Estimation of the physical release of organic matter from ice using observational data and a coupled ice-water box model

In order to estimate the physical release of organic matter from sea ice and biological production in the ice, we conducted a series of field observations (samplings of water beneath the ice and of an ice core, and deployment of sediment traps) on the ice on Saroma Ko lagoon, Hokkaido, Japan in 2004 and developed a coupled ice-water box model. The observations documented the accumulation of organic matter in the ice. The box model estimates biological production in the ice at 208mgCm^day^ (Mar. 1-2) and 60mgCm^day^ (Mar. 2-11), and estimates the fluxes of the physical release at 142mgCm^day^ (Mar. 1-2) and 68mgCm^day^ (Mar. 2-11), which account for more than 70% of biological production in the ice. The physical release efficiently transports organic matter from sea ices to water column

FIELD MEASUREMENT AND MODELLING OF THE MATERIAL CYCLE IN THE CULTIVATION POND OF PENAEID SHRIMP PENAEUS JAPONICUS

ABSTRACT Field measurement and modelling of the material cycle are carried out for the cultivation pond of penaeid shrimp Penaeus japonicus. The main purpose of the present study is to investigate the sustainability of coastal shrimp aquaculture, which is increasingly being questioned due to many problems like disease, excessive nutrient enrichment, and low levels of dissolved oxygen tension. Despite the great economic importance of shrimps and their suitability to aquaculture, little is known about the material cycle through the cultivation pond. Additionally, the collapse of shrimp aquaculture in most tropical countries may be attributed to the lack of ecological, biological, and environmental understanding. Hence field measurement of water quality is conducted in the shrimp cultivation pond, which locates in the Kyushu district of Japan. Various environmental factors such as water temperature, salinity, and the concentrations of dissolved oxygen, nutrients, and chlorophyll a are monitored for the water in the pond and that drawn from the outer sea during November and December of 2006. In addition to field measurement, one dimensional numerical model is developed for the shrimp cultivation pond to understand the material cycle through the pond in a quantitative manner. The numerical model consists of physical, lower trophic-level ecosystem, and shrimp growth submodels. The numerical values of physical and physiological parameters are calibrated to achieve the best agreement between observed and simulated results. By integrating results from field measurement and numerical simulation, it is revealed that the quality of water in the cultivation pond is quite different from that drawn from the outer sea. In particular the concentration of chlorophyll a is much higher in the cultivation pond due to large primary production. The results of the numerical simulation show that the high productivity is attributed partly to the activities of shrimps. The information from field measurement and the simulated results of the developed numerical model are useful to optimize the food quantity and quality, the population density of shrimps, and the design of watermills or the other equipments to improve the water quality for sustainable use of coastal shrimp cultivation pond

Application of the Ocean Health Index to assess ocean and coastal conditions of the Tokyo Metropolitan area

Ocean ecosystem services are fundamental to coastal economic development and climate regulation. The Tokyo Metropolitan Area (TMA) is one of the world’s most significant bay areas, with its economic development and residents relying on a healthy ocean and diverse marine ecosystem services. Post-World War II, the coastal zones of TMA have suffered from various human-induced stresses and impacts, jeopardizing the capacity of ocean ecosystem services and sustainable development. Although recent years have seen improvements in basic marine water quality, other ecosystem health issue, such as biodiversity, carbon storage, coastal protection are remain limited and require comprehensive enhancement. To better understand the current state of ocean health, promote more comprehensive ocean management decisions and plans, and support sustainable development in the region, it is essential to evaluate the ocean’s condition in the TMA and to assess future trends and risks. The Ocean Health Index (OHI) offers a comprehensive framework to evaluate global and regional ocean health conditions and their ecosystem services. This study applies the OHI to assess the ocean and coastal health of TMA, with indicators and reference points adjusted based on local conditions. From 2014 to 2019, the OHI assessment results indicate that TMA obtained an overall OHI score of 49 (out of 100), with goals ranging from 13 to 87. The environmental and social goals, such as Tourism and Recreation (87), Clean Water (67), Coastal Livelihoods and Economies (62), Sense of Place (62), and Artisanal Fishery Opportunity (51), are relatively high. In contrast, the ecological goals, such as Biodiversity (14), Carbon Storage (13), Coastal Protection (38), and Food Provision (24), are relatively low. This case study highlights strategies for improving ocean health conditions in TMA from both OHI goals and management structure perspectives. The methods and results provide a quantitative tool for regional marine and coastal management in TMA, aiding regional management organizations to establish quantifiable objectives for actions that were previously difficult to quantify. These results can indirectly promote the establishment of more comprehensive and holistic regional management organizations in TMA, which is currently fragmented, thereby effectively enhancing ocean health in TMA

An efficient coral survey method based on a large-scale 3-D structure model obtained by Speedy Sea Scanner and U-Net segmentation

Abstract Over the last 3 decades, a large portion of coral cover has been lost around the globe. This significant decline necessitates a rapid assessment of coral reef health to enable more effective management. In this paper, we propose an efficient method for coral cover estimation and demonstrate its viability. A large-scale 3-D structure model, with resolutions in the x, y and z planes of 0.01 m, was successfully generated by means of a towed optical camera array system (Speedy Sea Scanner). The survey efficiency attained was 12,146 m2/h. In addition, we propose a segmentation method utilizing U-Net architecture and estimate coral coverage using a large-scale 2-D image. The U-Net-based segmentation method has shown higher accuracy than pixelwise CNN modeling. Moreover, the computational cost of a U-Net-based method is much lower than that of a pixelwise CNN-based one. We believe that an array of these survey tools can contribute to the rapid assessment of coral reefs