共查询到20条相似文献,搜索用时 15 毫秒
1.
Takeshi Matsubara 《Hydrobiologia》1993,271(1):1-10
Seasonal changes in abundance and species composition of rotifers were surveyed at five locations under different physical and chemical conditions in the south basin of Lake Biwa during July 1987–June 1988. Total density of rotifers showed similar seasonal fluctuation with three peaks, although the maximum density showed north (low)-south (high) gradient. Polyarthra spp. (P. vulgaris and P. dolichoptera with low density) dominated except during July–October 1987 and April–May 1988. In the former period the species of Brachionus, Trichocerca, Filinia and Hexarthra, and in the latter, those of Synchaeta, Keratella and Kellicottia had somewhat different proportions in the communities of north and south stations, respectively. The difference in composition during July–October suggests a difference of trophic state between the northern and southern areas in the south basin of Lake Biwa. However, the dominance of Polyarthra and the difference in the composition during April–May 1988 could not be explained by such a difference in trophic state. No critical difference was observed in the community structure of the eastern area of the south basin, where the seasonal fluctuations in nutrient levels and phytoplankton community structure were different from other areas in the south basin. The present results, therefore, suggest that physical and chemical conditions were not effective in controlling the rotifer community structure in the south basin of Lake Biwa. 相似文献
2.
The effects of artificial water-level manipulations in Lake Biwa, initiated in 1992 to prevent flooding, on cyprinid fish
larvae were assessed by measuring and estimating the topographic change in the reed zones. The shallow, litter-accumulated
water in those zones was inhabited by larvae of two species, Carassius spp. and Cyprinus carpio. More than 70% (by volume) of these shallow areas in Lake Biwa was estimated to be lost when the water level was artificially
lowered by 30cm from June to October 1997. During the low water level period, significantly fewer eggs of these cyprinid fishes
were collected in a reed zone than in April and May of the same year, a comparison with a previous study suggesting that spawning
of the fishes was inhibited during the period of low water level. The artificial reductions in water level probably resulted
in a significant decrease in the volume of shallow water in the lake and may be linked to the drastic decline in these cyprinid
fishes. 相似文献
3.
The effect of low water levels on the water quality of Lake Biwa 总被引:1,自引:0,他引:1
Because of a lack of precipitation, water levels in Lake Biwa, Japan, were extremely low between the beginning of September 1984 and the end of February 1985. Approximately 13 million people depend upon the lake as a source of drinking water and for industrial use, and the severe water shortage became a serious concern for downstream communities. Also, there was concern that deterioration of water quality caused by rotting macrophytes and the release of nutrients from vegetation and nearshore sediments might create additional problems.In this paper, the release of nutrients from vegetation and sediments is examined under conditions which simulate both calm and turbulent water motions in the nearshore, and the magnitude of nutrient loadings are estimated in relation to the specific effects of low lake level.Sample stations were established around the south shore of Lake Biwa. Sampling was undertaken at the time of low water and during the rising water levels. Sediment samples were particle sized into 7 groups (<2000 µm). Other measured values ranged as follows: BOD (0.5–1.3), COD (1.2–3.5), TP (0.019–0.037), SRP (0.013–0.030), SOP (0.005–0.007), TN (0.45–0.90), NO2-N (0.004–0.007), NO3-N (0.04–0.08) and NH4-N (0.026–0.053), all as mgL-1. The sample data suggest that, overall, there was little impact on lake water quality as a result of low water levels. However, remedial actions may have had an important and beneficial impact on nearshore water quality in the southern basin of Lake Biwa. 相似文献
4.
