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Does turbidity induced by Carassius carassius limit phytoplankton growth? A mesocosm study

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Sustainable development, while simultaneously sustaining the ability of natural systems to provide ecosystem services on which the economy and society depend, is one of the most important development goals. In this review, the theories of five sustainable development pathways are presented, followed by a discussion on the influences of involuntary and voluntary practices. Specifically, this paper reviews the literature on limits to growth and on planetary boundaries, examines the critique of green growth, and outlines the debate between degrowth and a-growth. Then, the importance of economic recession as an involuntary instrument and working time reduction policies as a voluntary instrument in mitigating environmental pressure is examined. Policy implications are highlighted in the final section.
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Does turbidity induced by Carassius carassius limit
phytoplankton growth? A mesocosm study
Hu He
&En Hu
&Jinlei Yu
&Xuguang Luo
&Kuanyi Li
&Erik Jeppesen
Zhengwen Liu
Received: 17 March 2016 /Accepted: 11 December 2016 / Published online: 20 December 2016
#Springer-Verlag Berlin Heidelberg 2016
Abstract It is well established that benthivorous fish in shal-
low lakes can create turbid conditions that influence phyto-
plankton growth both positively, as a result of elevated nutri-
ent concentration in the water column, and negatively, due to
increased attenuation of light. The net effect depends upon the
degree of turbidity induced by the benthivores. Stocked
Carassius carassius dominate the benthivorous fish fauna in
many nutrient-rich Chinese subtropical and tropical shallow
lakes, but the role of the species as a potential limiting factor in
phytoplankton growth is ambiguous. Clarification of this re-
lationship will help determine the management strategy and
cost of restoring eutrophic lakes in China and elsewhere. Our
outdoor mesocosm experiment simulating the effect of high
density of crucian carp on phytoplankton growth and commu-
nity structure in eutrophic shallow lakes suggests that stocking
with this species causes resuspension of sediment, thereby
increasing light attenuation and elevating nutrient concentra-
tions. However, the effect of light attenuation was insufficient
to offset the impact of nutrient enhancement on phytoplankton
growth, and significant increases in both phytoplankton bio-
mass and chlorophyll aconcentrations were recorded. Crucian
carp stocking favored the dominance of diatoms and led to
lower percentages (but not biomass) of buoyant
cyanobacteria. The dominance of diatoms may be attributed
to a competitive advantage of algal cells with high sedimen-
tation velocity in an environment subjected to frequent crucian
carp-induced resuspension and entrainment of benthic algae
caused by the fish foraging activities. Our study demonstrates
that turbidity induced by stocked crucian carp does not limit
phytoplankton growth in eutrophic waters. Thus, removal of
this species (and presumably other similar taxa) from subtrop-
ical or tropical shallow lakes, or suspension of aquaculture, is
unlikely to boost phytoplankton growth, despite the resulting
improvements in light availability.
Keywords Crucian carp .Nutrients .Resuspension .
Suspended solids .Phytoplankton community .Shallow
lakes .China
In most shallow lakes, benthivorous fish such as common carp
(Cyprinus carpio) are important factors determining water
clarity (Weber and Brown 2009;Bernesetal.2013; Villizzi
et al. 2015). Benthivorous fish select food by sucking in sed-
iment and ejecting all but the retained food particles back into
the water column. The process often causes sediment resus-
pension, resulting in non-algal turbidity (hereafter referred to
as Bturbidity^) in the water column (Richardson et al. 1995).
Communicated by: Thomas Hein
Electronic supplementary material The online version of this article
(doi:10.1007/s11356-016-8247-z) contains supplementary material,
which is available to authorized users.
