Shallow Tropical Lake Research Articles

The importance of herbivory by protists in lakes of a tropical floodplain system

Inland aquatic ecosystems play a critical role in the global carbon cycle, processing a great fraction of the organic matter coming from terrestrial ecosystems, and the microbial food web is crucial in this process. Thus, we aimed to evaluate whether the food resource of planktonic protozoa comes mainly from small primary producers or heterotrophic bacteria in tropical shallows lakes, assuming the hypothesis that, in general, picocyanobacteria would be the main food resource for protists. We also expected that the autotrophic fraction would be mainly related to protists at the surface of the environments, while the heterotrophic fraction would be more important at the lower strata of the water column. We performed size-fractionation experiments to evaluate the effects of predation of protists on heterotrophic bacteria and picocyanobacteria. We also sampled planktonic organisms at the subsurface and bottom of 20 lakes in a Neotropical floodplain. We found an herbivory preference of heterotrophic flagellates, while ciliates seem to exert a stronger impact on heterotrophic bacteria. We also found no relationship between heterotrophic bacteria and protists in the field data, whereas positive relationships between picocyanobacteria and protists were observed in environments where there was sunlight. Thus, both heterotrophic bacteria and picocyanobacteria were important components in the food webs of tropical shallow lakes. Moreover, the trophic cascade caused by zooplankton predation suggests that protists are efficient in transferring the energy from the base of microbial food webs to higher trophic levels.

Is competition an interaction as relevant as predation for tropical planktonic cladocerans?

Abstract Aim To test the relevance of competition and predation for the two most abundant and frequent cladoceran populations, the medium-sized Ceriodaphnia richardi Sars, 1901 and the large-sized Daphnia gessneri Herbst, 1967, in a tropical shallow lake. Methods Laboratory experiments and weekly samplings in the lake for a year were performed to evaluate: density fluctuations and reproduction; predation on juveniles and adults by larvae of Chaoborus brasiliensis Theobald, 1901; competitive interactions and possible implications of competition and predation on the fluctuations of populations in the lake. Juveniles and adults of both cladocerans were offered to larvae instar IV of chaoborid, for testing selective predation in laboratory experiment. Competitive interaction between the two cladocerans was tested in experiments, with high (0.70 mg C.L-1) and low (0.25 mg C.L-1) concentrations of the edible chlorophycean Desmodesmus spinosus Chodat. Results C. richardi and D. gessneri were more abundant in the cool season, when their densities were inversely correlated, and when invertebrate predators, C. brasiliensis and the water mite Krendowskia sp., were less abundant. Despite higher concentrations of food and larger number of offsprings produced by the cladocerans in the warm season in the lake, their densities were lower, coincident with the increase of invertebrate predators, mainly chaoborid larvae. C. brasiliensis preyed on adult C. richardi and on young D. gessneri. In the competition experiments, the densities and the population growth rates of C. richardi were higher than those of D. gessneri. The competition results support the “small body size” and the “rmax” hypotheses. The exclusion of D. gessneri by C. richardi occurred only in experimental conditions, while they coexist in the lake, but without reaching their carrying capacity. Conclusions Predation is the key factor influencing the populations of cladocerans, whereas competition seems to play a secondary role, probably restricted to some periods of lower food concentration in the cool season.

Rapid isolation of culturable microalgae from a tropical shallow lake system

Microalgae diversity is constantly being studied and explored for biotechnological uses. The shallow lake system of Lencois Maranhenses (SLLM) is a unique coastal ecosystem in northeast Brazil found interspersed in a field of sand dunes. Organisms in these tropical lakes are constantly exposed to high temperatures and solar irradiance. Yet, little is known about the diversity of culturable microalgae in this aquatic ecosystem. This study reports the use of flow cytometry with fluorescence-activated cell sorting (FACS) to isolate single microalgae cells/coenobia from five lakes in SLLM, accessing the efficiency of this isolation technique with two types of culture media. To retrieve the highest diversity of culturable microalgae, planktonic, benthic, and epiphytic samples were collected and processed by FACS. The diversity of microalgae in natural lake communities was described by morphology-based taxonomy. Isolates of the most abundant phylum established in cultures (Chlorophyta) were characterized by gene sequencing (18S rDNA). A total of 3072 microalgal cells/coenobia were sorted into 96-well plates. From these, 945 wells presented algal growth (31% success rate). Based on morphological diversity and adaptability to culture conditions, a set of 171 strains were selected to be incorporated in a culture collection. Microalgae present in the lakes belonged to six phyla, with four of them represented in the cultured strains. Our sampling strategy coupled with FACS isolation retrieved a fairly large number and diversity of microalgal strains with minimum isolation effort from a unique coastal environment. The monoclonal cultures established in this study offer new opportunities for basic and applied research on microalgae biotechnology.

