FY2021 Annual Report

Mitarai Unit
Associate Professor Satoshi Mitarai

 

1. Abstract

The Marine Biophysics Unit (MBU) investigates biological processes in the ocean at varying spatial scales, from micrometers for microbes to thousands of kilometers for biogeographic events, by incorporating physical, mathematical, and biological/genetic approaches. The physical oceanographic resources and expertise at the MBU, coupled with tools in marine biology, molecular biology, and paleontology, provide a unique laboratory system for studying marine biological processes, influenced by powerful disturbances (e.g., typhoons) and climatic forcings (e.g., global warming). The MBU was established at OIST in 2009, because of Okinawa’s ideal geographic position and access to the outstanding research resources of OIST.

Okinawa’s beautiful coral reefs lie at the northern boundary of the region with high marine biodiversity, exposed to large seasonal variations in water temperature and strong disturbances created by typhoons. Okinawa is located close to hydrothermal vent fields that support ecosystems of endemic species that do not depend on photosynthesis. It is also situated in “Typhoon Alley”, the region with the most frequent and fully-developed tropical cyclones on Earth. The MBU takes advantage of these natural resources to study how marine ecosystems work. Okinawa is home to many rare species that live in unique ecosystems. In 2021, a chain of islands in Southwestern Japan, including some parts of Okinawa, were added to the UNESCO World Heritage list. By quantifying physical and biological processes in the ocean, we contribute to protecting them from human-induced changes that could otherwise lead to the collapse of these vulnerable ecosystems in Okinawa and the loss of rare species.

2. Staff

2.1 Members of the Marine Biophysics Unit in FY2021

  • Lead Investigator: Satoshi Mitarai
  • Research Unit Administrator: Tomoko Yoshino

Table 1. Members of the Marine Biophysics Unit in FY2021

  Name Funding source

Postdoctoral Scholars

 Angela Ares Pita OIST & External1,2
  Yosuke Yamada OIST & External3–6
  Heng Wu OIST
OIST Students Maki Thomas OIST
  Po-Shun Chuang OIST& External7
  Otis Bruner OIST
  Kota Ishikawa OIST
Technicians Kazumi Inoha OIST
  Akinori Murata OIST
  1. Grant-in-Aid for Early-Career Scientist, Japan Society for the Promotion of Science Scholarship (20K19986)
  2. Grant-in-Aid for Early-Career Scientist, Japan Society for the Promotion of Science Scholarship (18K18203)
  3. Sasakawa Scientific Research Grant, Japan Science Society (2021-6014)
  4. Fusion Oriented Research for disruptive Science and Technology, Japan Science and Technology Agency (JPMJFR2070)
  5. Grant-in-Aid for Early-Career Scientist, Japan Society for the Promotion of Science Scholarship (20K19960)
  6. Interdisciplinary Collaborative Research Grant, University of Tokyo
  7. Grant-in-Aid for JSPS Fellows DC1, Japan Society for the Promotion of Science Scholarship (18J20226)

2.2 Internship & Rotation Students

Internship Student

  • Kimika Takeyasu, Kobe University, October 1, 2021 – December 1, 2021

Rotation Student

  • Pradeep Palanichamy, 2020/2021 Term 3

3. Collaborations

3.1 Agreements

University of Guam

  • Topic: Connectivity and population dynamics of corals in the Western Pacific Ocean
  • Collaborators: Terry Donaldson, Atsushi Fujimura, David Combosch
  • Term: April 1, 2021 to March 31, 2025

11th Regional Coast Guard Headquarters

  • Topic: Improvement of drift prediction accuracy
  • Topic: Sophistication of ocean tide model and ocean current simulation in the sea around Okinawa
  • Term: April 1, 2021 to March 31, 2024

Scripps Institution of Oceanography

  • Topic: Research on coral ecosystem diversity and spatial distribution throughout the islands of Okinawa
  • Collaborator: Stuart Sandin
  • Term: September 1, 2018 to August 31, 2022

3.2 Visitors

Kimika Takeyasu (Master’s student, Kobe University)

