Proceedings of the Ninth and Tenth U.S.-Japan Meetings on Aquaculture

The United States and Japanese counterpart panels on aquaculture were formed in 1969 under the United States-Japan Cooperative Program in Natural Resources (UJNR). The panels currently include specialists drawn from the federal departments most concerned with aquaculture. Charged with exploring and developing bilateral cooperation, the panels have focused their efforts on exchanging information related to aquaculture which could be of benefit to both countries. The UJNR was started by a proposal made during the Third Cabinet-Level Meeting of the Joint United States-Japan Committee on Trade and Economic Affairs in January 1964. In addition to aquaculture, current subjects in the program are desalination of seawater, toxic microorganisms, air pollution, energy, forage crops, national park management, mycoplasmosis, wind and seismic effects, protein resources, forestry, and several joint panels and committees in marine resources research, development, and utilization. Accomplishments include: Increased communications and cooperation among technical specialists; exchanges of information, data, and research findings; annual meetings of the panels, a policy coordinative body; administration staff meetings; exchanges of equipment, materials, and samples; several major technical conferences; and beneficial effects on international relations. (PDF file contains 98 pages.

Marine shallow hydrothermal systems: imprint of their exclusive biogeochemistry on dissolved organic matter and chemosynthesis

Shallow submarine hydrothermal systems are extreme environments with unique biogeochemical conditions, originating from (1) the interaction of hot, reduced fluids and cold, oxygenated seawater, and (2) the possibility of simultaneous primary production by photo- and chemosynthesis. The flux of carbon, reduced molecules and trace elements from hydrothermal vents is mainly controlled by dissolved organic matter (DOM), which is one of the largest pools of organic carbon in the oceans and therefore plays a major role in key biogeochemical cycles. However, the influence of hydrothermal activity on DOM at a molecular level has not been investigated, and an holistic understanding of the functioning of marine shallow systems is currently lacking. The aim of this thesis was to investigate the imprint of the exclusive biogeochemistry of marine shallow hydrothermal systems on (1) the DOM molecular signature and associated redox processes at the interface between fluids and seawater (Chapters 3, 4, S8), and (2) the role of chemoautotrophy in carbon fixation at hydrothermally influenced sediments (Chapters 5, S7). The study sites were three contrasting shallow systems off Dominica (Caribbean Sea), Milos (Eastern Mediterranean) and Iceland (North Atlantic). In contrast to the predominantly meteoric fluids from Dominica and Iceland, hydrothermal fluids from Milos were mainly fed by recirculating seawater. Milos fluids were also strongly enriched in hydrogen sulfide (H2S) and dissolved organic sulfur (DOS), as indicated by high DOS/DOC ratios and by the fact that 93% of all assigned DOM molecular formulas exclusively present in the fluids contained sulfur. Evaluation of hypothetical pathways suggested DOM reduction and sulfurization during seawater recirculation in Milos seafloor. The four most effective pathways were those exchanging an O atom by one S atom in the formula or the equivalent H2S reaction. In all three systems, low O/C molar ratios in the fluids suggested shallow hydrothermal systems as a source of reduced DOM and DOS, which will likely get oxidized upon contact with oxygenated seawater (Chapter 3). In Dominica, hydrothermal fluids were strongly enriched in dissolved Fe(II), leading to the precipitation of Fe(III) oxides in the oxic surface sediment. The marine hydrothermal iron-DOM interaction was characterized at a molecular level and the role of chemosynthesis in carbon fixation was investigated. The formation of Fe(III) oxides upon aeration of the hydrothermal fluids for 10 h led to an 8% decrease in dissolved organic carbon (DOC), indicating co-precipitation of iron and DOM. Re-solubilization of iron precipitates revealed increased relative abundance of aromatic compounds in co-precipitated DOM, which is in accordance with iron-coagulation observed in terrestrial environments (Chapter 4). On the other hand, bacterial community structure analysis revealed the presence of key players in iron cycling generally known from deep-sea vents (e.g. Zetaproteobacteria), suggesting biologically mediated iron redox processes in the Dominica system. Uptake of 13C-bicarbonate into fatty acids under light and dark conditions revealed the potential of active photo- and chemoautotrophic communities, indicating that chemosynthesis was responsible for up to 65% of total carbon fixation (Chapter 5). In conclusion, this thesis (1) reveals novel insights about DOM and DOS dynamics in marine hydrothermal ecosystems, suggesting a conceptual framework for molecular-scale mechanisms in organic sulfur geochemistry; (2) provides evidence for co-precipitation of DOM with iron at hydrothermal systems as a selective process, which characteristically alters the molecular composition of DOM released with hydrothermal fluids; and (3) highlights shallow hydrothermal systems as hotspots for chemoautotrophy, emphasizing chemosynthesis as a major process of primary production in marine coastal environments with hydrothermalism

Environment and resources of seamounts in the North Pacific: Proceedings of a workshop, March 21-23, 1984, Shimizu, Japan

The trawl fishery for pelagic annorhead, Pseuaopentaceros wheeleri(fonnerly referred to as Pentaceros richardsoni), and alfonsin, Beryx splendens, over the central North Pacific seamounts has a relatively short history. Before 1967, fishery scientists were generally unaware of the resources on seamounts; however, the discovery of commercial concentrations of pelagic armorhead on seamounts in the southern Emperor Seamounts by a Russian commercial trawler in November 1967 led to almost immediate exploitation of the species by the Soviets. Unconfinned reports indicated that the schools of pelagic annorhead on the seamounts averaged 30 m thick and catches averaged from 3 to 50 metric tons on 10-20 min hauls (Sakiura 1972). Japanese trawlers entered the fishery in 1969. To assist in the development of this tishery, Japanese research vessels conducted extensive surveys in 1972 on the distribution and potential for development ofthe pelagic armorhead and alfonsin resources. The results of their surveys to the central North Pacific and mid-Pacific seamounts showed that many had summits that were too deep for trawling. Those found suitable were concentrated in the southern Emperor-northern Hawaiian Ridge. (PDF file contains 113 pages.

