記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：MDPI AG  

<jats:p>Heatwaves under global warming have negative impacts on ecosystem primary producers. This warming effect may be synergized or antagonized by local environments such as light and nutrient availability. However, little is known about the interactive effects of warming, irradiance, and nutrients on physiology of marine macroalgae, which are dominant in coastal ecosystems. The present study examined the combined effects of warming (23 and 26 °C), irradiance (30 and 150 µmol photon m−2 s−1), and nutrients (enriched and non-enriched) on specific growth rate (SGR) and biochemical compositions of the canopy-forming marine macroalga Sargassum fusiforme. The negative effect of warming on SGR and ratio of chlorophyll (Chl) c to Chl a was antagonized by decreased irradiance. Moreover, the negative effect of temperature elevation on carbon content was antagonized by nutrient enrichment. These results suggest that the effect of warming on the growth and carbon accumulation of this species can be mitigated by decreased irradiance and nutrient enrichment.</jats:p>

DOI： 10.3390/jmse10040479

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：FRONTIERS MEDIA SA  

In order to understand how global warming effects on ecosystem primary production may change depending on nutrient enrichment, a new classification is proposed to disentangle and recognize the combination of interactions among several factors, based on the effect direction (positive, negative, or neutral) and its changes induced in it by the other factor (synergizing, antagonizing, inducing no change, or changing it in some other way). Marine macroalgae were chosen (as primary producers for which there is the most experimental information available) to review the relevant studies on which this new classification can be tested. It was observed the positive effects of elevated temperature and nutrient enrichment often synergized each other within the temperature range between relatively low and optimal growth levels. However, the negative effect of further temperature elevation from optimal to higher levels was antagonized by nutrient enrichment in some studies but was synergized in others, depending on the range of temperature elevation. The positive effect of nutrient enrichment was antagonized (but still positive) by temperature increase above the optimum in many cases, although the effect sometimes switched to a negative effect depending on the magnitude of nutrient enrichment. These results predict that global warming will enhance bottom-up effects on primary production in cold seasons and areas, and there will be a negative warming effect on production in hot seasons and areas, but it may be possible to mitigate this effect by appropriate levels of nutrient enrichment.

DOI： 10.3389/fmars.2022.774801

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Ocean warming and the associated changes in fish herbivory have caused polarward distributional shifts in the majority of canopy-forming macroalgae that are dominant in temperate Japan, but have little effect on the alga Sargassum fusiforme. The regeneration ability of new shoots from holdfasts in this species may be advantageous in highly grazed environments. However, little is known about the factors regulating this in Sargassum species. Moreover, holdfast tolerance to high-temperature and nutrient-poor conditions during summer has rarely been evaluated. In the present study, S. fusiforme holdfast responses to the combined effects of temperature and nutrient availability were compared to those of sexually reproduced propagules. The combined effects of holdfast fragmentation and irradiance on regeneration were also evaluated. Propagule growth rate values changed from positive to negative under the combination of elevated temperature (20 °C-30 °C) and reduced nutrient availability, whereas holdfasts exhibited a positive growth rate even at 32 °C in nutrient-poor conditions. The regeneration rate increased with holdfast fragmentation (1 mm segments), but was unaffected by decreased irradiance. These results suggest that S. fusiforme holdfasts have a higher tolerance to high-temperature and nutrient-poor conditions during summer than propagules, and regenerate new shoots even if 1-mm segments remain in shaded refuges for fish herbivory avoidance.

DOI： 10.3390/plants10081522

PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Applied Phycology  

DOI： 10.1007/s10811-021-02425-z

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Phycological Research  

DOI： 10.1111/pre.12395

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Recent declines of macroalgal forests due to climate change imply that the aquaculture production of macroalgae may also be negatively affected by ocean warming. It has previously been shown that nutrient enrichment can offset the negative impact of warming on the survival and growth of the cultivated macroalga Undaria pinnatifida, although it can also increase the risk of herbivory by unrecognized mesograzers. Observations of several hundreds or thousands of the isopod Cymodocea japonica around U. pinnatifida cultivation ropes in autumn, prompted the analysis of their size-frequency distribution, relationship between body size and consumption rate, and combined effects of elevated temperature and nutrient enrichment on the consumption rate of the algae by the isopod in the current study. Although the body size of the isopods collected in autumn was smaller than those collected in winter and spring, the consumption rate of 600 small isopods was similar to the rate of a large individual. Additionally, the consumption rate doubled in response to an increase in temperature from 15 to 18 degrees C and nutrient enrichment, and tripled with their combination. These results suggest that ocean warming combined with nutrient enrichment increase the risk of herbivory during U. pinnatifida cultivation, especially during isopod outbreak periods.