*Hu He
State Key Laboratory of Lake Science and Environment, Nanjing
Institute of Geography and Limnology, Chinese Academy of
Sciences, 73 East Beijing Road, Nanjing 210008, China
College of Animal Science, Inner Mongolia Agricultural University,
Hohhot 010018, China
Department of Bioscience, Aarhus University, Aarhus, Denmark
Sino-Danish Centre for Education and Research, Beijing 100049,
Department of Ecology and Institute of Hydrobiology, Jinan
University, Guangzhou 510632, China
Environ Sci Pollut Res (2017) 24:50125018
DOI 10.1007/s11356-016-8247-z
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... High-density juvenile omni-benthivorous fish would inhibit growth and colonisation of submerged macrophytes by reducing underwater light through sediment resuspension, promoting phytoplankton reproduction through releasing of sediment nutrients (bottom-up effect) and reducing grazing pressure of zooplankton on phytoplankton (topdown effect; Chen, Su, et al., 2020;Gu et al., 2016;He et al., 2017;Lorenz et al., 2013). Therefore, developing new measures to suppress the negative effects of juvenile omni-benthivorous fish disturbance on submerged macrophytes is critical. ...
... In the present study, water quality was significantly affected by juvenile crucian carp. Higher ISS concentration in the presence of juvenile crucian carp indicated that juvenile crucian carp caused sediment resuspension, thereby directly reducing the underwater light intensity (Chen, Su, et al., 2020;Gu et al., 2016;He et al., 2017;Lorenz et al., 2013). Previous research has reported decreased (Badiou & Goldsborough, 2015;Kyeongsik et al., 2001;Wahl et al., 2011), unchanged (Chen, Liu, et al., 2020;Chen, Su, et al., 2020), and increased Chl a concentrations in the presence of fish disturbance Roozen et al., 2007;Zhang et al., 2016). ...
... In the present study, the significant increase in Chl a concentration in the presence of juvenile crucian carp may be explained by a combination of three factors. Firstly, juvenile crucian carp disturbed the sediment and the resuspension promoted the release of nutrients from pore water, e.g., TN, TP, and SRP, which promoted the growth of phytoplankton (Gu et al., 2016(Gu et al., , 2018He et al., 2017). Similarly, a stimulated growth of cyanobacteria is often recorded due to more nutrient resuspension after a typhoon passed in Lake Taihu, China (Zhu et al., 2014). ...
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• The re-establishment of submerged macrophytes is crucial in shallow lake restoration transforming a turbid into a clear water system, but it might be inhibited by juvenile omni-benthivorous fish. These fishes disturb the sediment, and even uproot new sprouts, creating turbid water through sediment resuspension and release of nutrients stored in the sediment. Lanthanum modified bentonite (LMB), an in-situ capping material, can immobilise phosphate and consolidate sediments, potentially weakening the negative effects of juvenile omni-benthivorous fish. • We hypothesised that applying LMB would improve water quality and promote the growth of submerged macrophytes by eliminating or weakening the increase of suspended solids, nutrient concentration, and algal reproduction due to juvenile omni-benthivorous fish disturbance. To test our hypothesis, a two-by-two factorial mesocosm experiment with two densities of juvenile crucian carp (absence and 10 g/m³) and two doses of LMB (absence and 800 g/m²) was conducted. • Juvenile crucian carp significantly inhibited the growth and reproduction of the macrophyte Vallisneria natans by reducing the underwater light and direct effects such as uprooting. No significant inhibition or promotion by LMB on the growth of V. natans in the absence of juvenile crucian carp was observed. However, LMB significantly inhibited the fish-induced sediment resuspension and nutrients increases. Consequently, algal production was reduced and underwater light conditions were improved, which promoted the growth and reproduction of V. natans, e.g., more ramets, biomass, and leaves of V. natans. • Our results indicated that submerged macrophytes could benefit from LMB application under high intensity disturbance by juvenile omni-benthivorous fish, thereby conducive to the maintenance of a clear water state in shallow lakes.
