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1.
This article reviews historical changes in the total phosphorus (TP) inputs to Loch Leven, Scotland, UK. Data derived from
palaeolimnological records suggest that inputs in the early 1900s were about 6 t TP year−1 (0.45 g TP m−2 year−1). By 1985, this had risen to about 20 t TP year−1 (1.5 g TP m−2 year−1) due to increases in runoff from agricultural land and discharges from point sources. By the late 1970s, increased TP inputs
were causing serious degradation of lake water quality. Most noticeably, there had been an increase in cyanobacterial blooms.
A catchment management plan was implemented in the early 1990s. This resulted in a 60% reduction in the annual TP input between
1985 (20 t TP year−1/1.5 g TP m−2 year−1) and 1995 (8 t TP year−1/0.6 g TP m−2 year−1). The main reduction was associated with better control of point source discharges, but attempts were also made to reduce
inputs from diffuse sources. The reduction in external TP loading to the lake led to a marked decline in TP retention by the
lake each year. 相似文献
2.
Eutrophication of moderately deep Dutch lakes during the past century: flaws in the expectations of water management? 总被引:1,自引:0,他引:1
We studied the trophic development of the past 30–100 years in eight moderately deep Dutch lakes based on their sedimentary
fossil diatom assemblages. The dominant diatoms indicating meso- to eutrophic conditions were Aulacoseira subarctica, Cyclotella ocellata, C. cyclopuncta, C. meneghiniana, Puncticulata bodanica, Aulacoseira granulata, Cyclostephanos dubius, C. invisitatus, Stephanodiscus hantzschii, S. medius, and S. parvus. Ordination of diatom data separated the lakes into four groups according to their total phosphorus concentrations (TP),
water supply, water management, and origin. The first group consists of dike-breach lakes, which were in stable eutrophic
to hypertrophic conditions throughout the past century with diatom-inferred TP (DI-TP) concentrations of between 70 and 300 μg l−1. The main factors influencing these dike-breach lakes are river management, ground water supply of riverine origin, and local
land use. The second group are artificial lakes of fluctuating oligo- to mesotrophic conditions and DI-TP concentrations of
10–30 μg l−1. Only one of the artificial lakes showed a DI-TP increase due to changes in catchment agricultural practice. A third group
includes an artificial moat and an inland dike-breach lake with DI-TP concentrations of 50–100 μg l−1. The fourth group contains an individual dike-breach lake with stable mesotrophic conditions of 50 μg l−1 throughout the past century. Rather than showing a regional pattern, the studied lakes behave very individualistically with
regard to their trophic history, reflecting changes in the local hydrology and in their nutrient sources. 相似文献
3.
Critical nutrient loads to prevent duckweed dominance loads in polder ditches were assessed using the eutrophication model
PCDitch. In this article the ecological target was set at 50% duckweed coverage. This may be very high for ditches with a
nature function, but is not unreasonable for ditches in agricultural areas, with upwelling nutrient rich groundwater, run-off
and drainage. Since the change from a ditch with submersed vegetation to duckweed coverage is often a sudden shift, the choice
of the amount of duckweed coverage does not influence the calculated loading very much. The main topic of this paper is to
present a method to calculate critical loads of nutrients when ecological targets have been set. Sediment type, residence
time and water depth influenced the critical loading rates. The calculated critical phosphorus load ranged from 1.8 to 10.2 g P m−2 year−1, while the calculated critical nitrogen load stretched from 12.1 to 43.8 g N m−2 year−1. The concentration ranges that were derived from the loading rate were 0.19–0.42 mg P l−1 and 1.3–3.3 mg N l−1. Since PCDitch does not distinguish between Lemna spp. and Azolla spp., no definite conclusions were drawn concerning the effects of nitrogen reduction. In a model situation a pristine ditch
was loaded with phosphorus, which resulted into complete duckweed coverage during summer within a few years. When reducing
the phosphorus load, it took 10 years before the original situation was reached again. Dredging would accelerate the process
of recovery significantly, because the water depth would increase and the phosphorus release from the sediments in summer
would decrease.