DOI： 10.1093/icesjms/fsaa069

Web of Science

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Frontiers Media SA  

DOI： 10.3389/fmars.2020.575721

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Phycological Research  

DOI： 10.1111/pre.12416

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Applied Phycology  

DOI： 10.1007/s10811-019-01967-7

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Phycological Research  

DOI： 10.1111/pre.12398

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Phycologia  

DOI： 10.1080/00318884.2019.1571355

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Applied Phycology  

DOI： 10.1007/s10811-018-1621-0

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Applied Phycology  

DOI： 10.1007/s10811-018-1655-3

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Fisheries Science  

DOI： 10.1007/s12562-018-1263-9

Scopus

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 日本水産学会  

DOI： 10.2331/suisan.WA2650

Scopus

J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Phycological Research  

DOI： 10.1111/pre.12332

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Phycologia  

DOI： 10.2216/18-26.1

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Applied Phycology  

DOI： 10.1007/s10811-018-1442-1

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Phycological Research  

DOI： 10.1111/pre.12220

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Applied Phycology  

DOI： 10.1007/s10811-017-1381-2

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Applied Phycology  

DOI： 10.1007/s10811-017-1344-7

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Evolutionary Applications  

DOI： 10.1111/eva.12592

Web of Science

Scopus

PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Applied Phycology  

DOI： 10.1007/s10811-017-1306-0

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Oceanography  

DOI： 10.1007/s10872-017-0442-0

Web of Science

Scopus

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2018 National Shellfisheries Association. All rights reserved. The sea urchin Mesocentrotus nudus is commercially harvested between June and August in northeastern Japan. A previous study showed that feeding on Saccharina japonica between April and June resulted in gonad quantity and quality improvement in this species from a barren. No information is available on the optimal culture period for harvest before the fishing season. The purpose of this study was to determine whether gonad size and quality (color, texture, and taste) can be improved before the fishing season and to verify the possibility of an early harvest. The sea urchins M. nudus were collected from a barren and placed under two types of culture conditions: suspended cages in a bay and a laboratory circulation system. They were fed S. japonica between December and May or March. Gonad indices, hardness, and color [L∗, a∗, and b∗, and ΔEab∗ (a unit of acceptable commercial color difference from a fishing ground for each treatment)], and free amino acid (FAA) contents of the urchin gonads at the start of rearing experiments and at the end of cage (C) and laboratory feeding (LF) cultures were measured. These variables were also compared between LF and laboratory-starved urchins to confirm the dietary effect of this kelp. Gonad indices in treatments C and LF were significantly higher than those at the start of the experiment and those in laboratory starvation (P < 0.01), although there was no significant difference between C and LF. Gonads in treatment C were significantly softer than that at the start of the experiment (P < 0.0001). ΔEab∗ of gonads in treatment C was the lowest, indicating that the gonad color was close to the preferred color. There was no significant difference in the total FAA content between C and LF treatments, whereas, of the umami FAA, glutamic acid content was significantly higher in gonads from C than LF. Of the bittertasting FAA, tyrosine and valine contents were significantly higher in LF gonads than in C gonads. These results suggested that gonad size, hardness, and color of M. nudus were improved before the fishing season by initiating culture in December with S. japonica feeding.

DOI： 10.2983/035.037.0318

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Regional Studies in Marine Science  

