著者

坂田 明

出版者

日本プランクトン学会

巻号頁・発行日

vol.50, no.1, pp.21-23, 2003 (Released:2011-03-05)

著者

眞子 裕友 小針 統 一宮 睦雄 小森田 智大 幅野 明正 東 隆文 久米 元

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.69, no.2, pp.93-101, 2022-08-25 (Released:2022-09-17)

参考文献数

53

---

It has been thought that food availability for fish larvae was poor in the Kuroshio because of the low standing stocks of plankton in the oligotrophic conditions under thermal stratification throughout the year. Despite a potential risk or disadvantage for larval survival and growth, Kuroshio and its neighbouring waters are nursery grounds for the early life stages of various fishes. Here, we compared the growth activity of fish larvae among 15 taxonomic groups, including 11 families in the Kuroshio and its neighbouring waters, based on protein synthetase activity and protein contents. Protein-specific (spAARS), individual-based aminoacyl tRNA synthetase activities (iAARS), and protein contents (PRO) of fish larvae ranged from 2 to 232 nmol PPi mg protein−1 h−1, from 1 to 21 μmol PPi ind−1 d−1, and from <1 to 26 mg ind−1, respectively. spAARS, iAARS and PRO were variable among the taxonomic groups and were not classified between mesopelagic groups and the others. Compiling these measurements among all taxonomic groups, a significant negative correlation was found for spAARS to PRO. The correlation showed no significant difference between the Kuroshio and its neighbouring coastal waters, indicating that growth activities to fish larvae body mass were comparable in the Kuroshio and its neighbouring waters. Based on nonmetric multidimensional scaling on spAARS, iAARS and PRO among 15 taxonomic groups, two different groups were classified for fish larvae, represented by the high iAARS under the high PRO but low spAARS (Group 1) and the low iAARS under the low PRO but high spAARS (Group 2), representing the different life strategies for larval growth among the taxonomic groups. The present findings suggest that these biochemical indices are useful for evaluating the growth activity of fish larvae among various taxonomic groups and that food availability is not poor enough to support larval growth in the Kuroshio and its neighbouring waters.

著者

眞子 裕友 小針 統 久米 元 兵藤 不二夫 野口 真希 一宮 睦雄 小森田 智大 河邊 玲 中村 乙水 米山 和良 土田 洋之

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.69, no.1, pp.18-24, 2022-02-25 (Released:2022-03-06)

参考文献数

38

---

The prey of whale sharks (Rhincodon typus) visiting the northern Satsunan area (western North Pacific Ocean) was investigated using microscopic and metabarcoding analysis of their faecal pellets. The stable isotope ratios of the dorsal fin and faecal pellets from the whale sharks were compared with those of their potential prey (plankton and fish larvae). Microscopic analysis identified protozoans (foraminifera) and metazoans (copepods, ostracods, and amphipods) but unclassified material was predominant in their faecal pellets. Metabarcoding analysis detected metazoans in the faecal pellets, represented by copepods, ostracods, amphipods, hydrozoans, and tunicates. Comparison of stable isotope ratios (δ13C and δ15N) from their dorsal fin and faecal pellets with those of zooplankton in the northern Satsunan area showed different feeding histories for the whale sharks appearing in the northern Satsunan area.

著者

名取 則明 桑田 正彦 田中 和明 戸田 龍樹

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.70, no.1, pp.1-9, 2023-02-25 (Released:2023-03-22)

