Future redistribution of fishery resources suggests biological and economic trade-offs according to the severity of the emission scenario
Irene D. Alabia, Jorge García Molinos, Takafumi Hirata, Daiju Narita, Toru Hirawake
PLOS ONE, 19, 6, e0304718, e0304718, Public Library of Science (PLoS), 06 Jun. 2024
Scientific journal, Climate change is anticipated to have long-term and pervasive effects on marine ecosystems, with cascading consequences to many ocean-reliant sectors. For the marine fisheries sector, these impacts can be further influenced by future socio-economic and political factors. This raises the need for robust projections to capture the range of potential biological and economic risks and opportunities posed by climate change to marine fisheries. Here, we project future changes in the abundance of eight commercially important fish and crab species in the eastern Bering Sea and Chukchi Sea under different CMIP6 Shared Socioeconomic Pathways (SSPs) leading to contrasting future (2021–2100) scenarios of warming, sea ice concentration, and net primary production. Our results revealed contrasting patterns of abundance and distribution changes across species, time periods and climate scenarios, highlighting potential winners and losers under future climate change. In particular, the least changes in future species abundance and distribution were observed under SSP126. However, under the extreme scenario (SSP585), projected Pacific cod and snow crab abundances increased and decreased, respectively, with concurrent zonal and meridional future shifts in their centers of gravity. Importantly, projected changes in species abundance suggest that fishing at the same distance from the current major port in the Bering Sea (i.e., Dutch Harbor) could yield declining catches for highly valuable fisheries (e.g., Pacific cod and snow crab) under SSP585. This is driven by strong decreases in future catches of highly valuable species despite minimal declines in maximum catch potential, which are dominated by less valuable taxa. Hence, our findings show that projected changes in abundance and shifting distributions could have important biological and economic impacts on the productivity of commercial and subsistence fisheries in the eastern Bering and Chukchi seas, with potential implications for the effective management of transboundary resources.

Pan-Arctic marine biodiversity and species co-occurrence patterns under recent climate
Irene D. Alabia, Jorge García Molinos, Takafumi Hirata, Franz J. Mueter, Carmen L. David
Scientific Reports, 13, 1, Springer Science and Business Media LLC, 11 Mar. 2023
Scientific journal, Abstract

The Arctic region is experiencing drastic climatic changes bringing about potential ecological shifts. Here, we explored marine biodiversity and potential species associations across eight Arctic marine areas between 2000 and 2019. We compiled species occurrences for a subset of 69 marine taxa (i.e., 26 apex predators and 43 mesopredators) and environmental factors to predict taxon-specific distributions using a multi-model ensemble approach. Arctic-wide temporal trends of species richness increased in the last 20 years and highlighted potential emerging areas of species accrual due to climate-driven species redistribution. Further, regional species associations were dominated by positive co-occurrences among species pairs with high frequencies in the Pacific and Atlantic Arctic areas. Comparative analyses of species richness, community composition, and co-occurrence between high and low summer sea ice concentrations revealed contrasting impacts of and detected areas vulnerable to sea ice changes. In particular, low (high) summer sea ice generally resulted in species gains (loss) in the inflow and loss (gains) in the outflow shelves, accompanied by substantial changes in community composition and therefore potential species associations. Overall, the recent changes in biodiversity and species co-occurrences in the Arctic were driven by pervasive poleward range shifts, especially for wide-ranging apex predators. Our findings highlight the varying regional impacts of warming and sea ice loss on Arctic marine communities and provide important insights into the vulnerability of Arctic marine areas to climate change.

Acclimation by diverse phytoplankton species determines oceanic carbon to nitrogen ratios
Yoshio Masuda, Yasuhiro Yamanaka, Sherwood Lan Smith, Takafumi Hirata, Hideyuki Nakano, Akira Oka, Hiroshi Sumata, Maki Noguchi Aita
Limnology and Oceanography Letters, Wiley, 14 Jan. 2023, [Peer-reviewed]
Scientific journal

Relative contributions of photophysiology and chlorophyll-a abundance to phytoplankton group-specific primary production in the Kuroshio region as inferred by satellite ocean color remote sensing (in press)
Takafumi Hirata, Koji Suzuki
Journal of Oceanography, Mar. 2022, [Peer-reviewed], [Lead author]
English, Scientific journal

Photoacclimation by phytoplankton determines the distribution of global subsurface chlorophyll maxima in the ocean
Yoshio Masuda, Yasuhiro Yamanaka, Sherwood Lan Smith, Takafumi Hirata, Hideyuki Nakano, Akira Oka, Hiroshi Sumata
Communications Earth & Environment, 2, 1, Springer Science and Business Media LLC, Dec. 2021, [Peer-reviewed], [International Magazine]
Scientific journal, Subsurface chlorophyll maxima are widely observed in the ocean, and they often occur at greater depths than maximum phytoplankton biomass. However, a consistent mechanistic explanation for their distribution in the global ocean remains lacking. One possible mechanism is photoacclimation, whereby phytoplankton adjust their cellular chlorophyll content in response to environmental conditions. Here, we incorporate optimality-based photoacclimation theory based on resource allocation trade-off between nutrient uptake and light harvesting capacity into a 3D biogeochemical ocean circulation model to determine the influence of resource allocation strategy on phytoplankton chlorophyll to carbon ratio distributions. We find that photoacclimation is a common driving mechanism that consistently explains observed global scale patterns in the depth and intensity of subsurface chlorophyll maxima across ocean regions. This mechanistic link between cellular-scale physiological responses and the global scale chlorophyll distribution can inform interpretation of ocean observations and projections of phytoplankton responses to climate change.

Performance of JAXA’s SGLI standard ocean color products for oceanic to coastal waters: chlorophyll a concentration and light absorption coefficients of colored dissolved organic matter
Atsushi Matsuoka, Janet W. Campbell, Stanford B. Hooker, François Steinmetz, Kazunori Ogata, Takafumi Hirata, Hiroto Higa, Victor S. Kuwahara, Tomonori Isada, Koji Suzuki, Toru Hirawake, Joji Ishizaka, Hiroshi Murakami
Journal of Oceanography, 78, 4, 187, 208, Springer Science and Business Media LLC, 23 Oct. 2021, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, We present the performance of JAXA's SGLI standard algorithms for estimating chlorophyll a (chl a) concentration and the light absorption coefficients of colored dissolved organic matter (CDOM) using recently compiled high-quality data obtained from oceanic to coastal waters. Prior to the evaluation of the algorithms, we first compare two forward models (Gordon et al. in J Geophys Res 93(D9):10909-10924, 1988: G88 and Park and Ruddick in Appl Opt 44(7):1236-1249, 2005: PR05) using a wide range of inherent optical properties (IOPs) to (1) examine if the water reflectance is appropriately reproduced and (2) correct measured reflectance in terms of its bidirectionality. Based on a good reproducibility of water reflectance using the PR05, the optimized IOPs are further used for explaining errors in estimates of chl a concentration and CDOM absorption when using the SGLI, the GSM (Maritorena et al. in Appl Opt 41:2705-2714, 2002), and the QAA (Lee et al. in Appl Opt 41:5755, 2002) inversion algorithms. Results show that the mean error for estimating chl a concentration using the SGLI algorithm is 110% for our dataset. Although this error is lower than that of the GSM and the QAA algorithms, a significant underestimate at chl a higher than 2.0 mg m(-3) is observed, which is further shown by independent match-up analyses. Another SGLI CDOM product includes the mean error of 50% and shows deviation at high CDOM range (> 1.0 m(-1)). A similar trend is observed for the GSM but not for the QAA when a global relationship of CDOM to colored detrital matter is applied. The sources of errors are discussed for potentially improving the retrievals.

Phytoplankton Increase Along the Kuroshio Due to the Large Meander
Daniel Andres Lizarbe Barreto, Ricardo Chevarria Saravia, Takeyoshi Nagai, Takafumi Hirata
Frontiers in Marine Science, 8, Frontiers Media SA, 10 Aug. 2021, [Peer-reviewed], [Last author], ［Internationally co-authored］, [International Magazine]
Scientific journal, The Kuroshio Large Meander (LM) is known to be highly aperiodic and can last from 1 to 10 years. Since a stationary cold core formed between the Kuroshio and the southern coast of Japan off Enshu-Nada and approaching warm saltier water on the eastern side of the LM changes the local environment drastically, many commercially valuable fish species distribute differently from the non-LM period, impacting local fisheries. Despite this importance of the LM, the influences of the LM on the low trophic levels such as phytoplankton and zooplankton have still been unclear. In this study, satellite daily sea surface chlorophyll data are analyzed in relation to the LM. The results show positive anomalies of the chlorophyll-a concentration along the Kuroshio path during the LM periods, 2004–2005 and 2017–2019, from the upstream off Shikoku to the downstream (140°E). These positive anomalies are started by the triggering meander generated off south of Kyushu, which then slowly propagates to the downstream LM region in both the LM periods. Even though the detailed patterns along the Kuroshio region in the two LM periods were different, similar formations of the positive anomalies on the western side of the LM with shallower mixed layer depth are observed. Furthermore, we found clear relationships between the minimum distance from several stations along the coast to the Kuroshio axis and the mean chlorophyll-a anomaly, with significant correlations with the distance from different stations.