Hama Takeo; Matsunaga Katsuji; Handa Nobuhiko; Takahashi Mikio 《Journal of plankton research》1990,12(1):125-131
The production rate of participate nitrogen (PN) in Lake Biwafrom March to June 1986 was calculated by monthly measurementsof the proteinaceous nitrogen production rates. The newproduction rate was estimated from the decrease in nitrate inthe euphotic zone; during this period (91 days) it was estimatedas 93 mg atoms m2, and accounted for 20% of the totalPN production (460 mg atoms m2). This implies that {smalltilde}80% of the PN produced might be recycled in the euphoticzone. The increase in PN in the euphotic zone during this period(27 mg atoms m2) accounted for 5.9% of the totalPN production. This indicates that the remaining 14% of PN producedin the euphotic zone was vertically transported. Sediment trapexperiments at 30 m depth indicate that 8.1% of the PN producedin the euphotic zone was measured as downward flux at 30 m depthduring the stagnation period. Decompositional loss of PN between12.5 (bottom of the euphotic zone) and 30 m depth was estimatedas 17 mg atoms m2. This was calculated on the basis ofaccumulation of ammonium, which accounted for 3.7% of the totalPN production. The flux from the euphotic zone thus accountedfor 12% of the total PN production, suggestingthe validity of the production model. 相似文献
5.
Unicellular autofluorescent picoplankton ranging from 0.4 to 1.5 µm in diameter were found to be a significant component of phytoplankton in the North Basin of Lake Biwa during early summer in 1989 and 1990. The abundance of these picoplankton varied seasonally by about three orders of magnitude with one maximum of up to 106 cells ml–1. Bloom-forming picoplankton were isolated by dilution and further cultivated in liquid medium. Three clones were found to be representative species of the bloom. Using epifluorescence and electron microscopy as well as absorption and fluorescence emission spectroscopy, we examined these clones according to shape and pigment composition. They have ringlike thylakoids, are photosynthetically active and have no nuclear envelope. The cyanobacterial clones isolated represent three types containing phycobilisomes with either phycocyanin or phycoerthrin as the dominant accessory pigment. They are described here as three new species, two phycoerythrin-rich types and one phycocyanin-rich type, all of them belonging to the Synechococcus group. The differences found by fluorescence emission of isolated clones are discussed with respect to in situ strain identification. 相似文献
6.
Nobuhide Fujitake Kumiko Tsuda Suzuka Aso Hiroki Kodama Masahiro Maruo Koyo Yonebayashi 《Limnology》2012,13(1):45-53
Seasonal characteristics of surface water fulvic acids (FAs) isolated from Japanese clear-water lakes were investigated. Qualitative changes in Lake Biwa and Lake Tankai FAs were determined and compared. Although the relative molecular weights determined by high-performance size-exclusion chromatography did not change remarkably, the elemental compositions, E6001% E_{600}^{1% } values and 1H- and 13C-NMR spectral properties varied with the season. Both the H/C and N/C ratios for Lake Biwa FAs tended to be higher than those for Lake Tankai FAs, but O/C ratios were lower and decreased from spring to winter. The E6001% E_{600}^{1% } values suggested that Lake Biwa FAs contained lower levels of unsaturated structures than Lake Tankai FAs, and the amounts of these structures increased in winter. The 1H and 13C NMR spectra indicated that Lake Biwa FAs are richer in saturated aliphatic chains, especially in spring. Overall, Lake Biwa FAs exhibited clearer seasonal changes in these characteristics than Lake Tankai FAs, suggesting that the seasonal variation may depend on changes in aquatic microbial activities. 相似文献
7.
It has been suggested that the populations of planktonic cyanobacteria that occupy the metalimnion of stratified lakes during the summer months may be aestivating between the main periods of growth during entrainment in the epilimnion in spring and summer. We determined the vertical distribution of the biomass and daily integral of photosynthesis of the population of Planktothrix ( Oscillatoria ) rubescens in Lake Zürich for 136 d from July to November 1995. The population showed an 80-fold increase during the stratified period but it only doubled over the subsequent period of entrainment. During the first eight days, part of the increase was attributed to recruitment of filaments floating up from greater depths but all of the subsequent production could be accounted for by photoautotrophic growth. On sunny days the biomass-specific photosynthesis of this population reached some of the highest values over the whole period despite its depth (>13 m). On very cloudy days, however, primary productivity was very low and on 4 days, when the mean depth of the population exceeded 15 m, there was no net production. Over the whole period of the study, the accumulated photosynthetic production exceeded the increase in biomass of the population by a factor of 9·5. Although much of this production occurred during the period of entrainment only a small proportion was translated into growth of the population. It is concluded that the growth that takes place in the period of stratification in the metalimnion is essential to subsequent production. 相似文献
8.
