GEOSS-AP: 20170112

The biologic responses on the marine calcifiers
to the Ocean acidificationin the Arctic and North PacificKatsunori Kimoto(Research and Development Center for Global Change
JAMSTEC)Aragonite saturation in 2100（Ωara)

polar & subarctic regions: low CO32saturation stateΩ = [Ca2+] [CO32-] / K’sp(Ω)→low Ω

K’sp : solubility product of calcite/aragonite
Ω>1: precipitation(shell preserved)
Ω<1: undersaturation (shell dissolved)

Target Areas

St. K2: 47N, 160E
deployment: 2008~ ongoing
Multiple sed. traps (200m, 500m, 1000m, 4800m)water depth 5,200m

Marine calcifiers as the sentinel of OA
Planktic foraminifers

Thecosomata (Sea butterfly)

200 µm1 mmajor calcium carbonate producer in the pelagic ocean (~80%

Unicellular marine protist living in the world
Planktic foraminifers oceans
Develop calcite shells and 1 month lifetime.
Inhabiting surface water (~200 m)
Pelagic gastropod living in the world oceans
Thecosomata(Shelled pteropods) Potential food source for fishes

Develop aragonite shells and yearly lifetime.
Inhabiting surface to deep water (~1000 m)

Inhibition of calcification by OA
Reducing of carbonate ions by ocean acidification will accelerate
inhibition of calcification of shelled plankton.
So far, however, it does not well developed quantitative andcomparable estimation method to evaluate biological impacts(damages) to the OA.

OA will make damages to theshell surface andthickness, probably affects
shell density.

Peck et al. (2016)

Quantitative estimation method of
biological impacts should be neededMicrofocus X-ray CT (MXCT) technique
Geometric layout

CT Number(proportional with density)

16 bit grayscale image(65,536 gradations)

1000(highest density)

Air (0)= Limestone
Carbonate
ShellLimestone(1000)

Carbonate shell= 600~1000
Soft body< 600600(lower density)

MXCT:High resolution 3D morphometry
Thecosomata (Shelled Pteropod): Limacina helicina(spatial resolution：0.8 µm, Cross sectional image with density)

density
high
1000

600
densitylow1 mm

MXCT:High resolution 3D morphometry
Planktic foraminifer: Globigerina bulloides(spatial resolution：0.8 µm, Cross sectional image with density)

densityhigh1000

200 µmMXCT can realize:

volume, surface area, thickness, density, and others
for individual specimen

Nondestructive

Quantitative600
densitylowShell density changes of planktic forams in NW
Pacific@St. K2~35 %decreased

SSTpH

~75 %
decreasedTime-series Mooring System in the Arctic OceanShell density changes of Pteropods in the Arctic(the result of more than 250 individuals)
NAP10tNAP11thighdensity

260m
Ave. = 856

lowdensity28%
decreased

highdensity

1300m
Ave. = 862

barrenlow
densityLarge changes of oceanic pH

Concluding remarks
Microfocus X-ray CT (MXCT) technique can be applied
successfully to evaluate the impact of OA for marine calcifies
quantitatively.
•Carbonate density of marine calcifies changes seasonally and~35 % reduction were observed in specific seasons in thesubarctic NP (winter) and Arctic Ocean (summer and early winter)•MXCT has a potential to be common standard method to evaluate
the shelled plankton responses on OA.-----more higher trophic
level plankton (e.g., Copepoda---chitinous substance)•To make carbonate density popular between OA communities,
JAMSTEC can provide the technique how to analyze carbonate
density by MXCT and is also preparing to receive measurement
request from the world.