... Sediment resuspension increases the turbidity of the water and thus reduces underwater light availability impacting submerged macrophytes (Lorenz et al., 2013;Gu et al., 2016;Chen et al., 2020a). Besides, resuspension may also promote internal nutrient release from the sediment, leading to increased phytoplankton growth and potentially deteriorated water quality (Roozen et al., 2007;Gu et al., 2016Gu et al., , 2018He et al., 2017). ...
... As a result of the relative high N and P fluxes, phytoplankton growth boosted in the controls, where cyanobacteria increased from <20 μg Chl a L − 1 to ~100 μg Chl a L − 1 and chlorophytes from <10 μg Chl a L − 1 to ~50 μg Chl a L − 1 . This is in line with other studies showing that nutrient release from the sediment to the overlying water caused by small crucian carp can significantly promote the growth of phytoplankton, especially cyanobacteria and chlorophytes (Gu et al., 2016(Gu et al., , 2018He et al., 2017;Han et al., 2021). V. natans significantly reduced cyanobacteria, and slightly lowered chlorophyte biomass. ...
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Bioturbation by omni-benthivorous fish often causes sediment resuspension and internal nutrient loading, which boosts phytoplankton growth and may lead to a shift of clear water lakes to a turbid state. Removal of large-sized omni-benthivorous individuals is a lake restoration measure that may revert lakes from a turbid to a clear water state, yet the rapid reproduction of small omni-benthivorous fish in tropical and subtropical shallow lakes may impede such lake recovery. In lake restoration, also a combination of lanthanum-modified bentonite (LMB) and planting submerged macrophytes has been used that may synergistically improve lake water quality. How the combined effect works in the presence of small omni-benthivorous fish has not been studied, which is needed given the high abundances of small omni-benthivorous fish in (sub)tropical lakes. We conducted a two-by-two factorial mesocosm experiment with and without the submerged macrophytes Vallisneria natans and with and without LMB, all in the presence of small crucian carp. At the end of the experiment, turbidity in the V. natans, LMB and combined LMB + V. natans treatments had decreased by 0.8%, 30.3% and 30.9%, respectively, compared with the controls. In addition, the nitrogen (N) and phosphorus (P) release from the sediment in the combined LMB + V. natans treatments had decreased substantially, by 97.4% and 94.3%, respectively, compared with the control. These N and P fluxes were also significantly lower in the combined LMB + V. natans treatments than in the sole LMB treatment (88.1% and 82.3%) or the V. natans treatment (93.2% and 90.3%). Cyanobacteria in the overlying water in the combined LMB + V. natans treatments significantly decreased by 84.1%, 63.5% and 37.0%, respectively, compared with the control and the sole LMB and V. natans treatments. Our results show that LMB and submerged macrophytes complement each other in effectively improving the water quality, even in the presence of small omni-benthivorous fish.
... These contrasts the findings in several other studies (e.g., Badiou and Goldsborough, 2015;Chen et al., 2020a) but it may reflect the high biomass of macrophytes, buffering the effect of fish disturbance and nutrient excretion (Kaldy, 2014). Previous studies have showed that fish disturbance has positive (He et al., 2017;Gu et al., 2018), neutral (Parkos et al., 2003;Chen et al., 2020b) and negative effects (Wahl et al., 2011;Badiou and Goldsborough, 2015) on the content of Chl a in the water column. In our study, the content of Chl a was not affected by fish disturbance, which may be explained by the following mechanisms: 1) the rather dense submersed macrophytes may control phytoplankton by producing allelochemicals that suppress phytoplankton growth rates (Vanderstukken, et al., 2014), and 2) submersed macrophytes may control phytoplankton by competing for nutrients (Jeppesen et al., 1998;Declerck et al., 2007). ...
