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1.
Fish manipulation as a lake restoration tool in shallow,eutrophic temperate lakes 1: cross-analysis of three Danish case-studies 总被引:19,自引:10,他引:9
Jeppesen E. Søndergaard M. Mortensen E. Kristensen P. Riemann B. Jensen H. J. Müller J. P. Sortkjær O. Jensen J. P. Christoffersen K. Bosselmann S. Dall E. 《Hydrobiologia》1990,200(1):205-218
The use of fish manipulation as a tool for lake restoration in eutrophic lakes has been investigated since 1986 in three shallow,
eutrophic Danish lakes. The lakes differ with respect to nutrient loading and nutrient levels (130–1000 μg P l−1, 1–6 mg N l−1). A 50% removal of planktivorous fish in the less eutrophic cyanobacteria-diatom dominated Lake V?ng caused marked changes
in lower trophic levels, phosphorus concentration and transparency. Only minor changes occurred after a 78% removal of planktivorous
fish in eutrophic cyanobacteria dominated Frederiksborg Castle Lake. In the hypertrophic, green algae dominated Lake S?byg?rd
a low recruitment of all fish species and a 16% removal of fish biomass created substantial changes in trophic structure,
but no decrease in phosphorus concentration. The different response pattern is interpreted as (1) a difference in density
and persistence of bloomforming cyanobacteria caused by between-lake variations in nutrient levels and probably also mixing-
and flushing rates, (2) a difference in specific loss rates through sedimentation of the algal community prevaling after the
fish manipulation, (3) a decreased impact of planktivorous fish with increasing mean depth and (4) a lake specific difference
in ability to create a self-increasing reduction in the phosphorus level in the lake water. This in turn seems related to
the phosphorus loading. 相似文献
2.
Influence of nutrients,disturbances and site conditions on carbon stocks along a boreal forest transect in central Canada 总被引:4,自引:0,他引:4
The interacting influence of disturbances and nutrient dynamics on aboveground biomass, forest floor, and mineral soil C stocks was assessed as part of the Boreal Forest Transect Case Study in central Canada. This transect covers a range of forested biomes–-from transitional grasslands (aspen parkland) in the south, through boreal forests, and into the forested subarctic woodland in the north. The dominant forest vegetation species are aspen, jack pine and spruce. Disturbances influence biomass C stocks in boreal forests by determining its age-class structure, altering nutrient dynamics, and changing the total nutrient reserves of the stand. Nitrogen is generally the limiting nutrient in these systems, and N availability determines biomass C stocks by affecting the forest dynamics (growth rates and site carrying capacity) throughout the life cycle of a forest stand. At a given site, total and available soil N are determined both by biotic factors (such as vegetation type and associated detritus pools) and abiotic factors (such as N deposition, soil texture, and drainage). Increasing clay content, lower temperatures and reduced aeration are expected to lead to reduced N mineralization and, ultimately, lower N availability and reduced forest productivity. Forest floor and mineral soil C stocks vary with changing balances between complex sets of organic carbon inputs and outputs. The changes in forest floor and mineral soil C pools at a given site, however, are strongly related to the historical changes in biomass at that site. Changes in N availability alter the processes regulating both inputs and outputs of carbon to soil stocks. N availability in turn is shaped by past disturbance history, litter fall rate, site characteristics and climatic factors. Thus, understanding the life-cycle dynamics of C and N as determined by age-class structure (disturbances) is essential for quantifying past changes in forest level C stocks and for projecting their future change. 相似文献
3.
Fish manipulation as a lake restoration tool in shallow,eutrophic, temperate lakes 2: threshold levels,long-term stability and conclusions 总被引:31,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
4.
Northern pike (Esox lucius L.) and aquatic vegetation,tools in the management of fisheries and water quality in shallow waters 总被引:12,自引:0,他引:12
M. P. Grimm 《Aquatic Ecology》1989,23(1):59-65
Species and size composition of fish communities in shallow stagnant waters appear to be associated with the type, abundance and pattern of the vegetation. Man-induced impacts as eutrophication, and suppression of vegetation for reasons of water quantity management or angling pleasure may induce irreversible changes in the aquatic ecosystem. Water quality management should aim at restoring former pike habitat. Submerged weeds are important to that effect. These habitats are characterized by relatively low densities of fish stocks. Stocking of bream and carp interferes strongly with these objectives. With respect to fish stocks, interests of water quality and fishery management may be opposed. 相似文献
5.