Received September 2003; accepted in revised form February 2005 相似文献
4.
Assessment of the importance of internal nutrient loading is essential for managing and restoring eutrophic shallow lakes.
To date, studies of internal loads have tended to focus on one of two abiotic processes, either molecular diffusion or sediment/nutrient
entrainment (resuspension). This study presents a new approach to determining the non-biological fluxes of nitrogen (N) and
phosphorus (P) from the sediment to the water column of shallow lakes. Three mutually exclusive flux processes: (i) molecular
diffusion, (ii) turbulent diffusion (eddy diffusivity) and (iii) wind-induced resuspension of N and P, were related to a gradient
of benthic shear stress. A model presented here allowed the durations and magnitudes of different non-biological fluxes to
be calculated over time, based on benthic shear stress. Two site-specific critical shear stress thresholds determined which
of the three flux processes dominated for any benthic shear stress value. The model was calibrated for a shallow lake and
the continuous flux of nutrient from the sediment to the overlying water generated by each process during that period was
calculated, enabling the estimation of the relative importance of each of the three flux processes over a one-year period.
Wind-induced resuspension dominated the internal nutrient flux, operating for 38% of the time and contributing 0.9 T P year−1 and 10.2 T N year−1 to the internal nutrient load. In contrast, molecular diffusion only contributed 0.01–0.02 T P year−1 and 0.12–0.20 T N year−1 to the water column, while turbulent diffusion provided up to 0.6 T P year−1 and 6.2 T N year−1. Our model suggests that turbulent diffusion is a neglected and potentially important process contributing to internal nutrient
loading in shallow lakes, whereas molecular diffusion appears to be relatively unimportant in lakes that experience turbulence
at the sediment–water interface.
Handling editor: L. Naselli-Flores 相似文献
5.
Sediment phosphorus cycling in a large shallow lake: spatio-temporal variation in phosphorus pools and release 总被引:12,自引:0,他引:12
Bryan M. Spears Laurence Carvalho Rupert Perkins Alex Kirika David M. Paterson 《Hydrobiologia》2007,584(1):37-48
Sediment and water column phosphorus fractions were recorded monthly for one year (April 2004–April 2005) in a shallow lake
recovering from nutrient pollution (Loch Leven, Scotland). Equilibrium phosphate concentration (EPC0) and gross sediment phosphorus
(P) release rates were estimated from laboratory experiments. Pore water and organic P pools were lowest during warm water
periods whereas bottom water P was lowest during cold water periods. Reductant-soluble, organic, metal oxide-adsorbed, residual
and sediment total phosphorus pools all varied significantly with overlying water depth. Short-term, high magnitude, redox
initiated P release events occurred in late summer and winter as a result of anoxic sediment conditions. Lower magnitude long-term
release conditions were maintained for most of the year, most likely as a result of organic P cycling and maintenance of high
concentration gradients between the pore and bottom water P pools. Estimates of summer P uptake/release rates, across an intact
sediment-water interface, suggested that maximum gross internal release was ~12 mg SRP m−2 lake surface area d−1 with EPC0 values ranging between 180 and 270 μg P L−1. This study highlights the biological mediation of internal loading in shallow eutrophic lakes, and in particular, the role
of sediment algae in decreasing, and sediment bacteria in enhancing, sediment P release. 相似文献
6.
Water and surficial sediment samples of Lake Chascomús and its tributaries were analyzed in order to relate changes in diatom
community structure to chemical variables. Over the course of 13 months of sampling, the lake exhibited major changes in water
level (1.15–1.98 m average depth), total dissolved solids (821–1972 mg l−1), silica (0.098–8.22 mg l−1), and total algal biomass (21.4–145.9 μg Chl a l−1). However, despite these large fluctuations, the diatom species composition was relatively stable. The dominant species in
the water column was always Synedra berolinensis (68.9%–90.1% total frustules), with Fragilaria construens and F. brevistriata as subdominants. In the sediments the latter two species dominated the frustule counts. These results indicate an unusual
floristic stability of this eutrophic ecosystem, with persistent dominance by broadly tolerant, generalist species.
