Ocean Acidification in the Southern California Bight

Transcription

1 Ocean Acidification in the Southern California Bight Karen McLaughlin SCCWRP Symposium March 1, 2017

2 What is Ocean Acidification? Ocean Acidification is the other CO 2 problem : Ocean ph decreases when CO 2 dissolves in seawater Atmospheric CO2 data from Mauna Loa Observatory, Hawaii ph data from the Hawaii Ocean Time Series Station (HOTS) Feely et al. (2009)

3 Effect of Adding CO2 to Seawater O C O CO 2 1. Dissolves in the ocean H 2 O CO 3 2 O O C O 2. Reacts with water to form bicarbonate ion H + and hydrogen ion HCO 3 O H + O C O H HCO 3 3. Most of the hydrogen ions react O with carbonate ions to form C bicarbonate ion O H O

4 Loss of Carbonate Ions Makes Life Difficult for Shell- Formation Many shelled organisms precipitate calcium carbonate Less carbonate ions = weaker shells Healthy Pteropod Scientists use aragonite saturation state to quantify availability of carbonate ions: Ω > 1 : Aragonite can precipitate Ω < 1 : Aragonite dissolves (corrosive) Dissolving Pteropod

5 Corrosive Waters Are Present At Shallow Depths All Across the US West Coast West Coast maps of the depth where water is undersaturated with respect to aragonite 2007 saturation depth Feely et al. (2008) and Bednarsek et al. (2014)

6 We Have Seen the Consequences in the Pacific Northwest The Pacific Northwest Shellfish industry has suffered unprecedented losses in larval oysters directly related to carbonate chemistry Oyster Larvae from same spawn grown in surface waters (Ω ~ 1.7) and deep waters (Ω ~ 0.5) (Barton et al. 2015)

7 What is the State of the Bight? Acidification surveys in the Bight are limited to two CALCOFI lines and 6 nearshore stations A more comprehensive dataset was needed to understand patterns in acidification

8 Collecting High Quality Acidification Data: Approach Collect bottle samples for ph and total alkalinity and calculate aragonite saturation state 5 agencies participating 72 grid stations; 2 3 depths per station Quarterly sampling for 2 years Samples analyzed by Andrew Dickson s laboratory at Scripps Gold standard for measurements 120 o W 119 o W 118 o W 117 o W 35 o N 34 o N 33 o N 32 o N 34 o 00'N 33 o 50'N 33 o 40'N A C B C D E F B D 119 o 15'W 119 o 00'W 118 o 30'W 118 o 15'W o 45'W 118 o 30'W 32 o 45'N 34 o 15'N 34 o 00'N 33 o 45'N 33 o 40'N 33 o 35'N 33 o 30'N E F 32 o 30'N 118 o 10'W 118 o 00'W 117 o 50'W 117 o 20'W 117 o 10'W

9 Aragonite Saturation State in the SCB Percent of Samples Waters undersaturated Pteropod dissolution Larval oyster growth Aragonite Saturation State

10 Aragonite Saturation Related to Depth But More Closely to Density Below Thermocline AboveThermocline Aragonite Saturation State Thresholds 0 A. 22 B Depth (m) Density (kg m -3 ) Density (kg m -3 ) Aragonite Saturation State Aragonite Saturation State

11 There is a Clear Seasonality in Aragonite Saturation State Spring (Upwelling) Fall > < m 20-40m 40-60m 60-80m m m m > < m 20-40m 40-60m 60-80m m m m

12 No Difference In Nearshore Versus Offshore

13 Next Steps Refine thresholds SCCWRP is partnering with the OPC to gain scientific consensus on the relevant endpoints Continue to collect high quality measurements of acidification Bight 13 also piloted an in situ calibration to collected better ph data SCCWRP is partnering with SCCOOS and member agencies to install moored sensors to collect high frequency acidification measurements Run models to characterize drivers

14 What Are the Drivers of Ocean Acidification? Models can be used to untangle different drivers of spatial and temporal variability in acidification Natural climate variability Anthropogenically induced climate change Anthropogenic inputs SCCWRP is partnering with leading modelers to develop an integrated model of the southern California bight Please attend Fayçal Kessouri s talk at 1:00 pm for more information

15 Questions? Karen McLaughlin