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Benthivorous fish disturbance and nitrogen loading are two important factors that influence the community structure of submersed macrophytes, but their interactive effect is not well elucidated. We conducted an outdoor mesocosm experiment to examine the individual and combined effects of these two factors on the growth of two submersed macrophytes of different growth forms, i.e., the rosette-forming Vallisneria natans and the canopy-forming Myriophyllum spicatum. The treatments involved two levels of fish (Carassius auratus) disturbance crossed with two levels (0 and 12 g NH 4 Cl per month) of ammonium (NH 4 +-N) loading. For M. spicatum, we found that maximum height (MH) was reduced by 30.7%, 26.4%, and 51.0% in fish addition alone (F) and nitrogen addition treatments (N, F + N), respectively, compared with the control (C) treatment. The density of M. spicatum declined by 20%, 62% and 68.8% in the F, N and F + N treatment. The above-ground biomass (AGB) of M. spicatum respectively reduced by 56.7%, 94%, and 96.5% in the F, N and F + N treatments, and the roots/shoots ratio (R/S) increased by 114%, and 176% in N and N + F treatments, respectively. Regarding V. natans, only the MH in the N treatment was reduced (71.9%), and the density exhibited a reduction of 59.1% and 64.5% in the N and F + N treatments, respectively. The AGB of V. natans was significantly lower in the N (90.3%) and N + F (78.4%) treatments compared with the C treatment, while increased by 60.3% in F treatment. The R/S of V. natans increased by 227%, and 74.4% in the N and F + N treatments compared with the C treatment. The interactive effect of fish disturbance and high N on MH and AGB of V. natans and density of M. spicatum were antagonistic. However, the interactive effect on density and BGB of V. natans and AGB of M. spicatum were negatively synergistic.
... Besides, (Lenhart et al. 2010) found that there were significant increase in turbidity and TSS in river water due to organic matter and inorganic sediments. This high level of turbidity reduced light intensity, which affected the phytoplankton growth negatively (He et al. 2017). High BOD, COD, TS, TSS and turbidity levels in the SCC area is related to untreated sewage, organic substance and inorganic sediments discharged via canal outlets from the built-up area. ...
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Surma River of Bangladesh is a representative of sub-tropical river system which is complex, dynamic and interacting socio-ecological system. Though land-based activities control the water quality of this river system, no studies have been conducted on the role of land-use patterns on water quality and biotic communities. Therefore, this study aimed to understand the impacts of water quality on the plankton community dynamics of Surma River basin. In addition, the study also examined the impacts of land-use patterns on water quality of river. Land-use patterns were identified by analyzing Landsat-8 imageries of the United State Geological Survey. Data on biotic and abiotic variables were collected from 15 sampling stations during dry season. Unsupervised and supervised classification techniques were used to identify the land-use patterns. Weighted arithmetic method was used to develop water quality index of river system. This study found four types of land-use patterns around Surma River basin (i.e., built-up area, barren land, river, vegetation and agriculture). Water quality index indicates that water quality is good in the rural area, while bad in the urban areas. Our study found that land-use pattern is a good predictor of water quality (R² = 0.97) of Surma River basin. Our study also found that high plankton species diversity coincides with the good water quality of the river. This study will serve as tool for the management of Surma River basin of Bangladesh.
... Crucian carp (Carassius carassius L.) is a widespread omni-benthivorous fish species in subtropical and tropical freshwater waterbodies and constitute a major threat to the water clarity in warm shallow lakes (Gao et al., 2014). Studies have shown that juvenile crucian carp can enhance eutrophication by unrooting submerged macrophytes, disturbing sediments, enhancing internal loading, and preying on herbivorous zooplankton and zoobenthos (Gu et al., 2016(Gu et al., , 2018He et al., 2017;Han et al., 2020). In hypereutrophic lakes, however, gut content analysis showed that crucian carp also ingest bloom-forming and/or filamentous phytoplankton (Kolmakov and Gladyshev, 2003;Liu, 2008). ...