参考文献数

7

---

The water freeze-drying method can be used to prepare samples for scanning electron microscopy (SEM) in which samples immersed in water are frozen and dried under vacuum. This method does not require chemical fixation of freshwater microorganisms, whose structures are easily disrupted during fixations, and mixed samples of different species can be processed simultaneously with minimal morphological damage. We optimised this method for plankton surveys using SEM. A membrane filter with a plastic frame was attached to the filtration device, and microorganisms in the collected water were filtered and concentrated. Immediately before the end of filtration, the framed filter was removed from the filtration device, whereas the concentrated microorganisms remained covered with water. The wet filter was frozen by contact with a cooled metal plate and vacuum-dried. After conductive coating of the filter, the microorganisms on the filter were identified and counted using SEM. This method is more time-consuming compared to conventional optical microscopy (OM) methods and provides no information on colours or internal structures, making species identification difficult. However, the number of microorganisms detected was two- to three-fold lager than that detected using OM, including some species that could not be detected using OM. This result can be explained as follows: there was almost no loss of microorganisms larger than the filter pore size, and the resolution of SEM is higher than that of OM. A further advantage of this method is that the measured samples can be stored for long periods without morphological damage, and the measurement results can be re-validated at a later date.

著者

CHANG KWANG-HYEON 花里 孝幸

出版者

日本プランクトン学会

巻号頁・発行日

vol.54, no.2, pp.99-110, 2007 (Released:2011-03-05)

著者

伊東 宏

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.66, no.1, pp.41, 2019-02-25 (Released:2019-02-28)

参考文献数

1

著者

大森 信

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.69, no.1, pp.25-33, 2022-02-25 (Released:2022-03-06)

参考文献数

17

---

The sakura-ebi [Lucensosergia lucens (Hansen, 1922)] fishery in Suruga Bay, Japan, sharply declined in 2018 and has not yet recovered (140 tons was reported for the spring catch in 2021). I have proposed two causal hypotheses to explain the slump:1) a decline in the spawning population in the inner area of the bay due to excessive fishing in the spring season and a shift in the spawning peak from early summer to late summer-autumn, and 2) a decline in biological productivity in the inner and western area of the bay after the 1980s due to recent coastal development and environmental deterioration. A delay in the spawning peak may causes a shift in the main spawning area from the inner area to the western area of the bay.Test the first hypothesis; we performed numerical experiments to investigate the transport processes of eggs and larvae of L. lucens in Suruga Bay, focusing on the physical effects of the current with a different peak in the spawning season and in the area using the particle tracing method. Particles regarded as eggs and early larvae were passively transported in flow fields for 1 month after being deployed at three locations: a) off the mouth of the Fuji River, the inner area, b) off the mouth of the Abe River, the western area, and c) off the mouth of the Oi River, in the southwestern area. The particles were tracked by two ocean circulation models using simplified hydrographic conditions in September 2007 and with predicted and real observations of current flow from 1 June to 1 October, 2020.In the first experiment, using simplified conditions without considering the effect of the Kuroshio current, approximately half of the particles deployed in the 0–24 m layer off the mouth of the Fuji River remained in the inner area of the bay after 1 month. Nearly 90% of the particles remained in the bay. However, only 22% of the particles deployed off the mouth of the Abe River and less than 10% deployed off the mouth of the Oi River remained in the bay after 1 month. In the case where the particles were deployed in the 24–60 m layer off the mouth of the Fuji River, 100% remained in the bay. In the second experiment with predicted and real observations of the current flow, 54% of the particles that were deployed off the mouth of the Fuji River remained in the bay, whereas only 23% from off the mouth of the Abe River and 15% from off the mouth of the Oi River remained in the bay after 1 month. In Sagami Bay, 76% of the particles that were deployed in the 25–45 m layer off the mouth of the Sakawa River were run out from the bay after 1 month. These results indicate the importance of the retention area in the inner area of Suruga Bay, where the eggs and larvae can stay for a long time.A good correlation was observed between the spawning peak during 1991 to 1997 and catch per unit effort (CPUE) (catch [kg] per 30 min tow) of the 0-year class shrimp, suggesting that earlier spawning in July causes an increase in the 0-year class shrimp population for the autumn catch.Thus, I believe that the first hypothesis is correct. Delays in peak spawning time cause a shift in the main spawning area from the inner area to the western and southwestern area of Suruga Bay, and therefore cause a remarkable loss of larvae to outside the bay. To restore the shrimp stock, it is essential to reduce fishing effort during the spring catch to facilitate spawning of larger eggs in June/July in the inner area, and hence many larvae remain and grow in the bay. Distinct differences exist in the hydrographic conditions between Suruga Bay and the neighbouring Sagami Bay. The eggs and larvae in Sagami Bay are easily run out from the bay, and hence the population cannot be maintained to the level of commercial fishery.

