Seasonal changes in nano/micro-zooplankton grazing on pico-, nano- and micro-size phytoplankton and heterotrophic nano-flagellates
(HNF) feeding on heterotrophic bacteria were quantified by the dilution technique in the surface layer off Cape Esan, southwestern
Hokkaido, Japan. Pico- and nano-size phytoplankton were major components throughout the year except in spring when a diatom
bloom was observed. Although there was little seasonal variation in bacteria and HNF biomass throughout the year, the micro-zooplankton
biomass varied appreciably with a peak in spring. Nano/micro-zooplankton grazing or feeding on pico-size chl-a and bacteria were well balanced throughout the year. However, nano-size and micro-size chl-a growth were much greater than grazing in summer. Nano/micro-zooplankton ingestion of phytoplankton was greater than their
ingestion of bacteria almost throughout the year, which suggests phytoplankton are more important as food sources of nano/micro-zooplankton
in microbial food webs off Cape Esan than bacteria off Cape Esan.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
The Algal Growth Potential (AGP) of water samples collected off Gamagori in Mikawa Bay was measured from May 1978 through February 1979, and the limiting nutrient was determined using regression analysis and enrichment bioassays. The surface and bottom water samples had AGP that produced increments of chemical oxygen demand (COD) of 2.1 mg l–1 and 3.1 mg l–1, respectively, on average. These values ofCOD correspond to 46% and 97% of the average COD values of the raw water samples at the surface and bottom, respectively. Seasonal changes of AGP showed a close correlation with those of dissolved inorganic nitrogen (DIN) concentration. Enrichment bioassays showed that DIN was the most deficient nutrient. The DIN:phosphate-phosphorus (PO43–-P) ratios and DIN: dissolved phosphorus (DP) ratios in the water samples were below the cellular N:P ratios of the natural algal populations. These results suggest that AGP was mainly limited by DIN concentration. 相似文献
Drowning accidents at beach in Japan are caused by rip currents. To reduce these accidents, a new technology that can detect rip currents and notify beachgoers by using the Internet of Things (IoT) and Artificial Intelligence (AI) was proposed. However, studies on the effect of visualizing rip currents or considering the effect of optimism bias have not been conducted. This study investigates if visualization of rip currents might help in preventing drowning accidents, while considering the effect of optimism bias. The participants were 90 Japanese beachgoers. They were asked to answer questions based on their knowledge of the beach and rip currents, their optimism bias regarding rip currents, and awareness with or without visualization. The results of the analyses suggest that despite optimism bias, the visualization of rip currents increases the tendency of beachgoers to perceive and avoid rip currents. As described above, it was found that by visualizing the rip current, beachgoers were able to perceive and avoid rip currents. In addition, an understanding of rip currents is positively related to the intent to avoid rip currents even when rip currents are visualized. Therefore, it is necessary not only to enhance the avoidance tendency by visualizing rip currents, but also to further enhance knowledge of beachgoers to deepen the understanding of rip currents including the danger associated and methods to avoid them.
Lipid fraction and cell-wall materials have been separated from three types of algae (blue green, Microcystis sp.; green, Scenedesmus sp. and diatomaceous Diatoma sp.) and their KMnO4 oxidation products (aliphatic dicarboxylic acids; aliphatic normal C14–C24 monocarboxylic acids; benzoic acid and C18 isoprenoidal ketone) examined by gas chromatography and gas chromatographymass spectrometry. The results suggest that the lipid material could make a greater contribution to polymethylene chains in kerogen than the cell-wall material, when the kerogens are mainly derived from algal components. 相似文献
The construction of formulas for sequentially computing solutions and a variance-covariance matrix with the bandtype system of observation equations, which is inherent in geodetic networks, is carried out; these formulas are illustrated with a simple numerical example in which the adjustment for the trilateration of triply coupled quadrilaterals is executed. 相似文献
Lipids, fulvic acid, humic acid and kerogen were isolated from a lacustrine sediment in which the organic matter is probably derived predominantly from phytoplankton (Lake Haruna, Japan). An alkaline KMnO4 oxidation study of the organic matter showed that distributions of polymethylene chain lengths in the lipids, humic acid and kerogen fractions are almost the same. The polymethylene chains in the sediment are dominant in the kerogen, lipids and humic acid, their relative abundance estimated by the oxidation being: kerogen (42% of the total amounts of polymethylene chains estimated) > lipids (38%) > humic acid (19%) > fulvic acid (1%). It was concluded that algal lipids may have been incorporated into the kerogen and humic acid fractions after the death of the algae and during, after, their deposition. 相似文献
Abstract Investigations were conducted on bathymetry, reef biota and sediments on the Hirota Reef, Tane‐ga‐shima, North Ryukyus, near the northern limit for coral‐reef formation. A bathymetric profile from shore to the reef edge was depicted along an approximately 420‐m transect on the Hirota Coast of this island. A total of 20 quadrats (1 m × 1 m) were analyzed along the profile at 10‐ or 20‐m intervals to clarify distribution of macrobenthos inhabiting the reef. The Hirota Reef is divided into four geomorphologic zones according to their depth, gradient, surface roughness, substrate and characteristic macrobenthos. They are, from shore to offshore, shallow lagoon, seaward reef flat, reef edge and reef slope. The shallow lagoon comprises a shoreward depression (∼160 m wide on the transect) with a sand/gravel bottom that inclines gently toward offshore, and a seaward patch zone (∼70 m wide). The patches (<2 m high) are covered with fleshy algae, coralline algae and hermatypic corals. The seaward reef flat (∼190 m wide) is a flat plane that is constructed by biogenic carbonates and is covered with turf algae, with hermatypic corals scattered. Although the seaward reef flat of the Hirota Reef cannot be differentiated into different geomorphologic zones, similar seaward reef flat areas in the Central and South Ryukyus can be clearly subdivided into inner reef flat, reef crest and outer reef flat. This difference may be attributed to a lower reef growth rate and/or the later reef formation of the Hirota Reef in Holocene time than the southern examples. The coral fauna on the Hirota Reef is delineated by low diversity and characterized by taxa typical of high‐latitude, non‐reefal communities. The algal flora consists of tropical to subtropical species associated with warm‐temperate species. These faunal and floral characteristics may be related largely to lower water temperature in Tane‐ga‐shima than those in typical coral‐reef regions. 相似文献
Abstract High-resolution seismic reflection profiles delineated the distribution of mound-shaped reflections, which were interpreted as reefs, beneath the insular shelf western off Irabu Island, Ryukyus, southwestern Japan. A sediment core through one of the mounded structures was recovered from the sea floor at a depth of −118.2 m by offshore drilling and was dated by radiometric methods. The lithology and coral fauna of the core indicate that the mounded structure was composed of coral–algal boundstone suggesting a small-scaled coral reef. High-precision α-spectrometric 230Th/234U dating coupled with calibrated accelerator mass spectrometric 14C ages of corals obtained reliable ages of this reef ranging from 22.18 ± 0.63 to 30.47 ± 0.98 ka. This proves that such a submerged reef was formed during the lowstand stage of marine oxygen isotope stages 3–2. The existence of low-Mg calcite in the aragonitic coral skeleton of 22.18 ± 0.63 ka provides evidence that the reef had once been exposed by lowering of the relative sealevel to at least −126 m during the last glacial maximum in the study area. There is no room for doubt that a coral reef grew during the last glacial period on the shelf off Irabu Island of Ryukyus in the subtropical region of western Pacific. 相似文献