Coastal ecosystem models have evolved alongside the shifting challenges of coastal environmental issues. Key developments include: (1) modeling of advection and diffusion to address organic pollution, (2) modeling of primary production in relation to eutrophication, (3) modeling of benthic systems to tackle hypoxia, (4) modeling of tidal flats and seaweed beds in response to their degradation, (5) integrating pelagic-benthic systems and shallow-central bay areas with nature-positive approaches, (6) modeling the lifecycle of large diatoms and winter nori discoloration, and (7) modeling the carbonate equilibrium system to address climate change mitigation. Looking ahead, models are expected to further advance by incorporating biodiversity and ecosystem networks connecting water quality, lower trophic organisms, and higher trophic organisms. This paper outlines the progression of mathematical modeling from stages (1) to (7).

Remote sensing technology for the marine environment has been developed over the past 50 years, leading to the collection and accumulation of various parameters. We will introduce physical parameters, such as sea surface temperature, salinity, sea surface height, sea ice, wind, and surface roughness. We will also provide a more in depth explanation of biological and chemical parameters, including chlorophyll-a, suspended matter, colored dissolved organic matter, primary production, phytoplankton groups, and seafloor conditions, using ocean color detection. While these data have primary been applied to open ocean studies due to coarse spatial resolution, their use in coastal applications has been growing and is expected to increase further in the near future. Assimilations with numerical models is also anticipated to expand, particularly for biological and chemical application.

Oceanographic sensors play a critical role in conducting scientific research and technological activities related to the ocean, becoming increasingly essential for understanding critical societal issues such as marine environment preservation, conservation of biodiversity, and sustainable fisheries. This paper reflects on the advancements in oceanographic sensor technology mainly over the past three decades, focusing on JFE Advantech Corporation’s exploration in sensing technologies and their foundational and ancillary developments. The paper highlights significant innovations in various types of sensors. For instance, the dissolved oxygen (DO) sensor has evolved from older electrochemical methods, which required frequent maintenance, to a more advanced phosphorescent technology that offers rapid responses and reduced maintenance requirements. Similarly, the chlorophyll sensor has transitioned from bulky halogen light sources to compact LED models, making it easier to handle. The electrical conductivity sensor has also improved, with JFE Advantech Corporation implementing a seven-electrode structure that minimizes measurement errors caused by external objects. Moreover, the paper discusses advancements in technologies to prevent biological fouling, which is a major challenge in long-term marine monitoring, and the development of automated calibration systems to enhance precision in measurements. The emergence of IoT and wireless communication has further transformed sensor applications, allowing for real time data collection and analysis. In conclusion, the ongoing progress in oceanographic sensor technologies is expected to continue addressing the needs of academic research, fisheries, and environmental understanding, with a focus on miniaturization, robustness, and long-term stability. The integration of advanced AI and cloud computing is anticipated to facilitate unprecedented data utilization, underscoring the critical role of marine measurement technologies in promoting oceanic environmental protection and sustainable growth.

An ocean-going autonomous underwater vehicle equipped with detailed-mapping acoustic instruments and a high-resolution underwater gravity measurement system was completed by Japan Agency for Marine-Earth Science and Technology. The instruments composed a multibeam echo sounder, a sidescan sonar and a subbottom profiler are synchronized their pings including DVL to prevent acoustical interferences. An underwater precise gravity measurements system uses for exploration of seafloor mineral deposits, mounted on a gimbal mechanism in a pressure housing with communication between the AUV that developed by the university of Tokyo, Earthquake Research Institute. This paper presents operational engineering for the systems, and results around hydrothermal area.

The real-time observation of the seafloor using the telecommunication submarine cables technology is the only method that can secure steady power and sufficient real-time data transmission capacity for observation equipment on the seafloor. In Japan, which has multiple seismogenic zones of mega thrust earthquake in the sea area around the country, there is a demand for disaster prevention to acquire real-time data in the seabed. For this reason, Japan has been developing and operating submarine cabled observatories for a long time. Currently, the cabled observatory is a system that is not limited to monitoring seismic activity, but can also realize multidisciplinary real-time observations by adding or replacing instruments. As a future goal, it is expected that various prediction studies will be conducted using these data, and that the results of the research will be implemented in society.

The Meteorological Research Institute (MRI) and the Japan Meteorological Agency (JMA) developed the ocean model and data assimilation system MOVE-JPN with the aim of providing more detailed information on coastal and open-ocean states around Japan, and began operation on October 28, 2020. This system itself and the data products generated from it (hereafter MOVE-JPN family) are used not only for operational use in JMA but also for various research activities both within and outside MRI. In this paper, we introduce the latest research activities using the MOVE-JPN family and discuss potential applications of the MOVE-JPN family in the future studies.

Ocean color remote sensing has evolved from the first global observation of phytoplankton chlorophyll-a pigment to multiple observations of biogeochemical and ecological quantities such as chromophoic dissolved organic matter and phytoplankton community structure. This evolution is a result of methodological advances in both hardware and software. Based on the author’s activities in the ocean color research so far, future perspective on the ocean color remote sensing is described in terms of mainly, but not limited to, the software development.