DOI： 10.1016/j.rsma.2017.07.006

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Fisheries Science  

DOI： 10.1007/s12562-017-1113-1

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

In northern Japan, Saccharine kelps are natural diets for sea urchins and are known to enhance sea urchin gonad size. However, little is known about the effects of the kelp diet on gonad quality and consistency among individuals. In the present study, Mesocentrotus nudus adults collected from a barren were cultured in a suspended cage from late February to early June 2014 in Shizugawa Bay, Miyagi Prefecture. They were fed stipes of Undaria pinnatifida for 56 d followed by fresh Saccharine japonica kelp for 42 d. At the end of the culture period, gonad indices, gonad hardness, gonad color (L* (lightness), a* (redness), b* (yellowness)), free amino acid (FAA) contents in the gonads, and sensory qualities of the cultured sea urchins (EC) were measured and compared to those of the natural population from the barren (EB) and those from the Eisenia bicyclis kelp bed (EK) in the bay. Gonad index and L* values of EC urchins were higher than those of urchins from the barren at the start of culture (SCB). Total color (L*, a*, b*) of the gonads of EC and EK urchins were similar. Gonad hardness of EC and EK urchins was similar and lower than that of EB urchins, and the coefficients of variation of gonad index, color, and hardness were lower than those from the barren (SCB and EB). Sweet tasting alanine contents of the gonads of EC urchins were markedly higher than those of the gonads from the other urchin specimens. Bitter tasting FAA contents of the EC urchin gonads were higher than those of EK and EB urchins, although arginine and lysine contents were lower than those of EB urchins. Sensory scores of overall taste of EC urchins were higher than those of EB urchins and similar to EK urchins, possibly due to the increased alanine content. These results suggest that gonad size, color, hardness, taste, and consistency among individuals of M. nudus collected from barrens can be improved to reach levels similar to those of urchins from the E. bicyclis kelp bed by cage culture with short-term feeding of Saccharine kelps. Changes in gonad qualities seemed to be mainly due to S. japonica as the food source because hard U. pinnatifida stipes were rarely eaten and had markedly low protein content. Extension of cage culture duration with S. japonica feeding from spring to summer would increase gonad size and further improve gonad quality.

DOI： 10.1016/j.aquaculture.2017.04.033

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Regional Studies in Marine Science  

DOI： 10.1016/j.rsma.2017.05.009

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Applied Phycology  

DOI： 10.1007/s10811-016-1036-8

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Evolutionary Applications  

DOI： 10.1111/eva.12455

Web of Science

Scopus

PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Phycological Research  

DOI： 10.1111/pre.12170

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

Short-term flow fluctuations in the southern central part of Onagawa Bay were examined using long-term mooring and hydrographic data observed during the period from May 2013 to April 2014. The short-term flow fluctuations were dominant in the periodic bands of 15-27 days and shorter than 10 days. The principal and minor components of these flow fluctuations were respectively along and across the local isobaths, which are almost parallel in the north direction. The northward flow fluctuations along the local isobaths were correlated with the northeastward wind fluctuations in both periodic bands, and these correlations were more evident from fall to winter. On the basis of these results, the northward flows are regarded as wind-induced barotropic coastal jets. On other hand, the eastward flow fluctuations across the local isobaths were related to inflow and outflow via the bay mouth or the Izushima Channel. Inflow and outflow with reverse flow at lower depths formed in summer, but those with vertically uniform flow tended to form in winter. The main summertime inflow and outflow were driven by horizontal gradients in density. These permit us to regard the main summertime inflow and outflow as gravitational circulation. Also, the summertime inflow can be intermittently caused by internal waves.

DOI： 10.1007/s10872-016-0360-6

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

AimOceanic currents are among the most pervasive hydrodynamic features in shaping community dynamics, population connectivity and phylogeographical structure of intertidal species. Here, we test whether population structure and biogeographical gradients of genetic diversity in the brown alga Sargassum thunbergii are correlated with oceanic currents in the north-west Pacific (NWP).
LocationNorth-west Pacific (25.07 degrees N-43.36 degrees N).
MethodsNuclear internal transcribed spacer-2 and mitochondrial cox3 sequences were obtained from 835 and 810 individuals of S. thunbergii respectively. Parsimony networks and phylogenetic trees (maximum parsimony and Bayesian inference) were constructed to evaluate phylogeographical structure. Pairwise F-ST estimates and analyses of molecular variance (AMOVA) at various hierarchical levels (latitude, longitude, marine provinces, biogeographical basins and zoogeographical zones) were conducted to elucidate population genetic differentiation. migrate software was used to estimate the number of migrants between adjacent populations.
ResultsSeveral lines of evidence indicate that S. thunbergii is characterized by shallow population structure. Geographical distances do not correlate with population pairwise genetic differentiations. The corridor/stepping-stone model-based coalescent analyses reveal high levels of asymmetric gene flow among S. thunbergii populations, with the numbers of migrants largely corresponding to the directions of oceanic current systems in the NWP. Genetic signatures also indicate that Jeju Island, Korea might act as a transition zone for dispersal of S. thunbergii in the NWP driven by the Kuroshio Current, thus facilitating subsequent transportation northward into the Sea of Japan and the Yellow-Bohai Sea.
Main conclusionsPopulation genetic homogeneity in S. thunbergii was mainly structured by oceanic currents rather than palaeoclimatic events. Our study illustrates an important phylogeographical case of how coastal hydrodynamic factors contributed to population connectivity and geographical shifts of genetic diversity for marine organisms without a pelagic stage.