Marine biodiversity refugia in a climate‐sensitive subarctic shelf
Irene D. Alabia, Jorge García Molinos, Takafumi Hirata, Franz J. Mueter, Toru Hirawake, Sei‐Ichi Saitoh
Global Change Biology, 27, 14, 3299, 3311, Wiley, Jul. 2021, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
Scientific journal, The subarctic shelf of the Eastern Bering Sea (EBS) is one of the world's most productive marine environments, exposed to drastic climate changes characterized by extreme fluctuations in temperature, sea ice concentration, timing, and duration. These climatic changes elicit profound responses in species distribution, abundance, and community composition. Here, we examined the patterns of alpha and temporal beta diversity of 159 marine taxa (66 vertebrates and 93 invertebrate species) from 29 years (1990–2018) of species observations from the NOAA bottom trawl surveys in the EBS. Based on these data, we identified geographically distinct refugial zones in the northern and southern regions of the middle shelf, defined by high species richness and similarity in community species composition over time. These refugial zones harbor higher frequencies of occurrence for representative taxa relative to the regions outside of refugia. We also explored the primary environmental factors structuring marine biodiversity distributions, which underpinned the importance of the winter sea ice concentration to alpha and temporal beta diversity. The spatial biodiversity distributions between high and low winter sea ice regimes highlighted contrasting signals. In particular, the latter showed elevated species richness compared to the former. Further, the temporal beta diversity between the high and low winter sea ice periods underpinned an overall increase in the compositional similarity of marine communities in the EBS. Despite these spatiotemporal differences in biodiversity distributions, the identified refugia represent safe havens of marine biodiversity in the EBS. Distinguishing these areas can help facilitate conservation and management efforts under accelerated and ongoing climatic changes.

Radiometric calibration for a multispectral sensor onboard risesat microsatellite based on lunar observations
Masataka Imai, Junichi Kurihara, Toru Kouyama, Toshinori Kuwahara, Shinya Fujita, Yuji Sakamoto, Yuji Sato, Sei Ichi Saitoh, Takafumi Hirata, Hirokazu Yamamoto, Yukihiro Takahashi
Sensors, 21, 7, Apr. 2021, [Peer-reviewed], [International Magazine]
Scientific journal, Radiometric calibration utilizing the Moon as a reference source is termed as lunar cali-bration. It is a useful method for evaluating the performance of optical sensors onboard satellites orbiting the Earth. Lunar calibration provides sufficient radiometric calibration opportunities without requiring any special equipment, and is suitable for nano/microsatellites. This study applies lunar calibration to a multispectral sensor, Ocean Observation Camera (OOC), on board a microsat-ellite named Rapid International Scientific Experiment Satellite. Simulating the brightness of the Moon based on the RObotic Lunar Observatory and SELENE/Spectrum Profiler models, sensitivity degradation was proven to be negligible in any of the four spectral bands of the OOC with the sensor temperature correction. A bluing trend in the OOC’s sensor sensitivity was revealed, indi-cating a shorter observation wavelength shows larger irradiance. Comparing the top-of-atmosphere reflectance of Railroad Valley Playa with the Radiometric Calibration Network dataset revealed that the derived calibration parameter from the lunar calibration was valid for correcting the bluing trend in the visible range. Although the lunar and vicarious calibration parameters for the infrared band were unexpectedly inconsistent, lunar calibration could potentially contribute toward estimating the contaminated background radiance in the Earth observation images.

Lunar Calibration and its Validation for a Multispectral Sensor Onboard Risesat Microsatellite.
Masataka Imai, Junichi Kurihara, Toru Kouyama, Toshinori Kuwahara, Shinya Fujita 0002, Yuji Sakamoto, Sei-Ichi Saitoh, Takafumi Hirata, Hirokazu Yamamoto, Yuji Sato, Yukihiro Takahashi
IEEE International Geoscience and Remote Sensing Symposium(IGARSS), 7775, 7778, IEEE, 2021
International conference proceedings

Inhibition of competitive exclusion due to phytoplankton dispersion: a contribution for solving Hutchinson's paradox
YoshioMasuda, YasuhiroYamanaka, Takafumi Hirata, Hideyuki Nakano, Takashi S.Kohyama
Ecological Modelling, 430, https://doi.org/10.1016/j.ecolmodel.2020.109089, 109089, Elsevier BV, Aug. 2020, [Peer-reviewed], [International Magazine]
English, Scientific journal

Multiple facets of marine biodiversity in the Pacific Arctic under future climate
Irene D. Alabia, Jorge García Molinos, Sei-Ichi Saitoh, Takafumi Hirata, Toru Hirawake, Franz J. Mueter
Science of The Total Environment, 744, https://doi.org/10.1016/j.scitotenv.2020.140913, 140913, Elsevier BV, 2020, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
Scientific journal

Satellite Ocean Colour: Current Status and Future Perspective　　　　　　　　　　　　　　　
Steve Groom, Shubha Sathyendranath, Yai Ban, Stewart Bernard, Robert Brewin, Vanda Brotas, Carsten Brockmann, Prakash Chauhan, Jong-kuk Choi, Andrei Chuprin, Stefano Ciavatta, Paolo Cipollini, Craig Donlon, Bryan Franz, Xianqiang He, Takafumi Hirata, Tom Jackson, Milton Kampel, Hajo Krasemann, Samantha Lavender, Silvia Pardo-Martinez, Frédéric Mélin, Trevor Platt, Rosalia Santoleri, Jozef Skakala, Blake Schaeffer, Marie Smith, Francois Steinmetz, Andre Valente, Menghua Wang
Frontiers in Marine Science, 6:485, doi: 10.3389/fmars.2019.00485, 2019, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal

Biological data assimilation for parameter estimation of a phytoplankton functional type model for the western North Pacific
Yasuhiro Hoshiba, Takafumi Hirata, Masahito Shigemitsu, Hideyuki Nakano, Taketo Hashioka, Yoshio Masuda, Yasuhiro Yamanaka
Ocean Science, 14, 3, 371, 386, COPERNICUS GESELLSCHAFT MBH, 2018, [Peer-reviewed], [International Magazine]
English, Scientific journal, Ecosystem models are used to understand ecosystem dynamics and ocean biogeochemical cycles and require optimum physiological parameters to best represent biological behaviours. These physiological parameters are often tuned up empirically, while ecosystem models have evolved to increase the number of physiological parameters. We developed a three-dimensional (3-D) lower-trophic-level marine ecosystem model known as the Nitrogen, Silicon and Iron regulated Marine Ecosystem Model (NSI-MEM) and employed biological data assimilation using a micro-genetic algorithm to estimate 23 physiological parameters for two phytoplankton functional types in the western North Pacific. The estimation of the parameters was based on a one-dimensional simulation that referenced satellite data for constraining the physiological parameters. The 3-D NSI-MEM optimized by the data assimilation improved the timing of a modelled plankton bloom in the subarctic and subtropical regions compared to the model without data assimilation. Furthermore, the model was able to improve not only surface concentrations of phytoplankton but also their subsurface maximum concentrations. Our results showed that surface data assimilation of physiological parameters from two contrasting observatory stations benefits the representation of vertical plankton distribution in the western North Pacific.

Distribution shifts of marine taxa in the Pacific Arctic under contemporary climate changes　　　　　　　　　　　　　　　
Irene D. Alabia, Jorge García Molinos, Sei-Ichi Saitoh, Toru Hirawake, Takafumi Hirata, Franz J. Muete
Diversity and Distributions, DOI: 10.1111/ddi.12788, Nov. 2017, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal

A synthesis of the environmental response of the North and South Atlantic Sub-Tropical Gyres during two decades of AMT
Jim Aiken, Robert J.W. Brewin, Francois Dufois, Luca Polimene, Nick J. Hardman-Mountford, Thomas Jackson, Ben Loveday, Silvana Mallor Hoya, Giorgio Dall'Olmo, John Stephens, Takafumi Hirata
Progress in Oceanography, 158, 236, 254, Elsevier Ltd, 01 Nov. 2017, [Peer-reviewed], [Last author], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Anthropogenically-induced global warming is expected to decrease primary productivity in the subtropical oceans by strengthening stratification of the water column and reducing the flux of nutrients from deep-waters to the sunlit surface layers. Identification of such changes is hindered by a paucity of long-term, spatially-resolved, biological time-series data at the basin scale. This paper exploits Atlantic Meridional Transect (AMT) data on physical and biogeochemical properties (1995–2014) in synergy with a wide range of remote-sensing (RS) observations from ocean colour, Sea Surface Temperature (SST), Sea Surface Salinity (SSS) and altimetry (surface currents), combined with different modelling approaches (both empirical and a coupled 1-D Ecosystem model), to produce a synthesis of the seasonal functioning of the North and South Atlantic Sub-Tropical Gyres (STGs), and assess their response to longer-term changes in climate. We explore definitive characteristics of the STGs using data of physical (SST, SSS and peripheral current systems) and biogeochemical variables (chlorophyll and nitrate), with inherent criteria (permanent thermal stratification and oligotrophy), and define the gyre boundary from a sharp gradient in these physical and biogeochemical properties. From RS data, the seasonal cycles for the period 1998–2012 show significant relationships between physical properties (SST and PAR) and gyre area. In contrast to expectations, the surface layer chlorophyll concentration from RS data (CHL) shows an upward trend for the mean values in both subtropical gyres. Furthermore, trends in physical properties (SST, PAR, gyre area) differ between the North and South STGs, suggesting the processes responsible for an upward trend in CHL may vary between gyres. There are significant anomalies in CHL and SST that are associated with El Niño events. These conclusions are drawn cautiously considering the short length of the time-series (1998–2012), emphasising the need to sustain spatially-extensive surveys such as AMT and integrate such observations with models, autonomous observations and RS data, to help address fundamental questions about how our planet is responding to climate change. A small number of dedicated AMT cruises in the keystone months of January and July would complement our understanding of seasonal cycles in the STGs.

