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1.
Nitrous oxide in brackish Lakes Shinji and Nakaumi, Japan 总被引:1,自引:0,他引:1
Nitrous oxide (N2O) was measured monthly from September 1997 to August 1998 in the brackish Lakes Shinji and Nakaumi, Japan. N2O (5–37 μg N l−1) was supersaturated in the overlying water on lake sediments from October 1997 to January 1998. The N2O concentration in the hypolimnion was higher than that in the epilimnion on 17 October 1997, when N2O was first observed in a water column of Lake Nakaumi. Afterward, N2O was almost uniform throughout the water column and then disappeared on 16 February 1998. On the one hand, large amounts
of N2O were found throughout the year in the interstitial water in Lake Shinji, where a high concentration of nitrate was discharged
from the Hii River. On the other hand, in Lake Nakaumi, stratified by halocline, a high concentration of N2O was observed in the interstitial water only from winter to spring. N2O concentrations in the interstitial water were about 10 to 1000 times as large as those in the overlying water. These results
imply that N2O was mainly produced at the sediment-water interface and was diffused to the overlying water. It was also suggested that
the accumulation of N2O in the sediment-water system was accelerated by a high concentration of hydrogen sulfide.
Received: July 6, 2000 / Accepted: November 30, 2000 相似文献
2.
Long-term changes in Secchi disk transparency in Lake Nakaumi, Japan, from 1932 to the present, which includes the periods
before and after the loss of eelgrass (Zostera marina L.) beds, were compiled from previous reports. During the first (July 1932–February 1934) and the second (January 1949–November
1950) periods, the mean transparency was greater than 3 m at all observed stations. Data during the third period (July 1954–March
1956) are only available for the station at the center of the lake. The mean transparency during the third period was significantly
lower than that of the second period but higher than the mean during the fourth period. This observation suggests that the
decrease of transparency occurred during the third period. Because the decline of eelgrass beds in Lake Nakaumi occurred in
the mid-1950s, the decrease of transparency most likely resulted from the shift in primary producers from submerged macrophytes
to phytoplankton. Although the maximum transparency sometimes exceeded 3 m, mean transparencies during the fourth period (May
1975–December 2003) were less than 2 m at all stations, significantly lower than those during the first and second periods.
The shift in the chief primary producer, from benthic macrophytes to phytoplankton, caused a subsequent shift in secondary
producers. The opportunistic filter-feeding bivalve Musculista senhousia, regarded as a biofouling species of local fisheries, increased in Lake Nakaumi. The long-term monitoring data of transparency
suggested that restoration of submerged aquatic vegetation may be indispensable for the remediation of the lake environment
in this shallow eutrophic lagoon. 相似文献
3.
A. K. Rai 《Limnology》2000,1(1):33-46
Limnological characteristics were studied and analyzed in the subtropical Lakes Phewa, Begnas, and Rupa of Pokhara Valley,
Nepal, from 1993 to 1997. The annual water temperature ranged from 12° to 29°C in all lakes. Lake Phewa and Lake Begnas were
monomictic and anoxic in the hypolimnion during thermal stratification from April to September. Dissolved oxygen was drastically
depleted in April and/or May in shallow Lake Rupa when the macrophyte community began to decompose. NH4
+-N accumulated below 5 m during March–September when dissolved oxygen was depleted in Lakes Phewa and Begnas. The PC : PP
ratio was higher, but the PC : PN and PN : PP ratios were close to the Redfield ratio (106C : 16N : 1P) in Lakes Phewa and
Begnas, denoting that P was limited. Annual net primary production showed that the lakes were productive but will tend to
become heterotrophic in the future. The seasonal variation of chlorophyll a concentration was high, but its annual variation was low. Ceratium hirundinella and Peridinium spp. in Lake Phewa, Microcystis aeruginosa and Aulacoseira granulata in Lake Begnas, and Tabellaria fenestra in Lake Rupa were the dominant species. The zooplankton population and species varied irregularly. On the basis of chlorophyll
a concentration in the euphotic zone and phytoplankton species composition, the lakes seem to be oligoeutrophic and to have
some characteristics of temperate lakes rather than tropical lakes.
Received: April 26, 1999 / Accepted: September 20, 1999 相似文献
4.