Effects of mass removal and variable recruitment on nutrient excretion by a planktivorous roach stock 总被引:1,自引:0,他引:1
J. Horppila 《Journal of fish biology》1998,52(5):951-961
The effects of intensive fishing and fish recruitment on the nutrient excretion rate by a planktivorous roach Rutilus rutilus stock in Lake Vesijärvi were estimated using a bioenergetics model. The values were compared with those given by the model assuming that no mass removal occurred or that the mass removal ceased after 2 years. According to the model, during June-August 1989 phosphorus (P) excretion by the pelagic roach stock corresponded to 18% of the annual external P loading and showed a maximum of 0.4 mg m−2 day−1 . As a result of mass removal, the maximum daily P excretion declined to 0.18 mg m−2 by 1990 and to 0.10 mg m−2 by 1992. The reduction was due to the lower number of roach, while the excretion rates of individual fish were unaffected. A 2-year mass removal would have temporarily reduced the P excretion rate, but in 1991 and 1992 the highest daily excretion rates would have been doubled compared with values after the 4-year mass removal. Assuming no fishing mortality, interannual differences were diminished and the excretion rates in 1991 and 1992 were 2.5 times higher than the values after the 4-year mass removal. The results suggest that nutrient recycling by fish stocks may be affected substantially by fisheries management. However, the effects are dependent on the timing of fishing due to the variations in the year class strength of fish. In Lake Vesijärvi the reduction in nutrient excretion was amplified coincidentally by the natural variation in recruitment of the roach stock. 相似文献
6.
Biomanipulation development in Norway 总被引:2,自引:2,他引:0
Since 1974 several studies have been carried out in Norway to investigate the interactions between planktivorous fish, zooplankton,
phytoplankton and water chemistry. Since 1978 a long-term national research program has been conducted by the Norwegian Council
for Scientific and Industrial Research (NTNF). In this program several whole lake manipulations of the fish stocks have been
performed to test hypotheses about trophic interactions. It was predicted that manipulations of planktivorous fish populations,
might also improve water quality in lakes undergoing eutrophication.
Two examples are given to illustrate the achieved results.
I: Whole lake fertilization experiment (1974–1978) carried out by Langeland and Reinertsen. The results revealed the importance
of top-down effects in the lake ecosystem. When cladocerans dominated, the zooplankton community was able to maintain a more
or less constant phytoplankton biomass and a rather low phytoplankton production even when nutrient levels were increased.
During years with rotifer dominance, algal biomass and productivity increased, despite the low amounts of added nutrients.
II: Experiment performed by Reinertsen, Jensen, Koksvik, Langeland and Olsen in the eutrophic Lake Haugatjern, total elimination
of the fish populations by rotenone in late 1980, resulted in a 4-fold decrease in the algal biomass. The species composition
changed from the dominance of large-sizedAnabaena flos-aquae andStaurastrum luetkemuelleri to smaller, fastgrowing species and gelatinous green algae.
The results are discussed in relation to management of inland waters by combined techniques of biomanipulation and reduced
external nutrient supply which increase food-chain efficiency. 相似文献
7.
Mesocosm experiments on nutrient and fish effects on shallow lake food webs in a Mediterranean climate 总被引:9,自引:2,他引:7
Susana Romo María R. Miracle María-José Villena Juan Rueda Carmen Ferriol Eduardo Vicente 《Freshwater Biology》2004,49(12):1593-1607
1. Nutrient and fish manipulations in mesocosms were carried out on food‐web interactions in a Mediterranean shallow lake in south‐east Spain. Nutrients controlled biomass of phytoplankton and periphyton, while zooplankton, regulated by planktivorous fish, influenced the relative percentages of the dominant phytoplankton species. 2. Phytoplankton species diversity decreased with increasing nutrient concentration and planktivorous fish density. Cyanobacteria grew well in both turbid and clear‐water states. 3. Planktivorous fish increased concentrations of soluble reactive phosphorus (SRP). Larger zooplankters (mostly Ceriodaphnia and copepods) were significantly reduced when fish were present, whereas rotifers increased, after fish removal of cyclopoid predators and other filter feeders (cladocerans, nauplii). The greatest biomass and diversity of zooplankton was found at intermediate nutrient levels, in mesocosms without fish and in the presence of macrophytes. 4. Water level decrease improved underwater light conditions and favoured macrophyte persistence. Submerged macrophytes (Chara spp.) outcompeted algae up to an experimental nutrient loading equivalent to added concentrations of 0.06 mg L?1 PO4‐P and 0.6 mg L?1 NO3‐N, above which an exponential increase in periphyton biomass and algal turbidity caused characean biomass to decline. 5. Declining water levels during summer favoured plant‐associated rotifer species and chroococcal cyanobacteria. High densities of chroococcal cyanobacteria were related to intermediate nutrient enrichment and the presence of small zooplankton taxa, while filamentous cyanobacteria were relatively more abundant in fishless mesocosms, in which Crustacea were more abundant, and favoured by dim underwater light. 6. Benthic macroinvertebrates increased significantly at intermediate nutrient levels but there was no relationship with planktivorous fish density. 7. The thresholds of nutrient loading and in‐lake P required to avoid a turbid state and maintain submerged macrophytes were lower than those reported from temperate shallow lakes. Mediterranean shallow lakes may remain turbid with little control of zooplankton on algal biomass, as observed in tropical and subtropical lakes. Nutrient loading control and macrophyte conservation appear to be especially important in these systems to maintain high water quality. 相似文献
8.