Obtaining phytoplankton diversity from ocean color: A scientific roadmap for future development
Astrid Bracher, Heather A. Bouman, Robert J.W. Brewin, Annick Bricaud, Vanda Brotas, Aurea M. Ciotti, Lesley Clementson, Emmanuel Devred, Annalisa Di Cicco, Stephanie Dutkiewicz, Nick J. Hardman-Mountford, Anna E. Hickman, Martin Hieronymi, Takafumi Hirata, Svetlana N. Losa, Colleen B. Mouw, Emanuele Organelli, Dionysios E. Raitsos, Julia Uitz, Meike Vogt, Aleksandra Wolanin
Frontiers in Marine Science, 4, Frontiers Media S. A, 03 Mar. 2017, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, To improve our understanding of the role of phytoplankton for marine ecosystems and global biogeochemical cycles, information on the global distribution of major phytoplankton groups is essential. Although algorithms have been developed to assess phytoplankton diversity from space for over two decades, so far the application of these data sets has been limited. This scientific roadmap identifies user needs, summarizes the current state of the art, and pinpoints major gaps in long-term objectives to deliver space-derived phytoplankton diversity data that meets the user requirements. These major gaps in using ocean color to estimate phytoplankton community structure were identified as: (a) the mismatch between satellite, in situ and model data on phytoplankton composition, (b) the lack of quantitative uncertainty estimates provided with satellite data, (c) the spectral limitation of current sensors to enable the full exploitation of backscattered sunlight, and (d) the very limited applicability of satellite algorithms determining phytoplankton composition for regional, especially coastal or inland, waters. Recommendation for actions include but are not limited to: (i) an increased communication and round-robin exercises among and within the related expert groups, (ii) the launching of higher spectrally and spatially resolved sensors, (iii) the development of algorithms that exploit hyperspectral information, and of (iv) techniques to merge and synergistically use the various streams of continuous information on phytoplankton diversity from various satellite sensors' and in situ data to ensure long-term monitoring of phytoplankton composition.

Inter-comparison of phytoplankton functional type phenology metrics derived from ocean color algorithms and Earth System Models
Tihomir S. Kostadinov, Anna Cabre, Harish Vedantham, Irina Marinov, Astrid Bracher, Robert J. W. Brewin, Annick Bricaud, Takafumi Hirata, Toru Hirawake, Nick J. Hardman-Mountford, Colleen Mouw, Shovonlal Roy, Julia Uitz
REMOTE SENSING OF ENVIRONMENT, 190, 162, 177, ELSEVIER SCIENCE INC, Mar. 2017, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Ocean color remote sensing of chlorophyll concentration has revolutionized our understanding of the biology of the oceans. However, a comprehensive understanding of the structure and function of oceanic ecosystems requires the characterization of the spatio-temporal variability of various phytoplankton functional types (PFTs), which have differing biogeochemical roles. Thus, recent bio-optical algorithm developments have focused on retrieval of various PFTs. It is important to validate and inter-compare the existing PFT algorithms; however direct comparison of retrieved variables is non-trivial because in those algorithms PFTs are defined differently. Thus, it is more plausible and potentially more informative to focus on emergent properties of PFTs, such as phonology. Furthermore, ocean color satellite PFT data sets can play a pivotal role in informing and/or validating the biogeochemical routines of Earth System Models. Here, the phenological characteristics of 10 PFT satellite algorithms and 7 latest-generation climate models from the Coupled Model Inter-comparison Project (CMIPS) are inter compared as part of the International Satellite PFT Algorithm Inter-comparison Project. The comparison is based on monthly satellite data (mostly SeaWiFS) for the 2003-2007 period. The phonological analysis is based on the fraction of microplankton or a similar variable for the satellite algorithms and on the carbon biomass due to diatoms for the climate models. The seasonal cycle is estimated on a per-pixel basis as a sum of sinusoidal harmonics, derived from the Discrete Fourier Transform of the variable time series. Peak analysis is then applied to the estimated seasonal signal and the following phenological parameters are quantified for each satellite algorithm and climate model: seasonal amplitude, percent seasonal variance, month of maximum, and bloom duration. Secondary/double blooms occur in many areas and are also quantified. The algorithms and the models are quantitatively compared based on these emergent phenological parameters. Results indicate that while algorithms agree to a first order on a global scale, large differences among them exist; differences are analyzed in detail for two Longhurst regions in the North Atlantic: North Atlantic Drift Region (NADR) and North Atlantic Subtropical Gyre West (NASW). Seasonal cycles explain the most variance in zonal bands in the seasonally-stratified subtropics at about 30 latitude in the satellite PFT data. The CMIP5 models do not reproduce this pattern, exhibiting higher seasonality in mid and high-latitudes and generally much more spatially homogeneous patterns in phenological indices compared to satellite data. Satellite data indicate a complex structure of double blooms in the Equatorial region and mid-latitudes, and single blooms on the poleward edges of the subtropical gyres. In contrast, the CMIP5 models show single annual blooms over most of the ocean except for the Equatorial band and Arabian Sea. (C) 2016 Elsevier Inc. All rights reserved.

A consumer's guide to satellite remote sensing of multiple phytoplankton groups in the global ocean
Colleen B. Mouw, Nick J. Hardman-Mountford, Séverine Alvain, Astrid Bracher, Robert J. W. Brewin, Annick Bricaud, Aurea M. Ciotti, Emmanuel Devred, Amane Fujiwara, Takafumi Hirata, Toru Hirawake, Tihomir S. Kostadinov, Shovonlal Roy, Julia Uitz
Frontiers in Marine Science, 4, Frontiers Media S. A, 21 Feb. 2017, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Phytoplankton are composed of diverse taxonomical groups, which are manifested as distinct morphology, size, and pigment composition. These characteristics, modulated by their physiological state, impact their light absorption and scattering, allowing them to be detected with ocean color satellite radiometry. There is a growing volume of literature describing satellite algorithms to retrieve information on phytoplankton composition in the ocean. This synthesis provides a review of current methods and a simplified comparison of approaches. The aim is to provide an easily comprehensible resource for non-algorithm developers, who desire to use these products, thereby raising the level of awareness and use of these products and reducing the boundary of expert knowledge needed to make a pragmatic selection of output products with confidence. The satellite input and output products, their associated validation metrics, as well as assumptions, strengths, and limitations of the various algorithm types are described, providing a framework for algorithm organization to assist users and inspire new aspects of algorithm development capable of exploiting the higher spectral, spatial and temporal resolutions from the next generation of ocean color satellites.

Competition and community assemblage dynamics within a phytoplankton functional group: Simulation using an eddy-resolving model to disentangle deterministic and random effects
Yoshio Masuda, Yasuhiro Yamanaka, Takafumi Hirata, Hideyuki Nakano
ECOLOGICAL MODELLING, 343, 1, 14, ELSEVIER SCIENCE BV, Jan. 2017, [Peer-reviewed], [International Magazine]
English, Scientific journal, To advance our understanding of competition and coexistence in phytoplankton species within a functional group, such as a diatom group, we developed a numerical model composed of 240 within tropic-level virtual species that can actually or potentially compete. We then explored how the phytoplankton assembly is structured by deterministic or stochastic processes, where the former process is typically represented using the traditional niche theory and the latter process is highlighted using the neutral theory. Because we used eddy-resolving resolution, phytoplankton dispersion and the resultant dispersal limitation were explicitly represented, where the dispersal limitation prevents the most competitive species from using its appropriate niche and subsequently enhances stochastic effects. In the simulation results, all surviving species have an oceanic volume in which the phytoplankton species has the highest specific growth rate in all the 240 species. The abundance in the most competitive space has a strong, positive correlation with the relative species abundance. Moreover, of the phytoplankton types whose abundances in the most competitive space are nearly equal, the survival of a species is affected by its residence time within its habitat; the surviving phytoplankton species tend to have larger residence times compared to the non-persistent species. These results led us to conclude that deterministic processes had significant contributions to a formation of phytoplankton assembly. This was supported by the result that a structure of phytoplankton assembly represented by species rank in abundance was invariant with time and hardly dependent on initial conditions of phytoplankton composition. (C) 2016 The Author(s). Published by Elsevier B.V.