  • Status at OIST: Research Intern
  • Research Project: Coral larval transportation on the coast of Okinawa Main Island
  • Funding Source: Kobe University/OIST
  • Dates: October 1, 2021 – December 1, 2021

Yuichi Nakajima (Professor, Nagahama Institute of Bio-Science and Technology)

  • Status at OIST: Visiting Researcher
  • Research Project: Population genetics and genomics in marine organisms
  • Funding Source: Nagahama Institute of Bio-Science and Technology
  • Dates: July 1–10, 2021

Hajime Kayane (Professor, University of Tokyo)

  • Status at OIST: Visiting Researcher
  • Research Project: Determination of marine physicochemical characteristics of Onna, Okinawa
  • Funding Source: University of Tokyo
  • Dates: Postponed to April 17–23, 2022, due to COVID-19

Tomoko Takeda (Ph.D., University of Tokyo)

  • Status at OIST: Visiting Researcher
  • Research Project: Determination of marine physicochemical characteristics of Onna, Okinawa
  • Funding Source: University of Tokyo
  • Dates: Postponed to April 17–23, 2022, due to COVID-19

Alex S. J. Wyatt (Professor, Hong Kong University of Science and Technology)

  • Status at OIST: Visiting Researcher
  • Research Project: Environmental drivers of coral reef ecosystems in the Ryukyu Archipelago
  • Funding Source: Hong Kong University of Science and Technology
  • Dates: Postponed to May 2022, due to COVID-19

4. Activities and Findings

4.1 Fieldwork Activities

Shore sampling and observation (on land)

  • Fieldwork application: FWA-2019-003-3
  • Location: Onna
  • Date: April 6

Shore sampling and observation (walking in water)

  • Fieldwork application: FWA-2019-004
  • Location: Ginowan, Nago, Onna, Ogimi
  • Date: April 1, 15, 28, May 13, 27, June 10, 24, July 8, 18, 28, August 6, 19, September 2, December 12, 21

Shore sampling and observation (boat/kayak)

  • Fieldwork application ID: FWA-2019-005-4, FWA-2019-005-5
  • Location: Onna
  • Date: May 23–June 1, November 12, 16, 19, December 14, March 4

JAMSTEC research cruise

  • Fieldwork application: FWA-2019-006
  • Location: Open water (Shinsei Maru, KS-21-7, Kushiro to Ishinomaki)
  • Date: May 3–11 

Reef observation (diving)

  • Fieldwork application: FWA-2021-016
  • Location: Onna
  • Date: September 27, October 15, 25, 29, November 4, 8, 30, December 21 

Wave Glider observations of surface winds and currents

  • Fieldwork application: FWA-2021-017-2
  • Location: Open water (off Itoman, off Ojima)
  • Date: September 25, October 21, November 25–27  

4.2 Animal Experiment

Physical reaction of garden eels and reef fish using a flume tank 

  • Animal experiment application: 2019-249-3
  • Location: OIST Marine Science Station at Seragaki
  • Date: December 13–26
  • Animal use: garden eels (Heteroconger hassi), blue-green chromis (Chromis viridis)

4.3 Laser Experiment

Effect of flows on transparent exopolymer particle release from corals 

  • Laser experiment application: LWP-2020-005
  • Laser class: 4
  • Location: OIST Marine Science Station at Seragaki
  • Date: October 11, 12, January 25, 27, 28, February 15, 16

4.4 Findings

Differential patterns of connectivity in Western Pacific hydrothermal vent  metapopulations: A comparison of biophysical and genetic models