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Biomanipulation by piscivore stocking has been widely used to combat eutrophication in north temperate lakes, but its applicability in warm lakes has not yet been well elucidated. Here, we used experimental mesocosms to test the effects of a native benthi-piscivore (snakehead, Channa argus Cantor) on water clarity under subtropical conditions where small omni-benthivorous fish like crucian carp (Carassius carassius L.) prevail. Our results showed that, despite of a great reduction of crucian carp biomass, snakehead stocking did not create a strong trophic cascade as neither (herbiv-orous) zooplankton biomass nor their grazing pressure, indicated by biomass ratio of (herbivorous) zooplankton to phytoplankton, changed significantly. Moreover, snakehead stocking significantly increased water non-algal turbidity as well as nutrient and chlorophyll-a concentrations, suggesting that these benthi-piscivores also disturbed sediments like crucian carp did. Our study showed that biomanipulation by stocking of snakehead does not facilitate clear-water state in warm shallow lakes, even on the short-term.
... For example, Razlutskij et al. [20], through 72 days of outdoor experiments, found that introducing Carassius auratus increased the biomass of Phyt. Recent ecological studies have revealed significant negative effects of crucian carp (Cruc) on the water quality and ecological states of shallow lakes, e.g., increasing nutrient levels, leading to reduced water clarity [21,22]. The current international guidance on the application of biological manipulation technology to the process of lake ecological restoration remains far from sufficient [23]. ...
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Maintaining the health of lake ecosystems is an urgent issue. However, eutrophication seriously affects lakes’ ecological functions. Eutrophication is also the main target of lake ecological restoration. It is vital to carry out research on lake eutrophication control and energy flow evaluation in ecosystems scientifically. Based on in situ survey results for the aquatic life data for Lianshi Lake from 2018 to 2019, the Ecopath model was used to establish an evaluation index system for the typical biological chain to screen out the key species in the water ecosystem, and the fuzzy comprehensive evaluation (FCE) method was used to screen all the biological chains controlling algae. A combination of the FCE coupled with the Ecopath screening method for typical biological chains for algal control was applied to the Lianshi Lake area; the results show that the typical biological chain for algal control is phytoplankton (Phyt)–zooplankton (Zoop)–macrocrustaceans (Macc)–other piscivorous (OthP). Upon adjusting the biomass of Zoop and Macc in the typical biological chain for algal control to three times that of the current status, the ecological nutrition efficiency of Phyt was increased from 0.308 to 0.906. The material flow into the second trophic level from primary producers increased from 3043 to 8283 t/km2/year. The amount of detritus flowing into primary producers for sedimentation decreased from 7618 to 2378 t/km2/year. Finally, the total primary production/total respiratory volume (TPP/TR) decreased from 9.224 to 3.403, the Finn’s cycle index (FCI) increased from 13.6% to 17.5%, and the Finn’s average energy flow path length (FCL) increased from 2.854 to 3.410. The results suggest that the problem of eutrophication can be solved by introducing Zoop (an algal predator) and Macc to a large extent, resulting in improved ecosystem maturity. The research results can facilitate decision making for the restoration of urban lake water ecosystems.
... In addition, the recurring resuspension of settled phytoplankton through the benthivorous fish disturbance also increased Chl a concentration in overlying water (Roozen et al. 2007). Practically,cruciancarpcanalsoreducetheefficacyofLMBon waterthroughthe"top-downeffect."Zooplanktonconstitutes alargeproportioninthedietofcruciancarp(Kloskowski2011; Gu et al. 2016), and the presence of juvenile crucian carp can reduce the zooplankton biomass and the grazing pressure of zooplankton on phytoplankton, thereby promoting phytoplanktongrowth (He et al. 2017;Guetal.2018) and ultimately reducing the efficacy of LMB. ...
