Sentinel studies of ocean acidification in the Arctic Ocean

and Japanese coasts

Naomi Harada1, Katsunori Kimoto1, Jun Kita2, Jonaotaro Onodera1, Masahiko Fujii3, Masahide Wakita1, Tetsuichi Fujiki1, Shintaro Takao4 and

Tsuneo Ono5

1 Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan. 2 Marine Ecology Research Institute, Kashiwazaki, Japan3 Hokkaido University, Sapporo, Japan4 National Institute of Polar Research, Tachikawa, Japan5 Japan Fisheries Research and Education Agency, Yokohama, Japan

CO O

What is ocean acidification?

+ HCO3- + H+

H+ is described as “pH” which is defined as the decimal logarithm of the reciprocal of the hydrogen ion activity aH+ in a solution.

Aragonite saturation in2100�Ω aragonite�

Sub-Arctic and Polar Seas: Low CO32- brings low Ω

Saturation index (Ω)Ω = [Ca2+] [CO32-] / K’sp K’sp : solubility product of calcite/aragonite

Ω>1: precipitation(shell preserved)

Ω<1: undersaturation (shell dissolved)

St. NAP: 75N, 162W 2 Sed.Traps: 200m, 1300m2010 ~

Observation sites at the Arctic Ocean and Japanese coasts

M1: Onjuku Station [Pacific side 1982 ~ ]M2: Kashiwazaki Station [Japan Sea 1997 ~ ]

• Change in pH• Response of typical organisms to OA

(pteropods, abalone, sillago)

Seasonal change in subsurface pH of the western Arctic Ocean measured by glass electrode sensor (Kimoto Co. LTD)

NHC

St. NAP

Measurement timing is once a 60min. Resolution is 0.001pH and response speed is within 20 sec. Repeat accuracy is within�0.01pH (The 3rd winner of Accuracy Prize, XPRIZE competition). All data is calibrated after observation.

51m depth

96m depth

35m depth

62m depth

• Remnant and newly ventilated Pacific Winter waters (having relatively low but different pH values) are intricately laminated between 50-150m water depth.

• Common trend1: Relatively low winter and relatively high summer• Common trend2: Minimum pH values during summer and the beginning of sea-ice

season

a. Specimen

b. Standard material(Calcite)

Reconstruct

Scan

Measurement of pteropods carbonate density by micro focus X-ray Computing Tomography method

a

b

c

Micro X-CT (MXCT)

Fluoroscopic image

Calcite CT Number as a shell density indexrelative value of X-ray attenuation coefficient in each voxels

µsample: X-ray attenuation coefficient of samplesµair: X-ray attenuation coefficient of the surrounding air = -1000µcalcite: X-ray attenuation coefficient of calcite (standard material: Calcite or Aragonite ) = 1000

Calcite CT Number = µsample - µair x 1000µcalcite - µair

Air (0)

Shel

l den

sity

(D)

(µg/

µm3 )

Mean CT Number

1200(higher density)

1000(reference)

Mean CT number vs Shell density

600(lower density)

Density of calcite (D) D = 0.00273x ‒ 0.769 (R2= 0.87)

Kimoto et al., in prep

Precise shell density analysis of Sea butterfly (Limacina helicina, Thecosomatous pteropod)

Transparent image (spatial resolution: 0.5 um)

Distribution of Shell density(Unit: ug/um3)

2010 2011M

ean

CT

num

ber

180 m trap1300 m trap

high

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

Max 40% decrease

low

shallower trapaverage

Kimoto et al. in prep

dissolved dissolved

Sea ice100

0

%

Local corrosive condition produced by diagenesis of organic compounds

Sea ice melting

Seasonal change in shell density of Arctic L. helicina

7.8

7.9

8.0

8.1

8.2

8.3

8.4

8.5

8.6

1980 1983 1987 1991 1995 1999 2003 2007 2011 2015 2019

7.8

7.9

8.0

8.1

8.2

8.3

8.4

8.5

8.6

1980 1983 1987 1991 1995 1999 2003 2007 2011 2015 2019

1983 1987 1991 1995 1999 2003 2007 2011 2015 20191980

1980 1983 1987 1991 1995 1999 2003 2007 2011 2015 2019Shut-off of all reactors

Seawater inlet (350m offshore, 11m depth)Intake quantity (75 m3/hour)

8.58.6

8.4

8.18.2

7.97.8

8.0

8.3

8.58.6

8.4

8.18.2

7.97.8

8.0

8.3

Changes in pH at Onjuku St, Pacific side and Kashiwazaki St, Japan Sea side

Kashiwazaki St. (Japan Sea coast 1997~)-0.011 / yr (Mar 2012 – Dec 2017)

Onjuku St. (Pacific coast 1982~)-0.007 / yr

Annual change in pH Comparison between pelagic and Japanese coastal zones

��

WMO GHG Bulletin 2014

Time series pH* (yr-1) Reference

BATS -0.0017 �0.0001

Bates et al., 2014

ESTOC -0.0014�0.0001

Bates et al., 2014; Gonzàlez-Dàvila et al., 2010

HOT -0.0017�0.0001

Bates et al., 2014; Dore et al., 2009

CARIACO -0.0024�0.0003

Bates et al., 2014; Astor et al., 2013

DYFAMED -0.0019�0.0009

Touratier and Goyet, 2011

MUNDA -0.0016�0.0003

Bates et al., 2014; Currie et al., 2011

KNOT/K2 -0.0024�0.0007

Wakita et al., 2013

Station P - Wong et al., 2010

137�E section at 10�N

-0.0011�0.0001

Midorikawa et al., 2010

Time series pH (yr-1)ONJUKU -0.007

KASHIWAZAKI -0.011

KASHIWAZAKIONJUKU

*calculated from T, S, Nutrients, DIC and TA

0

200

400

600

800

1000

1200

1400

1600

0 0.5 1 1.5 2 2.5 3

Days after initiation of experiment

Constant treatmentsTargeted pCO2400 µatm, 800 µatm, 1200 µatm

Results of monitoring (Dotted lines) 430�15, 732�19, 1175�20 µatm

Diel cycle treatmentsTargeted pCO2400-1200 µatm, 800-1600 µatm

Results of monitoring (Solid lines)420-1189 µatm, 739-1537 µatm

Effects of diurnally-fluctuating pCO2 on ezo-abalone larvae by rearing experiment