DOI： 10.1111/jbi.12856

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：INT PHYCOLOGICAL SOC  

In northern Japan, the production of Saccharina japonica exhibits marked annual fluctuation due to changes in seawater temperature and nutrient availability during winter and spring. To better understand this phenomenon, we examined the combined effects of temperature (5 degrees C, 10 degrees C, 15 degrees C and 20 degrees C) and nutrient availability (seawater enriched with 25% Provasoli's enriched seawater vs nonenriched seawater) on photosynthesis, growth and survival and nitrogen and chlorophyll a contents of juvenile sporophytes (2-3 cm) and larger size class sporophytes (100-150 cm) from southern Hokkaido. Both juvenile sporophytes and discs from 100-150-cm-class sporophytes cultured in enriched seawater showed significantly higher growth rates and photosynthetic activities than those cultured in nonenriched seawater. This difference likely was due to the significantly higher nitrogen and chlorophyll a contents of thalli grown in enriched seawater. Significant effects of temperature on growth and photosynthesis were also detected. A significant interaction between temperature and nutrient availability for relative growth rate (RGR) was detected. The positive effect of elevated nutrient availability on RGRs was magnified by an increase in temperature from 5 degrees C to 15 degrees C for juvenile sporophytes and from 5 degrees C to 10 degrees C for 100-150-cm-class sporophytes; whereas, the negative effect of elevated temperature from 10 degrees C to 15 degrees C on RGRs of 100-150-cm-class sporophytes was antagonised by a reduction in nutrient availability. In contrast to the 100% survival rate in enriched seawater, dead juvenile sporophytes and discs from 100-150-cm-class sporophytes were found at 15 degrees C and 20 degrees C in nonenriched seawater, and the survival rates decreased with increasing temperature. Therefore, the growth and survival of sporophytes of S. japonica are significantly affected by nutrient availability and temperature, which may lead to marked fluctuations in annual production.

DOI： 10.2216/16-91.1

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

Deforestation of the kelp Ecklonia cava has been widely reported in Japan, and may be due to physiological stress caused by warm seawater temperatures and low nitrogen availability. To test this hypothesis, we examined the effects of temperature (20, 26, 28, and 30 A degrees C) and nitrogen conditions (seawater enriched with 25 % PESI vs. non-enriched seawater) on photosynthesis, growth and survival, and nitrogen and chlorophyll a content of juvenile sporophytes (3-4 cm) along the coast of the Izu Peninsula, Japan. The juvenile sporophytes cultured in enriched medium showed significantly greater photosynthetic activity and relative growth rates than those cultured in non-enriched seawater at 20-28 A degrees C, likely because of the much higher nitrogen and chlorophyll a content in the enriched medium. A significant effect of temperature on photosynthesis and relative growth rates was also detected under both nitrogen conditions. However, in contrast to the excellent survival exhibited in the enriched medium, dead juveniles were observed in non-enriched seawater at all temperatures, and survival rates decreased with increasing temperature. These results reveal that growth and survival of E. cava juvenile sporophytes are negatively affected by low nitrogen availability and high seawater temperature, which may result in deforestation of this kelp.

DOI： 10.1007/s12562-016-0998-4

Web of Science

記述言語：英語   出版者・発行元：SPRINGER  

DOI： 10.1007/s10811-015-0654-x

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

Recent studies on global warming report that increases in seawater temperature cause coastal ecosystem changes, including a shift in marine algal distribution in temperate regions. To assess the influence of increased seawater temperature on ecophysiological responsiveness and potential shifts in abundance and distribution of kelp, we investigated the seasonal changes in standing biomass, growth, and maturation of natural populations of Saccharina japonica by taking monthly measurements in 2005, 2006, and 2007 in Matsushima Bay, northern Honshu, Japan, which is the southernmost range of this species. Compared to kelps collected in 2005, a sharp decline in standing biomass, later sporophyte occurrence, early growth, greater erosion, and failed sporophyte reproduction were found in kelps collected in 2006, which was a year characterized by relatively high seawater temperature. The population of S. japonica was absent in 2007, when the seawater temperature was higher than that in 2005 and 2006. These results suggest that the seawater temperature in Matsushima Bay is unfavorable for the development and reproduction of this cold-water kelp. If seawater temperatures in this bay remain high over long time periods because of continuous global warming, the southern limit of distribution of S. japonica likely will shift further north.