Enzyme electrophoresis was performed to investigate the genetic variation of Potamogeton anguillanus Koidz. in Lake Shinji, Shimane Prefecture, Japan. The collection was made in six local populations along the coast of the
lake, and a total of 78 shoot samples were obtained. No variation among samples occurred in the six enzymes analyzed, and
the whole population in Lake Shinji was proved to consist of only a single multienzyme phenotype. Clonal growth without sexual
reproduction may have resulted in the genetic uniformity. The implication of the lack of genetic variation is briefly discussed
from the viewpoint of conservation of the species in Lake Shinji.
Received: July 11, 2000 / Accepted: October 5, 2000 相似文献
5.
Grygier Mark J. Kusuoka Yasushi Ida Miyoshi Museum Field Reporters Lake Biwa 《Hydrobiologia》2002,486(1):133-146
A distributional survey of the large branchiopod crustaceans of the rice paddies of Shiga Prefecture, Japan, was conducted by the Lake Biwa Museum in May and June of 1999 and 2000. Collecting kits were issued to over 100 lay Field Reporters, who returned all samples, usually dried, to the museum for processing. Their 242 species-lots were augmented by 146 from Grygier, 46 from Ida, and 41 from other museum staff. Apart from this survey, 50 additional records in 1997–2000 were also taken into account. Seven species were recorded in the prefecture's southern half: Branchinella kugenumaensis (Ishikawa), Caenestheriella gifuensis (Ishikawa), and Lynceus biformis (Ishikawa) with wide distributions; Triops longicaudatus (LeConte) and Leptestheria kawachiensis Uéno limited to paddy areas around the south end of Lake Biwa; and Eulimnadia sp. mostly in remnant paddy areas threatened with urban development in Otsu city, with Triops granarius (Lucas) at a single such site in Otsu. In the prefecture's northern half, only B. kugenumaensis and C. gifuensis occurred to a limited degree. Possible reasons for these differences are discussed. Data pertaining to species co-occurrence and occurrence relative to the ongoing program of paddy field consolidation in the prefecture are presented and discussed. Success of the survey was due to the use of Field Reporters, who were able to provide a high degree of coverage of the study area, as well as the clearly defined habitat, the low number and easy recognizability of species, and the collection of voucher material from all sites. Conservation-related results included the listing of Eulimnadia sp. as a `rare' species by Shiga Prefecture. 相似文献
6.
Tetsuji Nakabo Kouji Nakayama Nozomu Muto Masayuki Miyazawa 《Ichthyological Research》2011,58(2):180-183
Oncorhynchus kawamurae (Osteichthyes: Salmonidae) (common name “Kunimasu”), a species endemic to Lake Tazawa, Akita Prefecture, Japan, was believed
to have been extinct since 1940. However, nine specimens were discovered in March and April 2010 in Lake Saiko, Yamanashi
Prefecture, one of the lakes to which eyed eggs of the species were introduced in 1935. These were identified as O. kawamurae because of having 47–62 pyloric caeca, 37–43 gill-rakers, a black-colored body, and spawning at 30–40 m depth in early spring,
which are unique characteristics within Oncorhynchus. Furthermore, the distinctiveness of Kunimasu from sympatric kokanee (O. nerka) was supported by microsatellite DNA data. 相似文献
7.
Masayoshi Maehata 《Ichthyological Research》2002,49(2):202-205
Mating behavior of the Far Eastern catfish, Silurus
asotus (Siluriformes: Siluridae), was observed in a ricefield system facing the shore of Lake Biwa in mid-May to early June in 1990–1997.
A set behavioral sequence similar to those of two other silurid fishes, S. biwaensis and S. lithophilus, both endemic to the Lake Biwa system, was observed: “chasing,”“clinging,”“enfolding” while “squeezing” by the male, and
“circling” by the spawning pair. This form of mating behavior is quite different from that of S. asotus reported from the Ooi River system in Kyoto Prefecture, which mainly spawns in running water in ditches.
Received: April 10, 2001 / Revised: November 5, 2001 / Accetped: November 20, 2001 相似文献
8.
A new shrimp-associated goby, Stonogobiops yasha sp. nov., is described on the basis of nine specimens collected from the Ryukyu Islands, Japan. This species is easily distinguished
from other congeneric species in having reddish-orange stripes on a white body and only two median cephalic sensory pores
on the head.
Received: July 21, 1999 / Revised: July 10, 2001 / Accepted: July 26, 2001 相似文献
9.