Dynamics of deep-submarine volcanic eruptions

Funder: Natural Environment Research Council; doi: http://dx.doi.org/10.13039/501100000270Deposits from explosive submarine eruptions have been found in the deep sea, 1-4 km below the surface, with both flow and fall deposits extending several km’s over the seafloor. A model of a turbulent fountain suggests that after rising 10-20 m above the vent, the erupting particle-laden mixture entrains and mixes with sufficient seawater that it becomes denser than seawater. The momentum of the resulting negatively buoyant fountain is only sufficient to carry the material 50-200 m above the seafloor and much of the solid material then collapses to the seafloor; this will not produce the far-reaching fall deposits observed on the seabed. However, new laboratory experiments show that particle sedimentation at the top of the fountain enables some of the hot, buoyant water in the fountain to separate from the collapsing flow and continue rising as a buoyant plume until it forms a radially spreading intrusion higher in the water column. With eruption rates of 106-107 kgs−1, we estimate that this warm water may rise a few 100’s m above the fountain. Some of the finer grained pyroclasts can be carried upwards by this flow and as they spread out in the radial intrusion, they gradually sediment to form a fall deposit which may extend 1000’s m from the source. Meanwhile, material collapsing from the dense fountain forms aqueous pyroclastic flows which may also spread 1000’s m from the vent forming a flow deposit on the seabed. Quantification of the controls on the concurrent fall and flow deposits, and comparison with field observations, including from the 2012 eruption of Havre Volcano in the South Pacific, open the way to new understanding of submarine eruptions

東シナ海の流れ藻に蝟集する稚魚の摂餌生態と海洋環境

Many commercially important fishes associate with drifting seaweeds in their juvenile stage, however, the ecological significance of drifting seaweeds for juvenile fishes is still unclear. We postulated that the following two hypotheses may be applicable for juvenile fishes associate with drifting seaweeds, the “concentration of food supply” hypothesis: juvenile fishes are attracted by phytal animals on the drifting seaweeds and the “indicator-log” hypothesis: fish use accumulations of drifting seaweed as an indicator of productive areas (e.g. frontal areas) for food. We investigated the frontal areas, zooplankton abundance around the drifting seaweed, and the food availability of fish juveniles associated with drifting seaweed accumulations in the East China Sea in 2012 and 2013. A total of 14 drifting seaweed mass and 22 species (n = 408) of fish juveniles were collected. We found that 49.7 - 99.7 % of the individual fed on planktonic food and the feeding incidence on phytal animals was less than 50 %. Although drifting seaweeds were aggregated around the frontal areas of surface currents, the zooplankton abundance was not significantly different between these frontal areas and other areas. Our findings indicate that ecological significance of drifting seaweeds as feeding habit is relatively low for juvenile fishes associated with drifting seaweeds.流れ藻には多くの水産上重要種の稚魚が付随するが，流れ藻の稚魚にとっての生態学的意義は明らかにされていない。筆者らは次の2仮説のいずれかが流れ藻付随稚魚に当てはまると考え，“concentration of food supply hypothesis”（流れ藻葉上生物を摂餌するため）と“indicator log hypothesis”（流れ藻をフロント域のような餌豊度の高い海域の目印とするため）を検証するため，2012年と2013年に東シナ海の流れ藻周辺の海洋環境，フロント域，動物プランクトン豊度，流れ藻付随稚魚の摂餌個体率を調べた。流れ藻は表層流の収束帯に集積されていたが，収束帯のプランクトン豊度は高くなかった。合計14個の流れ藻を採集し，合計22種（408尾）の稚魚の胃内容物を調査した結果，稚魚の49.7 - 99.7 %の個体はプランクトンを選択的に摂餌していたが，葉上生物の摂餌個体率は高くなかった（50 %未満）。以上の結果から流れ藻の稚魚にとっての生態学的意義は摂餌場でないことが示唆された

Growth and toxicity of geographically-distinct isolates of the fish-killing phytoflagellate, Heterosigma akashiwo

Harmful Algal Blooms (HABs)—an accumulation of toxic phytoplankton—often result from environmental changes reflecting the increasing global human footprint and climate change. One HAB species drawing attention is Heterosigma akashiwo, a fish-killing flagellate that can cause extensive fish loss or be benign, depending on location or environmental conditions. Here, I investigate if this difference in toxicity is regulated by environmental conditions or differences in cellular physiology. Six strains were examined. Three originate from the Salish Sea, where fish-kills are common, and three from Japan, where blooms of Heterosigma are common but fish-kills are rare. By measuring growth and toxicity of cells grown under two environmental stressors—temperature and salinity—I concluded the low frequency of fish-kills in Japan was due to absence of environmental conditions associated with highest toxic expression. However, reduced temperature conditions, which may occur more frequently with climate change, may stimulate toxicity in Japanese strains