Development of models for simulating linkages among physical, ecological, and human systems
Takahashi K, N Saigusa, T. Oikawa, M. Kawamiya, T. Hajima, Y. Yamanaka, T. Hirata, A. Abe-Ouchi
地球環境, 20, 2, 135, 142, 国際環境研究協会, 2015, [Peer-reviewed], [Domestic magazines]
Japanese, Scientific journal

Drivers and uncertainties of future global marine primary production in marine ecosystem models
C. Laufkoetter, M. Vogt, N. Gruber, M. Aita-Noguchi, O. Aumont, L. Bopp, E. Buitenhuis, S. C. Doney, J. Dunne, T. Hashioka, J. Hauck, T. Hirata, J. John, C. Le Quere, I. D. Lima, H. Nakano, R. Seferian, I. Totterdell, M. Vichi, C. Voelker
BIOGEOSCIENCES, 12, 23, 6955, 6984, COPERNICUS GESELLSCHAFT MBH, 2015, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Past model studies have projected a global decrease in marine net primary production (NPP) over the 21st century, but these studies focused on the multi-model mean rather than on the large inter-model differences. Here, we analyze model-simulated changes in NPP for the 21st century under IPCC's high-emission scenario RCP8.5. We use a suite of nine coupled carbon-climate Earth system models with embedded marine ecosystem models and focus on the spread between the different models and the underlying reasons. Globally, NPP decreases in five out of the nine models over the course of the 21st century, while three show no significant trend and one even simulates an increase. The largest model spread occurs in the low latitudes (between 30 degrees S and 30 degrees N), with individual models simulating relative changes between -25 and +40 %. Of the seven models diagnosing a net decrease in NPP in the low latitudes, only three simulate this to be a consequence of the classical interpretation, i.e., a stronger nutrient limitation due to increased stratification leading to reduced phytoplankton growth. In the other four, warming-induced increases in phytoplankton growth outbalance the stronger nutrient limitation. However, temperature-driven increases in grazing and other loss processes cause a net decrease in phytoplankton biomass and reduce NPP despite higher growth rates. One model projects a strong increase in NPP in the low latitudes, caused by an intensification of the microbial loop, while NPP in the remaining model changes by less than 0.5 %. While models consistently project increases NPP in the Southern Ocean, the regional inter-model range is also very substantial. In most models, this increase in NPP is driven by temperature, but it is also modulated by changes in light, macronutrients and iron as well as grazing. Overall, current projections of future changes in global marine NPP are subject to large uncertainties and necessitate a dedicated and sustained effort to improve the models and the concepts and data that guide their development.

Global Retrieval of Diatom Abundance Based on Phytoplankton Pigments and Satellite Data
Mariana A. Soppa, Takafumi Hirata, Brenner Silva, Tilman Dinter, Ilka Peeken, Sonja Wiegmann, Astrid Bracher
REMOTE SENSING, 6, 10, 10089, 10106, MDPI AG, Oct. 2014, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Diatoms are the major marine primary producers on the global scale and, recently, several methods have been developed to retrieve their abundance or dominance from satellite remote sensing data. In this work, we highlight the importance of the Southern Ocean (SO) in developing a global algorithm for diatom using an Abundance Based Approach (ABA). A large global in situ data set of phytoplankton pigments was compiled, particularly with more samples collected in the SO. We revised the ABA to take account of the information on the penetration depth (Z(pd)) and to improve the relationship between diatoms and total chlorophyll-a (TChla). The results showed that there is a distinct relationship between diatoms and TChla in the SO, and a new global model (ABA(Zpd)) improved the estimation of diatoms abundance by 28% in the SO compared with the original ABA model. In addition, we developed a regional model for the SO which further improved the retrieval of diatoms by 17% compared with the global ABA(Zpd) model. As a result, we found that diatom may be more abundant in the SO than previously thought. Linear trend analysis of diatom abundance using the regional model for the SO showed that there are statistically significant trends, both increasing and decreasing, in diatom abundance over the past eleven years in the region.

Bio-optical properties during the summer season in the Sea of Okhotsk
Shintaro Takao, Takahiro Iida, Tomonori Isada, Sei-Ichi Saitoh, Takafumi Hirata, Koji Suzuki
PROGRESS IN OCEANOGRAPHY, 126, 233, 241, PERGAMON-ELSEVIER SCIENCE LTD, Aug. 2014, [Peer-reviewed], [International Magazine]
English, Scientific journal, The Sea of Okhotsk is one of the most productive ocean regions in the world. However, the in situ bio-optical properties, which are crucial for satellite ocean-color of the productivity, remain uncertain in this region because little data have been available. We conducted an in situ observation and evaluated the bio-optical properties in terms of chlorophyll a (ChI a) concentration, spectral remote sensing reflectance (R-rs), and the light absorption coefficients of phytoplankton (a(j)), non-algal particles (a(NAP)), and chromophoric dissolved organic matter (a(CDOM)) in the summer of 2006. The data covered a wide range of Chl a levels in surface waters from 0.3 to 8.5 mg m(-3). At 443 nm, a(CDOM) dominated (64% on average) the total non-water absorption (a(t-w)) in this study area. Based on the in situ R-rs data, surface Chl a concentrations that were estimated using the sea-viewing wide field-of-view sensor (SeaWiFS) OC4v6 and the moderate-resolution imaging spectroradiometer (MOD'S) OC3M algorithms were significantly higher than the in situ data by more than 160% and 260%, respectively. In particular, the largest overestimation occurred in the region where a(CDOM) at 443 nm accounted for more than 80% of a(t-w) near the mouth of the Amur River. However, except the CDOM-rich stations, the performance of the OC4v6 and OC3M algorithms became better (i.e., their mean normalized biases were reduced to 50% and 66%, respectively). We conclude that the operational global algorithms were applicable to the summer season in the Sea of Okhotsk except the CDOM-rich region, in which new approaches for ocean-color algorithms (i.e., local algorithms) would be required. (C) 2014 Elsevier Ltd. All rights reserved.

Development and verification of GCOM-C1/SGLI ocean algorithms
Hirata, T, T. Hirawake, F. Sakaida, Yamaguchi, K. Suzuki, H. Murakami, J. Ishizaka, H. Kobayashi, A. Fujiwara, M. Toratani, S. Saitoh
Journal of the Remote Sensing Society of Japan, 34, 4, 278, 285, 2014, [Peer-reviewed], [Domestic magazines]
English, Scientific journal

Impacts of light shading and nutrient enrichment geo-engineering approaches on the productivity of a stratified, oligotrophic ocean ecosystem
Nick J. Hardman-Mountford, Luca Polimene, Takafumi Hirata, Robert J. W. Brewin, Jim Aiken
Journal of the Royal Society Interface, 10, 89, Royal Society, 06 Dec. 2013, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Geo-engineering proposals to mitigate global warming have focused either on methods of carbon dioxide removal, particularly nutrient fertilization of plant growth, or on cooling the Earth's surface by reducing incoming solar radiation (shading). Marine phytoplankton contribute half the Earth's biological carbon fixation and carbon export in the ocean is modulated by the actions of microbes and grazing communities in recycling nutrients. Both nutrients and light are essential for photosynthesis, so understanding the relative influence of both these geo-engineering approaches on ocean ecosystem production and processes is critical to the evaluation of their effectiveness. In this paper, we investigate the relationship between light and nutrient availability on productivity in a stratified, oligotrophic subtropical ocean ecosystem using a one-dimensional water column model coupled to a multi-plankton ecosystem model, with the goal of elucidating potential impacts of these geo-engineering approaches on ecosystem production. We find that solar shading approaches can redistribute productivity in the water column but do not change total production. Macronutrient enrichment is able to enhance the export of carbon, although heterotrophic recycling reduces the efficiency of carbon export substantially over time. Our results highlight the requirement for a fuller consideration of marine ecosystem interactions and feedbacks, beyond simply the stimulation of surface blooms, in the evaluation of putative geo-engineering approaches.

Generalized ocean color inversion model for retrieving marine inherent optical properties
P. Jeremy Werdell, Bryan A. Franz, Sean W. Bailey, Gene C. Feldman, Emmanuel Boss, Vittorio E. Brando, Mark Dowell, Takafumi Hirata, Samantha J. Lavender, Zhong Ping Lee, Hubert Loisel, Stéphane Maritorena, Fréderic Mélin, Timothy S. Moore, Timothy J. Smyth, David Antoine, Emmanuel Devred, Odile Hembise Fanton D'Andon, Antoine Mangin
Applied Optics, 52, 10, 2019, 2037, OSA - The Optical Society, 01 Apr. 2013, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Ocean color measured from satellites provides daily, global estimates of marine inherent optical properties (IOPs). Semi-analytical algorithms (SAAs) provide one mechanism for inverting the color of the water observed by the satellite into IOPs. While numerous SAAs exist, most are similarly constructed and few are appropriately parameterized for all water masses for all seasons. To initiate community-wide discussion of these limitations, NASA organized two workshops that deconstructed SAAs to identify similarities and uniqueness and to progress toward consensus on a unified SAA. This effort resulted in the development of the generalized IOP (GIOP) model software that allows for the construction of different SAAs at runtime by selection from an assortment of model parameterizations. As such, GIOP permits isolation and evaluation of specific modeling assumptions, construction of SAAs, development of regionally tuned SAAs, and execution of ensemble inversion modeling. Working groups associated with the workshops proposed a preliminary default configuration for GIOP (GIOP-DC), with alternative model parameterizations and features defined for subsequent evaluation. In this paper, we: (1) describe the theoretical basis of GIOP
(2) present GIOP-DC and verify its comparable performance to other popular SAAs using both in situ and synthetic data sets
and, (3) quantify the sensitivities of their output to their parameterization. We use the latter to develop a hierarchical sensitivity of SAAs to various model parameterizations, to identify components of SAAs that merit focus in future research, and to provide material for discussion on algorithm uncertainties and future emsemble applications. © 2013 Optical Society of America.

