共查询到20条相似文献,搜索用时 31 毫秒
1.
Oligotrophication as a result of planktivorous fish removal with rotenone in the small,eutrophic, Lake Mosvatn,Norway 总被引:3,自引:1,他引:2
In September 1987 the shallow, eutrophic, Lake Mosvatn was treated with rotenone to eliminate planktivorous fish (mainly whitefish,Coregonus lavaretus, L.), and the effects were studied. The first summer after treatment the zooplankton community changed markedly from rotifer
dominance and few grazers, to a community with few rotifers and many grazers. Accordingly there was a fivefold increase in
the biomass ofDaphnia galeata. Adult females ofD. galeata approximately doubled in weight. The decrease in rotifer biomass was probably mainly due to a loss of food by competition
with the daphnids. The phytoplankton community was also markedly affected. Prior to treatment Secchi depth was 1.7 m and Chl-a 23μg l−1 in the summer. After treatment there was an increase in the proportion of small and gelatinous algae and the mean chlorophyll
concentration fell to 7μg Chl-a l−1. Secchi depth increased to>2.3 m (bottom-sight most of the season). After the treatment there were also fewer cyanobacterial
blooms. This seems to be related to oligotrophication caused indirectly by increased grazing by the zooplankton. Total nutrient
concentrations were affected. Prior to treatment the mean summer concentration of total phosphate was 44μg P l−1. This decreased to 29μg P l−1 in the first summer and 23μg P l−1 the second summer after the treatment. Total nitrogen decreased from 0.68 mg N l−1 before treatment to 0.32 mg N l−1 the first summer after the treatment. The phosphate loading was not reduced, therefor it can be concluded that the fish removal
provided a biomanipulation which caused the more oligotrophic conditions. 相似文献
2.
The top and bottom of two sediment cores collected from an urban receiving basin in NW London, and stormwater samples from
the attendant catchment, have been analysed for their hydrocarbon content.
In surface sediments, basal sediments and stormwater, total aliphatic hydrocarbon levels are 445–690 μg g−1 dry wt., 43–224 μg g−1 and 0.36–1.10 mg l−1, respectively; and total levels of polyaromatic hydrocarbons (PAHs) are 780–1 100 μg g−1, 310–640 μg g1 and 5.83–18.21 mg l−1, respectively.
Biodegradation of aliphatics is assessed by phytane:n-C18 and pristane: n-C17 ratios. Hydrocarbon sources are determined from phytane: pristane ratios, odd: even carbon chain length ratios, the presence
of an unresolved complex mixture, and by comparison of the amount of methyl-substituted PAH s with that of the parent compounds.
Comparison of total levels between surface and basal sediments shows a 1 to 3 fold increase in total PAHs and a 3 to 10 fold
increase in aliphatic hydrocarbons over a 120 year period. 相似文献
3.
Kurt Jax 《Hydrobiologia》1996,333(3):201-208
The sulfate reduction rate was measured for almost four years in the profundal sediments of Lake Kizaki, a mesotrophic lake
in central Japan. The rate was generally highest in the surface layer and decreased with depth. Seasonally, sulfate reduction
tended to be high in spring and summer, and then to decrease until the end of stratification (December) in spite of a constant
in situ temperature of around 6 °C, although fluctuations were found in every year. The rate also fluctuated greatly according to
year. The maximum rate of sulfate reduction was 0.33 mmol m−2 d−1 in May, 1990, and the minimum was 0.004 mmol m−2 d−1 in March, 1993. These relatively low rates, compared with those reported for freshwater sediments, seem to be due to low
concentrations of sulfate in the sediments (5–23 μmol l−1 in the surface layer). The rate was highly correlated with the concentration of sulfate in the sediments. The addition of
sulfate stimulated sulfate reduction in all sediment samples tested, but adding lactate did not. Therefore, sulfate reduction
should be limited mainly by the supply of sulfate. Measurements of sulfate reduction rates at different concentrations of
added sulfate revealed a low concentration of half-saturation constant as low as 12 μmol l−1. 相似文献
4.