Hiroshi Kamiya Hitoshi Ohshiro Yu Tabayashi Yoshihiro Kano Koji Mishima Toshiyuki Godo Masumi Yamamuro Osamu Mitamura Yu Ishitobi 《Landscape and Ecological Engineering》2011,7(1):53-64
In situ phosphorus release rates in three contiguous shallow brackish lakes were calculated by considering the amount of water
inflow, changes in salinity and phosphorus stock, and loading from phosphorus inflow based on monthly data. The annual amount
of sedimental phosphorus relative to that of phosphorus inflow was different for each of the three water bodies: 16% for Lake
Shinji, 3% for the Honjo area, and −8% for Lake Nakaumi, as estimated in a 10-year period from January 1993 to December 2002.
During the warm season, the quantity of phosphorus released surpassed sedimentation in these three water bodies. The low annual
sedimentation ratio in Lake Nakaumi is related to a large seawater backflow resulting in phosphorus removal, in addition to
a stable stratified structure promoting phosphorus release from sediment due to oxygen depletion in the lower layer. In Lake
Nakaumi, field data shows that if dissolved oxygen at the sediment surface falls below 2.54 mg L−1, phosphorus release from the sediment begins to be accelerated. 相似文献
10.
11.
Masayoshi Maehata 《Ichthyological Research》2001,48(2):137-141
The physical factor inducing spawning of the Biwa catfish, Silurus biwaensis (Siluriformes: Siluridae), an endemic species of Lake Biwa, was investigated on the basis of field observations on 150 nights
at the spawning site, the rocky shore of the Seta River, the lake's outlet, and environmental data from April to July in 1989–1994.
The catfish gathered at the spawning site when the water level of the river rapidly rose and the rocky shoal became submerged,
within a wide range of water temperature (15.0°–30.0°C); their spawning was induced in relation to increases in the submerged
portion of the rocky shoal. This observation suggests that water level control operations in Lake Biwa might critically affect
the spawning of this and other fish species.
Received: December 17, 1999 / Revised: September 13, 2000 / Accepted: January 16, 2001 相似文献
12.
Fishes and fisheries of Lake Nubia,Sudan 总被引:1,自引:1,他引:0
M. T. Ali 《Hydrobiologia》1984,110(1):305-314
Developing lake conditions in Lake Nubia were found to offer good commercial fisheries potential. This prospect initiated fishery research since 1967.In this study, 26 fish species belonging to 10 families were recorded. Compared with previous studies the total number has decreased and some of the species that were commercially important during the early years of the lake formation, are now negligible in occurrence (Distichodus, Citharinus, Bagrus). The species widely distributed in the lake are Labeo niloticus, Lates niloticus, Sarotherodon niloticus, Hydrocynus forskallii, Alestes baremose and Eutropius niloticus. Their highest production occurs during two periods: February to May and July to September. The dominant fish species feed on different items in a balanced equilibrium with the ecological and biological conditions. 相似文献
13.
Eucalyptus despite the fact that Eucalyptus seedlings do form both endomycorrhiza and ectomycorrhiza early during their developement. In the present study, all the structures
of arbuscular mycorrhiza were observed within roots of four Eucalyptus species of 15, 17 and more than 50 years old at three different sites in northern Algeria. Arbuscular mycorrhiza frequency
was assessed in roots of 15-years old Eucalyptus camaldulensis species, during two periods in 2 consecutive years (July and November of 1996 and 1997). Intensity of root colonization was
dependent on the time of sampling and attained 42% in July 1997.
Accepted: 17 September 1999 相似文献
14.
Of 851 specimens ofTridentiger obscurus andt. brevispinis collected from Lake Hinuma (Ibaraki Prefecture, Japan) from July 1996 to February 1998, 49 (5.8%) comprised F1 hybrids and backcross progeny of the two species. Since the mitochondrial DNA haplotypes of the F1 hybrids reflected those ofT. brevispinis, most instances of hybridization are thought to have occurred between maleT. obscurus and femaleT. brevispinis. Although both allozyme and mitochondrial DNA analyses indicated backcrossing and introgression of mitochondrial DNA, the
frequency of backcross progeny was relatively low, suggesting the existence of a natural selection to backrossing. 相似文献
15.
16.
