The pH scale is logarithmic. A decrease of one whole pH unit means about ten times the hydrogen-ion concentration, not just a small equal step. Carbon dioxide entering the ocean also changes dissolved carbonate chemistry, which matters to organisms that build calcium-carbonate shells and skeletons.
Water and oceans · Discover & try
Can seawater acidify while it is still basic?
Reading level 2 of 5 · DevelopingChange
Word help
pH
A logarithmic measure related to hydrogen-ion activity.
Acidification
A decrease in pH, even if the solution remains basic.
Carbonate
A dissolved ion used in calcium-carbonate shells and skeletons.
Watch · Try · Explain
See how it works
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Selected pH states and exact logarithmic ratios; no local carbonate-system or biological forecast.
What to look for
- Read lower pH as more hydrogen ions.
- Check that every selected pH is still above seven.
- Separate the exact ratio from qualitative carbonate changes.
Explain what you noticed
A separate seawater sample changes from pH 8.3 to pH 8.0. Has it acidified?
Keep this idea: Acidification means a decrease in pH; seawater can become less basic without crossing pH 7.
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Source material checked 2026-10-28. Explanations and activities by Nepedia. Source links do not imply endorsement.
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