The ocean covers 71% of Earth's surface and contains an estimated 2.2 million species — most still undiscovered. But marine biodiversity is declining at an alarming rate, and chemical pollution is a significant but often overlooked driver.
The Biodiversity Crisis
The Living Planet Index shows marine vertebrate populations have declined by 49% since 1970. While overfishing, habitat destruction, and climate change are primary drivers, chemical pollution compounds these pressures — weakening organisms' ability to cope with other stressors.
How Chemicals Reduce Biodiversity
Chemical pollution affects biodiversity through multiple pathways:
Direct toxicity — chemicals at high concentrations kill organisms outright. Pollution incidents like oil spills or industrial discharges can devastate local ecosystems.
Sublethal effects — at lower concentrations, chemicals reduce fitness without killing. Impaired reproduction, weakened immune systems, and altered behaviour all reduce population viability over time. These subtle effects are harder to detect but may be more significant at a global scale.
Habitat degradation — nutrient pollution causes eutrophication and dead zones. Herbicides damage seagrass and kelp forests. Acidification from absorbed CO₂ dissolves coral and shellfish.
Food web disruption — when key species are affected, cascading effects ripple through ecosystems. The loss of filter feeders, for example, reduces water clarity, affecting photosynthetic organisms.
Why Biodiversity Matters
Marine biodiversity isn't just a conservation issue — it's an economic and food security one. Ocean ecosystems provide food for billions of people, regulate climate, produce oxygen, and support livelihoods. The economic value of marine ecosystem services is estimated at over $20 trillion annually.
Diverse ecosystems are more resilient to stress. As we lose species, we lose the ocean's ability to adapt to change — making every subsequent stress harder to weather.
The Knowledge Gap
For most marine species, we simply don't know how they respond to CECs. Regulatory testing focuses on a handful of model species that may not represent the vast diversity of marine life. The CONTRAST project is working to address this, developing tools that can predict effects across species.
What Needs to Happen
Protecting marine biodiversity requires reducing chemical inputs, expanding marine protected areas, enforcing existing regulations, and investing in research. It also requires recognising that chemical pollution, climate change, and biodiversity loss are interconnected crises that demand integrated solutions.
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.