The capacity of Mediterranean species to adapt to variable nutrient supply levels in a global change context can be a key factor to predict their future capacity to compete and survive in this new scenario. We aimed to investigate the capacity of a typical Mediterranean tree species, Pinus halepensis, to respond to sudden changes in N and P supply in different environmental conditions. We conducted a fertilisation, irrigation and removal of competing vegetation experiment in a calcareous post-fire shrubland with an homogeneous young (5 years old) population of P. halepensis in order to investigate the retranslocation and nutrient status for the principal nutrients (N, P, Mg, K, S, Ca and Fe), and the nutrient use efficiency (NUE) of the most important nutrients linked to photosynthetic capacity (N, P, Mg and K). P fertilisation increased P concentration in needles, P, N, Mg and K retranslocations, and NUE calculated as biomass production per unit of nutrient lost in the litterfall. The P fertilisation was able to increase the aboveground biomasses and P concentration 3 years after P fertiliser application. Those responses to P fertilisation were enhanced by the removal of competing vegetation. The N needle and litterfall concentration decreased after P fertilisation and this effect was greater when the P fertilisation was accompanied by removal of competing vegetation. The increase of P availability decreased the P-NUE and increased the N-NUE when these variables were calculated as aboveground biomass production per unit of P present in the biomass. Both P-NUE and N-NUE increased when calculated as total aboveground production per unit of nutrient loss. The results show that it is necessary to calculate NUE on a different basis to have a wider understanding of nutrient use. The irrigation did not change the needle nutrient concentrations and the litterfall production, but it significantly changed the nutrient litterfall concentrations and total aboveground contents (especially P and K). These results show a high capacity of P. halepensis to quickly respond to a limiting nutrient such as P in the critical phases of post-fire regeneration. The increase in P availability had a positive effect on growth and P concentrations and contents in aboveground biomass, thus increasing the capacity of growth in future periods and avoiding immediate runoff losses and leachate. This capacity also strongly depends on neighbour competition. 相似文献
9.
Lake Vesijärvi, southern Finland, suffered sewere eutrophication by sewage effluent from the city of Lahti during the 1960's and the early 1970's. The municipal sewage loading was diverted from the lake in 1976 and the lake started to recover. However, in the 1980's blue-green algal blooms increased again and the recovery of the lake faded. Enclosure experiments demonstrated that high roach (Rutilus rutilus) biomass is one of the key factors in the fading recovery of the lake. In this study, the influence of roach and another cyprinid fish species (bleak, Alburnus alburnus) to planktonic algal productivity and biomass in Lake Vesijärvi was examined. Enclosure experiments in the field showed the impacts of planktivorous bleak on water quality; in an enclosure with a density of 1 fish m–2 average daily algal production (1370 mg C m–2) and chlorophyll-a concentration (50–90 µg 1–1) were more than twice that in an enclosure without fish. Laboratory experiments showed that the availability of planktonic food affects the foraging behaviour of roach and consequently the internal nutrient loading from the sediment into the water. Roach caused the highest phosphorus loading and turbidity when there was no zooplanktonic food available in the water. The possible interactions between planktivorous and omnivorous fish species are discussed. 相似文献
10.
1. Oligotrophic softwater lakes represent a special type of aquatic ecosystem with unique plant communities where generalisations from other aquatic plant communities to rising CO2 in the water column may not apply. 2. In the present study, we set up large in situ mesocosms and supporting laboratory experiments with isoetid vegetation (Littorella uniflora) where water column CO2 and light could be manipulated in order to test whether (i) light and CO2 availability affect nutrient concentrations in isoetid vegetation, and (ii) if changes in light and CO2 climate affect fluxes of inorganic nitrogen (N) and phosphorus (P) from sediment to water column, which potentially could result in increased growth of epiphytic algae. 3. The results showed that the standing stocks of phosphorus and nitrogen in the L. uniflora vegetation were significantly influenced by CO2 concentration and light intensity. Both standing stocks of P and N were significantly higher in the mesocosm treatments with high CO2 concentration than in those at low CO2 concentration. Similarly, standing stocks of P and N enhanced with increasing light intensity. 4. Measurements of nutrient fluxes both in the field and the laboratory did not show any significant release of nutrients to the water column from plants or sediments at any of the light or CO2 treatments. However, mats of epiphytic algae developed from the beginning of June to late September and caused a light reduction for the isoetid vegetation. 5. Increasing CO2 concentrations in the water column may over time potentially result in a change in soft water plant communities. 相似文献