Received: April 24, 2001 / Accepted: January 23, 2002 相似文献
7.
To determine the sources and sinks of atmospherically deposited Pb at a forested watershed (Plastic Lake) in central Ontario,
Canada, Pb pools and fluxes through upland, wetland and lake compartments were measured during 2002/2003 and compared with
previous measurements taken between 1989 and 1991. In 2002/2003, annual bulk deposition of Pb was 0.49 mg m−2 compared with 1.90–1.30 mg m−2 in 1989–1991. Annual Pb concentrations in stream water draining the upland part of the catchment were very low (0.04 μg l−1) and were approximately half those measured in 1989–1991 (0.11–0.08 μg l−1). Leaching losses in stream water were small and mass balance estimates indicate almost complete retention (>95%) of atmospherically
deposited Pb in upland soils. In contrast, annual Pb concentrations in stream water draining a wetland were between 0.38 and
0.77 μg l−1, with the highest concentration occurring in 2002/2003 and mass balance calculations indicate that the wetland is a net source
of Pb in all measured years. Lead concentrations in the lake outflow were low and the average Pb concentration measured in
2002/2003 (0.09 μg l−1) was approximately half the value recorded in 1989–1991 (0.19 μg l−1 both years). Annual mass balance estimates indicate that the lake retained between 2.47 mg m−2 (1989/1990) and 1.42 mg m−2 (2002/2003) and that in 2002/2003 68% of the Pb input to the lake is derived from the terrestrial catchment. These estimates
are higher than sediment core records, which indicate around 18 mg m−2 Pb was retained in sediment during the 1990s. Nevertheless, Pb concentrations decrease with sediment depth and 206Pb/207Pb concentrations increase with depth, a pattern also observed in mineral soils that reflects the substantial contribution
of anthropogenic Pb to the watershed. Lead isotope data from soil and sediment indicate a recent anthropogenic Pb signal (206Pb/207Pb ∼ 1.185) in upper soils and sediments and an older anthropogenic signal (206Pb/207Pb ∼ 1.20) in deeper soil and sediment. Lead isotope data in sediment and vegetation indicate that practically all the Pb
cycled in the forest at Plastic Lake is anthropogenic in origin. 相似文献
8.
Phosphorus (P) dynamics in large shallow lakes are greatly influenced by physical processes such as wind-driven sediment resuspension,
at times scales from hours to years. Results from long-term (30 year) research on Lake Okeechobee, Florida (area 1,730 km2, mean depth 2.7 m) illustrate key features of these P dynamics. Variations in wind velocity result in changes in water column
transparency, suspended solids, and total P (TP). In summer there are diurnal changes in TP associated with afternoon winds,
and in winter, when strong winds occur for multiple days, monthly average TP remains high compared to summer. The magnitude
of daily and seasonal TP changes can exceed 100 μg l−1. Hurricanes and tropical storms also cause extreme changes in TP that are superimposed on seasonal dynamics. When a hurricane
passed 80 km south of the lake in October 1999, mean pelagic TP increased from 88 to 222 μg l−1. During large resuspension events, light attenuation is substantially increased, and this influences the biomass and spatial
extent of submerged plants, as well as water column TP. In Lake Okeechobee, TP concentrations typically are ∼20 μg l−1 when submerged plants are dense, and soluble reactive P concentrations are reduced below detection, perhaps by the periphyton
and plant uptake and by precipitation with calcium at high pH. In contrast, TP exceeds 50 μg l−1 when submerged plants and periphyton are absent due to prolonged deep water, and phytoplankton biomass and algal bloom frequency
both are increased. In Lake Okeechobee and other large shallow lakes, complex models that explicitly consider wind-wave energy,
hydrodynamics, and sediment resuspension, transport, and key biological processes are needed to accurately predict how lake
water TP will respond to different management options. 相似文献
9.