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Lanthanum-modified bentonite (LMB) is widely used for eutrophication control and has demonstrated good efficiency in some eutrophic lakes. However, the efficiency of LMB on eutrophication control in some eutrophic lakes, where the structure of food webs is mainly dominated by omni-benthivorous fish, remains ambiguous. Omni-benthivorous fish usually disturbs sediment and promotes the release of internal nutrients, the effect of which on the efficacy of LMB remains to be studied. Thus, a 30-day mesocosm experiment was conducted to determine whether omni-benthivorous fish disturbance and LMB would cause antagonistic responses. LMB significantly reduced dissolved P concentration in overlying water, converting mobile P to bound P in the surface layer of sediment in the absence of crucian carp (Carassius carassius). However, there were significantly negative interaction effects between LMB and crucian carp. Although LMB still effectively reduced the total dissolved phosphorus (TDP) and soluble reactive phosphorus (SRP) concentrations of overlying water in the presence of crucian carp, it had limited efficacy on inhibiting the increased concentrations of suspended solids, particulate nutrients, and chlorophyll a (Chl a) due to crucian carp disturbance. Furthermore, the crucian carp disturbance also increased the risk of mobile P releasing from surface sediment, whether with or without LMB application. The results indicated that the efficacy of LMB was insufficient to offset the negative effect of omni-benthivorous fish disturbance on eutrophication control. Hence, the omni-benthivorous fish also need to be considered for eutrophication control in shallow eutrophic lakes. Some measures need to be taken to control the biomass of omni-benthivorous fish.
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As the most widely distributed freshwater fish worldwide, common carp Cyprinus carpio can be either invasive or ‘naturalised’ in most areas of introduction. This leads to different levels of perception regarding its role in freshwater ecosystems, with experimental research focusing either on its ‘middle-out’ impacts or overall function in limnological processes. At the same time, the large scales at which carp dynamics operate may severely limit the validity of laboratory and, oftentimes, field experiments in extrapolating results to real-world ecosystems. In this study, 129 laboratory, field and ‘natural’ experiments were systematically reviewed through causal criteria analysis, and within an historical/biogeographical and risk assessment context. Of the 19 countries where experiments were conducted, only four were considered as ‘low risk’ and one as ‘no risk’, the other being ‘medium’ to ‘high risk’. Experimental findings from 373 component-wise assessments supported the framework of effects on water quality, vegetation, invertebrates and vertebrates, with the latter including also amphibians and waterfowl, previously unreported. Stronger evidence was provided by natural and field relative to laboratory experiments, reflecting the reductionism of the latter. Critical biomass for an impact was highly dependent on experimental set-up, even though the overall threshold of ≈200 kg ha−1 under natural conditions supported recent findings. Management of carp should reflect the level of current and potential risk posed by the species in its different areas of distribution, thereby accounting for projections of further spread but also for unsuccessful colonisation. Future experimentation should favour a holistic→reductionist over a reductionist→holistic approach.
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We examined the interactions of the common carp (Cyprinus carpio L.) and nutrient additions on water quality, sedimentation rates, and submerged macrophyte biomass in mesocosms in Delta Marsh, Manitoba, Canada. We wanted to determine if carp and nutrients interacted synergistically to increase phytoplankton biomass. A two-by three duplicated, factorial design had the following treatments: (1) control mesocosms with no carp or nutrient additions; (2) low carp density and no nutrient additions; (3) high carp density and no nutrient additions; (4) no carp and nutrient additions; (5) low carp density and nutrient additions; and (6) high carp density and nutrient additions. The presence of carp increased ammonia concentrations, turbidity, and phytoplankton biomass as expected but did not increase total reactive phosphorus concentrations. The presence of carp did not appear to interact synergistically with nutrient additions to increase phytoplankton as has been suggested by others. In mesocosms with high carp density and receiving nutrient enrichment, phytoplankton appeared to be suppressed relative to mesocosms receiving nutrient enrichment only, and nutrient enrichment and low carp density. Overall, the presence of carp appears to mimic the effects of eutrophication. Our results demonstrate that carp can cause a shift from a clear, macrophyte dominated state to a turbid phytoplankton-dominated state at a biomass of less than 600 kg ha-1.
