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1.
Stable carbon and nitrogen isotope ratios (δ13C and δ15N) are used to study the trophic structure of food web in the Yellow Sea and East China Sea ecosystem. The trophic continuum
of pelagic food web from phytoplankton to top preyer was elementarily established, and a trophic structure diagram in the
Yellow Sea and East China Sea was outlined in combination with carbon isotopic data of benthic organisms, which is basically
consistent with and makes some improvements on the simplified Yellow Sea food web and the trophic structure diagram drawn
based on the biomass of main resource population during 1985–1986. This result indicates that the stable isotope method is
a potential useful means for further studying the complete marine food web trophic continuum from viruses to top predators
and food web stability. 相似文献
2.
Phosphorus (P) to chlorophyll ratios and zooplankton–phytoplankton (Z:P) biomass ratios were assessed in 400 temperate lakes
over a gradient of phosphorus (P) and with different fish communities. Most of the lakes in this survey were oligotrophic,
with a median total P of 7.3 μg P L−1. Thus, the survey provided information on food web effects during the early phase of eutrophication. There was no tendency
toward a reduced yield of autotrophs per unit of P over the gradient covered in this survey. The zooplankton yield per unit
of P or chlorophyll a decreased slightly with increased nutrient concentrations, and Z:P biomass ratios decreased with fish community classes,
reflecting increased fish predation pressure. However, the variability in biomass ratios within a given range of P and fish
class was some 100 times higher than the difference over the gradients. This finding suggests that lake-specific properties,
community composition, and food quality are by far the most important determinants of biomass ratios and probably also trophic
efficiency in lakes; it further suggests that these factors are superimposed on the general effect of eutrophication, at least
up to 30 μg P L−1. 相似文献
3.
DIEDERIK VAN DER MOLEN & PAUL BOERS 《The Plant journal : for cell and molecular biology》2003,35(1):189-202
1. The flow of phosphorus and nitrogen through the food web of the shallow, eutrophic lake Wolderwijd was analysed for 2 different years before and for 1 year after food web manipulation.
2. After fish removal the water became clear and the growth of macrophytes began. Fish removal resulted in a significant reduction of the total nutrient pool in the water, but differences between the nutrient cycles before and after the experiment were mainly caused by a gradual change driven by a reduced phosphorus input.
3. The zooplankton biomass before and after food web manipulation did not change significantly. Unfavourable food conditions and predation by young fish limited zooplankton biomass after the food web manipulation.
4. After fish removal benthic algae, fish, zoobenthos and macrophytes form the largest pools of nutrients apart from the sediment top layer. However, they contribute only little to nutrient cycles in the water column. 相似文献
2. After fish removal the water became clear and the growth of macrophytes began. Fish removal resulted in a significant reduction of the total nutrient pool in the water, but differences between the nutrient cycles before and after the experiment were mainly caused by a gradual change driven by a reduced phosphorus input.
3. The zooplankton biomass before and after food web manipulation did not change significantly. Unfavourable food conditions and predation by young fish limited zooplankton biomass after the food web manipulation.
4. After fish removal benthic algae, fish, zoobenthos and macrophytes form the largest pools of nutrients apart from the sediment top layer. However, they contribute only little to nutrient cycles in the water column. 相似文献
4.
1. The flow of phosphorus and nitrogen through the food web of the shallow, eutrophic lake Wolderwijd was analysed for 2 different years before and for 1 year after food web manipulation.
2. After fish removal the water became clear and the growth of macrophytes began. Fish removal resulted in a significant reduction of the total nutrient pool in the water, but differences between the nutrient cycles before and after the experiment were mainly caused by a gradual change driven by a reduced phosphorus input.
3. The zooplankton biomass before and after food web manipulation did not change significantly. Unfavourable food conditions and predation by young fish limited zooplankton biomass after the food web manipulation.
4. After fish removal benthic algae, fish, zoobenthos and macrophytes form the largest pools of nutrients apart from the sediment top layer. However, they contribute only little to nutrient cycles in the water column. 相似文献
2. After fish removal the water became clear and the growth of macrophytes began. Fish removal resulted in a significant reduction of the total nutrient pool in the water, but differences between the nutrient cycles before and after the experiment were mainly caused by a gradual change driven by a reduced phosphorus input.
3. The zooplankton biomass before and after food web manipulation did not change significantly. Unfavourable food conditions and predation by young fish limited zooplankton biomass after the food web manipulation.
4. After fish removal benthic algae, fish, zoobenthos and macrophytes form the largest pools of nutrients apart from the sediment top layer. However, they contribute only little to nutrient cycles in the water column. 相似文献
5.