Tiia Pedusaar Ilkka Sammalkorpi Arto Hautala Jaana Salujõe Ain Järvalt Margus Pihlak 《Hydrobiologia》2010,649(1):95-106
Lake ülemiste, the drinking water reservoir of Estonia’s capital city Tallinn, was biomanipulated by manual removal of cyprinids
in 2004–2006 and its impact on water quality in the vegetation period was studied. A total biomass of 156 tonnes corresponding
to 160 kg ha−1 of fish, predominantly cyprinids, were removed. A decline in the unit catches of fishing was observed. The removed fish biomass
versus phosphorus concentration of the lake was considered sufficient to reduce the impact of cyprinids on water quality.
The phosphorus removed within fish biomass corresponded to 38 μg l−1 and 21% of the external phosphorus load of the fishing period. The mean total phosphorus concentration dropped from >50 to
≤36 μg l−1. However, the densities of planktivorous young-of-the-year percids remained high and the role of zooplankton grazing in improving
water quality was found non-significant or transient. The cladocerans biomass decreased and the small-sized Daphnia cucullata remained almost the only daphnid in Lake ülemiste during and after the manipulation. Predomination of filamentous cyanobacteria
was replaced by a more diverse phytoplankton composition and co-domination of micro- and pico-sized colonial cyanobacteria
during summer. Mean phytoplankton biomass decreased from 15 to 6 mg l−1 primarily as a result of decreased in-lake TP availability. The Secchi disc transparency increased only in May 2005–2007.
The effects of coincidental events, a decline of external loading of phosphorus and a simultaneous flushing induced by heavy
rainfall, on lake water quality are discussed with some implications to the future management of the reservoir. 相似文献
10.
Picoeukaryotes dominate the phytoplankton of Lake Balaton—the largest shallow lake in Central Europe—in the winter period.
We examined the annual dynamics of picoplankton abundance and composition in the lake in order to establish if the picoeukaryotes
merely survive the harsher winter conditions or they are able to grow in the ice-covered lake when the entire phytoplankton
is limited by low light and temperature. Lake Balaton has an annual temperature range of 1–29°C, and it is usually frozen
between December and February for 30–60 days. In the spring-autumn period phycocyanin and phycoerythrin rich Cyanobacteria
are the dominant picoplankters, and picoeukaryotes are negligible. Our five-year study shows the presence of three types of
picophytoplankton assemblages in Lake Balaton: (1) Phycoerythrin-rich Cyanobacteria—the dominant summer picoplankters in the
mesotrophic lake area; (2) Phycocyanin-rich Cyanobacteria—the most abundant summer picoplankters in the eutrophic lake area
and; (3) Picoeukaryotes—the dominant winter picoplankters in the whole lake. The observed winter abundance of picoeukaryotes
was high (up to 3 × 105 cells ml−1), their highest biomass (520 μg l−1) exceeded the maximum summer biomass of picocyanobacteria (500 μg l−1). Our results indicate that the winter predominance of picoeukaryotes is a regular phenomenon in Lake Balaton, irrespective
of the absence or presence of the ice cover. Picoeukaryotes are able to grow at as low as 1–2°C water temperature, while the
total phytoplankton biomass show the lowest annual values in the winter period. In agreement with earlier findings, the contribution
of picocyanobacteria to the total phytoplankton biomass in Lake Balaton is inversely related to the total phytoplankton biomass,
whereas no such relationship was observable in the case of picoeukaryotes. 相似文献
11.
In tropical lakes relatively little is known about the general relationship between nutrient concentration and phytoplankton biomass. Using data from 192 lakes from tropical and subtropical regions we examine the relationship between total P (TP) and chlorophyll (Chl). The lakes are all located between 30° S to 31° N include systems in Asia, Africa, and North and South America but are dominated by Brazilian (n=79) and subtropical N. American (n=67) systems. The systems vary in morphometry (mean depth and lake area), trophic state as well total N (TN) to␣total P (TP) ratios and light extinction. Despite a nearly 500-fold range in TP concentrations (2–970 μg P l−1), there was a poorer relationship between log TP and log Chl (r
2=0.42) than is generally observed for temperate systems from either narrow or broad geographic regions. N limitation is not a likely explanation for the relatively weak TP–Chl relationship in the tropical–subtropical systems. Systems had high average TN:TP ratios and neither a multiple regression with log TP and log TN nor separating systems with high TN:TP (>17 by weight) improved the predictive power of the log TP–log Chl relationship. 相似文献
12.
