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Shirai Lab
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The lab analyzes the shells of mollusks and the skeletons of corals to reconstruct past environments.
AboutAbout the lab
Reading the past ocean in shells and corals
The Shirai Lab reconstructs past environments by analyzing the calcium carbonate produced by organisms such as corals, bivalves, and foraminifera.
Some chemical compositions and isotope ratios in shells and skeletons change in sensitive response to changes in the surrounding environment, such as water temperature and salinity.
To predict future environments, the lab investigates in detail what past environments were like.
Fieldwork for sample collection is part of the research, but the core of the work is steady chemical analysis and microscope observation in the laboratory.
Key terms
- Isotope ratio
- The proportions of atoms of the same element that have different masses. Because these proportions change with environmental conditions such as water temperature, they serve as clues to past environments.
- Foraminifera
- Tiny single-celled marine organisms with calcium carbonate shells. When they die, their shells accumulate on the seafloor.
- Otolith
- Calcium carbonate crystals found in a fish's inner ear. They form rings as the fish grows and record the environments it has lived in.
NewsLab news
View More ↗ResearchResearch themes
Using calcium carbonate analysis and growth-line analysis as its main methods, the lab uncovers the history of how climate change, material cycling, and ecosystems have changed in interaction with one another. Findings obtained from modern samples are also applied to samples stored in museums, samples from archaeological sites such as shell middens, and fossils.
*Illustrative imageEnvironmental Change Recorded in Coral Skeletons
Corals form one pair of annual bands each year, and some grow for several hundred years. By analyzing skeletons going back in time, the lab reconstructs environmental changes such as global warming and El Niño over hundreds of years at intervals of a few weeks.
*Illustrative imageShort-Timescale Environments Read from Bivalve Shells
Bivalves grow by forming one (or sometimes two) daily growth lines per day. The lab analyzes shells at the level of daily growth lines to reconstruct environmental changes on timescales of a day or less, such as heavy rain, typhoons, and tides.
*Illustrative imageLong-Timescale Environments Read from Foraminiferal Shells
The lab collects seafloor sediments using research vessels and analyzes the foraminiferal shells they contain in order of depth. Fine time resolution is difficult to achieve, but in exchange, environments over very long periods can be reconstructed.
*Illustrative imageLife Histories Traced from Otoliths and Bones
The lab analyzes the hard tissues of mobile organisms, such as bones and fish otoliths, to reconstruct ecological life histories, including growth, migration, and diet.
MembersFaculty
- Associate ProfessorShirai KotaroPublications ↗
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Report an errorAbout the images
The top and research theme images are illustrative and were not taken at the lab. They are cropped from Wikimedia Commons images. Cropped CC BY-SA images are provided under the same CC BY-SA license as the original (version shown on each line).
- Top image: “Giant clam (Tridacna gigas) Michaelmas Cay” Charles J. Sharp / CC BY-SA 4.0 (cropped)
- Environmental Change Recorded in Coral Skeletons: “Porites lobata coral” Narrissa Spies / CC BY-SA 4.0 (cropped)
- Short-Timescale Environments Read from Bivalve Shells: “Arctica islandica 01” H. Zell / CC BY-SA 3.0 (cropped)
- Long-Timescale Environments Read from Foraminiferal Shells: “Benthic foraminiferas” ja:User:NEON / commons:User:NEON_ja / CC BY-SA 2.5 (cropped)
- Life Histories Traced from Otoliths and Bones: “Black rockfish otolith cross section - USGS” Vanessa von Biela/USGS / CC BY-SA 3.0 (cropped)
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