Structural and grazing responses of zooplankton community to biomanipulation of some Dutch water bodies 总被引:9,自引:9,他引:0
Structure and grazing activities of crustacean zooplankton were compared in five lakes undergoing manipulation with several
unmanipulated eutrophic (shallow) and mesotrophic (deep) lakes in The Netherlands. The biomanipulated lakes had lesser number
of species and their abundance, both of rotifers and crustaceans, and had much larger mean animal size (3–11 μg C ind.−1) than in the unmanipulated eutrophic lakes (0.65 μG C ind.−1). WhereasD. hyalina (=D. galeata) andD. cucullata generally co-occurred in the unmanipulated lakes, in the manipulated lakes bothD. hyalina and other large-bodied daphnids,D. magna,D. pulex (=D. pulicaria), were the important grazers. In the biomanipulated lakes an increase in the individual crustacean size and of zooplankton
mass were reflected in a decrease in seston concentration, higher Secchi-disc depth and a marked decrease in the share in
phytoplankton biovolume of cyanobacteria. Biomass relationship between seston (150 μm) and zooplankton indicated a Monod type
relationship, with an initial part of the curve in which the zooplankton responds linearly to the seston increase up to aboutca. 2 mg C l−1, followed by a saturation of zooplankton mass (0.39 mg C l−1) at 3–4 mg C l−1 seston, and an inhibitory effect on zooplankton mass at seston levels>4 mg C l−1. This latter is related to predominance in the seston of cyanobacteria.
In the biomanipulated lakes, the zooplankton grazing rates often exceeded 100% d−1, during the spring, and food levels generally dropped to <0.5 mg C l−1. The computed specific clearance rate (SCR) of zooplankton of 1.9 l mg−1 Zoop C is well within the range of SCR values (1.7–2.2 l mg−1 Zoop C) from deep and mesotrophic waters, but about an order of magnitude higher than in the eutrophic lakes, with the food
levels 10-fold higher. For 25% d−1 clearance of lake seston between 35 and 60 ind. l−1 are needed in the biomanipulated lakes against 1200–1300 ind. l−1 in eutrophic lakes. Similarly, about 10 to 15 times more crustacean grazers are required to eliminate the daily primary production
in the eutrophic lakes than in the biomanipulated lakes. These numbers are inversely related to the differences in animal
size. The corresponding biomass values of zooplankton needed to clear the daily primary production in the eutrophic waters
were 0.1–0.2 mg C l−1 in the biomanipulated lakes, but about 0.45 mg C l−1 in the unmanipulated eutrophic waters.
Only if the water was kept persistently clear by zooplankton was there a balanced seston budget between the inputvia primary production and elimination by zooplankton. Mostly, however, the input exceeded the assimilatory removal by zooplankton,
such that the estimated seston loss could be attributed to sedimentation and mineralization. 相似文献
5.
The Ria Formosa is a meso-tidal coastal lagoon experiencing enhanced nutrient concentrations. Assessment of sediment–seawater interaction is essential if nutrient dynamics and the risk of eutrophication are to be fully understood. Pore water concentrations of dissolved inorganic and organic phosphorus, ammonium, nitrate and nitrite were determined in cores from six sites. Changes in nutrients concentrations were measured in intertidal pools on sand and mud between tides. Dissolved inorganic phosphorus (DIP) concentrations (~200 μmol l−1) and effluxes (123 ± 14 μmol m−2 h−1) were greater from sand than mud (37 ± 10 μmol m−2 h−1), possibly due to the binding of P with the <63 μm fraction. NH4+ effluxes were high outside the Anc?o Basin (821 ± 106 μmol m−2 h−1) and were associated with Enteromorpha sp. mats. The greatest NO3− efflux was from sediments near a salt marsh (170 ± 67 μmol m−2 h−1). These sediment fluxes of P were not sufficient to account for elevated P concentrations seen by other workers on the ebb tide from the Anc?o Basin. Intertidal pools were sinks for Dissolved Inorganic Nitrogen (DIN) and DIP over the 6 h exposure period. Thus, tidepools may be an important route of nutrients into sediments that enhances the effects of sediments on seawater nutrient concentrations. 相似文献
6.