Effect of suspended clay on growth rates of the cyanobacterium Cylindrospermopsis raciborskii

Recent studies have shown that sediment resuspension may lead to the collapse of C. raciborskii dominance, which suggests that clay might have a negative effect on the growth of C. raciborskii. To test the hypothesis that suspended clay creates an unfavorable environment for growth of C. raciborskii, we exposed four different strains of this species to various concentrations of the clays kaolinite and bentonite, and monitored the biomass of each strain over the course of 1-week microcosm experiments. Contrary to our hypothesis, C. raciborskii was able to grow in suspensions of both clays. While kaolinite clay caused higher turbidity than bentonite, the growth rates of all four C. raciborskii strains were higher in kaolinite than in bentonite suspensions. C. raciborskii could still grow in clay concentrations that cause turbidity far above the levels found in natural lakes. Our study suggests that the reported collapse of C. raciborskii blooms with high concentrations of suspended sediments in tropical shallow lakes is probably not caused by the effects of suspended clay on light attenuation, but rather is a consequence of cell sinking or, possibly a response to disturbance events responsible for sediment suspension.

Factors that drive zooplankton diversity in Neo-Tropical Savannah shallow lakes

Abstract Zooplankton is an important community in aquatic ecosystems due to its linkage between primary producers and secondary consumers also playing a key role in cycling of organic materials. Aim: Therefore, our objective was to evaluate the effects of physicochemical variables of the water on the diversity of zooplankton community in seven tropical shallow lakes of Brazilian savannah. Methods Zooplankton samples were taken using a bucket and filtered 200 L by a 64 µm-mesh-plankton-net, and preserved for subsequent identification. Water temperature, dissolved oxygen, pH, electrical conductivity, turbidity, chlorophyll-a, ammonium, nitrate, nitrite, total phosphorus, and soluble reactive phosphorus were measured. Results The turbidity (decreases the temperature, luminosity and the system productivity) and ammonium (increases the toxicity) values were the major factors responsible for structuring the zooplankton community. On the other hand, also nitrogen and phosphorus (increase the productivity) are limiting in savannah lentic systems for the zooplankton. The higher α diversity was positively associated with aquatic macrophytes (increase of niches and refuge), whereas lakes with geographic proximity increase the similarity in species composition, decreasing the β diversity. Conclusions We conclude that the deterministic processes (niche theory), due to species have different ecological requirements, are different responses to environmental gradients and increase the diversity in heterogenic lentic systems.

Limnology of the neotropical high elevation shallow lake Yahuarcocha (Ecuador) and challenges for managing eutrophication using biomanipulation

Temperate and tropical shallow lakes differ in several fundamental aspects with respect to management of eutrophication. High altitude tropical shallow lakes are a special case, showing similarities with temperate and tropical lakes. We studied the ecology of the eutrophic high-altitude tropical lake Yahuarcocha in the Ecuadorian Andes and evaluated the potential of biomanipulation to control eutrophication. With a toxin-producing Cylindrospermopsis bloom, low Secchi depth and low submerged macrophyte cover, Yahuarcocha is clearly in a turbid ecosystem state. Relatively low nutrient concentrations should theoretically allow for a shift to a clear water state through biomanipulation. Top-down control of phytoplankton by zooplankton, however, is complicated by the (1) absence of predatory fish, (2) fish community dominated by small poecelid species, (3) lack of a refuge for zooplankton from fish predation within the macrophytes, and (4) persistent, grazing resistant bloom of the cyanobacterium Cylindrospermopsis. In these aspects, lake Yahuarcocha is more similar to tropical shallow lakes, probably because water temperature is high relative to the mean air temperature and because of the absence of a cold season. The fish and macrophyte communities consisted almost entirely of exotic species. The exotic fish species probably stabilized the turbid state in the lake.

Emergent Macrophytes Support Zooplankton in a Shallow Tropical Lake: A Basis for Wetland Conservation.