著者

葛西広海 梅田晴子

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.68, no.2, pp.36-45, 2021-08-25 (Released:2021-09-02)

参考文献数

27

---

To standardize the netplankton datasets in terms of sampling gear and sampling depth, previous plankton data obtained from the oceanographic A-line surveys in the western subarctic Pacific were analyzed. Comparable netplankton sampling was carried out using two plankton sampling gears, the mini-Bongo net and the NORPAC (North Pacific Standard) net, installed with 335 µm mesh. Considering the two sampling depths, 0–50 m and 0–150 m, the mean ratio of dry weight (DW) of plankton biomass in unit volume was 2.22±1.19. Using the data of plankton population, the ratio of population at the sampling depths was close to DW, suggesting that the plankton biomass at the sampling depths was comparable. On the other hand, individuals of species/taxa in most samples did not differ significantly in terms of sampling depth and sampling gear. However, plankton populations of some species, mainly distributed below the surface mixing layer, was higher in the layer of 0–150 m than in the layer of 0–50 m. This result indicated the need for careful biomass evaluation for some species at different sampling depths.

著者

佐藤 直 徳弘 航季 松野 孝平

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.69, no.1, pp.11-17, 2022-02-25 (Released:2022-03-06)

参考文献数

45

---

Limacina helicina, a species of Pteropoda (Cuvier, 1804), plays an important role in the food web and carbon cycle in subpolar and polar regions. The presence of aragonite unsaturated water in the Pacific sector of the Arctic Ocean necessitates the need to examine damage caused by ocean acidification on species with aragonite shells. According to previous studies that examined the impact of acidification on shell-bearing species by employing incubation experiments, young stages (veligers and juveniles) are more vulnerable than adults. In the present study, vertical distribution of the young stages of L. helicina in the Arctic Ocean during autumn was observed to evaluate the effects of environmental factors on their distribution. Veligers and juveniles showed high abundances from the surface to 30 m depth in the basin regions around the Chukchi Plateau (Stations 39, 45, and 49) but were restricted to a depth of 20–30 m, overlying a strong halocline formed by the inflow of less saline water. Veligers were predominant in the basin regions, indicating that active reproduction occurred in September. Since adult females involved in reproduction were abundant in the shelf regions, their reproduction patterns varied with different periods and regions. Unsaturated aragonite waters and damaged shells were not observed in the study area, possibly due to dilution by sea ice melt water inflowing from the shelf regions. This study showed that the distribution of the young stages of L. helicina was predominantly concentrated in the upper 30 m of the basin due to stratification with a strong halocline in the shallow layers caused by the inflow of sea ice melt water.

著者

伊東 宏

出版者

日本プランクトン学会

巻号頁・発行日

no.1, pp.53-63, 2006 (Released:2011-03-05)

著者

櫻井久惠 佐野 雅美 高橋 邦夫

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.69, no.1, pp.34-38, 2022-02-25 (Released:2022-03-06)

参考文献数

5

---

In recent years, learning styles involving observation and experimentation have been recommended for schools as a form of active learning. The National Institute of Polar Research is promoting the improvement and increased production of resin-embedded zooplankton specimens for use in marine education. Based on trials and questionnaires completed by current teachers, we created a marine educational workshop kit comprising resin-embedded specimens, observation tools, a booklet, worksheets, introductory videos for participants, and workshop programs. The kit is designed mainly for junior high school students and can be used for remote (online) workshops to facilitate online learning necessitated by the COVID-19 pandemic. We have requested school teachers to try using the kit and identify various applications of the kit. We began loaning out the kits in November 2021. We hope that many teachers who have not had the chance to conduct marine education will start using this kit.