Hydrothermal ecosystems face threats from planned deep-seabed mining activities, despite the fact that patterns of realized connectivity among vent-associated populations and communities are still poorly understood. Since populations of vent endemic species depend on larval dispersal to maintain connectivity and resilience to habitat changes, effective conservation strategies for hydrothermal ecosystems should include assessments of metapopulation dynamics. In this study, we combined population genetic methods with biophysical models to assess strength and direction of gene flow within four species of the genus Alviniconcha (A. boucheti, A. kojimai, A. strummeri and A. hessleri) that are ecologically dominant taxa at Western Pacific hydrothermal vents. In contrast to predictions from dispersal models, among-basin migration in A. boucheti occurred predominantly in an eastward direction, while populations within the North Fiji Basin were clearly structured despite the absence of oceanographic barriers. Dispersal models and genetic data were largely in agreement for the other Alviniconcha species, suggesting limited between-basin migration for A. kojimai, lack of genetic structure in A. strummeri within the Lau Basin and restricted gene flow between northern and southern A. hessleri populations in the Mariana back-arc as a result of oceanic current conditions. Our findings show that gene flow patterns in ecologically similar congeneric species can be remarkably different and surprisingly limited depending on environmental and evolutionary contexts. These results are relevant to regional conservation planning and to considerations of similar integrated analyses for any vent metapopulations under threat from seabed mining.

Effects of prey density and flow speed on plankton feeding by garden eels: a flume study 

Feeding by zooplanktivorous fish depends on their foraging movements and the flux of prey to which they are exposed. While prey flux is a linear function of zooplankton density and flow speed, those two factors are expected to contribute differently to fish movements. Our objective was to determine effects of these factors for garden eels, stationary fish that feed while anchored to the sandy bottom by keeping the posterior parts of their bodies inside a burrow. Using a custom-made flume with a sandy bottom, we quantified effects of prey density and flow speed on feeding rates by spotted garden eels (Heteroconger hassi). Feeding rates increased linearly with prey density. However, feeding rates did not show a linear relationship with flow speed and decreased at 0.25 m s−1. Using label-free tracking of body points and three-dimensional movement analysis, we found that the reduction in feeding rates was related to modulation of the eel's movements, whereby the expected increase of energy expenditure was avoided by reducing exposure and drag. No effects of flow speed on strike speed, reactive distance, or vectorial dynamic body acceleration (VeDBA) were found. A foraging model based on the body length extended from the burrow showed correspondence with observations. These findings suggest that due to their unique foraging mode, garden eels can occupy self-made burrows in exposed shelter-free sandy bottoms where they can effectively feed on drifting zooplankton.

Genetic changes involving the coral gastrovascular system support the transition between colonies and bailed-out polyps: evidence from a Pocillopora acuta transcriptome

A coral colony is composed of physiologically integrated polyps. In stony corals, coloniality adopts a wide diversity of forms and involves complex ontogenetic dynamics. However, molecular mechanisms underlying coloniality have been little studied. To understand the genetic basis of coloniality and its contribution to coral ecology, we induced polyp bail-out in a colonial coral, Pocillopora acuta, and compared  transcription profiles of bailed-out polyps and polyps in normal colonies, and their responses to heat shock and hyposalinity. Consistent with morphological formation of a gastrovascular system and its neural transmission and molecular transport functions, we found genetic activation of neurogenesis and development of tube-like structures in normal colonies that is absent in bailed-out polyps. Moreover, relative to bailed-out polyps, colonies showed significant overexpression of genes for angiotensin-converting enzymes and endothelin-converting enzymes. In response to hyperthermal and hyposaline treatments, a high proportion of genetic regulation proved specific to either bailed-out polyps or colonies. Elevated temperatures even activated NF-κB signaling in colonies. On the other hand, colonies showed no discernible advantage over bailed-out polyps in regard to hyposalinity. The present study provides a first look at the genetic basis of coloniality and documents different responses to environmental stimuli in P. acuta colonies versus those in bailed-out polyps. Overexpression of angiotensin-converting enzymes and endothelin-converting enzymes in colonies suggests possible involvement of these genes in development of the gastrovascular system in P. acuta. Functional characterization of these coral genes and further investigation of other forms of the transition to coloniality in stony corals should be fruitful areas for future research.

