Hisatomo Waga

• PhD
• Research Assistant Professor at University of Alaska Fairbanks

Light condition, day length, and amount of incident sunlight vary widely with season in the Arctic. Absorption-based primary production (PP) models incorporate light absorption coefficients and photosynthetically active radiation (PAR); however, algorithm sensitivity to such parameters has not been investigated in the Arctic Ocean. Therefore, we as...

Sediment-laden sea ice is a ubiquitous phenomenon in the Arctic Ocean and its marginal seas. This study presents a satellite-based approach at quantifying the distribution of sediment-laden ice that allows for more extensive observations in both time and space to monitor spatiotemporal variations in sediment-laden ice. A structural-optical model co...

The western subarctic Pacific and adjacent Bering Sea are recognized as one of the most productive regions supported by spring diatom bloom among the world’s oceans. Yet, phytoplankton growth and photosynthesis are often suppressed during summer. Little is known about factors controlling the summer primary productivity and phytoplankton community s...

The northern Bering and Chukchi seas are biologically productive regions but, recently, unprecedented environmental changes have been reported. For investigating the dominant phytoplankton communities and relative contribution of small phytoplankton (<2 µm) to the total primary production in the regions, field measurements mainly for high-performan...

The Arctic is experiencing rapid changes in sea-ice seasonality and extent, with significant consequences for primary production. With the importance of accurate monitoring of spring phytoplankton dynamics in a changing Arctic, this study further examines the previously established critical relationship between spring phytoplankton bloom types and...

The northern Bering Sea (NBS) and southern Chukchi Sea (SCS) contain several water masses with different characteristics that have been conventionally classified using temperature and salinity data. However, recent warming and sea ice decline can change these water properties, which suggests that classifying water masses using temperature–salinity...

The structure of demersal fish assemblages was investigated based on a total of 134 trawl samples collected in the northern Bering Sea (NBS) and Chukchi Sea (CS) during 12 summers between 1990 and 2013. In recent years, the timing of sea ice retreat has become earlier in the NBS. The present study was performed to clarify the environmental factors...

The substantial loss of Arctic sea ice will alter marine ecosystems in many ways. Recent studies have reported a distributional shift in benthic macrofaunal biomass in the Pacific Arctic, likely caused by changes in food availability for benthic organisms. Here, we assessed the influence of differences in post-bloom supply of phytoplankton to the s...

Arctic ecosystems are altered profoundly by climate changes. However, the responses of Arctic marine and terrestrial ecosystems as well as their biodiversity to global warming remain largely unknown. This article provides comprehensive insights into the results and major findings from the Arctic Challenge for Sustainability (ArCS) Project – an Arct...

Phytoplankton blooms in the Pacific Arctic have been characterized as a huge single bloom in spring. However, several studies have reported recent increases in the occurrence of fall blooms during the period after dissipation of the spring bloom. Here, we explored spatiotemporal variations in the occurrence of fall blooms in the region, using satel...

There is growing evidence that increased Pacific water transport into the Arctic affects the marine ecosystem. One of the theoretical predictions for a future Arctic characterized by such environmental change is that subarctic taxa will expand northward and invade the native Arctic ecosystem. This study focuses on variation in macrofaunal community...

The impact of mesoscale eddies on phytoplankton communities attracts considerable research attention because phytoplankton play numerous roles in marine ecosystems. Using remote sensing techniques, this study considered a synoptic relationship between phytoplankton size structure, which is a determinant of energy transfer efficiency in marine ecosy...

Phytoplankton blooms in the Pacific Arctic Region (PAR) has been characterized as a huge single bloom in spring when light availability is high, the mixed layer is shallow and nutrients are abundant due to winter deep mixing. However, several studies have reported that recent increases in occurrence of a relatively small but evident second bloom in...

Phytoplankton plays a critical role in a number of key ocean processes. One of the most important functions of phytoplankton is to determine the energy transfer efficiency in marine ecosystems. Although the energy flow from the base of the food web to higher trophic levels depends on both the biomass and size structure of phytoplankton community, p...

Bering Strait is the single gateway between the Arctic and Pacific Oceans, and has localized strong currents, which can exceed 100 cm s⁻¹. Although massive spring phytoplankton blooms and the subsequent production of particulate organic matter that sinks to the seafloor are observed in the surrounding regions of the Bering Strait, the impact of the...

The size structure of the phytoplankton community strongly affects energy flow through food webs; hence, monitoring the spatial and temporal dynamics of phytoplankton size structure is crucial to evaluate variability in marine ecosystems. In this study, the spatiotemporal changes in phytoplankton size structure and their impact on benthic macrofaun...

There is growing evidence that increased Pacific water transport into the Arctic Ocean affects the marine ecosystem. One of the theoretical predictions during this period of change is that new taxa will expand or invade the native ecosystem. Although benthic organisms are less mobile than pelagic one, it seems relevant that benthic organisms with p...

The size structure of the phytoplankton community strongly affects energy flow through food webs, and hence monitoring the spatial and temporal dynamics of phytoplankton size structure is crucial to evaluate variability of marine ecosystem. In this study, spatiotemporal change in phytoplankton size structure and its impact on benthic infaunal distr...

Species distributions are changing with various rates and directions in response to recent global warming. The velocity of sea surface temperature (SST) has been used to predict species migration and persistence as an expectation of how species track their thermal niches; however, several studies have found that evidence for species shifts has devi...

Increased understanding on how marine species shift their distribution is required for effective conservation of fishery resources under climate change. Previous studies have often predicted distributional shifts of fish using satellite derived sea surface temperature (SST). However, SST may not fully represent the changes in species distribution t...

Dominant cell size of phytoplankton is an important factor in determining the number of trophic levels of marine ecosystem. We aimed to develop an algorithm to derive phytoplankton size structure, fraction of micro-, nano-, and pico-phytoplankton (fm, fn, and fp), based on the Junge-type power-law distribution for their biomass. In this study, phyt...