Research and Projects

Research in the laboratory

"How the biogenic carbonate minerals respond to global environmental" has been the major concern in this laboratory,

  1. Solution Chemistry of CaCO3 Crystallization

    For this purpose, firstly, we have studied the fundamental solution chemistry of calcium carbonate: such as (1) the polymorphic crystallization of CaCO3 in the presence of trace additive ions in solution: Divalent metal ions with smaller ionic radii (such as Mg2+, Zn2+, Cu2+; etc) favors aragonite formation whereas those of larger ionic radii (Ba2+, UO22+, Hg2+ etc) favors calcitic carbonate formation. And also, (2) distribution coefficient of trace elements such as Mg2+, Sr2+, UO22+ and etc. has been studied. Which are considered to be suitable for paleo-chemistry and/or paleo-temperature of seawater (Oomori et. al.,1987).



    (3) As the second step, trace element content of biogenic carbonate skeletons such as corals and sclero-sponge were analyzed according to the growth band. It was elucidated that growth band of corals and sclerosponge are excellent proxy of paleo-ocean environmental change.

    Sclero Sponge

    X-ray Density Band
  2. Monitering of Carbonate System in Coral Reef(PCO2 , FCO2 , IP and OP)

    According to the increase in atmospheric CO2 awing to the fossil fuel combustion by anthropogenic activity, global warming and ocean acidification began to give serious threats on the survival of calcifying marine organisms and affect on the degradation of biodiversity of marine ecosystem. Breaching events are observed frequently in shallow tropical to subtropical coral reefs. (1) We have studied the PCO2 in coral reef water in Miyako-jima Island and Sesoko-jima island, and Organic and inorganic productions of corals and coral reef community under the normal and breaching conditions at Sesoko-jima Island and Re Union Island. (2) Long-term continuous monitoring of PCO2 in sea water and air-sea CO2 flux were also observed on site at coral reef. (3) We have developed a incubation methods of corals with continuous flow complete mixing (Fujimura et al. 2008). It was found that CO2 budget of coral-algal symbiosis and coral reef community level are mainly control by photosynthesis of symbiotic algae and calcification of coral.
    Time Series Monitering of PCO2 and Air-Sea CO2 Flux at Sesoko-jima
    Automatic Monitering System of Total Alkalinity and TIC
    Closed Titration Cell
  3. Chemical Impacts of Hazardous Substance on Coral Reef Ecosystem

    In addition, acute effect of chemical impacts such as of antifouring pesticides, organic tin compounds, and herbicide such as diuron and irgarol as well as photo-chemically produced Reactive Oxygen Compounds and hydroxyl radicals on coral metabolisms (photosynthesis and calcification) were studied in laboratory incubation experiments. Effect of seawater chemistry on the calcification mechanism of coral skeletal formation is now being studied in this laboratory.
    Polyp of Juvenile Coral
  4. Extraction, Identification and Function of Matrix Protein in Sclerite of Soft Corals

    Recently, we studied on the calcification mechanism of sclerites of soft corals. we separated carbonate sclerite of soft corals and have developed a extraction-purification method of matrix protein of sclerite of soft corals. We have newly found several noble proteins with characteristic nature of carbonic anhydrase(CA) enzyme activity, Ca-binging as well as regulation of morphology and mineralogy of CaCO3. crystallization in vitro.
    Sclerite of Soft Coral
    Calcite Aggregates Formed from Artificial Sea Water in the Presense of Matrix Protein

  5. Biodiversity of Deep-sea Gorgonians and Response to Grobal Environmental Change

    How the deep sea organisms respond to global warming and ocean acidification is also a challenging subject of carbonate chemistry. Knowledge on the effect of global change is increasing for shallow and deep sea scleractinian corals whereas nothing is known for deep sea gorgonian corals. Japanese waters have one of the highest biodiversities of gorgonian corals in the world and these endemic communities are hotspots of deep ocean biomass, providing critical habitat for fishes and invertebrates. These gorgonians have the characteristic to show very low growth rates but high longevity of about thousands years. Hardly nothing is known on the biology of these gorgonians and still less on how they will be affected by global change since their study has been delayed by technical sampling difficulties. We challenge here to study the biodiversity and response to global change of Japanese deep-sea gorgonians by collecting representative deep species and studying them in the laboratory.

    Red Coral

    Red Coral
  6. Shallow Submarine Hydrothermal Activity in Coral Reef at Taketomi-jima

    The typical coral reef in the Ryukyu Islands is named Sekisei Showko (Coral Lagoon). In this lagoon, at the east end, hot spring water with 60 ℃ is gushing out accompanied with natural gas from the bottom of coral reef. Biogeochemical observation around this vent site revealed the ecosystem diversity around this vent site with chemosynthesis and photosynthesis communities. A typical microorganisms with chlorophyll d containing cyanobacteria was identified around the active vents of Taketomijima shallow submarine hot springs.
  7. Biogeochemical Observation of Deep-sea Hydrothermal Vent Fields by SINKAI2000 and SINKAI6500

    Comparative study of geochemical feature of submarine hydrothermal vent system were carried out through dive studies of manned submersible SINKAI2000 and SINKAI6500 at backarc basin (Mid Okinawa Trough 1989-1997, South-West Okinawa Trough 2000). It is found that typical geochemical feature of Okinawa Trough is high CO2 contents in hydrothermal water and decreased pH in plume waters. Liquid CO2 evolves from the bottom and forms clathrate of hydrated CO2 (Sakai et al 1990).. Additional dive expeditions are Mid Oceanic Ridges (East Pacific Rise 1994, Mid Atlantic Ocean 1998) and Hot Spot(4773m depth at near Loihi of off Hawaii 1999). to study on the radioactive age determination of chimney ore formation and heavy metal contents of hydrothermal ores. Geochemical Ocean expedition also carried out at Okinawa Trough, Manus basin in South Pacific, Triple Junction at Indian Ocean(KH93-3) and Gulf of Aden.
  8. Radiochemical and Neutron Activation Analysis of Marine and Coral reef sediments and Hydrothermal Ores collected by Submersible Expedition.


  1. Response of coral reef to global warming and ocean acidification and possible drastic change..(JSPS)
  2. Chemical Impact of toxic substances on coral reef ecosystem: coupling effect with global warming and ocean acidification(JSPS).
  3. Calcification of of soft coral and response to global environmental change(JSPS)
  4. Comprehensive studies on biodiversity at coral reef-archipelago system(21ST COE) 2004-2009.3)

Ocean expedition and Field observation

  • SINKAI2000 Dive study of hydrothermal activity at Okinawatrough
  • SINKAI6500 Dive study of hydrothermal activity at East-Pacific Rise, Pacific Ocean and off-Hawaiii hydrothermal activity
  • R/V HAKUHO-MARU expedition at Indian Ocean.
  • R/VNAGASAKI-MARU expedition on deep sea water around Okinawa Islands.
  • Coral Reef studies on Carbonate chemistry at Miyako-jima, Sesoko-jima, Ishigaki-Shiraho, -Kabira, and La Re Union Is.
  • Geochemical studies of Taketomi hot springs on Geochemistry of water and sediments, and microbiology.