Stoichiometric Constraints on Food-Web Dynamics: A Whole-Lake Experiment on the Canadian Shield 总被引:5,自引:1,他引:4
James J. Elser Thomas H. Chrzanowski Robert W. Sterner Kenneth H. Mills 《Ecosystems》1998,1(1):120-136
A whole-lake manipulation of food-web structure (introduction of a top predator, northern pike, to a minnow-dominated lake)
was performed in a Canadian Shield lake (L110) to examine the stoichiometric consequences of changes in planktonic community
structure generated by altered food-web structure. Minnow abundance, zooplankton biomass and community composition, microconsumer
abundance, and concentration and carbon–phosphorus (C:P) ratio of suspended particulate matter were monitored in L110 and
unmanipulated L240 before (1992) and after (1993–95) pike introduction. Algal biomass in L110 determined from microscopic
examination for postmanipulation and premanipulation periods was also compared with dynamics in a suite of unmanipulated reference
lakes from long-term monitoring records. Pike were added in spring in 1993 and 1994 in sufficient quantity to raise pike biomass
to levels of around 22 kg ha−
1 by 1994. Minnow populations in L110 responded dramatically, decreasing to levels 30% (1993), 10% (1994), and less than 1%
(1995) of premanipulation values. However, most components lower in the food web did not respond in a manner consistent with
predictions of existing food-web theory, such as the idea of cascading trophic interactions (CTI). While Daphnia biomass increased in L110 in the first year following manipulation, consistent with CTI, this effect was temporary and Daphnia collapsed in 1995, the year of lowest minnow abundance. Total zooplankton biomass in both lakes declined during the study
period and, contrary to CTI, this decline appeared somewhat stronger in L110 than in L240. Dominant microconsumers (heterotrophic
microflagellates) did not differ among years in either lake and did not appear to respond to food-web manipulation. At the
bottom of the food web, no changes in bacterial biomass occurred in either lake. However, total concentrations of particulate
matter appeared to increase in L110 after manipulation (contrary to expectations based on the theory of CTI) while algal biomass
did not change in the manipulated lake relative to reference systems. Finally, particulate C:P increased in both L110 and
L240 during the study period. The lack of strong response of Daphnia, the lack of response of the microbial food web, decreases in zooplankton biomass and increases in particulate biomass following
reduction of minnow populations after piscivore introduction are at odds with expectations from existing food-web theory,
such as the idea of CTI as currently formulated. However, the extremely high C:P ratios in particulate matter at the base
of the food webs in these lakes, the coincidence of zooplankton declines and increases in particulate C:P ratios, and the
results of small-scale mesocosm food-quality experiments are consistent with a hypothesis of a stoichiometric constraint operating
on food-web dynamics in this and similar ecosystems.
Received 22 April 1997; accepted 8 July 1997. 相似文献
6.
Anne Liljendahl-Nurminen Jukka Horppila Laura Uusitalo Juha Niemistö 《Aquatic Ecology》2008,42(1):25-33
The abundance of pelagic invertebrate predators in relation to turbidity and depth gradients in Lake Hiidenvesi (southern
Finland) were studied. In the shallow (<5 m) and the most turbid (up to 75 NTU) part of the lake, the community of invertebrate
predators consisted of cyclopoid copepods (max biomass >500 μg dw l−1) and Leptodora kindtiii (Focke) (17 μg dw l−1), while in the less turbid (10–40 NTU) stratifying area Chaoborus flavicans (Meigen) dominated (max 146 μg dw l−1). In the temporarily stratifying and moderately turbid basin Chaoborus and small-bodied invertebrate predators co-existed. Mysis relicta (Lovén) occurred only in the stratifying area (max 15 μg dw l−1). The results suggested that both water depth and turbidity contributed to the community structure of Chaoborus flavicans. Depth great enough for stratification was of special importance and its effect was amplified by elevated turbidity, while
high turbidity alone could not maintain chaoborid populations. Mysis relicta also requires a hypolimnetic refuge but is more sensitive to low oxygen concentrations and may therefore be forced to the
epilimnion where it is vulnerable to fish predation. Cyclopoids as rapid swimmers can take advantage at elevated turbidity
levels and coexist in high biomass with fish even in shallow water. Leptodora kindtii can form high biomass despite planktivorous fish providing that turbidity exceeds 20 NTU. The results demonstrated that depth
and water turbidity can strongly regulate the abundance and species composition of invertebrate predators. These factors must
thus be taken into account when applying food web management, which aims to reduce phytoplankton biomass by depressing planktivorous
fish. 相似文献
7.