 

5. Publications

5.1 Journals

In Review

  1. Pezner, A. K., Courtney, T. A., Barkley, H. C., Chou, W.-C., Chu, H.-C., Clements, S. M., Cyronak, T., DeGrandpre, M. D., Kekuewa, S. A. H., Kline, D. I., Liang, Y.-B., Martz, T. R., Mitarai, S., Page, H. N., Rintoul, M. S., Smith, J. E., Soong, K., Takeshita, Y., Tresguerres, M., Wei, Y., Yates, K. K., & Andersson, A. J. Global coral reefs will experience moderate to severe hypoxia before the end of the century. In review, submitted on February 15, 2022.
  2. Brunner, O., Chen, C., Giguère, T., Kawagucci, S., Tunnicliffe, V., Watanabe, H., & Mitarai, S. Species Assemblage networks identify regional connectivity pathways among hydrothermal vents in the Northwest Pacific. In review, submitted on January 28, 2022.
  3. Rintoul, M. S., Courtney, T. A., Dohner, J. L., Giddings, S. N., Kekuewa, S. A. H., Mitarai, S., Monismith, S. G., Pezner, A. K., & Andersson, A. J. The effects of light intensity and flow speed on biogeochemical variability within a fringing coral reef in Onna-son, Okinawa, Japan. In review, submitted on December 12, 2021.

In Revision

  1. Brisbin, M. M., Mitarai, S., Saito, M. A., & Alexander, H. Microbiomes of the bloom-forming alga, Phaeocystis globosa, are stable, consistently recruited communities with symbiotic and opportunistic modes. In revision, submitted on February 6, 2022.
  2. Thomas, M., Nakajima, Y., & Mitarai, S. Rare, stochastic, and continuous island mangrove connectivity reveal fine-scale spatiotemporal patterns: Guidance for effective mangrove conservation. In revision, submitted on December 2, 2021.
  3. Nakajima, Y., Wepfer, P. H., & Mitarai, S. Clonal distribution and spatial genetic structure in the reef-building coral, Galaxea fascicularis. In revision, submitted on November 4, 2021.
  4. Wepfer, P. H., Nakajima, Y., Fujimura, A., Mikheyev, A. S., Economo, E. P. & Mitarai, S. The oceanographic isolation of the Ogasawara Islands and genetic divergence in a reef-building coral. In revision, submitted on September 13, 2021.
  5. Ares, A., Sakai, S., Sasaki, T., Mitarai, S., & Nunoura, T. Sequestration and efflux largely account for Cd and Cu resistance in the deep sea Epsilonproteobacteria, Nitratiruptor sp. In revision, submitted on September 9, 2021.

To appear

  1. Ishikawa, K., Wu, H., Mitarai, S., & Genin, A. Effects of prey density and flow speed on plankton feeding by garden eels: a flume study. To appear, submitted on October 12, 2021, accepted on March 17, 2022.

Published

  1. Breusing, C., Johnson, S. B., Mitarai, S., Beinart, R. A., & Tunnicliffe, V. (2021). Differential patterns of connectivity in Western Pacific hydrothermal vent metapopulations: A comparison of biophysical and genetic models. Evolutionary Applications. https://doi.org/10.1111/eva.13326
  2. Takeyasu, K., Uchiyama, Y., Zhang, X., Matsushita, K., & Mitarai, S. (2021). Three-dimensional connectivity of coral larvae in reef areas on the northwest coast of Okinawa main island, Japan, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering). https://doi.org/10.2208/kaigan.77.2_i_883
  3. Chuang, P.-S., & Mitarai, S. (2021). Genetic changes involving the coral gastrovascular system support the transition between colonies and bailed-out polyps: evidence from a Pocillopora acuta transcriptome. BMC Genomics. http://dx.doi.org/10.1186/s12864-021-08026-x
  4. Nakamura, M., Nomura, K., Hirabayashi, I., Nakajima, Y., Nakajima, T., Mitarai, S., & Yokochi, H. (2021). Management of scleractinian coral assemblages in temperate non-reefal areas: insights from a long-term monitoring study in Kushimoto, Japan (33°N). Marine Biology. https://doi.org/10.1007/s00227-021-03948-2
  5. Uwizeye, C., Mars Brisbin, M., Gallet, B., Chevalier, F., LeKieffre, C., Schieber, N. L., Falconet, D., Wangpraseurt, D., Schertel, L., Stryhanyuk, H., Musat, N., Mitarai, S., Schwab, Y., Finazzi, G., & Decelle, J. (2021). Cytoklepty in the plankton: A host strategy to optimize the bioenergetic machinery of endosymbiotic algae. Proceedings of the National Academy of Sciences of the United States of America. https://doi.org/10.1073/pnas.2025252118