Winter limnology: a comparison of physical,chemical and biological characteristics in two temperate lakes during ice cover 总被引:3,自引:3,他引:0
The winter dynamics of several chemical, physical, and biological variables of a shallow, polymictic lake (Opinicon) are compared
to those of a deep, nearby dimictic lake (Upper Rock) during ice cover (January to early April) in 1990 and 1991. Both lakes
were weakly inversely thermally stratified. Dissolved oxygen concentration was at saturation (11–15 mg l−1) in the top 3 m layer, but declined to near anoxic levels near the sediments. Dissolved oxygen concentrations in the deep
lake were at saturation in most of the water column and approached anoxic levels near the sediments only. Nutrient concentrations
in both lakes were fairly high, and similar in both lakes during ice cover. Total phosphorus concentrations generally ranged
between 10–20 μg l−1, NH4-N between 16–100 μg l−1, and DSi between 0.9–1.9 mg l−1; these concentrations fell within summer ranges. NO3-N concentrations were between 51–135 μg l−1 during ice cover, but occurred at trace concentrations (<0.002 μg l−1) during the summer. The winter phytoplankton community of both lakes was dominated by flagellates (cryptophytes, chrysophytes)
and occasionally diatoms. Dinoflagellates, Cyanobacteria and green algae were poorly represented. Cryptophytes often occurred
in fairly high proportions (20–80%) throughout the water column, whereas chrysophytes were more abundant just beneath the
ice. Zooplankton population densities were extremely low during ice cover (compared to maximum densities measured in spring
or summer) in both lakes, and were comprised largely of copepods. 相似文献
7.
Fish manipulation as a lake restoration tool in shallow,eutrophic, temperate lakes 2: threshold levels,long-term stability and conclusions 总被引:20,自引:11,他引:20
Jeppesen E. Jensen J. P. Kristensen P. Søndergaard M. Mortensen E. Sortkjær O. Olrik K. 《Hydrobiologia》1990,(1):219-227
In order to evaluate short-term and long-term effects of fish manipulation in shallow, eutrophic lakes, empirical studies
on relationships between lake water concentration of total phosphorus (P) and the occurrence of phytoplankton, submerged macrophytes
and fish in Danish lakes are combined with results from three whole-lake fish manipulation experiments. After removal of less
than 80 per cent of the planktivorous fish stock a short-term trophic cascade was obtained in the nutrient regimes, where
large cyanobacteria were not strongly dominant and persistent. In shallow Danish lakes cyanobacteria were the most often dominating
phytoplankton class in the P-range between 200 and 1 000μg P l−1. Long-term effects are suggested to be closely related to the ability of the lake to establish a permanent and wide distribution
of submerged macrophytes and to create self-perpetuating increases in the ratio of piscivorous to planktivorous fish. The
maximum depth at which submerged macrophytes occurred, decreased exponentially with increasing P concentration. Submerged
macrophytes were absent in lakes>10 ha and with P levels above 250–300μg P l−1, but still abundant in some lakes<3 ha at 650μg P l−1. Lakes with high cover of submerged macrophytes showed higher transparencies than lakes with low cover aboveca. 50μg P l−1. These results support the alternative stable state hypothesis (clear or turbid water stages). Planktivorous fish>10 cm numerically
contributed more than 80 per cent of the total planktivorous and piscivorous fish (>10 cm) in the pelagical of lakes with
concentrations above 100μg P l−1. Below this threshold level the proportion of planktivores decreased markedly toca. 50 per cent at 22μg P l−1. The extent of the shift in depth colonization of submerged macrophytes and fish stock composition in the three whole-lake
fish manipulations follows closely the predictions from the relationships derived from the empirical study. We conclude that
a long-term effect of a reduction in the density of planktivorous fish can be expected only when the external phosphorus loading
is reduced to below 0.5–2.0 g m−2 y−1. This loading is equivalent to an in-lake summer concentration below 80–150μg P l−1. Furthermore, fish manipulation as a restoration tool seems most efficient in shallow lakes. 相似文献
8.
Effects and accumulation of cadmium were studied in unialgal 10-1 batch-culture experiments with the dinoflagellateProrocentrum micans Ehrenberg. Tests were made using sterile filtered North Sea water enriched with nitrate and phosphate only in order to avoid
disturbances by complex formation. Cadmium was added to the cultures in amounts of 100 to 0.13μg l−1. In one series it was added at the start of the experiments and in a second one after a growth period of 1 week. Addition
of only 1.2μg Cd l−1 reduces multiplication rates and maximum cell densities of the algae. Not until 0.4μg Cd−1 does growth correspond to that of the controls. Cadmium concentrations were measured, after filtration, in the culture medium
and in the biomass by means of flameless AAS. The cadmium content in algae increased from 2.7μg g−1 (dry weight) in controls to 500μg g−1 (dry weight) in media containing 100μg Cd l−1. Uptake occurred rapidly during the first few days of the experiments, slowed down somewhat during exponential growth stage,
and increased during decay of the cultures. Cadmium content of culture media remained nearly constant (Series 1) or decreased
only slowly during experimental time (Series 2). The highest concentration factor was measured in the controls. It decreased
with increasing metal concentration in the medium and increased with experimental time. Structural modifications of the cells
were visible after Lugol fixation only, indicating brittleness of the cell walls.P. micans has shown to be extremely sensitive to cadmium and to accumulate this metal. 相似文献
9.