著者

道山 晶子 藤井 暁彦 山田 京平 梅田 智樹 高田 順司 内川 純一 細田 誠也 山口 浩 松山 幸彦

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.69, no.2, pp.83-92, 2022-08-25 (Released:2022-09-17)

参考文献数

34

---

In Ariake Bay, catches of the manila clam Ruditapes philippinarum have decreased considerably due to the low rate of larval return to adult habitats, shrinkage of larval networks among each local population, and shortening of the occurrence period of larvae. In this study, we examined the seasonal and annual occurrence trends of planktonic clam larvae and the environmental factors related to the quantity of larvae based on surveys conducted in the Ariake Sea between 2015 and 2018. In the Ariake Sea, emergence peaks with population densities of more than 1,000 m−3 individuals occurred during the spring and fall spawning seasons. In spring, the peak onset often occurred between late April and May, but trends also varied from year to year. In autumn, the peak period was observed at approximately the same time every year, from mid-October to November. The peak emergence of plankton larvae was thought to be related to water temperature.

著者

夏池 真史 金森 誠 前田 高志 嶋田 宏 坂本 節子

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.69, no.1, pp.1-10, 2022-02-25 (Released:2022-03-06)

参考文献数

31

---

In Hokkaido, Japan, the toxic dinoflagellate Alexandrium catenella (A. tamarense species complex Group I) is the source of frequent contamination of bivalves with paralytic shellfish toxins over the last 40 years, whereas A. pacificum (Group IV) has rarely been reported. Recently, A. pacificum cells were identified based on their morphology and DNA sequences in Hakodate and Funka bays, southern Hokkaido. To understand their seasonal occurrence, A. pacificum and A. catenella cells in the two bays were detected using microscopy and multiplex polymerase chain reaction (PCR) over a 2-year period (May 2018–May 2020). Microscopic observation showed that cells of A. pacificum, a species without the ventral pore between the 1′ and 4′ plates, occurred in Hakodate Bay from July to November 2018 and in July 2019, with a maximum cell density of 4450 cells L−1 in November 2018. It also occurred in Funka Bay in October 2018, with a maximum cell density of 50 cells L−1. Multiplex PCR using Alexandrium species-specific primers showed a similar seasonal occurrence of A. pacificum in Hakodate Bay. In contrast, A. catenella was found from February to May in Funka Bay but its occurrence was uncertain in Hakodate Bay because the microscopy and PCR tests were not simultaneously positive. The occurrence of A. pacificum was limited to the period (July to November) of optimum water temperature for growth (15–25℃), suggesting that the occurrence of motile cells was affected by water temperature. When A. pacificum bloomed at a relatively high density in Hakodate Bay during autumn 2018, warmer water temperature and lower salinity in the surface layer were observed compared to the previous 5 years. These environmental conditions were thought to be established due to warmer air temperatures, a longer sunshine duration, and a large amount of precipitation from October to November 2018. Such environmental and meteorological conditions were suggested to be suitable for the growth of A. pacificum in Hakodate Bay.

著者

松島 伸代 加藤 舞斗 中村 敦樹 石井 晴人

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.68, no.2, pp.46-57, 2021-08-25 (Released:2021-09-02)

参考文献数

38

---

Mass occurrences of scyphozoan jellyfish, such as Aurelia coerulea, have been reported in various waters; however, little is known about the hydrozoans and ctenophores in Tokyo Bay. In this study, the abundance of these jellyfishes was monitored for four years(April 2015–November 2016, April 2018–July 2019)in Tokyo Bay. Thirteen hydrozoan species and three ctenophores were observed. The dominant hydrozoan species identified were Cytaeis uchidae, Podocoryne minima, Rathkea octopunctata, Diphyes chamissonis, and Liriope tetraphylla, while Bolinopsis mikado was the most dominant among the ctenophores. Cytaeis uchidae, P. minima, and R. octopunctata appeared for a short period with extremely high abundance. Cytaeis uchidae occurred when the salinity was low, but P. minima occurred under high water temperature and high salinity conditions during summer. The abundance of R. octopunctata increased with decreasing water temperature during winter. On the other hand, D. chamissonis and L. tetraphylla presented prolonged abundance during most of the studied period. Diphyes chamissonis occurred in summer when the water temperature was high, and L. tetraphylla was observed at low temperatures and high salinities in autumn. It was suggested that these two species, without polyp stages, had entered from the adjacent waters in Sagami Bay. Diversity for the species composition of hydrozoans and ctenophores is very low, with some species dominant in Tokyo Bay; the occurrence of these dominant species is greatly affected by water temperature and salinity in the ambient seawater. These species play an important role in the gelatinous plankton ecosystem in Tokyo Bay.