Richard Seifert Nikolai Delling Hans Hermann Richnow Stephan Kempe Jens Hefter Walter Michaelis 《Biogeochemistry》1999,44(1):73-91
The vertical distributions of ethylene and methane in the upper water column of the subtropical Atlantic were measured along a transect from Madeira to the Caribbean and compared with temperature, salinity, oxygen, nutrients, chlorophyll-a, and dissolved organic carbon (DOC).Methane concentrations between 41.6 and 60.7 nL L-1 were found in the upper 20 m of the water column giving a calculated average flux of methane into the atmosphere of 0.82 g m-2 h-1. Methane profiles reveal several distinct maxima in the upper 500 m of the water column and short-time variations which are presumably partly related to the vertical migration of zooplankton.Ethylene concentrations in near surface waters varied in the range of 1.8 to 8.2 nL L-1. Calculated flux rates for ethylene into the atmosphere were in the range of 0.41 to 1.35 g m-2 h-1 with a mean of 0.83 g m-2 h-1. Maximum concentrations of up to 39.2 nL L-1 were detected directly below the pycnocline in the western Atlantic. The vertical distributions of ethylene generally showed one maximum at the pycnocline (about 100 m depth) where elevated concentrations of chlorophyll-a, dissolved oxygen, and nutrients were also found; no ethylene was detected below 270 m depth. This suggests that ethylene release is mainly related to one, probably phytoplankton associated, source, while for methane, enhanced net production occurs at various depth horizons. For surface waters, a simple correlation between ethylene and chlorophyll-a or DOC concentrations could not be observed. No considerable diurnal variation was observed for the distribution and concentration of ethylene in the upper water column. 相似文献
9.
The spatial distribution and seasonal variation in the concentration and carbon isotopic composition of dissolved methane in a river–lake ecosystem were studied in Lake Biwa, Japan, and its tributary rivers. Methane concentrations in all subsystems examined were supersaturated with respect to the atmosphere. The epilimnion showed higher concentrations of dissolved methane than the hypolimnion in the pelagic zone. Peak methane concentrations were observed at the thermocline. The largest amount of methane in the pelagic water column was recorded at the end of a stagnant period, at which the bottom water of the sublittoral zone (30m in depth) exhibited increased methane concentration. Transect observation of dissolved methane revealed three methane peaks at different water depths in the lake, and river water and the sediments in littoral and sublittoral zones were suggested to be the corresponding sources. Water at the river mouth was replete with dissolved oxygen but also contained a high concentration of methane. The present results suggest that river water and littoral sediment are potential sources of dissolved methane in Lake Biwa, and other sources, such as internal waves, are responsible for increased methane in the pelagic zone at the end of stagnant periods. Carbon stable isotope analysis indicated that there were different sources of dissolved methane, although it was difficult to identify the origins due to high variation of the isotopic composition of methane from different sources. 相似文献
10.
Takeshi Kikko Yoshiaki Kai Masayuki Kuwahara Kouji Nakayama 《Ichthyological Research》2008,55(2):141-147
The genetic variations—and the time dependence of such variations—of natural populations of the white-spotted charr ,Salvelinus leucomaenis, in the Lake Biwa water system as well as those of a hatchery-reared population were inferred from AFLP. Upon the application
of principal coordinate analysis using 118 polymorphic AFLP fragments based on the Jaccard similarity index, specimens of
each of six natural local populations from the inlet rivers of Lake Biwa grouped roughly together, suggesting that each local
population was genetically differentiated. The hatchery-reared population was shown to be closely related to the local population
in the Seri River, suggesting that the Seri River population originated from hatchery-reared charr due to extensive stocking.