Toshiya Katano Shin-ichi Nakano Hiroyuki Ueno Osamu Mitamura Kaori Anbutsu Masayuki Kihira Yasuhiro Satoh Takeshi Satoh Valentin V. Drucker Yuji Tanaka Yuki Akagashi Masahito Sugiyama 《Limnology》2008,9(3):243-250
The abundance and composition of phytoplankton were investigated at six stations along a transect from the Barguzin River
inflow to the central basin of Lake Baikal in August 2002 to clarify the effect of the river inflow on the phytoplankton community
in the lake. The water temperature in the epilimnion was high near the shore at Station 1 (17.3°C), probably due to the higher
temperature of the river water, and gradually decreased offshore at Station 6 (14.5°C). Thermal stratification developed at
Stations 2–6, and a thermocline was observed at a 17–22-m depth at Stations 2–4 and an 8–12-m depth at Stations 5 and 6. The
concentrations of nitrogen and phosphorus nutrients in the epilimnion at all stations were <1.0 μmol N l−1 and <0.16 μmol P l−1, respectively. Relatively high concentrations of nutrients (0.56–7.38 μmol N l−1 and 0.03–0.28 μmol P l−1) were detected in the deeper parts of the euphotic zone. Silicate was not exhausted at all stations (>20 μmol Si l−1). The chlorophyll a (chl. a) concentration was high (>10 μg l−1) near the shore at Station 1 and low (<3 μg l−1) at five other stations. The <2 μm fraction of chl. a in Stations 2–6 ranged between 0.80 and 1.85 μg l−1, and its contribution to total chl. a was high (>60%). In this fraction, picocyanobacteria were abundant at all stations and ranged between 5 × 104 and 5 × 105 cells ml−1. In contrast, chl. a in the >2 μm fraction varied significantly (0.14–11.17 μg l−1), and the highest value was observed at Station 1. In this fraction, the dominant phytoplankton was Aulacoseira and centric diatoms at Station 1 and Cryptomonas, Ankistrodesmus, Asterionella, and Nitzschia at Stations 2–6. The present study demonstrated the dominance of picophytoplankton in the pelagic zone, while higher abundance
of phytoplankton dominated by diatoms was observed in the shallower littoral zone. These larger phytoplankters in the littoral
zone probably depend on nutrients from the Barguzin River. 相似文献
13.
Mark S. Castro Keith N. Eshleman Louis F. Pitelka Geoff Frech Molly Ramsey William S. Currie Karen Kuers Jeffrey A. Simmons Bob R. Pohlad Carolyn L. Thomas David M. Johnson 《Biogeochemistry》2007,84(3):333-348
The objective of this study was to evaluate the nitrogen (N) biogeochemistry of an 18–22 year old forested watershed in western
Maryland. We hypothesized that this watershed should not exhibit symptoms of N saturation. This watershed was a strong source
of nitrate (NO3
−) to the stream in all years, with a mean annual export of 9.5 kg N ha−1 year−1 and a range of 4.4–18.4 kg N ha−1 year−1. During the 2001 and 2002 water years, wet deposition of inorganic N was 9.0 kg N ha−1 year−1 and 6.3 kg N ha−1 year−1, respectively. Watershed N export rates in 2001 and 2002 water years were 4.2 kg N ha−1 year−1 and 5.3 kg N ha−1 year−1, respectively. During the wetter water years of 2003 and 2004, the watershed exported 15.0 kg N ha−1 year−1 and 18.4 kg N ha−1 year−1, rates that exceeded annual wet deposition of N by a factor of two (7.5 kg N ha−1 year−1 in 2003) and three (5.5 kg N ha−1 year−1 in 2004). Consistent with the high rates of N export, were high concentrations (2.1–3.3%) of N in foliage, wood (0.3%) and
fine roots, low C:N ratios in the forest floor (17–24) and mineral soil (14), high percentages (83–96%) of the amount of mineralized
N that was nitrified and elevated N concentrations (up to 3 mg N l−1) in soil solution. Although this watershed contained a young aggrading forest, it exhibited several symptoms of N saturation
commonly observed in more mature forests. 相似文献
14.