DOI： 10.1007/s10811-014-0417-0

Web of Science

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

Apart from certain studies on Macrocystis pyrifera (Linnaeus) C. Agardh, very few in situ experimental studies on production have been carried out to verify that "bottom-up effects" (relating to nutrient supply) are more important than "top-down" effects (relating to herbivory) in temperate kelp forests. The effects of nutrient supply on recruitment and production of hatchery-raised gametophytes of Saccharina japonica, cultivated on a rope, and wild Saccharina religiosa, cultivated on a rope and on new concrete reefs placed at the sea bottom, were examined at an experimental site with artificial nutrient addition continuously from October 2008 to May 2009 and compared to kelp that was cultivated from October 2008 to May 2009 without nutrient supply, at a natural site in Tomari (Sea of Japan, southwestern Hokkaido, Japan). At both sites, sea urchins were removed for exclusion of top-down effect. At the natural site, no hatchery-raised S. japonica and wild S. religiosa grew on the rope. No wild S. religiosa grew on the porous-concrete reefs and rocks. At the nutrient-enhanced site, S. japonica and S. religiosa grew rapidly on the rope, at rates of 47.7 and 33.3 plants/10 cm length rope, respectively. S. religiosa grew on the concrete reefs at a concentration of 9.7 plants/0.3 m(2). At the nutrient-enhanced site, the concentrations of NH4-N, NO3-N, NO2-N, and PO4-P ranged from 35.2-173.2, 2.1-10.9, 0.3-1.5, and 0.8-2.6 mu mol L-1, respectively, being markedly higher than those at the natural site, where these nutrient concentrations were almost equal to the averages off Tomari. These results indicate that the production of Saccharina kelp is restricted by bottom-up effects (at a low nutrient concentration) in the Sea of Japan, southwestern Hokkaido. Nutrient supply would be essential for growth enhancement of Saccharina kelp production in a marine environment around Japan where, in recent times, water temperatures have increased by ca. 0.5 A degrees C and nutrient concentrations have decreased.

DOI： 10.1007/s10811-013-0196-z

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

In northern Japan, massive production of high-quality specimens of the kelp Undaria pinnatifida prior to the traditional harvest season is strongly needed to meet commercial demand. To address this need, we tested the effects of controlled thinning by cutting small plants on the growth and maturation of sporophytes cultivated in Matsushima Bay, northern Japan. In early December 2009, the stocking densities of cultivated kelps were thinned to 10 and 5 plants per 4 cm thread section in two experimental groups. In contrast, no thinning was conducted during cultivation until March 2010 in the control group (about 16-20 plants per 4 cm thread section). Morphological features, photosynthesis, and carbon and nitrogen contents were compared among the three groups. Compared to kelps of control group, total length, stipe width, the length and width of sporophyll, and dry weights of blade and sporophyll showed significantly higher values in kelps of the two experimental groups. However, stipe length of kelps of control group was significantly greater than those of the two experimental groups. The photosynthetic rates and nitrogen contents of kelps of the two experimental groups were significantly greater than those of the control from January to March. No significant differences occurred in all these parameters between kelps of the two experimental groups. Based on these results, the growth and maturation of U. pinnatifida sporophytes can be promoted greatly by experimental thinning, and this will improve production of high-quality specimens of kelps and increase economic returns before the traditional harvest season.

DOI： 10.1007/s10811-013-0071-y

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

Although large perennial brown algae are known to show great morphological plasticity responding to specific environmental factors such as depth and wave exposure, there are few reports showing this morphological variability taking into account age or size composition. Here, we conducted age- and size-based morphological comparison between the perennial brown alga Sargassum macrocarpum C. Agardh from their upper depth limit, middle depth, and lower depth limit at an exposed coast in northern Kyoto, Japan. Model II regression was fitted for the relationships between age or stipe diameter (SD) and morphological variables including SD, holdfast weight (HW), number of main branches (MBN), total weight of main branches (MBW), thallus weight (TW), and thallus length (TL) of 30 specimens collected seasonally from each depth zone. The differences between depths in these regression equations were analyzed using SMATR. Although SD, HW, and MBN of the specimens did not differ between depths under both age- and SD-basis, there were significant differences between depths in MBW, TW, and TL, suggesting that the differences in TW between depths are resulted from differences in MBW. Whereas TW at the lower depth limit was lower than that at the upper depth limit or middle depth in many months, TL at the upper depth limit was shorter than that at the middle depth or lower depth limit in some months. These results suggest that S. macrocarpum at shallower depths tend to have short and bushy morphology, whereas those at deeper depths have long and less bushy morphology.