Understanding the biodiversity value of littoral zones of lakes is a priority for aquatic biodiversity conservation. However, less emphasis has been given to the littoral part of tropical African lakes, with many of the previous researches focusing only on the open water side. The aim of the present study was, therefore, to investigate the impact of the littoral zone of a shallow freshwater tropical lake (Ziway, Ethiopia), dominated by two emergent macrophytes, on zooplankton community structure. We hypothesized that the wetland vegetation serves as a preferred microhabitat for zooplankton communities. A lake with substantial coverage of emergent macrophytes was monitored monthly from January to August, 2016. The monitoring included the measurements of physical, chemical, and biological parameters. Sampling sites were selected to represent areas of the macrophyte vegetation (Typha latifolia and Phragmites australis) and the open water part of the lake. Sites with macrophyte vegetation were found to be the home of more dense and diverse zooplankton community. However, during the period of high vegetation loss, the density of crustacean zooplankton showed significant reduction within the patches of macrophytes. From biodiversity conservation perspective, it was concluded that the preservation of such small areas of macrophytes covering the littoral zone of lakes could be as important as protecting the whole lake. However, the rapid degradation of wetland vegetation by human activities is a real threat to the lake ecosystem. In the not-too-far future, it could displace and evict riparian vegetation and the biota it supports.

Mercury accumulation rates in Caço Lake, NE Brazil during the past 20.000 years

Total Hg, TC, TN, goethite and siderite distributions in sediment cores from two locations across Caçó Lake (Brazil) identified paleoclimate factors that had affected the Hg deposition in this shallow tropical lake and its relationship with past climate and basin processes. Concentrations and fluxes of Hg were maximum in the Last Glacial Maximum (LGM), with averages of 397 ng g−1 and 24.3 μg m−2 yr−1, respectively, decreasing during the Heinrich Stadial 1 (H1) and further during the Meltwater pulse 1A (MWP-1A). The higher values during LGM and H1 were strongly associated with dust deposition as observed in Greenland ice cores. After a period of lower values, there was a significant increase of concentrations and fluxes during the Younger Dryas (193 ng g−1 and 4.1 μg m−2 yr−1), still associated in part with dust deposition but also being influenced by the high volcanic activity of this period. Concentrations and fluxes decreased again to the lowest values during the Holocene from about 9500 to 2000 cal yr BP (114 ng g−1 and 1.25 μg m−2 yr−1). Analyses of 210Pb dated shorter cores shows increasing Hg accumulation rates during the past century, larger than in other period in the past but could not evidence the influence of colonial gold mining as suggested by earlier studies.

Phytoplankton functional dynamics in a shallow polymictic tropical lake: the influence of emergent macrophytes

This study aimed at investigating the phytoplankton dynamics by employing taxonomic and functional models to test the hypothesis that emergent macrophytes could influence phytoplankton dynamics by increasing the stability of water column and harboring zooplankton. It was also hypothesized that functional models are better than taxonomic approaches to depict phytoplankton community structure in a polymictic tropical lake (Ziway, Ethiopia) with substantial macrophyte cover. Twelve sampling sites, extending from the macrophyte vegetation (Typha latifolia and Phragmites australis) covered littoral part to an open water side of the lake, were monitored monthly (January to August, 2016) for physical, chemical and biological parameters. A total of 93 taxa, distributed among six major taxonomic groups, 14 Reynolds functional groups and six morphology-based functional groups, were identified. The phytoplankton groups, which prefer stable water column and tolerate grazing dominated towards the macrophyte zones, while the phytoplankton capable of surviving strong mixing succeeded towards the completely mixing open water side of the lake. The results of the present study also suggest that the functional classification schemes are robust ways of detecting phytoplankton dynamics along the macrophyte-open water gradient in shallow tropical lakes.

Distribution and fluctuations of backswimmers (Notonectidae) in a tropical shallow lake and predation on microcrustaceans.

