Century-scale trends and seasonality in pH and temperature for shallow zones of the Bering Sea

Jan Fietzke, Federica Ragazzola, Jochen Halfar, Heiner Dietze, Laura C. Foster, Thor Henrik Hansteen, Anton Eisenhauer, Robert S. Steneck

Research output: Contribution to journalArticlepeer-review

168 Downloads (Pure)


No records exist to evaluate long-term pH dynamics in high-latitude oceans, which have the greatest probability of rapid acidification from anthropogenic CO2 emissions. We reconstructed both seasonal variability and anthropogenic change in seawater pH and temperature by using laser ablation high-resolution 2D images of stable boron isotopes (δ(11)B) on a long-lived coralline alga that grew continuously through the 20th century. Analyses focused on four multiannual growth segments. We show a long-term decline of 0.08 ± 0.01 pH units between the end of the 19th and 20th century, which is consistent with atmospheric CO2 records. Additionally, a strong seasonal cycle (∼0.22 pH units) is observed and interpreted as episodic annual pH increases caused by the consumption of CO2 during strong algal (kelp) growth in spring and summer. The rate of acidification intensifies from -0.006 ± 0.007 pH units per decade (between 1920s and 1960s) to -0.019 ± 0.009 pH units per decade (between 1960s and 1990s), and the episodic pH increases show a continuous shift to earlier times of the year throughout the centennial record. This is indicative of ecosystem shifts in shallow water algal productivity in this high-latitude habitat resulting from warming and acidification.

Original languageEnglish
Pages (from-to)2960–2965
Number of pages6
JournalProceedings of the National Academy of Sciences
Issue number10
Early online date23 Feb 2015
Publication statusPublished - 10 Mar 2015


  • ocean acidification
  • boron isotopes
  • isotope imaging
  • laser ablation ICP–MS
  • crustose algae


Dive into the research topics of 'Century-scale trends and seasonality in pH and temperature for shallow zones of the Bering Sea'. Together they form a unique fingerprint.

Cite this