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Nitrogen (N) and phosphorus (P) are key factors that limit phytoplankton growth in freshwater lakes. Controlling external P loading is a widely recognized measure for reducing eutrophication, but the usefulness of limiting N inputs remains under debate. Shallow lakes with frequent sediment resuspension events exacerbate internal P loading and limit the potential for in-lake P reduction. A two-way factorial mesocosm experiment was carried out using two levels of N inputs (with and without addition of potassium nitrate as N source) and sediment resuspension (with and without resuspension) for 35 days in order to examine the effect of N inputs on phytoplankton growth during sediment resuspension events. N addition alone did not affect phytoplankton biomass in mesocosms in treatments without sediment resuspension, likely due to the P limitation. However, internal P loading, via sediment resuspension, shifted mesocosms from P- to N-limited systems in which N addition significantly boosted phytoplankton biomass. Our results suggested that external loading comprising N alone may enhance phytoplankton growth in shallow, eutrophic lakes with frequent resuspension events like Lake Taihu, China. In such lakes, P-only management is unlikely to usefully reduce eutrophication, and a strategy to reduce both N and P is needed.
Background In recent decades, many attempts have been made to restore eutrophic lakes through biomanipulation. Reducing the populations of planktivorous and benthivorous fish (either directly or through stocking of piscivorous fish) may induce ecosystem changes that increase water transparency and decrease the risk of algal blooms and fish kills, at least in the short term. However, the generality of biomanipulation effects on water quality across lake types and geographical regions is not known. Therefore, we have undertaken a systematic review of such effects in eutrophic lakes in temperate regions throughout the world. Methods Searches for literature were made using online publication databases, search engines, specialist websites and bibliographies of literature reviews. Search terms were developed in English, Danish, Dutch and Swedish. Identified articles were screened for relevance using inclusion criteria set out in an a priori protocol. To reduce the risk of bias, we then critically appraised the combined evidence found on each biomanipulation. Data were extracted on outcomes such as Secchi depth and chlorophyll a concentration before, during and/or after manipulation, and on effect modifiers such as lake properties and amounts of fish removed or stocked. Results Our searches identified more than 14,500 articles. After screening for relevance, 233 of them remained. After exclusions based on critical appraisal, our evidence base included useful data on 128 biomanipulations in 123 lakes. Of these interventions, 85% had been made in Europe and 15% in North America. Meta-analysis showed that removal of planktivores and benthivores (with or without piscivore stocking) leads to increased Secchi depth and decreased chlorophyll a concentration during intervention and the first three years afterwards. Piscivore stocking alone has no significant effect. The response of chlorophyll a levels to biomanipulation is stronger in lakes where fish removal is intense, and in lakes which are small and/or have high pre-manipulation concentrations of total phosphorus. Conclusions Our review improves on previous reviews of biomanipulation in that we identified a large number of case studies from many parts of the world and used a consistent, repeatable process to screen them for relevance and susceptibility to bias. Our results indicate that removal of planktivorous and benthivorous fish is a useful means of improving water quality in eutrophic lakes. Biomanipulation tends to be particularly successful in relatively small lakes with short retention times and high phosphorus levels. More thorough fish removal increases the efficacy of biomanipulation. Nonetheless successes and failures have occurred across a wide range of conditions.