Lake ülemiste is a shallow, eutrophic lake which has served the city of Tallinn as a water reservoir for many centuries. Its
light climate was studied by combining a routinely measured data set with a modelling approach. For 26 years (1978–2004),
data was collected on such optically active substances (OAS) and water parameters as water colour, turbidity and phytoplankton
biomass. Simple modelling enabled the quantification of long-term time-series data and the subsequent calculation of the diffuse
attenuation coefficient, euphotic depth and average light of the mixed layer. Several changes in the hydrological cycle have
taken place during the period under study, among which are an increase in the water level of about 0.5 m and a decrease in
the external water load from 108 million m3 year−1 to about 25 million m3 year−1. At the same time euphotic depth has shown a distinct trend towards increasing since the early 1990s. The euphotic depth
also showed an increase (from 1.1 to 1.4 m) due to an improvement in underwater light conditions – mainly in the spring (April
and May) and autumn (October and November) because of the lower amount of dissolved organic matter in the lake. The average
light availability in the mixed layer has increased, but this has not affected the phytoplankton biomass as the latter is
not light-limited during the summer period. 相似文献
15.
Daniela R. de Figueiredo Mário J. Pereira António Correia 《World journal of microbiology & biotechnology》2010,26(6):1067-1077
At the present time, there is still a lack of information about environmental parameters modulating variations on bacterial
diversity in temperate lakes, particularly from Portugal. Fermentelos Lake (Central Portugal) is a shallow water body that
sustains an important wetland area. The strong nutrient inputs from agriculture and industrial runoffs have led to its current
eutrophic status. The present work aimed to understand which factors modulate the seasonal bacterioplankton diversity at this
lake using 16S rRNA PCR-denaturing gradient gel electrophoresis (DGGE) and multivariate analysis. Environmental data demonstrated eutrophic features
throughout all samples with nitrate concentrations reaching 12.0 mg N (NO3
−) l−1 in March 2006, while the highest conductivity (609 μS cm−1), soluble reactive phosphorus (0.37 mg l−1), total suspended solids (87.2 mg l−1) and chlorophyll a (286.6 μg l−1) levels were recorded in August 2007. Over the past two decades there was a general increase in nitrate, pH and conductivity
levels at this lake, suggesting the eutrophication process is still in progress. Multivariate analysis showed that summer
versus winter DGGE patterns could be established for bacterial assemblages and were mainly defined by water temperature and
chlorophyll a. Actinobacteria were dominant throughout the study period although a general preference for higher temperature, pH, total suspended solids,
conductivity, soluble reactive phosphorus (SRP) and chlorophyll a levels was observed. The highest concentrations of nitrogen sources were related to Bacteroidetes and phototrophic eukaryote (cryptophycean) dominance. The expansion of Betaproteobacteria, Alphaproteobacteria and Cyanobacteria phylotypes was generally associated to high temperature, pH, conductivity and SRP values. 相似文献
16.
Outbreak of blue-green algal blooms, with associated unsightly scum and unpleasant odor, occurs frequently in eutrophic lakes.
