Research Topics

Diversity and biogeography of zooplankton

Marine zooplankton comprise an abundant and diverse group including >7,000 described species.We investigate diversity and biogeography of marine zooplankton in the global oceans using metabarcoding approach. In addition, we aim to deposit genetic data of important zooplankton species on public database for reference sequence libraries.

Diversity and ecological role of viruses infecting marine zooplankton 

Zooplankton and viruses play a key role in marine ecosystems; however, their interactions have not been examined. We investigate impact of viral infections on population dynamics and physiological changes of marine zooplankton using molecular-based methods.

Environmental adaptation of coastal marine zooplankton

We investigate the life history strategy of coastal marine zooplankton to understand their adaptation to highly variable environments. In particular, we focus on interpopulation variation in phenological and physiological traits of zooplankton dormancy.

Dynamics of microplastic in the ocean

Microplastic pollution is an important issue for marine environment. We monitor the abundance and distribution of microplastics in various regions of the world’s oceans. In addition, we investigate the sedimentation of microplastics through biological processes to understand its fate in the ocean.

Microbial dynamics in sea surface microlayer and sea spray aerosols

The sea surface microlayer (SML) refers to the layer corresponding to the thickness of the extreme surface layer of the sea of 1 mm or less, and is the region corresponding to the boundary between the atmosphere and the ocean. Focusing on the microbial dynamics in the ocean surface microlayers and the aerosols produced from them as the key to controlling the feedback of marine biological activity to the climate system, we make full use of our unique sampling equipments and the latest environmental DNA/RNA analysis technology to analyze the structure and function of microbial communities.

Microbial biogeochemistry in the polar oceans

In recent years, global warming has been particularly pronounced in polar regions, accelerating the melting of sea ice. The sea ice reduction will have a great impact on the polar organisms, especially phytoplankton, bacteria, and archaea, which are at the bottom of the trophic pyramid. We aim to elucidate the functions and biogeochemical roles of polar microorganisms and their responses to the environmental changes through field-based observations.

Novel photoreceptor proteins in marine microbes

Almost all biological processes on Earth are driven by solar energy. Recently, large-scale metagenomic analyses have revealed that microbes with novel photoreceptors (called rhodopsins) are ubiquitous in the ocean surface layer. We aim to elucidate the ecology and evolution of rhodopsin-possessing microbes applying bioinformatics and molecular biological techniques.

Isolation of novel marine bacteria and proposal of new species

A vast number of undescribed microbes inhabit the oceans. Through isolation and genome analysis of marine microbes, we propose new microbial species and search for novel biological functions. 

Evolution and ecology of deep-sea invertebrates including hot vent and trench endemics

Deep-sea environments including hydrothermal vent fields and hadal trenches harbor endemic and highly adapted animal communities, which provide unique opportunities to investigate evolutionary processes, adaptation and dispersal in the ocean. Our current studies on deep-sea invertebrates include genetic population analyses and species- and higher-level phylogenies based on the comparison of DNA sequences and morphological traits. We are also investigating the early development and dispersal mechanisms of the vent endemics and other deep-sea species by rearing pelagic larvae and analyzing the chemical composition of gastropod shells.

Evolutionary history of benthic animals in the Sea of Japan 

The Sea of Japan is a semi-closed sea connected with neighboring seas by shallow and narrow straits and thought to have experienced environmental deterioration during the last glacial maximum. In order to evaluate the effects of climate changes on marine ecosystems, we are comparing the genetic population structures of various benthic animals between the Sea of Japan and neighboring seas.

Phylogeography of coastal animals 

Benthic animals often show limited dispersal ability with a short pelagic larval period or direct development, and hence genetic population differentiation. We are investigating their population structures along the coasts of Japan to evaluate the effects of past and future environmental changes.

Natural history of amphidromous snails

Many snail species in tropical coastal streams have wide geographic ranges thanks to their amphidromous life cycle. Hatched swimming larvae are swept downstream to the ocean where they spend weeks to many months; metamorphosis occurs at brackish reaches and young snails crawl upstream where they reproduce. We aim at unraveling their ecology and evolution from genetic, morphological, behavioral and ontogenetic perspectives for a global understanding of insular stream ecosystems.