In underwater environments where electro-magnetic waves and light cannot travel far, sound waves have long been used for exploration and communication. This lecture introduces the recent developments of active and passive acoustic technologies. The lecture will also explore future technological prospects. In active technologies, a major turning point has been the application of multi-channel and wide-band methods. For example, multibeam sonar equips multiple receiving elements for the beam forming to separate reflected sounds from various directions as well as the echo delay time for the seabed topography, fish school shapes, subsurface exploration for mining using air guns, and even underwater visual-like imaging using acoustic lenses. Additionally, wide-band technologies provide various type of target information in addition to the location and time. Passive technology development has been largely driven by the detection of submarines. After the Cold War, underwater acoustic technologies were made available for civilian use. Not only marine mammals like whales and dolphins, but also sound-producing species such as fish and crustaceans, are now being monitored using passive technologies. These techniques are currently used globally for environmental assessments of the oceans. In these years, Underwater Domain Awareness is strongly demanded for the sustainable use of ocean. For active technologies, precise mapping and wide-band communication in long range is needed. For passive technologies, identifying the sources is a big issue. Annotated reference data of phonating targets is needed. The rising underwater noise levels from various human activities have become an international concern due to their impact on marine life.

Two types of methane hydrate have been identified in the deep ocean areas around the Japanese archipelago. The sand type is buried literally in the deep sand layers, whereas the surface type exists just beneath the seabed or in the relatively shallow mud layers. These are attracting attention as the next generation of domestic energy resources in Japan, and the Ministry of Economy, Trade and Industry (METI) has been promoting research and development of methane hydrate. The authors are participating in a research and development project on surface methane hydrates and are conducting environmental impact assessment of methane hydrate development on the marine environments from physical, chemical, biological and ecological aspects. Here, we present the environmental impact assessment in this project and the progress of the research to date. We have been actively introducing various new techniques of field-observation protocols and analytical methodologies to improve and optimize environmental impact assessment for methane hydrate development. A novel technology of highly sensitive stable isotope probe method combined with conventional geochemical and genetic analyses revealed the importance of complex microbially-mediated processes in sediments to reduce the methane flux from the seabed to the over-lying seawater. Laboratory exposure experiments with comprehensive gene expression analysis were conducted to investigate the potential effects on benthic organisms induced by various environmental disturbances including high turbidity, low oxygen, high methane, hydrogen sulfide and low salinity. This study was conducted as a part of the methane hydrate research project funded by METI (the Ministry of Economy, Trade and Industry, Japan).

Seafloor information obtained from sea surface is limited, and direct access using underwater robots is necessary to investigate the deep seafloor in detail. Furthermore, the measurement range in deep-sea is limited due to attenuation of light and electromagnetic waves, so the area that can be observed at one time is limited. Therefore, automation of deep seafloor observation using Autonomous Underwater Vehicles (AUVs) is essential to cover a vast area of the ocean. AUVs have been becoming a powerful tool in deep seafloor observation, such as resource survey, scientific survey, and searching for sunken ship. Unmanned survey operation, further expansion of the survey range of the AUV itself, and diversification of missions will be important keywords for further development of AUVs and accelerating the automation of deep seafloor observation. In this paper, the author will present the current situation and prospects of automation of deep seafloor observation using robots centered around AUVs, and report on the development of the 8000m-class Urashima 8000 and automatic data collection from a seafloor-based observation device using an AUV.

In order to understand and predict the seismogenic processes of large earthquakes that repeatedly occur in the Nankai Trough region, we aim to monitor the status of plate boundary locking by not only monitoring earthquakes and tsunamis but also conducting real-time observations of seafloor crustal deformation. To achieve this, we have been conducting technical developments and implementing them in the Nankai Trough region, including long-term seafloor pressure observation through in-situ calibration of seafloor pressure gauges, seafloor tilt and strain measurements, distributed optical fiber sensing using submarine optical fiber cables, and the development and deployment of long-term borehole observation systems in wide area. Based on these technological developments, several future technological challenges and areas for further development have been identified. These include the integrated real-time analysis of earthquake and seafloor crustal deformation data, high-precision seafloor mapping and leveling over wide areas using autonomous unmanned vehicles, high-precision temperature and strain measurement using optical fiber sensing, and deep seafloor drilling to reach plate boundary and the installation of borehole sensors. Furthermore, long-term maintenance of the submarine cable observation network infrastructure is essential for understanding the transition in the seismic cycle of the large earthquake zone, and thus, updating and enhancing the infrastructure with new technologies is necessary.

It is not easy to talk about the future of AI technology, which has been developing explosively in recent years, however, I will introduce the AI technology that we have been using since around 2017, as well as examples of applied research on AI technology that we are currently working on in our research group. In addition, the current issues and future prospects are also mentioned in this lecture.