, hard SPS, hard LPS and soft corals representative of Indo-Pacific, Caribbean and Mediterranean reefs. The same chemical can read as a sub-lethal photo-toxicant on one species and as no-observed-effect on another, so a credible test samples the regions a brand sells into. A claim is only ever as broad as the panel purchased.
Test coral is cultivated closed-loop from maintained mother colonies in Brittany, every batch carries traceable mother-colony provenance, with no wild collection, so the testing lets a brand avoid putting reef-harmful chemistry into the water without drawing coral from the wild.
Frequently asked questions
How is harm attributed to my product and not a heatwave?
Coral stress is etiologically non-specific, bleaching looks the same whatever causes it, so field observation cannot attribute cause. A controlled bioassay holds genotype, light and carrier constant and varies only your formulation, isolating its effect from thermal and other background stressors.
How many coral species are tested?
Up to 50 coral species across 30 genera, hard SPS, hard LPS and soft corals representative of Indo-Pacific, Caribbean and Mediterranean reefs. The panel depends on the test purchased; a claim is only ever as broad as the panel actually tested.
Is the free pre-evaluation the same as ReeFilter?
No. The free pre-evaluation is ReefTox's upstream predictive scoring methodology (six pillars + ICP-OES + ingredient screening), run before any coral is exposed. ReeFilter is a live-coral acute test on individual SPF ingredients. They are different products.
Does coral-safe testing prove a product is "reef-safe"?
No test proves absolute field safety. Controlled testing demonstrates that a defined formulation caused no measurable harm to the coral tested under defined conditions. That supports the comparative wording "Reef Safer" and gives you defensible, publishable coral ecotox data, not an absolute "reef-safe" claim.
What does coral-safe testing measure?
It measures dose-response effects on living coral. Acute endpoints are EC50, LOEC and NOEC; the optional 3-month chronic program adds EC10 and EC50. Responses scored include bleaching, tissue loss, mortality, polyp retraction and morphological anomalies, sub-lethal effects fire well below mortality.
Where does your coral come from?
Our test coral never comes from a reef. ReefTox cultivates its own mother colonies in a closed-loop laboratory in Brittany and produces cuttings on-site, so every batch carries traceable mother-colony provenance with no wild collection, so the testing lets a brand avoid putting reef-harmful chemistry into the water, without drawing coral from the wild.
Is sunscreen testing for coral safety the same as SPF testing?
No. SPF testing measures sun-protection efficacy; coral-safety testing measures whether the product harms reef-building corals when it washes off. A sunscreen can pass SPF testing and still be untested for coral impact, the two are different disciplines, not substitutes. Coral-safety testing screens the formulation against reef-protection ingredient bans, then exposes live coral to the finished product at environmentally realistic concentrations and measures bleaching, deformity, DNA damage, and mortality.
Is checking the ingredient list enough to know a sunscreen is reef-friendly?
No. Screening a formulation against a banned-ingredient list (oxybenzone, octinoxate, sometimes octocrylene) establishes legality but does not characterise the finished product as sold, two sunscreens that both clear the same list can behave differently on live coral, and mineral filters are not automatically safer because coating chemistry, not the organic-versus-inorganic label, governs coral compatibility. Ingredient screening is the necessary floor; a finished-formulation coral bioassay is the ceiling.
Start with a free predictive pre-evaluation
Six pillars + ICP-OES + Hawaii Act 104 / US Virgin Islands Act 8185 screening, before any coral is exposed.