著者

仲村 康秀 松岡 數充 今井 一郎 石井 健一郎 桑田 晃 河地 正伸 木元 克典 鈴木 紀毅 佐野 雅美 José M. Landeira 宮本 洋臣 西川 淳 西田 周平

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.66, no.1, pp.22-40, 2019-02-25 (Released:2019-02-28)

参考文献数

137

---

Plankton are aquatic organisms unable to swim against the current, and they include diverse taxa of different phylogenetic origins. The taxonomy, phylogeny and ecology of nine plankton groups are reviewed in this paper, in order to comprehensively understand the latest information and current situation of plankton studies. The order-level classification of dinoflagellates was re-arranged, but the classification system is still not well organized at the family-level. The taxonomy of raphidophytes and dictyochophytes was partly confused, however, molecular studies provided clear categorization between these groups. The diatoms could be identified by observing some important morphological characteristics. Yet, these characteristics are sometimes not observable because of inappropriate specimen treatments, and furthermore, the morphological terms are not enough unified, resulting that the species-level identification is complicated and difficult. Recent studies revealed the cryptic diversity and high abundance of some microalgae, such as haptophytes and prasinophytes. The diversity and ecology of planktonic foraminifers have been clarified, but those of radiolarians and phaeodarians are still wrapped in mystery. The classification needs to be re-arranged especially for collodarians, phaeodarians and acantharians. The phylogeny of copepods has been elucidated, and this group was re-classified into 10 orders. Future studies should clarify their evolutionary process and create useful databases for easier identification. The methods to reveal the larva-adult correspondence are established for decapods, and further clarification of the correspondence is expected. The classification system of chaetognaths has been updated, and the intra-species diversity is also being studied. The species diversity of scyphozoans has not been well clarified especially for deep-sea species, and their classification still involves problems such as cryptic species. The dataset including DNA sequences and different types of images (taken in the field and under the microscope, etc.) should be accumulated for comparing the data from different methods (e.g., direct microscopy, optics-based survey and environmental DNA analysis).

著者

奥 修

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.51, no.1, pp.25-33, 2004-02-25

参考文献数

15

著者

高橋 一生

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.51, no.1, pp.46-72, 2004-02-25

被引用文献数

2

著者

坂田 明

出版者

日本プランクトン学会

雑誌

日本プランクトン学会報 (ISSN:03878961)

巻号頁・発行日

vol.50, no.1, pp.21-23, 2003-02-25

---

私が淡水のミジンコ類を飼育採集するにいたった経緯は、自宅で飼育する金魚、タナゴ類、メダカ等の稚仔魚の餌料生物として、ミジンコが適当であると考えたからであります。私が、ミジンコを中心にしたプランクトンを観察してきたのは大体20年位です。しばらくして、あまりの面白さに、『ミジンコ倶楽部』などを結成し、10年ほど、そこらじゅうで「ミジンコだ」、「ミジンコですよ」、「ミジンコがいますよ」、などと叫んで歩いたわけですね。そうしたら、民百姓の諸君も面白がって、おまけにぞろぞろとミジンコの研究者が釣れた訳です。

著者

奥 修

出版者

日本プランクトン学会

巻号頁・発行日

vol.51, no.1, pp.25-33, 2004 (Released:2011-03-05)

著者

遠部 卓

出版者

日本プランクトン学会

巻号頁・発行日

vol.25, no.1, pp.41-54, 1978 (Released:2011-03-05)