Furthermore, specimens of the Yasu River grouped in a somewhat different position from the other natural populations, agreeing
well with its geographic distance from the other populations. The nucleotide diversities of six natural populations (Harihata
River, Ishida River, two reaches of the Takatoki River, Ane River, and Yasu River) in 2002 or 2003 were relatively low (π = 0.067–0.146%)
compared with that of the Seri River (0.278%) and the hatchery-reared charr (0.316%). The nucleotide diversity in the five
local populations (Ishida River, two reaches of the Takatoki River, Ane River, and Yasu River) remained at a low level from
1994 to 2002/2003, but only the nucleotide diversity in the Harihata River actually decreased. From 1994 to 2002/2003, the
nucleotide diversity in the Seri River remained at a higher level among the natural populations from 1994 to 2002/2003; it
was enhanced by the artificial release of hatchery-reared charr before 1994. In order to conserve the genetic diversity of
the white-spotted charr in the Lake Biwa water system, it is necessary to prevent the stocking of hatchery-reared charr in
reaches where hatchery-reared charr have not previously been stocked. 相似文献
11.
Phytoplankton community structure and succession in the water column of Lake Naivasha,Kenya: a shallow tropical lake 总被引:1,自引:1,他引:1
Lake Naivasha is a shallow freshwater lake in the Rift Valley of Kenya. Since the 1980s, when the lake showed a seasonal shift between diatom and cyanobacterial dominance it has become moderately eutrophic. Its algal assemblage is now dominated by a persistent Aulacoseira italica population both numerically and in terms of contribution to overall primary production. Algal and cyanobacterial counts were used to derive Simpson's diversity, succession rate and total community succession, focusing on the 10 most numerically abundant taxa. 170 species were identified, 43 of which were in common with the 143 found in 1979–80, before the increase in trophic state. Most diatoms are indicators of moderate to high nutrient conditions. There is little horizontal or vertical variation in successional processes throughout the lake and although the absolute abundance of cells varies widely, proportional composition is relatively stable. In Crescent Island lagoon, the only regularly stratified site, hypolimnetic succession rates are lower than those in the epilimnion. Overall, community composition is controlled by mixing (and hence light regime) and nutrient availability. With `endless summer' conditions and full mixing, there is a successional pattern of `muted seasonality' adapted to physical instability and environmental stability. 相似文献
12.
Release of phosphorus from sediments in Lake Biwa 总被引:16,自引:0,他引:16
Two sulfur-mediated reactions are resulting in the eutrophication of Lake Biwa, Japan. The iron (II) phosphate mineral vivianite
is dissolving in sulfide-enriched sediments that in places results in porewater concentrations of phosphate exceeding 3 mg
l−1. The dissolution of phosphate is evident in profiles of total phosphorus where zones of dissolution and a zone of precipitation
in the most oxic surface sediments are visible. At times sulfate reduction in these surface sediments results in pH values
as high as 9.9, which can dissolve phosphate adsorbed to iron (III). This release of phosphorus from sediments is at least
partially responsible for the recent appearance of blue-green algal blooms.
Received: August 4, 2000 / Accepted: March 19, 2001 相似文献
13.
Dale W. Toetz 《Hydrobiologia》1979,63(3):255-262
This paper describes the effects of total lake mixing with 16 axial flow (Garton) pumps on the water quality, algal biomass and community metabolism of Arbuckle Lake, Oklahoma.Pumping began on July 1, 1977, and subsequently lowered the thermocline throughout the lake. The concentration of dissolved oxygen rose in formerly anoxic strata. Water quality in the former hypolimnion improved. Concentration of ammonia and BOD5 decreased, and concentrations of manganese remained unchanged in 1977 compared to the control year (1976). But, concentrations of sulfide in the hypolimnion were higher in 1977 than in 1976. Algal biomass as chlorophyll a was about the same in 1977 as in 1978. The depth of the Secchi disc was also the same. An algal bloom did not occur. Pumping decreased the ratio gross production: community respiration as measured by a free water method, suggesting that lakes which are artificially mixed will have lower net primary productivities than lakes which are not artificially mixed. 相似文献
14.