We conducted feeding experiments to study ingestion and digestion of Microcystis aeruginosa by tilapia (Oreochromis niloticus) under laboratory conditions and field testing to reduce Microcystis blooms by stocking tilapia in Lake Yuehu and other eutrophic waters in Ningbo, China between 2000 and 2003. Our results show
that tilapia was capable of ingesting and digesting a large quantity of Microcystis. Digestion efficiency ranged from 58.6 to 78.1% at water temperature of 25 °C. Ingestion rate increased with increasing fish
weight and water temperature. Intensive blooms occurred in Lake Yuehu in both 1999 and 2000. The lake was stocked with silver
carp (Hypophthalmichthys molitrix), bighead (Aristichthys nobilis) and a freshwater mussel (Hyriopsis cumingii) at a total biomass of 9.8 g m−3 in early 2001, and tilapia at 3–5 g m−3 in April of 2002. From June to October, average phytoplankton density decreased from 897.6×106 cells l−1 in 2000 to 291.7×106 cells l−1 in 2001 and 183.0×106 cells l−1 in 2002. Compared to 2000, the annual average phytoplankton biomass in 2001 and 2002 decreased by 48.6% and 63.8%, respectively.
The blue-green algal biomass which made up 70% of the total phytoplankton biomass in 2000 was reduced to 22.1% in 2001 and
11.2% in 2002. Meanwhile, Secchi depth increased from 20–50 cm to 55–137 cm during the same time period. Similar results were
observed in some other eutrophic waters. For example, algal bloom disappeared about 20 days after tilapia fingerlings were
stocked (8–15 g m−3) to a pond in Zhenhai Park. Chlorophyll a concentration and phytoplankton production declined dramatically whereas water transparency increased substantially. However,
the impacts of tilapia on nitrogen and phosphorus dynamics in natural lakes need further investigation. Our studies revealed
that stocking tilapia is an effective way to control algal blooms in eutrophic waters, especially in lakes where nutrient
loading cannot be reduced sufficiently, and where grazing by zooplankton cannot control phytoplankton production effectively. 相似文献
17.
Manabu Fukui Jungin Suh Yoshitaka Yonezawa Yoshikuni Urushigawa 《Ecological Research》1997,12(2):201-209
To clarify the anaerobic microbial interactions in the process of carbon mineralization in marine eutrophic environments,
the microbial sulfate reduction and methane production rates were examined in coastal marine sediments of Ise Bay, Japan,
in autumn 1990. Sulfate reduction rates (51–210 nmol ml−1 day−1 at 24°C) were much higher than the methane production ones (<1.78 nmol ml−1 day−1) in the surface sediments (top 2 cm) at the six stations surveyed (water depth: 10.7–23.3 m). Substrates for sulfate-reducing
bacteria (SRB) were estimated after the addition of a specific inhibitor for SRB (20 mmol l−1 molybdate) into the sediment slurry, from the substrate accumulation rates. In the presence of the inhibitor, sulfate reduction
was completely stopped and volatile fatty acids (mainly acetate) were accumulated, although hydrogen was not. Methane production
occurred markedly accompanied by consumption of the accumulated acetate from the third day after the addition of molybdate.
The maximum rate of methane production was 1.2–1.9 μmol ml−1 day−1, which was similar to those in highly polluted freshwater sediments such as the Tama River, Tokyo, Japan. These results show
that acetate is a common major substrate for sulfate reduction and methane production, and SRB competitively inhibit potential
acetoclastic methanogenesis in coastal sediments. Methanogens may potentially inhabit the sediments at low levels of population
density and activity. 相似文献
18.
A study was conducted in Mona Lake, a small eutrophic lake located in western Michigan (USA) to address the temporal and spatial
variability of external and internal phosphorus loading. External P load varied among subbasins, which was mostly related
to discharge, but also to land use. Black Creek, which drains lands with natural cover and agriculture, accounted for the
majority of flow, and total phosphorus (TP) and soluble reactive phosphorus (SRP) load, to Mona Lake. However, the relative
contribution of SRP load was greater in Little Black Creek, which flows through a mostly urbanized subbasin, than in Black
Creek. The relative importance of internal loading was strongly related to season, as internal TP loads contributed only ∼9%
of the overall P load in April 2005, but ∼68–82% of the overall P load in the summer and early fall seasons. Internal TP and
SRP loading was greater under anaerobic than aerobic conditions. Mean anaerobic TP release rates ranged from 0.80 to 15.56 mg P m−2 d−1, varying with site and season. Spatial variability in both internal phosphorus loading and sediment P concentration was also
evident. By taking into account the spatial and temporal variability of different loading sources, management practices can
be targeted to optimize nutrient source control strategies. 相似文献
19.