Phytoplankton competition during the spring bloom in four plankton functional type models
T. Hashioka, M. Vogt, Y. Yamanaka, C. Le Quere, E. T. Buitenhuis, M. N. Aita, S. Alvain, L. Bopp, T. Hirata, I. Lima, S. Sailley, S. C. Doney
BIOGEOSCIENCES, 10, 11, 6833, 6850, COPERNICUS GESELLSCHAFT MBH, 2013, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, We investigated the mechanisms of phytoplankton competition during the spring bloom, one of the most dramatic seasonal events in lower-trophic-level ecosystems, in four state-of-the-art plankton functional type (PFT) models: PISCES, NEMURO, PlankTOM5 and CCSM-BEC. In particular, we investigated the relative importance of different ecophysiological processes on the determination of the community structure, focusing both on the bottom-up and the top-down controls. The models reasonably reproduced the observed global distribution and seasonal variation of phytoplankton biomass. The fraction of diatoms with respect to the total phytoplankton biomass increases with the magnitude of the spring bloom in all models. However, the governing mechanisms differ between models, despite the fact that current PFT models represent ecophysiological processes using the same types of parameterizations. The increasing trend in the percentage of diatoms with increasing bloom magnitude is mainly caused by a stronger nutrient dependence of diatom growth compared to nanophytoplankton (bottom-up control). The difference in the maximum growth rate plays an important role in NEMURO and PlankTOM5 and determines the absolute values of the percentage of diatoms during the bloom. In CCSM-BEC, the light dependency of growth plays an important role in the North Atlantic and the Southern Ocean. The grazing pressure by zooplankton (top-down control), however, strongly contributes to the dominance of diatoms in PISCES and CCSM-BEC. The regional differences in the percentage of diatoms in PlankTOM5 are mainly determined by top-down control. These differences in the mechanisms suggest that the response of marine ecosystems to climate change could significantly differ among models, even if the present-day ecosystem is reproduced to a similar degree of confidence. For further understanding of plankton competition and for the prediction of future change in marine ecosystems, it is important to understand the relative differences in each physiological rate and life history rate in the bottom-up and the top-down controls between PFTs.

Distribution of phytoplankton functional types in high-nitrate, low-chlorophyll waters in a new diagnostic ecological indicator model
A. P. Palacz, M. A. St John, R. J. W. Brewin, T. Hirata, W. W. Gregg
BIOGEOSCIENCES, 10, 11, 7553, 7574, COPERNICUS GESELLSCHAFT MBH, 2013, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Modeling and monitoring plankton functional types (PFTs) is challenged by the insufficient amount of field measurements of ground truths in both plankton models and bio-optical algorithms. In this study, we combine remote sensing data and a dynamic plankton model to simulate an ecologically sound spatial and temporal distribution of phyto-PFTs. We apply an innovative ecological indicator approach to modeling PFTs and focus on resolving the question of diatom-coccolithophore coexistence in the subpolar high-nitrate and low-chlorophyll regions. We choose an artificial neural network as our modeling framework because it has the potential to interpret complex nonlinear interactions governing complex adaptive systems, of which marine ecosystems are a prime example. Using ecological indicators that fulfill the criteria of measurability, sensitivity and specificity, we demonstrate that our diagnostic model correctly interprets some basic ecological rules similar to ones emerging from dynamic models. Our time series highlight a dynamic phyto-PFT community composition in all high-latitude areas and indicate seasonal coexistence of diatoms and coccolithophores. This observation, though consistent with in situ and remote sensing measurements, has so far not been captured by state-of-the-art dynamic models, which struggle to resolve this "paradox of the plankton". We conclude that an ecological indicator approach is useful for ecological modeling of phytoplankton and potentially higher trophic levels. Finally, we speculate that it could serve as a powerful tool in advancing ecosystem-based management of marine resources.

A comparison between phytoplankton community structures derived from a global 3D ecosystem model and satellite observation
Takafumi Hirata, Stephane Saux-Picart, Taketo Hashioka, Maki Aita-Noguchi, Hiroshi Sumata, Masahito Shigemitsu, J. Icarus Allen, Yasuhiro Yamanaka
Journal of Marine Systems, 109-110, 129, 137, Jan. 2013, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Phytoplankton functional types (PFTs) derived from a global 3D marine ecosystem model, MEM-OU, are compared with those observed by satellite. The climatological field of the large phytoplankton (diatoms) and small phytoplankton (nano- and picoplankton) showed the model and satellite observation generally agrees in their spatial distribution but showed some biases in the equatorial oceans and higher latitudes. Grid-by-grid correlation derived from the time series of the model and satellite observation showed a significant dependence on latitude, and it was found that lower (higher) correlation coefficients were not necessarily found in the regions where higher (lower) bias was found. Spatial PCA analysis of monthly climatology of PFTs showed that a major spatial pattern of PFTs results from a steady state distribution superimposed by regional seasonal distribution. The model and the satellite observation both showed such seasonality, but we found that the model remarkably showed strong seasonality in the Southern Oceans and the equatorial oceans. The wavelet pattern comparison analysis was applied to quantify the spatial scale(s) at which the agreement in spatial distributions of PFTs can be obtained. The objective skill score determined using the pattern matching/mismatching analysis by the wavelet showed that the model has a skill to represent observed spatial patterns at horizontal scales over 1800 km (i.e. basin and global scale). The agreement is found even at the spatial scales down to 200. km (i.e. meso-scales), when the pigment biomass of the PFTs at the scales is relatively small. Our comparison enabled an objective and quantitative examination of the validity and weakness of the model by clarifying the spatial scale(s) to which the present PFT model has skill, and adds a value on conventional comparison procedure based on univariate statistics. © 2012 Elsevier B.V.

The influence of the Indian Ocean Dipole on interannual variations in phytoplankton size structure as revealed by Earth Observation
Robert J. W. Brewin, Takafumi Hirata, Nick J. Hardman-Mountford, Samantha J. Lavender, Shubha Sathyendranath, Ray Barlow
DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, 77-80, 117, 127, PERGAMON-ELSEVIER SCIENCE LTD, Nov. 2012, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Using a decade of satellite ocean-colour observations and a model that links chlorophyll-a to the size of the phytoplankton cells, parameterised using pigment data from the Indian Ocean, we examine the implications of the Indian Ocean Dipole (IOD) for phytoplankton size structure. The inferred interannual anomalies in phytoplankton size structure are related to those in sea-surface temperature (SST) and sea-surface height (SSH), derived using satellite radiometry and altimetry, and stratification, derived using the Simple Ocean Data Assimilation (SODA) database. In regions influenced by the Indian Ocean Dipole, we observe a tight correlation between phytoplankton size structure and the physical variables, such that interannual variations in the physical variables accounts for up to 70% of the total variance in phytoplankton size structure. For much of the Indian Ocean, low temperature. low SSH and low stratification (indicative of a turbulent environment) are correlated with larger size classes, consistent with theories on coupling between physical-chemical processes and ecosystem structure. To the extent that phytoplankton function is related to its size structure, changes in physical forcing are likely to influence biogeochemical cycles in the region and the pelagic food web. The limitations of our approach are discussed and we highlight future challenges in satellite ocean-colour monitoring, should climate change lead to any modification in our marine ecosystem. (c) 2012 Elsevier Ltd. All rights reserved.

Comparing satellite-based phytoplankton classification methods
Takafumi Hirata, Nick Hardman-Mountford, Robert J. W. Brewin
Eos, 93, 6, 59, 60, 2012, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Satellite Phytoplankton Functional Type Algorithm Intercomparison Workshop
Sapporo, Japan, 22-23 November 2011 Satellite observations of ocean color have become synonymous with derivations of chlorophyll a concentration as a proxy for phytoplankton biomass. In addition, a number of satellite algorithms for estimating the phytoplankton community structure have been developed that provide size-structure estimates of phytoplankton and detect taxonomic groups (termed phytoplankton functional types, or PFTs). These new algorithms provide an increased level of observational detail for ecosystem and biogeochemical studies of the role of phytoplankton in marine systems.

