Research Fields

My current study is "Reconstruction of Ancient Cheosynthetic Ecosystems" during the period from late Mesozoic to Neogene. The goal of this study is to understand how modern-type chemosynthetic ecosystem were established and evolved through geological time.

What is a "Chemosynthetic Ecosystem"?

A chemosynthetic ecosystem can be defined as an ecosystem that is dependent on chemosynthetic microbes. Chemosynthetic bacteria, such as sulfur-oxidizing bacteria and methane-oxidizing bacteria, obtain their energy through the oxidation of reduced compounds. Some animals house such chemosynthetic bacteria in their gills or other parts of their body and take nourishment from them. This kind of ecosystem was first discovered in 1977 at the Galapagos Rise in the eastern Pacific. After the discovery, large-scale explorations were carried out, and numerous examples of chemosynthetic ecosystems were found in the world's oceans.

Chemosynthetic ecosystems are established in extreme environments

The environment where a chemosynthetic ecosystem has been established is usually characterized by extreme condition. Methane and hydrogen sulfide are the major energy sources of the ecosystem. Methane is a strong reducing agent and consumes oxygen. Animals can't survive without oxygen! Hydrogen sulfide is a crucial toxic compound for metazoans. Furthermore, hydrothermal vents and methane seeps are usually located in deep-sea, high-pressure areas. Thus, we can say that an extreme environment is a characteristic of a chemosynthetic ecosystem.

My questions and targets

My questions are:,(1) How did animals evolved in chemosynthetic ecosystems through the geological ages? (2) What are the factors that control the initial establishment of each ecosystem? My targets which I hope will reveal answers to the above questions are ancient methane seeps during late Mesozoic to Neogene (past 150 million years) in the Pacific Ocean.

My tool

To reconstruct ancient chemosynthetic ecosystems, I'm using several techniques drawn from paleontology, geology and geochemistry. For examples, standard observations of the mode of occurrences of fossils, taxonomy, petrological observations of slab samples and thin sections, electron probe micro analysis, scanning electron microscope observations, isotopic analyses of carbonate and organic compounds, and biomarker analysis.