Whole-lake food-web manipulation as a means to study community interactions in a small ecosystem 总被引:12,自引:12,他引:0
Whole-lake food-web manipulation was carried out in the hypertrophic Lake Zwemlust (The Netherlands), with the aim of studying
the effects on the lake's trophic status and to gain an insight into complex interactions among lake communities. Before manipulation
this small (1.5 ha) and shallow (1.5 m) lake was characterized byMicrocystis blooms in summer and high chlorophyll-a concentrations were common (ca. 250 μg 1−1). In March 1987 the planktivorous and benthivorous fish species in the lake were completely removed (ca. 1000 kg ha−1), a new simple fish community (pike and rudd) was introduced and artificial refuges were created. The effects of this manipulation
on the light climate, nutrient concentrations, phytoplankton, zooplankton, fish, macrophytes, and macrofauna were monitored
during 1987, 1988 and 1989. Community interactions were investigated in phytoplankton bioassays and zooplankton grazing experiments.
After the manipulation, despite the still high P and N loads to the lake (ca. 2.2 g P m−2 y−1 andca. 5.3 g N m−2 y−1), the phytoplankton density was low (Chl-a<5μg l−1), due to control by large-sized zooplankton in spring and N-limitation in summer and autumn. A marked increase in the abundance
of macrophytes and filamentous green algae in 1988 and 1989, as well as N loss due to denitrification, contributed to the
N limitation of the phytoplankton. Before manipulation no submerged macro-vegetation was present but in 1988, the second year
after manipulation, about 50% of the lake bottom was covered by macrophytes increasing to 80% in 1989. This led to substantial
accumulation of both N and P, namely 76% and 73% respectively of the total nutrients in the lake in particulate matter. Undesirable
features of the increase in macrophytes were: 1) direct nuisance to swimmers; and, 2) the large scale development of snails,
especiallyL. peregra, which may harbour the parasite causing ‘swimmers' itch’. But harvesting of only about 3% of the total macrophyte biomass
from the swimmers' area, twice a year, reduced the nuisance for swimmers without adversely affecting the water clarity. 相似文献
10.
The abundance and activity of culturable manganese-oxidizing bacteria were assessed from near-bottom water samples of the
tectonically active Carlsberg Ridge. Retrievable counts as colony forming units (CFU) on dilute nutrient agar medium (dilNA
= 2 gm l−1 nutrient broth+2% agar) and on dilNA supplemented with 1, 2 and 3 mM MnCl2·4H2O were in the order of 106 CFU l−1. Retrievability of heterotrophs ranged from non-detectable levels (ND) to 2.82 × 106 CFU l−1. The retrievable counts on Mn amended dilNA ranged from ND to 3.21× 106, 1.47 × 106 and 1.45 × 106 CFU l−1 on 1, 2 and 3 mM, respectively. About 87% of the Mn tolerant isolates (n = 39) showed taxonomic affinities to Pseudomonas I and II sp. Two representative strains CR35 and CR48 (CR–Carlsberg Ridge) isolated on manganese-supplemented media were
tested for their ability to tolerate a range of Mn amendments from 1 nM to 100 mM in terms of growth and respiration. CR35
represents 66% of the total CFU (3.04 × 106 CFU l−1), while CR48 represented only 6% of the total CFU (1.05 × 106 CFU l−1). The colonies of these two isolates were dark brown in color suggesting precipitation of Mn as oxide. Tests for the effect
on growth and respiration were conducted in media simulating heterotrophic (amended with 0.01% glucose) and lithotrophic (unamended)
conditions. Maximum stimulation in growth and respiration of CR35 occurred at 100 μM Mn both in unamended and amended media. At levels of Mn greater than 100 μM the counts decreased steadily. Total respiring cells of CR48 were stimulated to a maximum at 1 μM Mn in unamended medium and 1 nM in amended medium. Total cells counts for the same decreased beyond 100 μM Mn in unamended and 1 nM in amended medium. The isolates were tested for their ability to oxidize Mn ammendments from 1 μM to 10 mM Mn. At the end of a 76-day incubation period, there was evidence of manganese oxide precipitation at high Mn concentrations
(≥1 mM) as a dark brown coloration on the sides of culture tubes. Highest Mn oxidation rates were observed at 10 mM Mn(II)
concentration with CR35 oxidizing 27 and 25 μM Mn day−1 in unamended and amended condition, respectively. CR48 oxidized Mn at the rate of 26 μM Mn day−1 in unamended medium and 35 μM Mn day−1 in amended medium. Scanning electron microscope (SEM) observations of both isolates revealed free-living cells in clustered
matrices ≈2 μm diameter. Energy dispersive spectrum of the cell matrix of CR35 cultured in 1 mM Mn detected 30% Mn, while
the cell aggregates of CR48 harbored 7–10% Mn. The relatively high specific activity of these mixotrophic bacteria under relatively
oligotrophic conditions suggests that they may be responsible for scavenging dissolved Mn from the Carlsberg Ridge waters
and could potentially participate in oxidation. 相似文献
11.