DOI： 10.1007/s10811-013-0002-y

Web of Science

記述言語：英語  

To elucidate sexual differences in gonad size and color in sympatric two sea urchins (Strongylocentrotus nudus and Hemicentrotus puicherrimus), we examined S. nudus and H. puicherrimus with gametes in the gonads, in the Sargassum yezoense bed in the Oshika Peninsula, northern Honshu, Japan during July-November and September-June, respectively, from 2008 to 2010. The changes in the gonad indices of H. pulcherrimus in the Sargassum bed were compared with those in the Undaria pinnatIda and Saccharinajaponica kelp bed, using a data set obtained from Ogasawara et al. (2011). The gonad indices, by sex, of S. nudus rapidly decreased from September to a minimum in November, while those of H. pulcherrimus decreased from October to a minimum in December, February or April. For both species of sea urchin, the proportion of brown-colored gonads increased with a decrease in the gonad indices during spawning. A significant positive correlation between brown-colorization and gonad size was also detected. In H. pulcherrimus, the female gonad size was smaller than that of males during the spawning stage in both the Sargassum bed and the kelp bed. Gonadal regrowth of females during post-spawning was much slower in the Sargassum bed.

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

Improved cultivation technology for the kelp Undaria pinnatifida is greatly needed to increase production to meet increasing commercial demand. A previous cultivation trial indicated that the crop yield of U. pinnatifida sporophytes could be increased greatly by thallus excision in late February due to compensatory growth of the remaining tissues. To develop this potential new cultivation technology, it is essential to identify the time period during which this kelp can compensate and its physiological responses to thallus excision. In this study, U. pinnatifida sporophytes were excised at about 30 cm above the meristem at the beginning of January, February, March, and April, respectively. Morphological features, photosynthesis, nutrient uptake, and carbon and nitrogen contents of excised kelps were measured and compared with these parameters in control kelps grown without excision. Both experimental and control kelps were farmed together in Matsushima Bay, northern Japan. The kelps excised in January and February showed significant increases in the lengths and dry weights of the blade, photosynthetic rates, nutrient uptake rates, and carbon and nitrogen contents compared with the control kelps, and the growth phase was prolonged for at least 1 month. No significant increases were found in dry weights and carbon and nitrogen contents of sporophylls until early April, which indicated that the maturation period was delayed. At the end of this experiment, the nitrogen contents of sporophyll tissues formed after excisions were significantly lower than those of tissues formed before excisions. In contrast, the kelps excised in March and April showed no significant increases in morphological and physiological parameters compared with control kelps. These results suggest that U. pinnatifida sporophytes exhibited great compensation when excisions were conducted during the growing phase in January and February but not in March and April when the maturation phase had started. The regulation of resource allocation to growth and maturation after thallus excisions in January and February likely results in prolongation of the growth phase and maturation phase in excised kelps.

DOI： 10.1007/s10811-013-9989-3

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

In recent years, the crop yield of cultivated Undaria pinnatifida (Harvey) Suringar has not been able to meet commercial demand and so advances in cultivation technology are strongly needed to increase production. Interestingly, cultivation work has shown the yield of U. pinnatifida sporophytes may be increased significantly by thallus excision, which may cause compensatory growth of the remaining tissues. To test this hypothesis and clarify correlative mechanisms, we examined seasonal morphological characteristics, photosynthetic rates, nutrient uptake rates, and carbon and nitrogen contents of U. pinnatifida sporophytes after thallus excision at a point 30 cm from the meristem in late February and compared these parameters with control kelps grown without excision, which were cultivated together in Matsushima Bay, northern Japan. Compared to control kelps, the length and dry weight of blades increased significantly after excision, and the growth phase was prolonged for about 1 month. The photosynthetic rates, nutrient uptake rates, and carbon and nitrogen contents of excised kelps were significantly higher than those of the controls. After vegetative growth stopped, resources accumulating in thalli were translocated significantly to sporophylls for maturation, indicating maturation was not negatively affected by thallus excision. These results indicate U. pinnatifida exhibits a very strong compensatory ability in response to thallus excision and consequently, the yield could be increased due to an increase in harvest frequency.