Bopaiah A. Biddanda Dwight F. Coleman Thomas H. Johengen Steven A. Ruberg Guy A. Meadows Hans W. Van Sumeren Richard R. Rediske Scott T. Kendall 《Ecosystems》2006,9(5):828-842
Dissolution of the Silurian-Devonian aquifer in the Lake Huron Basin has produced several karst formations in the bedrock
(sinkholes), through which groundwater emerges onto the lake floor. During September 2003, we explored a recently discovered
submerged sinkhole ecosystem (55 m × 40 m × ∼1 m) located at a depth of 93 m with a remotely operated vehicle (ROV) equipped
with a conductivity-temperature-depth (CTD) system, an acoustic navigational system, a video camera, and a water sampling
system. In addition to two morphotypes of benthic mats, a 1–2 m thick visibly cloudy near-bottom nepheloid-like layer (sinkhole
plume) with a strong hydrogen sulfide odor prevailed just above the seepage area of clear water. Relative to lake water, water
samples collected within the sinkhole plume were characterized by slightly higher (by 4°C) temperatures, very high levels
of chloride (up to 175 mg l−1) and conductivity (1,700 μS cm−1), as well as extremely high concentrations of sulfate (1,400 mg l−1), phosphorus (3 mg l−1) and particulate organic matter (400 mg C l−1). Compared to background lake water, sinkhole plume water was characterized by approximately twofold lower C:N ratios and
tenfold higher levels of dissolved organic carbon, bacterial biomass as well as heterotrophic bacterial production. Significant
uptake of 14C-bicarbonate in dark incubations provided preliminary evidence for occurrence of chemosynthesis, possibly mediated by specialized
Bacteria and Archea present in this submerged sinkhole ecosystem in the Laurentian Great Lakes. 相似文献
20.
Effects of hypolimnetic oxygenation on water quality: results from five Danish lakes 总被引:1,自引:0,他引:1
Lone Liboriussen Martin Søndergaard Erik Jeppesen Inge Thorsgaard Simon Grünfeld Tue S. Jakobsen Kim Hansen 《Hydrobiologia》2009,625(1):157-172
Stratified eutrophic lakes often suffer from hypolimnetic oxygen depletion during summer. This may lead to low redox conditions
and accumulation of phosphate and ammonia in the hypolimnion. Hypolimnetic oxygenation has been used as a lake management
strategy to improve the water quality in five eutrophic dimictic Danish lakes where oxygenation was conducted for 4–20 years.
In one lake, the hypolimnetic oxygen concentration clearly improved by oxygenation, whereas the other four lakes still exhibited
low mean summer levels (<2.2 mg O2 l−1). Oxygenation generally increased the hypolimnetic water temperature by 0.5–2°C, but in one lake it increased by 4–6°C. In
all lakes, oxygenation significantly reduced the hypolimnetic concentrations of phosphorus and ammonia during stratification.
The accumulation of phosphorus and ammonia typically decreased by 40–88%. In two lakes oxygenation was stopped for 1–2 years
and here hypolimnion concentrations of both phosphorus and ammonia increased again. Surface water quality only improved in
one lake, but was likely also influenced by simultaneously occurring changes in external nutrient loading. Overall, it is
concluded that hypolimnetic oxygenation reduces the hypolimnetic accumulation of phosphorus and ammonia and may prevent anoxia
in the deeper parts of the lake. However, long-term oxygenation is required and it is uncertain whether the overall lake water
quality can be improved by oxygenation. Reduction of the external nutrient loading is still essential to improve lake water
quality.
Handling editor: Luigi Naselli-Flores 相似文献