Pore water and solid phase distributions of C, N, P and Si in sediments of the Arctic Ocean (Svalbard area) have been investigated.
Concentrations of organic carbon (Corg) in the solid phase of the sediment varied from 1.3 to 2.8% (mean 1.9%), with highest concentrations found at shallow stations
south/southwest of Svalbard. Relatively low concentrations were obtained at the deeper stations north/northeast of Svalbard.
Atomic carbon to nitrogen ratios in the surface sediment ranged from below 8 to above 10. For some stations, high C/N ratios
together with high concentrations of Corg suggest that sedimentary organic matter is mainly of terrigenous origin and not from overall biological activity in the water
column. Organic matter reactivity (defined as the total sediment oxygen consumption rate normalized to the organic carbon
content of the surface sediment) correlated with water depth at all investigated stations. However, the stations could be
divided into two separate groups with different reactivity characteristics, representing the two most dominant hydrographic
regimes: the region west of Svalbard mainly influenced by the West Spitsbergen Current, and the area east of Svalbard where
Arctic polar water set the environmental conditions. Decreasing sediment reactivity with water depth was confirmed by the
partitioning between organic and inorganic carbon of the surface sediment. The ratio between organic and inorganic carbon
at the sediment-water interface decreased exponentially with water depth: from indefinite values at shallow stations in the
central Barents Sea, to approximately 1 at deep stations north of Svalbard. At stations east of Svalbard there was an inverse
linear correlation between the organic matter reactivity (as defined above) and concentration of dissolved organic carbon
(DOC) in the pore water. The more reactive the sediment, the less DOC existed in the pore water and the more total carbonate
(Ct or ΣCO2) was present. This observation suggests that DOC produced in reactive sediments is easily metabolizable to CO2. Sediment accumulation rates of opaline silica ranged from 0.35 to 5.7 μmol SiO2 m−2d−1 (mean 1.3 μmol SiO2 m−2d−1), i.e. almost 300 times lower than rates previously reported for the Ross Sea, Antarctica. Concentrations of ammonium and
nitrate in the pore water at the sediment-water interface were related to organic matter input and water depth. In shallow
regions with highly reactive organic matter, a pool of ammonium was present in the pore water, while nitrate conoentrations
were low. In areas where less reactive organic matter was deposited at the sediment surface, the deeper zone of nitrification
caused a build-up of nitrate in the pore water while ammonium was almost depleted. Nitrate penetrated from 1.8 to ≥ 5.8 cm
into the investigated sediments. Significantly higher concentrations of “total” dissolved nitrogen (defined as the sum of
NO3, NO2, NH4 and urea) in sediment pore water were found west compared to east of Svalbard. The differences in organic matter reactivity,
as well as in pore water distribution patterns of “total” dissolved nitrogen between the two areas, probably reflect hydrographic
factors (such as ice coverage and production/import of particulate organic material) related to the dominant water mass (Atlantic
or Arctic Polar) in each of the two areas.
The data presented were collected during the European “Polarstern” Study (Arctic EPOS) sponsored by the European Science Foundation 相似文献
12.
Loch Achray is a warm monomictic lake in the Scottish highlands with water temperature ranging from 4 °C to 18.7 °C. The oxygen
distribution is mainly clinograde with saturation values ranging from 76 to 112%. The general pattern of nutrient variation
is irregular particularly for phosphate. Dissolved silica (measured as silicate) showed a range of 24 μg at. Si l−1; phosphate varied from 0.24 to 0.03 μg at. P l−1 while nitrate ranged from 3.5 to 15.2 μg at. N l−1. The pH remained below 7 for the entire year and the alkalinity was very low, ranging from 2.5 to 6 mg CaCO3 1−1.