An intercomparison of bio-optical techniques for detecting dominant phytoplankton size class from satellite remote sensing
Robert J. W. Brewin, Nick J. Hardman-Mountford, Samantha J. Lavender, Dionysios E. Raitsos, Takafumi Hirata, Julia Uitz, Emmanuel Devred, Annick Bricaud, Aurea Ciotti, Bernard Gentili
REMOTE SENSING OF ENVIRONMENT, 115, 2, 325, 339, ELSEVIER SCIENCE INC, Feb. 2011, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Satellite remote sensing of ocean colour is the only method currently available for synoptically measuring wide-area properties of ocean ecosystems, such as phytoplankton chlorophyll biomass. Recently, a variety of bio-optical and ecological methods have been established that use satellite data to identify and differentiate between either phytoplankton functional types (PFTs) or phytoplankton size classes (PSCs). In this study, several of these techniques were evaluated against in situ observations to determine their ability to detect dominant phytoplankton size classes (micro-, nano- and picoplankton). The techniques are applied to a 10-year ocean-colour data series from the SeaWiFS satellite sensor and compared with in situ data (6504 samples) from a variety of locations in the global ocean. Results show that spectral-response, ecological and abundance-based approaches can all perform with similar accuracy. Detection of microplankton and picoplankton were generally better than detection of nanoplankton. Abundance-based approaches were shown to provide better spatial retrieval of PSCs. Individual model performance varied according to PSC, input satellite data sources and in situ validation data types. Uncertainty in the comparison procedure and data sources was considered. Improved availability of in situ observations would aid ongoing research in this field. (C) 2010 Elsevier Inc. All rights reserved.

Synoptic relationships between surface Chlorophyll-a and diagnostic pigments specific to phytoplankton functional types
T. Hirata, N. J. Hardman-Mountford, R. J. W. Brewin, J. Aiken, R. Barlow, K. Suzuki, T. Isada, E. Howell, T. Hashioka, M. Noguchi-Aita, Y. Yamanaka
BIOGEOSCIENCES, 8, 2, 311, 327, COPERNICUS GESELLSCHAFT MBH, 2011, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Error-quantified, synoptic-scale relationships between chlorophyll-a (Chl-a) and phytoplankton pigment groups at the sea surface are presented. A total of ten pigment groups were considered to represent three Phytoplankton Size Classes (PSCs, micro-, nano- and picoplankton) and seven Phytoplankton Functional Types (PFTs, i.e. diatoms, dinoflagellates, green algae, prymnesiophytes (haptophytes), pico-eukaryotes, prokaryotes and Prochlorococcus sp.). The observed relationships between Chl-a and PSCs/PFTs were well-defined at the global scale to show that a community shift of phytoplankton at the basin and global scales is reflected by a change in Chl-a of the total community. Thus, Chl-a of the total community can be used as an index of not only phytoplankton biomass but also of their community structure. Within these relationships, we also found nonmonotonic variations with Chl-a for certain pico-sized phytoplankton (pico-eukaryotes, Prokaryotes and Prochlorococcus sp.) and nano-sized phytoplankton (Green algae, prymnesiophytes). The relationships were quantified with a leastsquare fitting approach in order to enable an estimation of the PFTs from Chl-a where PFTs are expressed as a percentage of the total Chl-a. The estimated uncertainty of the relationships depends on both PFT and Chl-a concentration. Maximum uncertainty of 31.8% was found for diatoms at Chla = 0.49 mg m(-3). However, the mean uncertainty of the relationships over all PFTs was 5.9% over the entire Chl-a range observed in situ (0.02< Chl-a < 4.26 mg m(-3)). The relationships were applied to SeaWiFS satellite Chl-a data from 1998 to 2009 to show the global climatological fields of the surface distribution of PFTs. Results show that microplankton are present in the mid and high latitudes, constituting only similar to 10.9% of the entire phytoplankton community in the mean field for 1998-2009, in which diatoms explain similar to 7.5%. Nanoplankton are ubiquitous throughout the global surface oceans, except the subtropical gyres, constituting similar to 45.5%, of which prymnesiophytes (haptophytes) are the major group explaining similar to 31.7% while green algae contribute similar to 13.9%. Picoplankton are dominant in the subtropical gyres, but constitute similar to 43.6% globally, of which prokaryotes are the major group explaining similar to 26.5% (Prochlorococcus sp. explaining 22.8%), while pico-eukaryotes explain similar to 17.2% and are relatively abundant in the South Pacific. These results may be of use to evaluate global marine ecosystem models.

A three-component model of phytoplankton size class for the Atlantic Ocean
Robert J. W. Brewin, Shubha Sathyendranath, Takafumi Hirata, Samantha J. Lavender, Rosa M. Barciela, Nick J. Hardman-Mountford
ECOLOGICAL MODELLING, 221, 11, 1472, 1483, ELSEVIER SCIENCE BV, Jun. 2010, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, A three-component model was developed which calculates the fractional contributions of three phytoplankton size classes (micro-, nano- and picoplankton) to the overall chlorophyll-a concentration in the Atlantic Ocean. The model is an extension of the Sathyendranath et al. (2001) approach, based on the assumption that small cells dominate at low chlorophyll-a concentrations and large cells at high chlorophyll-a concentrations. Diagnostic pigments were used to infer cell size using an established technique adapted to account for small picoeukaroytes in ultra-oligotrophic environments. Atlantic Meridional Transect (AMT) pigment data taken between 1997 and 2004 were split into two datasets; 1935 measurements were used to parameterise the model, and a further 241 surface measurements, spatially and temporally matched to chlorophyll-a derived from SeaWiFS satellite data, were set aside to validate the model. Comparison with an independent global pigment dataset (256 measurements) also supports the broader-scale application of the model. The effect of optical depth on the model parameters was also investigated and explicitly incorporated into the model. It is envisaged that future applications would include validating multi-plankton biogeochemical models and improving primary-production estimates by accounting for community composition. (C) 2010 Elsevier B.V. All rights reserved.

Marine ecosystem models for earth systems applications: The MarQUEST experience
J. Icarus Allen, James Aiken, Thomas R. Anderson, Erik Buitenhuis, Sarah Cornell, Richard J. Geider, Keith Haines, Takafumi Hirata, Jason Holt, Corinne Le Quere, Nicholas Hardman-Mountford, Oliver N. Ross, Bablu Sinha, James While
JOURNAL OF MARINE SYSTEMS, 81, 1-2, 19, 33, ELSEVIER SCIENCE BV, Apr. 2010, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, The MarQUEST (Marine Biogeochemistry and Ecosystem Modelling Initiative in QUEST) project was established to develop improved descriptions of marine biogeochemistry, suited for the next generation of Earth system models. We review progress in these areas providing insight on the advances that have been made as well as identifying remaining key outstanding gaps for the development of the marine component of next generation Earth system models. The following issues are discussed and where appropriate results are presented; the choice of model structure, scaling processes from physiology to functional types, the ecosystem model sensitivity to changes in the physical environment, the role of the coastal ocean and new methods for the evaluation and comparison of ecosystem and biogeochemistry models. We make recommendations as to where future investment in marine ecosystem modelling should be focused, highlighting a generic software framework for model development, improved hydrodynamic models, and better parameterisation of new and existing models, reanalysis tools and ensemble simulations. The final challenge is to ensure that experimental/observational scientists are stakeholders in the models and vice versa. (C) 2010 Elsevier B.V. All rights reserved.

A spectral response approach for detecting dominant phytoplankton size class from satellite remote sensing
Robert J. W. Brewin, Samantha J. Lavender, Nick J. Hardman-Mountford, Takafumi Hirata
ACTA OCEANOLOGICA SINICA, 29, 2, 14, 32, SPRINGER, Mar. 2010, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, An important goal in ocean colour remote sensing is to accurately detect different phytoplankton groups with the potential uses including the validation of multi-phytoplankton carbon cycle models; synoptically monitoring the health of our oceans, and improving our understanding of the bio-geochemical interactions between phytoplankton and their environment. In this paper a new algorithm is developed for detecting three dominant phytoplankton size classes based on distinct differences in their optical signatures. The technique is validated against an independent coupled satellite reflectance and in situ pigment dataset and run on the 10-year NASA Sea viewing Wide Field of view Sensor (SeaWiFS) data series. Results indicate that on average 3.6% of the global oceanic surface layer is dominated by microplankton, 18.0% by nanoplankton and 78.4% by picoplankton. Results, however, are seen to vary depending on season and ocean basin.

An inherent optical property approach to the estimation of size-specific photosynthetic rates in eastern boundary upwelling zones from satellite ocean colour: An initial assessment
Takafumi Hirata, Nick J. Hardman-Mountford, Ray Barlow, Tarron Lamont, Robert Brewin, Tim Smyth, James Aiken
PROGRESS IN OCEANOGRAPHY, 83, 1-4, 393, 397, PERGAMON-ELSEVIER SCIENCE LTD, Oct. 2009, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, We derived size-specific photosynthetic rates for eastern boundary upwelling regions using satellite ocean colour, by a simple approach that links photosynthetic rate to phytoplankton size classes with the optical absorption of phytoplankton. Comparisons with a conventional chlorophyll-based photosynthetic algorithm and with in situ measurements showed good agreement with our approach (r(2) = 0.728, p < 0.001). Preliminary results from satellite observations for upwelling regions suggest that production in nano phytop lankton-dominated communities may be larger than for those where microphytoplankton is predominant, due to the greater spatial extent of the former. However, photosynthetic rate per unit volume is shown to be larger for microphytoplankton-dominated communities. (C) 2009 Elsevier Ltd. All rights reserved.

