Multi-Species Coral Testing: Why One Species Is Not Enough

Multi-species coral testing exposes several coral species, ideally from different growth forms and genera, to the same substance or product, because species do not respond equally and a result on one species cannot be assumed for another. Published studies show sensitivity gaps between coral species that range from small to more than an order of magnitude depending on the chemical. A wider panel narrows the risk of missing a sensitive species and supports a claim that is as broad as the panel actually tested, no broader.

Published 26 October 2026. Sources checked on that date.

Do coral species respond differently to the same chemical?

Yes, and the size of the difference depends on the chemical. The examples below come from studies that tested more than one coral species under the same conditions.

Study	Chemical	Species compared	What differed
Downs et al. 2016	Oxybenzone	Cultured cells of 7 coral species	4-hour LC50 values spread from 8 to 340 µg/L, about a 40-fold range
He et al. 2019	Four benzophenone filters	Seriatopora caliendrum, Pocillopora damicornis	Larvae of one species were affected where those of the other were not, at the concentrations tested
Jones and Kerswell 2003	Irgarol 1051, diuron	Seriatopora hystrix, Acropora formosa	EC50s for photosynthetic yield of 0.7 and 1.3 µg/L (irgarol) and 2.3 and 2.8 µg/L (diuron): similar across the two species
Puisay et al. 2015	Copper	Acropora cytherea, Acropora pulchra gametes	Fertilisation EC50 of 69.4 and 75.4 µg/L, very close for two species of the same genus

The lesson is not that species always differ widely. It is that the gap cannot be known in advance: for some chemicals two species give almost the same answer, for others one species reacts and another does not.

Life stage, season and temperature also shift sensitivity

Species is one variable among several. Hédouin et al. (2016) tested copper on Pocillopora damicornis and found the adult LC50 lower in summer (175 µg/L) than in winter (251 µg/L), and the larval LC50 falling from 167 to 129 µg/L with a 3 °C rise in temperature.

A multi-species panel run under one set of conditions therefore answers the species question, not every question. The other design choices are covered in coral toxicity testing methods.

What is a species sensitivity distribution, and do corals have one?

In regulatory ecotoxicology, a species sensitivity distribution (SSD) is a curve fitted to toxicity values for many species, usually chronic EC10 or NOEC values. From it, assessors estimate a concentration expected to protect most species. Regulatory methods ask for data on many species spread across several taxonomic groups, such as algae, crustaceans, molluscs and fish.

Corals are rarely among them. The systematic review by Ouédraogo et al. (2023) compiled 847 studies on tropical reef-building corals and derived thresholds for 56 chemicals or mixtures. For most of them, reference values set for other marine organisms appeared protective of corals; copper, diuron and irgarol 1051 were the exceptions.

That is the case for adding coral to the species mix rather than replacing it: coral data test whether a value derived from other species also protects reef-building corals.

How to choose a coral panel

•Start from the claim. The scope of any statement should match the species tested. A one-species result supports a one-species statement.
•Cover growth forms. Small-polyp stony corals, large-polyp stony corals and soft corals differ in tissue, skeleton and symbiosis.
•Cover regions. A product sold for Hawaii, the Caribbean and the Mediterranean is better supported by species representative of each.
•Decide between depth and breadth. More concentrations on few species give dose-response values; one concentration on many species gives a broad screen. They answer different questions.

How ReefTox coral panels are built

ReefTox cultivates its own mother colonies of up to 50 coral species from 30 genera, representative of Indo-Pacific, Caribbean and Mediterranean reefs. For cosmetic formulations, the panel is chosen by breadth. All acute formulation tests run 96 hours of contact with no recovery period.

Test	Species	Design	What it tells you
ReefTox 1	Montipora digitata (hard, small-polyp)	1 concentration, 6 replicates, 6 blanks	Whether acute effects are observed on one species
ReefTox 3	Adds Acropora sp. and the soft coral Xenia sp.	1 concentration, 6 replicates, 6 blanks per species	The same question across three species, hard and soft
ReefTox 12	12 species, hard and soft	1 concentration, 2 replicates, 1 blank	A broad cross-species screen
ReefTox 50	Up to 50 species from 30 genera	1 concentration, 2 replicates, 1 blank	The broadest cross-species screen

For SPF ingredients, ReefFilter takes the depth route instead: 1 to 3 corals, 6 concentrations, and EC50, LOEC and NOEC values. The optional Reef Chronic 1 add-on runs 3 months of exposure plus 1 month of recovery across 5 concentrations for EC10 and EC50 values. In marine programmes, coral is added as a complementary species, described in the marine methodology.

The limits of a wide panel

•A single-concentration screen shows whether effects appear at that concentration. It does not give EC50 values and cannot build a species sensitivity distribution.
•Broad screens use fewer replicates per species than the one- and three-species tests, so they are designed to flag sensitive species, not to estimate each one precisely.
•Adult fragments in a laboratory are not larvae on a reef. Field exposure, life stage and heat stress can all change the outcome.
•No coral test guideline exists yet. Adult-fragment methods such as the one described by Brefeld et al. (2024) are still on the path to validation across laboratories.

Frequently asked questions

Why is one coral species not enough?

Because sensitivity differs between species in ways that are hard to predict. He et al. (2019) found that benzophenone filters affected larvae of one coral species but not the other at the concentrations tested. A single-species result is valid for that species and those conditions, and should be described that way.

How many coral species should be tested?

There is no regulatory number for corals, because there is no coral test guideline yet. The right panel depends on the claim: a claim about one species needs one species, while a claim meant to cover reefs in several regions needs species from those regions and from different growth forms.

What is a species sensitivity distribution?

It is a statistical curve fitted to toxicity values, usually EC10 or NOEC values, for many species. Regulators use it to estimate a concentration that protects most species. It needs a multi-concentration test for every species, so a broad single-concentration screen cannot produce one.

Are soft corals tested as well as hard corals?

They can be. Hard stony corals (small-polyp and large-polyp) and soft corals differ in structure and symbiosis, so ReefTox panels from three species upward include soft corals alongside hard stony species.

Does a wider panel mean a better result?

A wider panel means a broader result, not a better one. It covers more species, so it is more likely to reveal a sensitive one. The resulting claim covers exactly the species tested.

Sources

Peer-reviewed sources, checked 26 October 2026. Values are specific to each study's species, life stage and conditions.

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