Grazing by the planktonic phytoflagellate, Pyramimonas gelidicola McFadden (Chlorophyta: Prasinophyta), and heterotrophic nanoflagellates (HNAN) in meromictic saline Ace Lake in the Vestfold Hills, eastern Antarctica was investigated in the austral summers of 1997 and 1999. Up to 47% of the P. gelidicola population ingested fluorescently labeled prey (FLP). Ingestion rates varied with depth. In January 1997 and November 1999, maximum P. gelidicola ingestion rates of 6.95 and 0.79 FLP·cell?1·h?1, respectively, were measured at the chemocline (6–8 m) where a deep chl maximum composed of phototrophic nanoflagellates (PNAN DCM), predominantly P. gelidicola, persisted all year. During the summers of 1997 and 1999, the grazing P. gelidicola community removed between 0.4% and approximately 16% of in situ bacterial biomass, equivalent to between 4% and>100% of in situ bacterial production. Because of their higher abundance, the community clearance rates of HNAN in Ace Lake generally exceeded those of P. gelidicola, but HNAN removed approximately only 3%–4% of bacterial biomass, equivalent to between 28% and 32% of bacterial production. Pyramimonas gelidicola growth rates were highest at the PNAN DCM concomitant with the highest ingestion rates. It is estimated that during the summer P. gelidicola can derive up to 30% of their daily carbon requirements from bacterivory at the PNAN DCM. This study confirms mixotrophy as an important strategy by which planktonic organisms can survive in extreme, polar, lacustrine ecosystems. 相似文献
17.
Spatiotemporal changes in the biomass and abundance of the two dominant bivalve species Corbicula japonica and Arcuatula senhousia were investigated at 14 stations positioned along the Ohashi River from November 2005 to August 2007. Corbicula japonica predominantly inhabited the upstream section of the primary branch and Kensaki stream of the Ohashi River, whereas A. senhousia predominantly inhabited the downstream section of the Ohashi River. However, the distributions were highly variable among stations and seasons. Intrusions of saline water from Lake Nakaumi varied with astronomical and climatological factors, and consequently, the halocline of the Ohashi River is subject to spatiotemporal changes. Changes in distributions of C. japonica and A. senhousia occurred in relation to a flood event, indicating that environmental disturbances affect the distributions of the two bivalve species. Responses of the two species to continual saline water intrusion were also observed during the period of normal flow conditions. We suggest that the distribution of the two species is closely related to the dynamics of the ambient saline water, which is the most important factor correlated to changes in the distributions of C. japonica and A. senhousia in the Ohashi River. 相似文献
18.
Two new species from Japan, Amanita areolata and Amanita griseoturcosa, are described. The former, found in a broad-leaved forest in Aichi Prefecture, is a medium- to large-sized mushroom characterized
by an areolate, brownish pileus, a nonstriate and appendiculate margin of the pileus, and amyloid basidiospores. The latter,
found in forests with Fagaceae or Pinaceae in Tokyo, Chiba Prefecture, and Miyagi Prefecture, is a medium-sized mushroom characterized
by a grayish-turquoise pileus, a nonstriate margin of the pileus, a saccate volva, an apical membranous annulus, and amyloid
basidiospores.
Received: July 10, 2001 / Accepted: June 5, 2002 相似文献
19.
A new species of carabid beetles, Pterostichus hejkali sp. n. is described from Northwest Greece (type locality: Epirus District, Ioannina Prefecture, Ioannina Lake environs).
Diagnostic characters include distinctive shape of the median lobe of aedeagus, of right paramere and of sexual modification
on last visible sternum in males as well as shape of pronotum and size of body. Members of the new species are most similar
to P. minor. A key to the identification of the Balkan taxa of Pseudomaseus is presented. 相似文献
20.
In order to understand the role of nitrification and denitrification in the accumulation of nitrous oxide (N2O) in the hypolimnetic water of brackish Lake Nakaumi, the effects of dissolved oxygen (DO) concentration on these activities
were investigated by incubation experiments. N2O was produced during the oxidation of NH4
+ to NO2
− in nitrification and during the reduction of NO3
− to N2 in denitrification. N2O-producing activity by nitrification (N2ON) increased markedly with decreasing concentrations of DO. Low DO (10%–30% saturation) induced high N2ON. In contrast to nitrification, N2O-producing activity by denitrification (N2OD) decreased with decreasing concentrations of DO. Little N2O was accumulated during denitrification under low-level conditions of DO (10%–30%), because of further reduction of N2O to N2. It can therefore be assumed that N2O produced as the by-product of nitrification is concurrently reduced to N2 by denitrification under low-DO conditions. This would result in no substantial accumulation of N2O during active nitrification in the hypolimnetic water of Lake Nakaumi.
Received: July 6, 2001 / Accepted: December 10, 2001 相似文献