DOI： 10.1007/s10811-012-9925-y

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

The kelp Undaria pinnatifida has a widespread latitudinal range in Japan, with populations exposed to very different temperature regimes. To test the hypothesis that U. pinnatifida exhibits genetic differentiation in its temperature response, juvenile sporophytes from a warmer location (Naruto, southern Japan) and two colder locations (Okirai Bay and Matsushima Bay, northern Japan) were collected and transplanted to long lines, cultivated under the environmental conditions in Matsushima Bay. These plants were bred using successive self-crossing methods for three generations and the characteristics of photosynthesis, growth, survival, and nitrogen contents of the third-generation juvenile sporophytes (2-3 cm) then were measured and compared. The plants from Naruto showed significantly higher photosynthetic activities and respiration than those from the northern populations at warmer temperatures of 20-35A degrees C. The juvenile sporophytes from all three locations had similar growth rates below 18A degrees C, but significant differences were observed at 18-24A degrees C. The optimum temperatures for growth were 14-16A degrees C in plants that originated from Okirai Bay and Matsushima Bay and 18A degrees C in plants that originated from Naruto. These results reflected the differences in latitude. Dead plants were observed at high temperatures of 22 and 24A degrees C in the northern population plants, whereas no plants from Naruto died. Juvenile sporophytes from Naruto exhibited the greatest capacity to accumulate high nitrogen reserves. These results suggest that the differences in high-temperature tolerance in juvenile U. pinnatifida sporophytes from geographically separated populations are due to genetic differentiation rather than phenotypic plasticity.

DOI： 10.1007/s10811-012-9891-4

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Some seaweeds protect themselves physically or chemically against epiphytes, but this antifouling effect may differ among species. Abundance, size and fertility of epiphytic Neosiphonia harveyi growing on four sargassacean basiphytes (Myagropsis myagroides, Sargassum hemiphyllum, Sargassum patens and Sargassum siliquastrum) were examined for 1 year in Wakasa Bay, Japan. The mean density of N. harveyi was lowest on S. siliquastrum, whereas the mean length of N. harveyi was similar among the four basiphyte species. To elucidate the cause of different densities among the basiphytes, settlement rates of N. harveyi carpospores were compared among the different basiphytes under a culture condition. Although the initial number of attached carpospores was similar, the number of carposporelings attached S. siliquastrum fell significantly after six days of incubation. This suggests that the antifouling effect against N. harveyi functions after attachment of the epiphyte spores. SEM observation of the basiphyte blades showed more frequent and wider areas of cuticle peeling in S. siliquastrum, which may have caused the lower survival of N. harveyi. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aquabot.2012.10.008

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

Recently, withering of farmed juvenile sporophytes of the kelp Undaria pinnatifida (Harvey) Suringar has led to reduced production of this species in northern Japan, possibly because of the high water temperature and low nutrient concentration in cultivation areas. This problem may be solved by introducing parental plants with greater tolerance to high temperature and low nutrient conditions. We examined the combined effects of various temperatures (15, 20, 24, and 27 A degrees C) and nutrient availabilities (seawater enriched with 25 % PESI medium and non-enriched seawater) on the growth and survival of cultivated juvenile sporophytes (1-2 cm) collected from Matsushima Bay, Miyagi Prefecture in northern Japan and Naruto, Tokushima Prefecture in southern Japan. The relative growth rates of juvenile sporophytes from both locations were significantly greater at 15 and 20 A degrees C than at 24 and 27 A degrees C. The juvenile sporophytes cultured in enriched medium had significantly higher relative growth rates than those cultivated in non-enriched seawater. Dead juveniles were observed in non-enriched seawater at all temperatures and the survival percentage decreased with increasing seawater temperatures. Compared to the juvenile sporophytes from Matsushima Bay, those from Naruto showed greater tolerance to high temperature even under the low nutrient condition. These results suggest that the withering of juvenile sporophytes is caused by the combined effects of low nutrient availability and high temperature. A potential solution to this problem is to introduce ecotypes with greater tolerance to high temperature and low nutrient conditions from a warmer region of Japan.