5.2 Books and other one-time publications

  • Nothing to report

5.3 Oral and poster presentations

Submitted

  1. Rintoul, M., Courtney, T., Dohner, J., Giddings, S., Inoha, K., Kekuewa, S., Mitarai, S., Monismith, S., Pezner, A., & Andersson, A. (2022). Modulation of biogeochemical variability by physical processes on a fringing coral reef. 15th International Coral Reef Symposium, Bremen, Germany, July 3–8, 2022.

Accepted

  1. Kataoka, K., Takeyasu, K., Uchiyama, Y., & Mitarai, S. (2022). Quantifying wave-induced effects on Lagrangian transport: with an application to larval dispersal of corals. 69th Annual Conference on Coastal Engineering, Yokosuka, Japan (hybrid), November 8–11, 2022. 
  2. Kosaka, N., Iizuka, T., Umemiya, Y., Itami, G., Murata, A., & Mitarai, S. (2022). A comparison of satellite and reanalysis with in-situ ocean observation utilizing an autonomous Wave Glider. International Geoscience and Remote Sensing Symposium 2022, Kuala Lumpur, Malaysia, July 17–22, 2022. (Accepted, April 5, 2022)
  3. Kosaka, N., Nakamura, T., Kura, T., Iizuka, T., Umemiya, Y., Itami, G., Murata, A., & Mitarai, S. (2022). Evaluation of typhoon observation data utilizing an autonomous Wave Glider. AOGS2022 the 19th Annual Meeting, Online, August 1–5, 2022. (Accepted, March 23, 2022)
  4. Wu, H., Yamada, Y., Chuang, P.-S., Ishikawa, K., & Mitarai, S. (2022). Effects of ambient flows on the transparent exopolymer particle release from branch corals and the associated bacterial growth. Microscale Ocean Biophysics 2022, Mallorca, Spain, May 22–27, 2022.  (Accepted, March 1, 2022)
  5. Ishikawa, K., Wu, H., Mitarai, S., & Genin, A. (2022). Effects of flow speed on plankton feeding by garden eels: a flume study. Microscale Ocean Biophysics 2022, Mallorca, Spain, May 22–27, 2022. (Accepted, March 1, 2022)

Scheduled

  1. Vogt-Vincent, N., & Mitarai, S. (2022). The Kuroshio Current at the Last Glacial Maximum and implications for coral paleobiogeography. EGU General Assembly 2022, Vienna, Austria,  April 3–8, 2022. (Oral, May 23, 2022)
  2. Kosaka, N., Nakamura, T., Kura, T., Iizuka, T., Umemiya, Y., Itami, G., Murata, A., Mitarai, S. (2022). A comparison of satellite and reanalysis temperature products with in-situ Wave Glider and UAV ocean observations. Meteorological Society of Japan 2022 Spring Meeting, Online, May 17–21, 2022. (Poster, May 20, 2022)
  3. Mitarai, S., Nakamura, M., Nakajima, Y., Touber, E., & Winn, S. (2022). Toward modeling propagule dispersal of corals, seagrasses, macroalgae, and mangroves. Japan Geoscience Union Meeting 2022, Makuhari, Chiba, Japan, May 22–27, 2022. (Oral, May 27, 2022)
  4. Kosaka, N., Nakamura, T., Kura, T., Iizuka, T., Umemiya, Y., Itami, G., Murata, A., Mitarai, S. (2022). A comparison of satellite and reanalysis wind products with in-situ Wave Glider and UAV ocean observations. Japan Geoscience Union Meeting 2022, Makuhari, Chiba, Japan, May 22–27, 2022. (Poster, May 30, 2022)
  5. Umemiya, Y., Kosaka, N., Iizuka, T., Itami, G., Nakamura, T., Kura, T., Murata, A., & Mitarai, S. (2022). Validation of a vertical model of ocean wind using “synchronous ocean observation” data from UAV (multicopter) and Wave Glider. Japan Geoscience Union Meeting 2022, Makuhari, Chiba, Japan, May 22–27, 2022. (Poster, May 30, 2022)