R. Lefébure R. Degerman A. Andersson S. Larsson L‐O. Eriksson U. Båmstedt P. Byström 《Global Change Biology》2013,19(5):1358-1372
Both temperature and terrestrial organic matter have strong impacts on aquatic food‐web dynamics and production. Temperature affects vital rates of all organisms, and terrestrial organic matter can act both as an energy source for lower trophic levels, while simultaneously reducing light availability for autotrophic production. As climate change predictions for the Baltic Sea and elsewhere suggest increases in both terrestrial matter runoff and increases in temperature, we studied the effects on pelagic food‐web dynamics and food‐web efficiency in a plausible future scenario with respect to these abiotic variables in a large‐scale mesocosm experiment. Total basal (phytoplankton plus bacterial) production was slightly reduced when only increasing temperatures, but was otherwise similar across all other treatments. Separate increases in nutrient loads and temperature decreased the ratio of autotrophic:heterotrophic production, but the combined treatment of elevated temperature and terrestrial nutrient loads increased both fish production and food‐web efficiency. CDOM: Chl a ratios strongly indicated that terrestrial and not autotrophic carbon was the main energy source in these food webs and our results also showed that zooplankton biomass was positively correlated with increased bacterial production. Concomitantly, biomass of the dominant calanoid copepod Acartia sp. increased as an effect of increased temperature. As the combined effects of increased temperature and terrestrial organic nutrient loads were required to increase zooplankton abundance and fish production, conclusions about effects of climate change on food‐web dynamics and fish production must be based on realistic combinations of several abiotic factors. Moreover, our results question established notions on the net inefficiency of heterotrophic carbon transfer to the top of the food web. 相似文献
8.
9.
Decreased trophic position as a function of increasing body size of a benthic omnivorous fish from the largest freshwater lake in China 总被引:1,自引:0,他引:1
Potential body size-trophic position relationships of the Darkbarbel catfish Pelteobagrus vachelli (Richardson 1846) were examined using stable isotope analysis. Pelteobagrus vachelli is a benthic feeding fish from Lake Poyang, the largest freshwater lake in China. Two-source mixing model with mussel (Corbicula fluminea) and snail (Bellamya aeruginosa) as baseline primary consumers of planktonic and benthic food webs, respectively, was used to estimate contribution of carbon
derived from planktonic vs. benthic food web. Results showed that as an indicator of trophic position, δ15N was negatively correlated with the body length and weight of the fish; on the other hand, as an indicator of the end-member
food sources, δ13C was not correlated with fish size. The mixing model results showed that the averaged trophic position of our sampled 3.3–12.7 cm
Pelteobagrus vachelli was 3.1 ± 0.2 and derived 68 ± 27% of their food from the benthic food web, confirming that the feeding behavior of the catfish
favors benthic food sources. 相似文献
10.
To assess the effects of physical dimension and planktivorous fish on phytoplankton standing crop, we repeated an experiment
at different scales in plastic enclosures during summer 1995 in Lake Créteil, France. Enclosures were scaled for a constant
surface (1.5 × 1.5 m) as depth was increased from 2.5 to 4.5 m. Even-link (zooplankton and phytoplankton) and odd-link (planktivorous
fish, zooplankton and phytoplankton) food webs were established in both shallow and deep enclosures. Fish densities in the
deep enclosures were scaled to allow comparisons with shallow ones for both in individuals m−2 or individuals m−3. We explicitly designed this experiment to examine the scale-dependent behavior of the top-down mechanism of algal biomass
control in lakes, and in particular to test the hypothesis of stronger cascading effects of fish on lower trophic levels at
reduced depth. Both fish and enclosure size had highly significant effects on phytoplankton biomass over the duration of the
experiment. No depth × fish interaction effects were observed. The presence of planktivorous fish enhanced phytoplankton biomass
in both shallow and deep enclosures, although the reduction in depth generally produced a stronger effect. The mean concentration
of chlorophyll a in the deep odd-link systems (ca 5 mg m−3) was lower than in the shallow even-link systems (ca 17 mg m−3). Statistical interpretation did not change when data were expressed as phytoplankton biomass per unit of surface area. Light
limitation and zooplankton grazing are the most probable mechanisms explaining our results in these nutrient-enriched systems.
Moreover, we found that the strength of the cascading effect of fish on plankton was not a function of depth. We believe that
further studies on scaling effects should be conducted in order to improve our understanding of ecological patterns and to
extrapolate results from micro/mesocosms to natural ecosystems.
Received: 18 January 1999 / Accepted: 7 June 1999 相似文献