Relationship between the distribution function of ocean nadir radiance and inherent optical properties for oceanic waters
Takafumi Hirata, Nicholas Hardman-Mountford, James Aiken, James Fishwick
APPLIED OPTICS, 48, 17, 3129, 3138, OPTICAL SOC AMER, Jun. 2009, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, The distribution function of the ocean nadir radiance, defined by the upward radiance-to-irradiance ratio, is investigated as functions of the absorption coefficient and the volume scattering function to understand their relationship rather than to develop a numerical algorithm. It is shown for oceanic waters that the distribution function is directly proportional to the volume scattering function normalized by the back-scattering coefficient. The relatively small spectral variation of the distribution function is explained by the small spectral variation of the normalized volume scattering function, as well as by a function that describes the contribution of the backscattering-to-absorption ratio to the distribution function. The interpretation described was verified against in situ data, highlighting factors controlling the distribution function of oceanic waters. (C) 2009 Optical Society of America

An objective methodology for the classification of ecological pattern into biomes and provinces for the pelagic ocean
Nick J. Hardman-Mountford, Takafumi Hirata, Kirsten A. Richardson, Jim Aiken
REMOTE SENSING OF ENVIRONMENT, 112, 8, 3341, 3352, ELSEVIER SCIENCE INC, Aug. 2008, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, Based on the view of ecological pattern being steady state, rather than an equilibrium phenomenon, we assert that, if real, ecological biomes and provinces in the ocean should be detectable in surface fields obtained from satellite data as coherent, co-varying spatial regions with a high degree of permanence. Likewise, hierarchy is an important property of ecological systems that should be exhibited by Such patterns if they represent real ecological structure. In this paper, we apply a combination of multivariate statistics and classification techniques to a time series of satellite-derived, surface-ocean chlorophyll data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), (a) to provide an objective characterisation and classification of ecological pattern in the ocean and (b) to investigate the characteristic system Properties (persistence, hierarchy) of the broad-scale patterns observed to test whether they behave as autonomous ecological systems. Comparison of this classification with Longhurst [Longhurst, A. (1998), Ecological Geography of the Sea. San Diego: Academic Press, 398 pp.] suggests the need for equatorial forcing processes to be taken into account to explain observed ecological pattern at the biome level. (C) 2008 Elsevier Inc. All rights reserved.

Estimation of the in situ UV-A absorption of seawater by a simple irradiance inversion model
Hirata, T
Journal of Oceanography, 64, 4, 561, 566, Aug. 2008, [Peer-reviewed], [International Magazine]
English, Scientific journal

An absorption model to determine phytoplankton size classes from satellite ocean colour
T. Hirata, J. Aiken, N. Hardman-Mountford, T. J. Smyth, R. G. Barlow
REMOTE SENSING OF ENVIRONMENT, 112, 6, 3153, 3159, ELSEVIER SCIENCE INC, Jun. 2008, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, We have developed a model linking phytoplankton absorption to phytoplankton size classes (PSCs) that uses a single variable, the optical absorption by phytoplankton at 443 nm, a(ph)(443), which can be derived from the inversion of ocean colour data. The model is based on the observation that the absolute value of aph(443) co-varies with the spectral slope of phytoplankton absorption in the range of 443-510 nm, which is also a characteristic of phytoplankton size classes. The model when used for analysis of SeaWiFS global data, showed that picoplankton dominated similar to 79.1% of surface waters, nanoplankton similar to 18.5% and microplankton the remainder (2.3%). The N. and S. Atlantic and the N. and S. Pacific Oceans showed seasonal cycles with both micro and nanoplankton increasing in spring and summer in each hemisphere, while picoplankton, dominant in the oligotrophic gyres, decreased in the summer. The PSCs derived from SeaWiFS data were verified by comparing contemporary 8-day composites with PSCs derived from in situ pigment data from quasiconcurrent Atlantic Meridional Transect cruises. (C) 2008 Elsevier Inc. All rights reserved.

Relationship between the irradiance reflectance and inherent optical properties of seawater
Takafumi Hirata, Niels K. Hojerslev
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 113, C3, AMER GEOPHYSICAL UNION, Mar. 2008, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, A new expression for relationship between the surface irradiance reflectance and Inherent Optical Properties (IOPs) of homogeneous seawater is presented. Physical parameters largely responsible for the relationship are identified. These are the average cosines of the backward volume scattering function and of the downward radiance. Lorenz-Mie computations show that the average cosine of the backward volume scattering function is quasi-constant (0.493 +/- 0.135) for most marine waters, even if the backward volume scattering function itself is considerably variable. As a result, a base magnitude of the proportionality between the irradiance reflectance and IOPs are largely set by the average cosine of the backward volume scattering function and eventually determined by the average cosine of the downward radiance that is primarily driven by the sun angle. Independent numerical simulations of radiative transfer support results of the new expression to show that it gives significant improvement in both physical understanding and numerical prediction of the relationship.

Functional links between bioenergetics and bio-optical traits of phytoplankton taxonomic groups: an overarching hypothesis with applications for ocean colour remote sensing
Jim Aiken, Nick J. Hardman-Mountford, Ray Barlow, James Fishwick, Takafumi Hirata, Tim Smyth
JOURNAL OF PLANKTON RESEARCH, 30, 2, 165, 181, OXFORD UNIV PRESS, Feb. 2008, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, We review the concept of phytoplankton functional types (PFTs) in marine ecosystems as a means of advancing bio-mechanistic models that can be coupled to the global carbon cycle and the Earth's climate system. Conventional classification of phytoplankton by size may seem arbitrary, but there appears clear links between size and environmental characteristics (availability of essential nutrients and light) that regulate photosynthesis, phytoplankton selection and succession. Taking a minimalist approach, small phytoplankton (picoplankton) survive in permanently stratified systems with low nutrients, high surface light and low light in deep clines, whereas large phytoplankton (microplankton) thrive in high nutrient, turbulent, high light, near surface systems. Nutrient-light environmental conditions are characteristic properties of globally, latitudinal-dispersed biogeochemical provinces. These contrasting nutrient-light regimes define the extreme ends of the bio-energetic scale of photosynthesis and set the end points of the primary range of phytoplankton functional processes. To determine PFTs from remotely sensed ocean colour data, there must be a specific bio-optical trait (BOT) that can be associated with the phytoplankton species or taxa. We investigate the connection of the bio-energetic scale to phytoplankton types and their BOTs, which is the first, but crucial step for classifying PFTs on the basis of functional processes, from which refinements and further partitioning can be developed.

Numerical radiative transfer simulations to examine shape of the phase function of suspended particles on the ocean colour reflectance
Hirata, T, G. F. Moore
La Mer, 45, 2, 91, 98, 日仏海洋学会, 2007, [Peer-reviewed], [Lead author], ［Internationally co-authored］, [International Magazine]
English, Scientific journal

Semianalytical model for the derivation of ocean color inherent optical properties: description, implementation, and performance assessment (vol 46, pg 429, 2007)
T. J. Smyth, G. F. Moore, T. Hirata, J. Aiken
APPLIED OPTICS, 46, 3, 429, 430, OPTICAL SOC AMER, Jan. 2007, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal

Semianalytical model for the derivation of ocean color inherent optical properties: description, implementation, and performance assessment
Timothy J. Smyth, Gerald F. Moore, Takafumi Hirata, James Aiken
APPLIED OPTICS, 45, 31, 8116, 8131, OPTICAL SOC AMER, Nov. 2006, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, A semianalytical approach to the problem of determining inherent optical properties from satellite and in situ ocean color data is presented. The model uses empirically derived spectral slopes between neighboring wavebands in combination with radiative transfer modeling to determine the spectral absorption (a) and backscatter (b(b)); these values are then further decomposed into absorption due to phytoplankton, detrital, and colored dissolved organic matter components. When compared with over 400 in situ data points the model makes good retrievals of the total absorption and backscatter across the entire spectrum, with regression slopes close to unity, little or no bias, high percentage of variance explained, and low rms errors. (c) 2006 Optical Society of America.

Irradiance inversion theory to retrieve volume scattering function of seawater
T Hirata
APPLIED OPTICS, 42, 9, 1564, 1573, OPTICAL SOC AMER, Mar. 2003, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, \An attempt to retrieve the volume scattering function (VSF) of source-free and no-inelastic-scattering ocean water is made from the upwelhng irradiance E-u and downwelling irradiance E-d. It will be shown, from the radiative transfer equation, that the VSF of seawater can be calculated by the planar irradiances when the scattering phase function of the suspended particles in the backward direction and the molecular VSF are known. On the derivation of the hydrosol VSF, several optical properties such as the absorption coefficient a; the scattering coefficients of hydrosol, b, b(f,) b(b) and those of the suspended particles, b(p), b(fp), b(bp); the beam attenuation coefficient c; the average cosines mu, mu(d), and mu(u); and the backscattering shape, factor for the downwelling light stream, r(du), will also be obtained. On the derivation of those optical parameters, classical knowledge related to interrelationships between inherent optical properties and apparent optical properties and obtained with Monte Carlo numerical simulations is analytically verified. The present theory can be applied to surface waters and any wavelengths, except for waters and wavelengths with an extremely low b(b)/a ratio. (C) 2003 Optical Society of America.