The S cycle in the water column of a small, soft-water lake was studied for 9 years as part of an experimental study of the effects of acid rain on lakes. The two basins of the lake were artificially separated, and one basin was experimentally acidified with sulfuric acid while the other served as a reference or control. Spatial and seasonal patterns of sulfate uptake by plankton (53–70 mmol m–2 yr–1), deposition of sulfur to sediments in settling seston (53 mmol m–2 yr–1), and sulfate diffusion (0–39 mmol m–2 yr–1) into sediments were examined. Measurements of inputs (12–108 mmol m–2 yr–1) and outputs (5.5–25 mmol m–2 yr–1) allowed construction of a mass balance that was then compared with rates of S accumulation in sediments cores (10–28 mmol m–2 yr–1) and measured fluxes of S into the sediments. Because of the low SO4
2– concentrations (µmole L–1) in the lake, annual uptake by plankton (53–70 mmol m–2 yr–1) represented a large fraction (>50%) of the SO4
2– inventory in the lake. Despite this large flux through the plankton, only small seasonal fluctuations in SO4
2– concentrations (µmole L–1) were observed; rapid mineralization of organic matter (half-life <3 months) prevented sulfate depletion in the water column. The turnover time for sulfate in the water column is only 1.4 yr; much less than the 11-yr turnover time of a conservative ion in this seepage lake. Sulfate diffusion into and reduction in the sediments (0–160 µmole m–2 d–1) caused SO4
2– depletion in the hypolimnion. Modeling of seasonal changes in lake-water SO4
2– concentrations indicated that only 30–50% of the diffusive flux of sulfate to the sediments was permanently incorporated in solid phases, and about 15% of sulfur in settling seston was buried in the sediments. The utility of sulfur mass balances for seepage lakes would be enhanced if uncertainty about the deposition velocity for both sulfate aerosols and SO2, uncertainty in calculation of a lake-wide rate of S accumulation in sediments, and uncertainty in the measured diffusive fluxes could be further constrained. 相似文献
15.
Phytoplankton populations in perennially ice-covered Lake Bonney, Antarctica grow in a unique non-turbulent environment. The absence of turbulence generated by winds or major streams, combined with strong vertical gradients in temperature and nutrients, create vertically stratified environmental conditions that support three discrete phytoplankton populations in the east lobe of this lake. Phytoplankton biomass and photosynthesis were measured in the east lobe of Lake Bonney during the winter-spring transicion (September) to mid-summer (January). During this period, irradiance beneath the ice increased from 0.03 to 1.9 mol quanta m−2 d−1. Chlorophylla concentrations ranged from 0.03 to 3.8 μl−1 within the trophogenic zone (just beneath the permanent ice cover to 20 m) and photosynthesis ranged from below detection to 3.2 μg Cl−1 d−1. Our results indicate: (1) phytoplankton photosynthesis began in late winter (before 9 September, our earliest sampling date); (2) maxima for phytoplankton biomass and production developed sequentially in time from the top to the bottom of the trophogenic zone, following the seasoral increase in irradiance; and (3) the highest photosynthetic efficiencies occurred in early spring, then decreased over the remainder of the phytoplankton growth season. The spring decrease in photosynthetic rates for shallower phytoplankton appeared to be related to nutrient availability, while photosynthesis in the deeper populations was solely lightdependent. 相似文献
16.
A monthly survey of dissolved concentrations of various trace elements was performed in Lake Biwa. Particulate concentrations of the elements were also measured in early autumn and winter. Based on these results, the geochemical behaviors of trace elements are discussed. The redox-sensitive elements Mn and Fe showed characteristic vertical distribution profiles. Profiles of Mn changed drastically with the progression of the stagnation period. The dynamics of Ba were affected by the redox cycle of Mn. Dissolved V concentration showed a clear seasonal variation. In contrast, dissolved concentrations of Sr, Mo, Cu, Zn, and Ni were almost uniform, i.e., not dependent on the season or the depth. The distribution ratios of these elements between lake water and Mn nodules formed in the lake were calculated to assess their geochemical behaviors. 相似文献
17.