DOI： 10.1007/s10811-012-9861-x

Web of Science

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語  

記述言語：日本語   出版者・発行元：京都府農林水産技術センター海洋センター  

J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（大学，研究機関等紀要）  

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER TOKYO  

As a possible factor leading to the low recruitment level of sea urchins in kelp forests, the inhibitory effect of 2,4-dibromophenol (DBP) and 2,4,6-tribromophenol (TBP) released from the large perennial brown algae Ecklonia kurome and Eisenia bicyclis on survival and metamorphosis of eight-armed larvae of the sea urchin Strongylocentrotus nudus was examined. The percentage of larvae that underwent metamorphosis in filtered sea water after 1 h exposure to one-half dilution of saturated dibromomethane solution (similar to 60 ppm) as a chemical inducer reached approximately 100% after 1 h, while that in filtered sea water containing 1 ppm TBP was reduced to 73%. This was further reduced to less than 40% in the presence of 10 and 20 ppm TBP after 2 h. In filtered sea water containing 1 and 10 ppm DBP, the proportion of metamorphosed larvae was reduced markedly to 43 and 5% after 2 h, respectively. All larvae exposed to 50 ppm TBP and to 20 and 50 ppm DBP died after 1 h. These findings suggest that DBP is more toxic than TBP for sea urchin larvae, strongly inhibiting their metamorphosis.

DOI： 10.1111/j.1444-2906.2008.01596.x

Web of Science

記述言語：英語   出版者・発行元：Faculty of Agriculture, Tohoku University  

Monthly collection of marine algae from the intertidal to subtidal zones in Hirota Bay (38°56&#039; N, 141°42&#039; E) on the Pacific coast of northeastern Honshu, Japan, was carried out from August 2005 to July 2006. A total of 95 species were listed, 12 of which belong to Chlorophyta, 24 to Phaeophyta, 58 to Rhodophyta, and one to sea grass. In these algae, the 10 species, Urospora penicilliformis, Pachydictyon coriaceum, Chordaria flagelliformis, Myagropsis myagroides, Bangia gloiopeltidicola, Lithophyllum okamurae, Titanoderma tumidulum, Chondracanthus tenellus, Polysiphonia abscissa and P. sphaerocarpa, were newly recorded to the marine algae from the coasts adjacent to Hirota Bay. The floral index of I/H value in Hirota Bay was 1.1, suggesting that the marine algal flora in Hirota Bay belongs to the typical subarctic zone.

CiNii Books

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：INTER-RESEARCH  

The vertical distribution and food of Strongylocentrotus nudus and Hemicentrotus pulcherrimus in fucoid beds at depths of 0.3 to 2.4 m and coralline flats at depths of 2.4 to 4.7 m were studied monthly from May 2001 to May 2002 off the Oga Peninsula, Akita prefecture, northern Japan. No seasonal migration of S. nudus from coralline flats to the fucoid beds occurred, as sufficient food was available in the form of sessile animals. Crustose corallines were generally predominant in the gut contents of sea urchins in fucoid beds, where their density was extremely low. Hemicentrotus pulcherrimus inhabit both fucoid beds and coralline flats. The main foods required for this sea urchin's gonad production are the dominant algae and sessile animals found in each algal community. The low amounts of fucoids in the gut contents of each species suggest low consumption, possibly because of difficulty in grazing fully grown and erect thalli and feeding deterrents.

DOI： 10.3354/meps07121

Web of Science

記述言語：英語   出版者・発行元：Faculty of Agriculture, Tohoku University  

CiNii Books

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   出版者・発行元：「野生生物と社会」学会  

Marine algae from Sasunohama, on the southern coast of Oshika Peninsula (38°24′N, 140°22′E), northeast Honshu, were collected monthly from April 2002 to March 2003, and the floral characteristics were analyzed. The species identified were two sea grasses and 106 species of marine algae, 17 of which belonged to Chlorophyta, 24 to Phaeophyta and 65 to Rhodophyta. The I/H value, the ratio of the number of species with isomorphic alternation of generations to heteromorphic alternation of generations (Nakahara and Masuda 1971), in Sasunohama was 1.4, whereas that in Tomarihama, adjacent to the north, was 1.2 (Agatsuma et al. 2000), and that in Matsushima Bay, adjacent to the south, was 1.8 (Takamatsu 1936). Of the fucoid species principally distributed in the warm-current floral region, five were from Sasunohama, nine from Tomarihama and 13 from Matsushima Bay. The results suggest that the algal florae in Sasunohama belong to the subarctic region.

DOI： 10.20798/biospherecons.7.1_29

CiNii Books