Presented

  1. Wu, H., Yamada, Y., Chuang, P.-S., Ishikawa, K., & Mitarai, S. (2022). Effect of flows on transparent exopolymer particle release from corals. 2022 Ocean Sciences Meeting, February 24 – March 4, 2022, Online. 
  2. Ishikawa, K., Wu, H., Mitarai, S., & Genin, A. (2022). Effects of prey density and flow speed on plankton feeding by garden eels: a flume study. 2022 Ocean Sciences Meeting, February 24 – March 4, 2022, Online.
  3. Rintoul, M., Courtney, T., Dohner, J., Giddings, S., Inoha, K., Kekuewa, S., Mitarai, S., Monismith, S., Pezner, A., & Andersson, A. (2022). Modulation of biogeochemical variability by physical processes on a fringing coral reef in Okinawa. 2022 Ocean Sciences Meeting, February 24 – March 4, 2022, Online.
  4. Pezner, A. K., Barkley, H. C., Chou, W.-C., Chu, H.-C., Clements, S. M., Courtney, T. A.,  Cyronak, T., DeGrandpre, M. D., Kekuewa, S. A. H., Kline, D. I., Liang, Y.-B., Martz, T. R., Mitarai, S., Page, H. N., Rintoul, M. S., Smith, J. E., Soong, K., Takeshita, Y., Tresguerres, M,  Wei, Y., Yates, K. K., & Andersson, A. J. (2022). Global coral reefs will experience moderate to severe hypoxia before the end of the century. 2022 Ocean Sciences Meeting, Online, February 24 – March 4, 2022.
  5. Brunner, O., Mitarai, S., & Tunnicliffe, V. (2021). Hydrothermal vent community assemblage networks of the North-West Pacific, 6th Deep-Sea Biology Symposium, Brest, France, September 12–17, 2021 (Online).
  6. Takeyasu, K., Uchiyama, Y., Zhang, X., & Mitarai, S. (2021). Nearshore three-dimensional connectivity of coral larvae in reef Areas on the Northwest Coast of Okinawa main island, AOGS2021 the 18th Annual Meeting, Online, August 1–6, 2021.
  7. Chuang, P.-S., & Mitarai, S. (2021). Transcriptome analysis reveals parallel mechanisms in hyperosmosis-induced polyp bail-out. 14th International Coral Reef Symposium, Bremen, Germany, July 19-23, 2021 (Online).

5.4 Intellectual Property Rights and Other Specific Achievements

  • Nothing to report

6. Meetings and Events

6.1 Invited lectures

Scheduled

  • Mitarai, S., Nakamura, M., Nakajima, Y., Touber, E., & Winn, S. (2022). Toward modeling propagule dispersal of corals, seagrasses, macroalgae, and mangroves. Japan Geoscience Union Meeting 2022, Makuhari, Chiba, Japan, May 22–27, 2022.

Presented

  • Mitarai, S. (2022). Pumice stones from Fukutoku-Okanoba submarine volcano. Onna-Village SDGs meeting, Onna, Okinawa, February 10, 2022 (via Zoom).
  • Mitarai, S. (2022). Pumice stones from Fukutoku-Okanoba submarine volcano. University of the Ryukyus Forum, Nishihara, Okinawa, February 5, 2022.
  • Mitarai, S. (2021). Beautiful Okinawan ocean. Japan Chart 150th Anniversary, Naha, Okinawa, November 30, 2021. https://vimeo.com/652369719

6.2 Mini-symposium

  • None

6.3 Workshop

  • None