The relationship between bacterial respiratory quinone (RQ) concentration and biomass was assessed for Lake Biwa bacterial assemblages to evaluate the utility of bacterial RQ concentration as an indicator of bacterial carbon. The biomass estimated from the RQ concentration correlated well with that from cell volume, indicating that RQ concentration is an appropriate indicator of bacterial biomass. The estimated carbon content per unit of RQ (carbon conversion factor) of bacteria was 0.67 mg C nmol RQ?1. Bacterial carbon biomass, which was estimated from the RQ concentration using the conversion factor, ranged between 0.008 and 0.054 mg C L?1 (average 0.025 mg C L?1) at 5 m depth and between 0.010 and 0.024 mg C L?1 (average 0.015 mg C L?1) at 70 m depth. Ubiquinone-8-containing bacteria dominated the epilimnion and hypolimnion. Compared to conventional image analysis, bacterial RQ analysis is a less laborious method of simultaneously determining bacterial biomass and community. 相似文献
18.
Dissolved methane was investigated in the water column of eutrophic Lake Plusssee and compared to temperature, oxygen, and sulfide profiles. Methane concentrations and delta-13C signatures indicated a zone of aerobic methane oxidation and additionally a zone of anaerobic methane oxidation in the anoxic water body. The latter coincided with a peak in hydrogen sulfide concentration. High cell numbers of aerobic and anaerobic methane-oxidizing microorganisms were detected by fluorescence in situ hybridization (FISH) or the more sensitive catalyst-amplified reporter deposition-FISH, respectively, in these layers. 相似文献
19.
Summary Four autotrophic compartments were recognised in Lake Kitiesh, King George Island (Southern Shetland) at the beginning of the summer in 1987: snow microalgae, ice bubble communities, phytoplankton in the water column and benthic communities of moss with epiphytes. Chlorophyll a concentration and pigment absorption spectra were obtained in these four compartments before and/or after the thawing of the ice cover. During the ice free period, carbon fixation and biomass was measured in the phytoplankton and in the benthic moss Campyliadelphus polygamus. From these measurements we conclude that the benthic moss is the most significant autotrophic component in this lake in terms of biomass, chlorophyll a content and primary productivity. The integral assimilation number (The ratio of carbon fixation per unit area to biomass per unit area) values were similar for both phytoplankton and the moss, ranging from 3.6 to 5.4 mg C (mg Chl a)–1h–1in phytoplankton and from 4.0 to 6.4 mgC (mg Chl a)–1h–1 in the benthic moss. This approach allows comparisons of carbon fixation efficiency of the chlorophyll a under a unit area between compartments in their different light environments. 相似文献
20.
The average composition of water, bottom sediments, manganese (Mn) crusts, and Mn concretions from Lake Biwa (the largest
freshwater lake in Japan) are re-examined, in conjunction with those of seawater, oceanic pelagic clay, and deep-sea Mn nodules.
The purpose is to gain additional insights into the geochemical behaviors of elements in Lake Biwa and the ocean, which are
quite different in ionic strength (or salinity), pH, water residence times, sediment accumulation rates, carbon fluxes to
sediments, and the redox potential in sediments. Excluding a few millimeters of oxic surface sediment, there is no appreciable
accumulation of Mn in the Lake Biwa bottom sediments due to reducing condition there. Consequently, other B-type cations [such
as iron (Fe), gallium (Ga), copper (Cu), lead (Pb), cobalt (Co), tin (Sn), and bismuth (Bi), with subshell valence electron
configuration of d
1−10] are also less concentrated in the lake sediments than in the oceanic pelagic clay. In turn, B-type cations have much higher
dissolved concentrations in the lake water than in the ocean. The rare earth elements (REE) mainly form organic complexes
in the lake water and carbonate complexes in the ocean. REE are mostly associated with detritus aluminosilicate phases in
Lake Biwa sediments but with phosphate phases in deep-sea sediments. Fe and Mn oxide phases are clearly separated in marine
Mn nodules and crusts but not in Mn crusts and concretions from Lake Biwa. Useful parameters such as the enrichment factor
(E
Al) and logarithms of the distribution coefficient (log K
d) of elements between solid and liquid phases were estimated in both systems for further discussions. 相似文献