Impact of elevated, variable pCO2 on the Pacific razor clam

(Siliqua patula) in Alaska

Marina Washburn1, Dr. Amanda Kelley1

1College of Fisheries and Ocean Sciences, University of Alaska Fairbanks

Photo: Kenai River Lodge

Robert and Kathleen

Byrd Award

Ocean Acidification• Increasing anthropogenic CO2 leads to decreasing oceanic

pH • Evidence that decrease in pH can impact biocalcifiers• Impacts of OA may be greater on early life stages

Ocean Acidification in Alaska• Effects of OA exacerbated in cold waters• Nearshore environments highly dynamic in terms of

carbonate chemistry• Limited studies on OA in Alaska

Kelley et al. in prep

The Pacific razor clam (Siliqua patula)• Commercial, recreational and subsistence fishery• Recreational fishery closed along East Cook Inlet

Cordova Historical Society Alaska Department of Fish and Game

Alaska Department of Fish and Game

Objective Determine the physiological effects of ambient, variable, and elevated pCO2/reduced pH on embryonic and larval S. patula.Examine:

• Growth• Shell Composition• Shell mineralization• Intracellular response

Spawning razor clams• Strip spawning • Two different spawning events

• Developmental assessment • Experimental batch

Sperm

Eggs

Development of S. patula

The Experiment

• Conducted over 28 days• Three treatments:

• Ambient- 350 μatm/8.0 pH

• High- 860 μatm/7.7 pH

• Variable- Fluctuated between high and ambient every 12 hours

• Variable treatment• Mimics 12-hour diel oscillation cycle• Measured carbonate chemistry with Ross Electrode, Burke-O-

Lator, and SeaFET

The ExperimentpC

O2

(μat

m)

pH

7/14/18 7/20/18 7/23/187/17/18 8/01/18 8/04/18 8/07/187/26/18 7/29/18

800

600

400

7.9

7.8

7.7

8.0

Experimental Growth Analysis7 DPF

28 DPF21 DPF

14 DPF

Variable culture bucket V3 from 7 days post fertilization to 28 days post fertilization

Experimental Growth Analysis* Length of S. patula in ambient

conditions was significantly longer than other shells

Length

Width Area

Day 14 Day 21 Day 28Day 14 Day 21 Day 28Day 7 Day 7 Day 14 Day 21 Day 28Day 7

Day 14 Day 21 Day 28Day 7 Day 14 Day 21 Day 28Day 7

Shell Composition Analysis• Using x-ray spectroscopy

• Elemental spectrums quantified using iXRF software

• Examined percent composition of Calcium, Magnesium, Silicon, Sulfur, and Chloride

Point 1: Highest point of shell.

Point 2: Middle of largest leading edge, five μm from edge. CaS ClSiMg

CaS ClSiMg

Shell Composition Analysis

* Percent chloride was significantly different for 21DPF and 28 DPF within the variable treatment

Cl

Point 1

Point 2

Elemental Composition over time

Point 1

Point 2

Summary

• Growth • Ambient treatment shell length significantly different

• Shell Composition• Some significant

variation in Chloride incorporation

Continuing Work• Continuing compositional

Analysis• Increasing sample sizes

• Cellular response • Analyzing gene expression of

Carbonic Anhydrase and HSP-70 using qPCR

Acknowledgements• Dr. Amanda Kelley• Dr. Sarah Hardy• Dr. Katrin Iken• Jeff Hetrick• Jacqueline Ramsey • Cale Miller• Advanced Instrumentation

Laboratory (University of Alaska Fairbanks)

Robert and Kathleen

Byrd Award

Questions?