The examination of net samples showed Loch Achray to possess a poor phytoplankton population, consisting mainly of desmids
and a few diatoms. The quantitative investigation showed a different picture of variation. There was no clear phytoplankton
increase till May when a simultaneous increase occurred involving Melosira, Asterionella, Tabellaria fenestrata and Cyclotella. In July the population was dominated by Anabaena, while Cyclotella and Staurastrum became dominant in August. 相似文献
13.
Phyto/zooplankton composition, chlorophyll a, and some water quality parameters were investigated in a spring-originated pond in Central Anatolia between February 2001
and January 2002. Water temperature, pH, dissolved oxygen, Secchi depth, total and calcium hardness, nitrate-nitrogen, nitrite-nitrogen,
ammonia-nitrogen, total phosphorus, and soluble reactive phosphorus levels were analyzed. A total of 49 species belonging
to Bacillariophyceae, Chlorophyceae, Cyanophyceae, Cryptophyceae, and Dinophyceae were identified. The highest phytoplankton
abundance was found in August, whereas the lowest was determined in January. Phytoplankton abundance increased from February
to August and declined in the following months. The Bacillariophyceae were dominant in the phytoplankton community. A total
of 21 species of Rotifera, 2 species of Cladocera, and 1 genus of Copepoda were found. The zooplankton community was dominated
by Rotifera. The highest abundance of zooplankton was recorded in July and the lowest value in November. The annual mean concentration
of chlorophyll a was measured as 1.90 μg l−1. In spite of these eutrophic levels (mean values of total phosphorus and nitrate-nitrogen: 0.069 mg P l−1 and 0.68 mg N l−1), phytoplankton cannot grow satisfactorily because of the short water retention time (0.6 day−1). The shallowness of the pond together with the low phytoplankton biomass and the high concentrations of nutrients are discussed. 相似文献
14.
This study provides the most comprehensive physico-chemical and phytoplankton data yet available for Australian dune lakes,
which are among the world's most naturally acidic and oligotrophic freshwaters. Seasonal and spatial variations were examined
in Blue Lagoon and Lake Freshwater, two ‘water-table window’ lakes in south-east Queensland. Like other dune lakes, they are
acidic (minimum pH 4.20 and 4.55, respectively), polymictic water bodies with low concentrations of marine-derived major ions
and almost undetectable levels of trace metals. While linmologically similar in winter, during spring-summer Lake Freshwater
has significantly higher levels of chlorophyll-a, total phosphorus (TP) and turbidity than Blue Lagoon and other dune lakes, indicating seasonal mesotrophy. The key nutrient
is TP, which has recently increased to a maximum of 17 μ· l−1, due either to inputs from recreational sources, or to the death and decomposition of littoral vegetation resulting from
falling water levels over the last decade. Inorganic nitrogen, though present only in small amounts, does not appear to limit
the eutrophication process because of a shift in phytoplankton dominance from the usual desmids and dinoflagellates to N2-fixing blue-green algae.
A chlorophyll - TP linear regression derived for dune lakes indicates that at TP < 20 μg · l−1 chlorophyll ‘yield’ is higher than in other lake types represented by regressions from the literature. This may be due to
a more efficient utilization of the limited available phosphorus by dune lake algae which have adapted to the naturally oligotrophic
environment. The implications of these findings for lake management are discussed. 相似文献
15.
David A. Flemer Roman S. Stanley Barbara F. Ruth Charles M. Bundrick Paul H. Moody James C. Moore 《Hydrobiologia》1995,308(2):85-101
Two six-week laboratory experiments were conducted to evaluate effects of pesticides and microcosm size on benthic estuarine
macroinvertebrate recolonization. Sediments fortified with the pesticides (fenvalerate: controls, 5 (low) and 50 μg g−1 wet sediment (high); endosulfan: controls, 1 (low) and 10 μg g−1 wet sediment (high)) were fine-grained, organically rich (approximately 3.5% organic carbon and 22% dry weight) material.
Relative dominance of the four most abundant taxa in both experiments was consistent among treatments with few exceptions.
The amphipod,Corophium acherusicum, dominated abundance in both experiments.
In the fenvalerate experiment, large trays (400 cm2) contained significantly (p<0.05) more total number of taxa (TNT) than small microcosms (144 cm2) but tray size was not significantly related to total number of organisms (TNO). When size was adjusted to a common unit
area, small trays contained significantly more TNO than large containers. Adjusted abundance of small trays was 2.5 times
that of large containers; a ratio close to that of microcosm sizes (i.e., 2.8). This result suggests that larval supply may have been inadequate to ‘aturate’ the available sediment in large containers.