通过食物组成分析和渔获物组成调查, 并结合历年渔获量统计和环境监测资料, 研究了太湖鲫鱼数量变化的规律、机制及与环境间的相互关系。渔获物调查和渔获量统计资料均表明:近年鲫鱼数量不断增加, 已成为太湖仅次于鲚鱼的重要鱼类。2004年渔获物调查中, 鲫鱼占鱼类总重量的8.40%±2.69%, 占鲤、鲫鱼渔获量的65.08%±15.47%;历年渔获量统计显示, 1952-1998年鲤、鲫鱼渔获量相对稳定在1010.1±367.2t、占鱼类总量8.89%±5.33%, 1999年上升达到2547.4t、占9.45%, 2000年达到3708.7t, 占12.18%;年龄组成分析表明, 鲫鱼低龄化趋势在加剧。食性分析表明:在7-12月, 微囊藻占鲫鱼食物体积的83.65%-93.99%。分析认为:太湖鲫鱼以微囊藻为主要食物;富营养化加重为其提供了充足饵料, 实施禁渔期、禁渔区等措施使其繁殖得到保障, 捕捞强度过高导致其年龄组成低龄化、个体小型化。而太湖鲫鱼以蓝藻为主要食物, 可能对蓝藻有抑制作用。Based on the analysis of food content and the survey of the composition in fish catches and the data of fish catches in Lake Taihu, the amount changes of catches of Carassius auratus Linnaeus and Their Mutual Relationship with Environment were studied.The results of the survey of fish composition in 2004 and the statistics data of fish catches from 1952 to 2004 showed that:Within recent years, the catches of Carassius auratus Linnaeus had been increasing and had become the second dominant fishes following Coilia ectenes taihuensis Yen et Lin.The a-nalysis of age structure showed that the percentage of 0⁺ fishes increased and the average fish body size decreased.For example, the percentage of 0⁺Carassius auratus Linnaeus had been increasing according to the trend of y=19.154e0.0566x(y means the percentage of 0⁺fishes %, x means time a).And the average body length had been decreasing according to the trend of y=115.45e-0.0312x(y means body size cm, x means time a).The results of food content analysis showed that:the percentage of blue-algae accounted for about 83.65%-93.99% of food volume of Carassius auratus Linnaeus.Under the conditions of eutrophication in Lake Taihu, Carassius auratus Linnaeus mainly fed on blue-algae;eutrophication resulted in the increasing of blue-algae which could be eaten by the fish.The measures of protecting fishes were carried out to ensure the fish propagating.In addition, the trend of percentage of low age fishes increasing and the trend of body size of the fishes decreasing were caused by over-fishing.Carassius auratus Linnaeus might restrain blue-algae increasing because it mainly fed on blue-algae.
Conference Paper
Fish manipulation has been used to restore lakes in the temperate zone. Often strong shortterm cascading effects have been obtained, but the long term-perspectives are less clear. Fish manipulation methods are far less advanced for warm lakes, and it is debatable whether it is, in fact, possible to create a trophic cascade in warm lakes due to the dominance and high densities of fast-reproducing omnivorous fish. However, other important aims of fish manipulation, for instance, the removal of benthic feeding fish, are to reduce disturbance of the sediment, which not only affects the nutrient level but also the concentration of suspended organic and inorganic matter with reduced clarity as a result, and hampers growth of submerged macrophytes. We conducted a biomanipulation experiment in two basins of Chinese Huizhou West Lake that has remained highly turbid after extensive nutrient loading reduction. A third basin was used as control (controltreatment pairing design). Removal of a substantial amount of plankti-benthivorous fish was followed by planting of submerged macrophytes and stocking of piscivorous fish. We found strong and relatively long-lasting effects of the restoration initiative in the form of substantial improvements in water clarity and major reductions in nutrient concentrations, particularly total phosphorus, phytoplankton and turbidity, while only minor effects were detected for crustacean zooplankton grazers occurring in low densities before, as well as after the restoration. Our results add importantly to the existing knowledge of restoration of warm lakes and are strongly relevant, not least in Asia where natural lakes frequently are used extensively for fish production, often involving massive stocking of benthivorous fish. With a growing economy and development of more efficient fish production systems, the interest in restoring lakes is increasing world-wide. We found convincing evidence that fish removal and piscivores stocking combined with transplantation of submerged macrophytes may have a substantial role in conservation and management of warm water lakes.