Satellite view of the group-specific primary productivity in the Kuroshio waters
平田 貴文, 鈴木 光次, 海洋と生物, 37, 5, 478, 485, Oct. 2015
生物研究社, Japanese

リモートセンシング事典　　　　　　　　　　　　　　　
正規化海水射出輝度の推定
日本リモートセンシング学会（編） 丸善出版, Dec. 2022, 9784621307762, [Contributor]

リモートセンシング事典　　　　　　　　　　　　　　　
水中光学特性の推定
日本リモートセンシング学会（編） 丸善出版, Dec. 2022, 9784621307762, [Contributor]

Advances in Phytoplankton Ecology　　　　　　　　　　　　　　　
Chapter 7: Applications of satellite remote sensing technology to the analysis of phytoplankton community structure on large scales
Dec. 2021, [Joint work]

海洋生態系解析のためのSGLI海色プロダクトの検証と改良　　　　　　　　　　　　　　　
第3回地球観測研究公募
Apr. 2022 - Mar. 2025
JAXA, Principal investigator

Arctic biodiversity change and its consequences: Assessing, monitoring and predicting the effects of ecosystem tipping cascades on marine ecosystem services and dependent human systems　　　　　　　　　　　　　　　
Horizon2020
Jun. 2020 - May 2024
European Commission (欧州委員会), Coinvestigator not use grants

Study on sea ice condition and navigability risk of Northern Sea Route
Grants-in-Aid for Scientific Research
01 Apr. 2021 - 31 Mar. 2024
大塚 夏彦, 平田 貴文
本年度は、①変形氷域を特定するための衛星データの収集と基本的な分析、②航行実態と海氷による航行障害事例を把握するための船舶航行軌跡の収集と整理、ならびに海氷状況と実際の航行速度の関係の基本的な分析を行い、本研究の主目的である変形氷域およびそれによる航行障害の把握を行うための基本的な知見を得るとともに、実際的な研究手法について検討した。
①については、C-Band合成開口レーダー(SAR)観測データ(Sentinel-1)において、Beaufort Gyre Exploration Project（BGEP）がボーフォート海で実施している海氷ドラフト観測点を含む観測データを抽出し、顕著な変形氷と思われる大きな海氷ドラフト観測時における、SAR観測における後方散乱係数ならびに氷盤等の状況を比較分析した。これより、長径が5~40kmとなる平坦で大きな氷盤が連なる海域において、氷盤の間で局所的に後方散乱係数が大きくなる数km程度の範囲の氷域が認められ、これが大きなドラフトを呈する変形氷域であることが予想された。
②については、北極海航路を航行した貨物船の航行記録（衛星AIS）と、航行時の海氷状況（TOPAZ4 データ同化システム）を収集整理し、氷海航行におけるリスクマネジメントシステムPOLARIS（国際海事機関IMOによる）を用いて、船のアイスクラスと海氷状況より算出されるリスクインデックスRIOを求め、実際の航行速度と対比した。この結果、海氷による航行障害の発生事例において、RIOは航行障害による速度低下事象と比較的よく相関するが、ここで用いている密接度と氷厚だけでは十分に説明できないこと、氷盤サイズや密集度および局所的な変形氷域の影響を考慮する必要性を認識した（学会発表）。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 21K04511

小型衛星 RISESAT 搭載海洋観測カメラによる観測とその応用　　　　　　　　　　　　　　　
2019 - 2024
株）パスコ

海洋植物プランクトンに関する形質空間の概念確立と気候変動に伴う将来予測
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
Apr. 2018 - Mar. 2023
山中 康裕, 平田 貴文
本年度は海洋におけるクロロフィル濃度分布の形成メカニズムを明らかにした論文が、Nature系の新雑誌であるCommunications Earth & Environmentに受理された。また、植物プランクトンが細胞内の炭素・窒素比を環境に応じて変化させるメカニズムを明らかにした論文を投稿した。
海洋のクロロフィル濃度は表層でなく亜表層で最大値を取る。この亜表層クロロフィル極大は海洋には普遍的に存在するが、特定の海域を除いて、形成される原因が明確でなかった。受理された論文では世界で初めて亜表層クロロフィル極大の全球分布の再現に成功し、植物プランクトンが細胞内のクロロフィル含有量を環境に応じて変化させることで全ての海域の亜表層クロロフィル極大の形成が説明できると明らかにした。この論文は細胞スケールの生理がグローバルスケールの現象を決めるメカニスティックな基礎となることを示している。
植物プランクトン細胞の炭素・窒素比は光合成によって海洋に固定される炭素量と海洋表層に供給される窒素量の比であり、海洋の炭素循環と窒素循環をリンクさせる役割を果たす。もし、気候変動に伴って植物プランクトン細胞の炭素・窒素比が変わると海洋が吸収するCO2量が変わる。投稿中の論文では植物プランクトン細胞の炭素・窒素比の変化は、生体資源の最適化によって説明できることを明らかにした。また、海洋全体で平均した植物プランクトンの炭素・窒素比は伝統的に用いられていたRedfield比より大きくなることを示した、これは光合成による海洋のCO2吸収量は、従来考えられていたよりも大きいことを意味する。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 18H04130

再帰反射構造を有しＳＡＲ衛星で観測可能な海上浮力体の研究開発　　　　　　　　　　　　　　　
SCOPE 戦略的情報通信研究開発推進事業
2019 - 2022
総務省, 北極域研究センター, Coinvestigator

衛星を利用した持続可能なサケ資源生産支援プロジェクト　　　　　　　　　　　　　　　
課題解決に向けた先進的な衛星リモートセンシングデータ利用モデル実証プロジェクト
Aug. 2020 - Mar. 2021
内閣府, Coinvestigator

SGLI/GCOM-C 海色アルゴリズムの改良と海色プロダクトの検証および応用　　　　　　　　　　　　　　　
2nd Research Announcement on the Earth Observations
2019 - 2021
Takafumi Hirata
JAXA, Principal investigator, Competitive research funding

衛星データを利用した北極域における海洋モニタリングに関する研究　　　　　　　　　　　　　　　
2019 - 2020
Green & Life Innovation, Inc., Coinvestigator

画像処理技術と生物光学を融合した新型海洋一次生産者別基礎生産算出アルゴリズム　　　　　　　　　　　　　　　
Grants-in-aid for scientific Research
2017 - Mar. 2019
Takafumi Hirata
Japan Society For The Promotion of Science, Principal investigator, Competitive research funding

Calibration, Validation and Application of the SGLI/GCOM-C ocean algorithms　　　　　　　　　　　　　　　
地球環境変動観測ミッション第６回研究公募
Apr. 2016 - Mar. 2019
平田貴文
JAXA, Principal investigator, Competitive research funding

画像処理技術と生物光学を融合した新型海洋一次生産者別基礎生産算出アルゴリズム　　　　　　　　　　　　　　　
Grants-in-aid for scientific Research
Apr. 2016 - Mar. 2018
Takafumi Hirata
Japan Society For The Promotion of Science, Principal investigator, Competitive research funding

Development and calibration of GCOM-C ocean algorithms to derive marine biogeochemical and ecosystem variables towards satellite-model integrated analysis　　　　　　　　　　　　　　　
地球環境変動観測ミッション第４回研究公募
Apr. 2013 - Mar. 2016
Takafumi Hirata
JAXA, Principal investigator, Competitive research funding

Ocean Color Climate Change Initiative　　　　　　　　　　　　　　　
Climate Change Initiative
2014 - 2016
European Space Agency, Ocean Colour Climate Change Initiative

Development of GCOM-C Ocean algorithm to derive Ecosystem Indicators for a satellite-model integrated analysis of marine ecosystem function and global biogeochemical cycles　　　　　　　　　　　　　　　
地球環境変動観測ミッション第２回研究公募
2009 - Mar. 2013
Takafumi Hirata
JAXA, Principal investigator, Competitive research funding

総長室事業推進経費
2013 - 2013
平田貴文
北海道大学, Principal investigator, Competitive research funding

海色衛星観測と生態系モデルによる一次生産者群集構造と海洋二酸化炭素分圧との関係　　　　　　　　　　　　　　　
Grants-in-aid for scientific Research
2010 - 2011
Takafumi Hirata
Japan Society For The Promotion of Science, Principal investigator, Competitive research funding

Irradiance inversion to estimate the volume scattering function of natural waters　　　　　　　　　　　　　　　
助成金
2000
スカンジナビア・ニッポン ササカワ財団, コペンハーゲン大学, Principal investigator