Fenvalerate significantly reduced abundance in the high treatment compared to both controls and low treatment but low treatment
was not significantly different from controls. The amphipod,Corophium acherusicum, accounted for most of the decrease in abundance in response to fenvalerate. The holothruroid,Leptosynpta sp. and the polychaete,Mediomastus ambiseta, increased in abundance significantly with increased concentration of fenvalerate.
Combined effects of actual microcosm size and concentration of endosulfan were not significant for TNO or TNT. As in the fenvalerate
experiment, adjusted abundance of small microcosms was 2.6 times that of large trays which approximated the ratio of unit
area between microcosm sizes. Abundance of a few taxa responded significantly to adjusted and unadjusted unit area. Abundance
of the tunicate,Molgula manhattensis, increased significantly with increased concentration of endosulfan. Abundance was affected by sample location (e.g., interiorvs exterior cores) within microcosms. Abundance adjusted to unit area resulted in significantly greater TNO in externalvs internal cores. This has importance for sequential sub-sampling of microcosms to determine temporal dynamics.
Statistically significant effects were measured in benthic community structure associated with microcosm size; however, the
magnitude was relatively small. There appears to be no major biological reason to select one microcosm size over the other
for screening for contaminant effects. Where feasible, the small trays provide savings in sample preparation and analysis,
allow more replicates where laboratory space is limiting and generate less chemical waste. These benefits may be off-set by
less ‘artifacts’ associated with edge effects of larger microcosms and the need for a larger mass of sediment to accommodate
additional analytical requirements (e.g., thin vertical surficial samples to refine contaminant exposure at the sediment/water
interface). 相似文献
16.
Coscinodiscus granii Gough was cultivated at low cell densities in aged Atlantic sea water containing very little dissolved organic carbon; the
water was enriched with low levels of nutrients but no chelators were added. Cadmium additions provided final concentrations
of 0.1 to 26.5 μg Cd l−1, zinc being kept constant at a level of 38 μg Zn l−1. Carrier-free109Cd and65Zn were used as tracers for the two metals. Growth in terms of cell numbers and primary productivity capacity, using the14C uptake rate, was followed during the exponential growth phase for the first 5 days of the experiment and then for a further
3 days during the stationary phase. On each day, the metal contents of the cells were determined. Cadmium concentrations of
20 μg Cd l−1 and more resulted in growth inhibition whereas 17.5 μg Cd l−1 reduced the growth only slightly. The physiological state of the cells influenced the heavy-metal uptake per cell at sublethal
Cd levels. Dead cells had a higher heavy-metal concentration than living cells. Microscopical observations revealed that cells
just about to divide were less sensitive to a given toxic heavy-metal concentration than cells which had recently divided.
This might have been due to different surface/volume ratios. 相似文献
17.
Measurements of plankton community structure and trophic resourcespotentially available to planktonic copepods were made in
the mangroveestuaries of six rivers in Northeastern Australia. The Pascoe, Claudie,Lockhart, McIvor and Daintree Rivers represent
wet tropical systems on CapeYork, whereas the Haughton River estuary has restricted freshwater inflowbecause of a drier climate
and freshwater diversion for agriculture. TheHaughton River was sampled approximately monthly between October 1992 andMay
1994, and had a mean abundance of zooplankton >37 μm of 200l−1 (range 60–500 l−1). The Cape Yorkrivers were sampled infrequently, and zooplankton abundances ranged between0.4 and 1400 l−1. The zooplankton of all rivers was dominatedby copepods, particularly representatives of the genus Oithona which werecharacteristic
of a distinct mangrove fauna. Physical forcing influencedthe zooplankton of mangrove estuaries much more than the measured
biologicalvariables. The water column was characterised by high concentrations ofparticulate matter, up to 3.3 mg l−1 C and 1.1 mgl−1 N, of low food quality (as indicated by the C:N ratio).Phytoplankton biomass (as chlorophyll a) in all six rivers was on
averagefour-fold greater than in neighbouring coastal waters (1.1–12.6μg l−1), and 25% of this chlorophyll a wasderived from cells >10 μm, and thus potentially available tocopepods. The degree of mixing,
determined by the combination of tidal stateand the extent of freshwater input, appears to drive both the quantity andquality
of particulate material available to higher consumers and thedistribution of zooplankton communities within mangrove estuaries.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
Wade C. McGregor Sabina I. Swierczek Brian Bennett Richard C. Holz 《Journal of biological inorganic chemistry》2007,12(5):603-613
The catalytically competent Mn(II)-loaded form of the argE-encoded N-acetyl-l-ornithine deacetylase from Escherichia coli (ArgE) was characterized by kinetic, thermodynamic, and spectroscopic methods. Maximum N-acetyl-l-ornithine (NAO) hydrolytic activity was observed in the presence of one Mn(II) ion with k
cat and K
m values of 550 s−1 and 0.8 mM, respectively, providing a catalytic efficiency (k
cat/K
m) of 6.9 × 105 M−1 s−1. The ArgE dissociation constant (K
d) for Mn(II) was determined to be 0.18 μM, correlating well with a value obtained by isothermal titration calorimetry of 0.30 μM
for the first metal binding event and 5.3 μM for the second. An Arrhenius plot of the NAO hydrolysis for Mn(II)-loaded ArgE
was linear from 15 to 55 °C, suggesting the rate-limiting step does not change as a function of temperature over this range.