Onitsuka et al., 2018 Mar. Env. Res., 134, 28-36.

Results : Effects on ezo-abalone larval fitness

0

5

10

15

20

25

0

20

40

60

200

250

300

350

Larval shell length

Mortality

Malformation

400 800 400-1200

800-1600

1200

pCO2 (µatm)

*

a abab

bc

cNormal Abnormal

Slightly high: 400-1200, 800, 800-1600 µatm

Significantly high: 1200µatm and 800-1600 µatm

Significantly short: 800-1600 µatm

Onitsuka et al., 2018 Mar. Env. Res., 134, 28-36.

Results 2: Effect of “integral pCO2” on larval fitness

0

10

20

30

40

50

200

220

240

260

280

300

0 2000 4000 6000 8000

Malformation

Larval shell length

Integral pCO2 over 1100 µatm(µatm h)

Open circles: incubation with diel cycle pCO2Solid circles: incubation with constant pCO2

• Malformation rate increased around 1.1 of Ωarawhich corresponds to ≅1100 µatm of pCO2.

• The impacts of OA on growth of larval abalone can be determined by intensity and time of exposure to pCO2 over the threshold called as “Integral pCO2 over 1100 µatm”.

• Integral pCO2 over 1100 µatm

=∑ # − 1100 'P: pCO2 over 1100 µatmi: exposed hours to pCO2 over 1100 µatm

• Larval shell length decreased with the increasing of integral pCO2 over 1100 µatm.

Onitsuka et al., 2018 Mar. Env. Res., 134, 28-36.

Sillago japonicaModel marine-fish for pollutant contamination tests

Maximum Size: 30 cmRange: Temperate zone of Japanese coastImportant fish for fisheries industry

Egg diameter ca. 700 μm

1 days after hatch, TL 2.7 mm

3 days after hatch, TL 3.0 mm

8 days after hatch, TL 4.5 mm

Early life development of S. japonica

15 days after hatch, TL 8.0 mm

38 days after hatch, TL 30 mm

Phytoplankton:Tetraselmis tetrathele and Pavlova lutheri

Zooplankton:Branchionus plicatilis sp. complex

Fish rearing tank

Rearing system for larval S. japonica

Temp: 26℃Sal: 32.5Total alkalinity: 2250µmol/kgsw

Rearing experiments of larval S. japonica with different pH condition

Rearing tank for larval fish from 0 to 30 days

pH modifying tank

Vigorous aeration

Inflow with pH 8.05(pCO2 580 μatm)

pH modifying

tank

Outflow pH 8.18(pCO2 400 μatm)

Tank 1: Initial pH: 8.09 Without pH control during experiment

Tank 2: Initial pH: 8.15 Without pH control during experiment

Tank 3: Initial pH: 8.13With slightly pH controlled using water

passed through the pH modifying tank by aeration to make pCO2 equal to pCO2air

Tank 4: Initial pH:8.13 With slightly pH controlled using water passed through the pH modifying tank by aeration to make pCO2 equal to pCO2air

Days after hatch

0 2 4 6 8 10

pH o

f sup

plie

d SW

8.04

8.06

8.08

8.10

8.12

8.14

8.16

8.18

8.20

Days after hatch vs #8 pH Days after hatch vs #9-1 pH Days after hatch vs #9-3 pH Days after hatch vs 2016 pH

pH changes during rearing and survival rate at 8 days

70%

43%

49%

pH threshold ??

83%

Impacts of change in pH on larval S. japonica

7.8

7.9

8.0

8.1

8.2

8.3

8.4

8.5

8.6

1982 1987 1992 1997 2002 2007 2012 2017

pH

��

pH threshold ??

year

pH

“Threshold” is also important for juvenile's survival of Sillagojaponica?

Note: pH is that of inflow water of tank (water inside the tank was not taken for pH monitor because the larval S. japonica is very delicate)

Summary

• Subsurface pH in the western Arctic Ocean observed from Sep 2015 to Sep 2016 showed large seasonality with dynamic range of 0.5 pH unit. The pH largely dropped in summer and the beginning of sea-ice seasons.

• Pteropods shell density decreased maximum 40% responding to the reduction of aragonite saturation degree (Ωara) during summer and the beginning of sea-ice seasons in the western Arctic Ocean.

• At Japanese coastal stations, the annual pH reduction rate was -0.007 and-0.011 at the Pacific and Japan Sea sides, respectively. These are twice or three times larger than those of monitoring sites in pelagic oceans.

• Popular commercial organisms, ezo-abalone and Sillago japonica responded to ocean acidification. Rearing experiments showed that their juvenile received immediately negative impact when the pH (or Ωara or pCO2) drops under the threshold.

• Adaptation strategies for marine organisms such as seed production of commercially important fish are necessary to overcome progress in future ocean acidification.