By the time pollution damage is visible — dead fish, bleached coral, algal blooms — it's often too late for effective intervention. Biomarkers offer a way to detect harm much earlier, reading the subtle molecular warning signs that organisms produce when stressed by chemicals.
What Are Biomarkers?
A biomarker is any measurable biological response that indicates exposure to, or effects of, a pollutant. They operate at multiple levels:
- **Molecular biomarkers** — changes in gene expression, enzyme activity, or protein levels
- **Cellular biomarkers** — DNA damage, changes in cell structure
- **Physiological biomarkers** — altered immune function, hormone levels, growth rates
- **Behavioural biomarkers** — changes in feeding, swimming, or reproduction
Key Biomarkers in Marine Science
Some biomarkers have become standard tools:
Vitellogenin in male fish — this egg yolk protein, normally only produced by females, indicates exposure to oestrogenic chemicals. Its presence in male fish is one of the clearest signals of endocrine disruption.
EROD activity — this enzyme, induced in fish liver by certain pollutants (particularly PAHs and dioxins), indicates the body's attempt to detoxify harmful chemicals.
Acetylcholinesterase inhibition — reduced activity of this nervous system enzyme indicates exposure to organophosphate or carbamate pesticides.
Metallothionein levels — elevated levels of this protein indicate exposure to heavy metals as the organism attempts to bind and neutralise them.
The CONTRAST Approach
CONTRAST researchers are developing next-generation biomarker approaches using "omics" technologies. Rather than measuring single biomarkers, they analyse thousands of molecular changes simultaneously — creating comprehensive "fingerprints" of pollutant exposure.
This approach can detect effects at lower concentrations, distinguish between different types of pollution, and identify novel biomarkers for emerging contaminants.
From Lab to Field
The challenge is translating laboratory biomarker knowledge to field conditions, where organisms face multiple stressors simultaneously. Temperature, salinity, food availability, and natural variation all influence biomarker responses. Distinguishing pollution effects from natural variability is an active area of research.
This article is part of the CONTRAST project, funded by the European Union under Horizon Europe. Views expressed are those of the author(s) only.