The activation energy, determined from the slope of this plot, was 50.3 kJ mol−1. Other thermodynamic parameters were ΔG
‡ = 58.1 kJ mol−1, ΔH
‡ = 47.7 kJ mol−1, and ΔS
‡ = –34.5 J mol−1 K−1. Similarly, plots of lnK
m versus 1/T were linear, suggesting substrate binding is controlled by a single step. The natural product, [(2S,3R)-3-amino-2-hydroxy-4-phenylbutanoyl]leucine (bestatin), was found to be a competitive inhibitor of ArgE with a K
i value of 67 μM. Electron paramagnetic resonance (EPR) data recorded for both [Mn(II)_(ArgE)] and [Mn(II)Mn(II)(ArgE)] indicate
that the two Mn(II) ions form a dinuclear site. Moreover, the EPR spectrum of [Mn(II)Mn(II)(ArgE)] in the presence of bestatin
indicates that bestatin binds to ArgE but does not form a μ-alkoxide bridge between the two metal ions. 相似文献
19.
Geochemical partitioning and bioavailability of copper to aquatic plants in an artificial oxide-organic sediment 总被引:2,自引:0,他引:2
This study investigated the effects of competition between binding substrates (organic matter and iron oxide) and between
metals (cadmium and copper), on the partitioning of sedimentary copper and its subsequent bioavailability to an aquatic plant.
Organic matter and a synthesized iron oxide, ferrihydrite, were added singly and in combination to a series of sand sediments,
which were then dosed with environmentally realistic concentrations of cadmium and copper and planted with rice,Oryza sativa.
Organic matter controlled copper partitioning and bioavailability, whereas the synthetic ferrihydrite bound negligible amounts
of either metal, even in the absence of organic matter. As organic matter concentrations increased, operationally-defined
leachable copper decreased, organic-associated copper increased and the survival of rice plants improved in an approximately
linear fashion. At a nominal starting copper concentration of 5.8 μg g dry wt−1, plant survival after four weeks averaged 0–8% in sediments without organic matter, 25% in a sediment containing 0.18% organic
matter and 58% in a sediment containing 0.36% organic matter. These results suggest that organic-associated forms of copper
are unavailable to plants, and that the operational definition of ‘leachable’ copper (extracted with dilute ammonium acetate)
adequately represents the species of copper that is (are) available to plants. Our study using a well-characterized artificial
sediment supports the copper fractionation patterns and correlations between copper partitioning and bioavailability reported
from the heterogeneous, poorly characterized sediments of natural lake and river sediments. 相似文献
20.
Trophic status of Tilitso,a high altitude Himalayan lake 总被引:1,自引:1,他引:0
Morihiro Aizaki Akira Terashima Hiroyuki Nakahara Takayuki Nishio Yuzaburo Ishida 《Hydrobiologia》1987,153(3):217-224
The trophic status and water quality of Lake Tilitso (4920 m above sea level) in a high altitude region in central Nepal were
surveyed in September, 1984. The lake is rather large with a maximum depth of 95 m and a surface area of 10.2 km2. The lake water was turbid due to glacier silt and the euphotic layer was only 5 m deep. The nutrient concentration was very
low with total phosphorus concentration 1–6 μg l−1, and DTN concentration 0.10–0.22 mg l−1. The phytoplankton biomass and chlorophyll-a concentration were also low. Primary production was estimated to be about 12
mg C m−2 d−1. The concentrations of particulate matter and most cations and bacterial number were higher in the epilimnion than in the
hypolimnion. The trophic status of this lake was estimated as ultraoligotrophic. 相似文献