Notonectids are widely distributed in freshwaters and can prey on zooplankton in temperate lakes. However, its role in structuring the zooplankton community is unknown in tropical lakes. Thus, our objective was to study the notonectid Martarega uruguayensis in a Brazilian tropical shallow lake to evaluate its potential as a zooplankton predator. Its horizontal distribution was analized in the lake throughout one year in fortnightly samplings. Backswimmers were more abundant (mean density 162.9 ± 25.8 ind.m-2) in the cool-dry season, with a strong preference by the littoral zone (mean density 139.9 ± 17.5 ind.m-2). Laboratory experiments were undertaken with young and adult notonectid and the two most abundant cladocerans, Daphnia gessneri and Ceriodaphnia richardi, as prey. Predation by backswimmers in the laboratory showed that only juveniles fed on microcrustaceans (mean ingestion rate of 1.2 ± 0.2 Daphnia and 1.0 ± 0.2 Ceriodaphnia per predator per hour), without size selectivity. Adult insects probably have difficulties in detecting and manipulating small planktonic organisms. On the other hand, young instars might influence zooplankton community, especially in the littoral zone of the lake. This study does contribute to a better understanding of trophic interactions in tropical shallow lakes and is the first to investigate the predation of a notonectid on microcrustaceans from Lake Monte Alegre.

Spatial and temporal variation of Cladocera in a tropical shallow lake

We studied cladoceran species richness, community composition, habitat preference and density in three spatial habitats over 1 year at Thale-Noi, a large shallow tropical lake in southern Thailand. Monthly sampling conducted with activity traps deployed overnight in littoral (Hydrilla and Ceratophyllum beds), open water (Hydrilla beds) and marginal zone (Utricularia beds), revealed that the macrophyte beds support similar cladoceran diversities regardless of the habitat. Total species richness in all studied habitats ranged between 30 and 34 species, supporting up to 22 species in a trapping area of 0.09 m2 at peak times, the majority belonging to the Chydoridae. In total, 40 species were recorded over the year, half of which were chydorids. Mixed cladoceran densities reached maxima of 160 333 ind.m−2 for a single habitat at a given moment. The dominant species included Chydoridae (Anthalona , Kurzia , Dunhevedia and Ephemeroporus ), Daphniidae (Ceriodaphnia ), Macrothricidae (Macrothrix ) and Ctenopoda (Latonopsis ). Monthly variation in species richness was most obvious in the littoral zone, whereas monthly variation in densities occurred at all sites. Community composition and habitat preference were mainly structured by depth and pH, resulting in different assemblages per habitat, but with uniform communities in the littoral (Hydrilla and Ceratophyllum ) beds in a single area. This study presents the first ecological survey of Cladocera using activity traps in a shallow tropical lake.

Are the littoral zone conditions suitable for tropical planktonic microcrustaceans?

The occupation of the littoral and limnetic zones by planktonic species has led to questions about whether littoral macrophytes would be a suitable habitat or refuge. These questions guided our field and laboratory studies on the spatial occupation and the food suitability for microcrustaceans of a shallow tropical lake. Replicated zooplankton samples were collected over 18 days, at intervals of 3 days, at three zones (the middle and edge of the stands of the emergent macrophyte, Ludwigia sp., and the limnetic zone). Some species, such as the cladocerans Diaphanosoma birgei and Daphnia ambigua , showed preference for the littoral zone and the limnetic zone, respectively. Copepodites, and adult copepods Thermocyclops decipiens and Tropocyclops prasinus meridionalis are mainly limnetic dwellers. The size of the cladocerans Ceriodaphnia richardi and Daphnia gessneri did not differ between the zones, nor did the clutch size of the former species; smaller individuals of D. ambigua were found within macrophyte stands. In laboratory experiments, the seston of the three zones did not negatively affect the development of the cladocerans C . richardi and D. birgei . On the contrary, the seston of the middle of the macrophyte stands promoted better growth rates of both cladocerans and some of the life table parameters of D. birgei than the seston of the other two zones. Food quantity and quality are not negative factors to microcrustaceans in the littoral and limnetic zones. The preference or indifference of microcrustaceans to habitats may be part of their adaptive strategies regarding other factors, including predation.

Biomanipulation-induced reduction of sediment phosphorus release in a tropical shallow lake

Biomanipulation via fish regulation combined with submerged plant introduction is an effective measure to restore eutrophic shallow lakes. Improved water quality and clarity promote growth of benthic algae, which with submerged plants may limit sediment phosphorus (P) release, thereby reinforce lake recovery. Our study sought to evaluate the effect of such a biomanipulation on water quality, benthic algal development and sediment P release in a shallow, tropical lake by (1) comparing porewater and lake water quality, light intensity and benthic algal development in restored and unrestored sections; (2) conducting a 32P radiotracer experiment to track P release from sediment cores sampled from both sections. The biomanipulation led to lower total P, total dissolved P, and soluble reactive P concentrations in lake water, lower phytoplankton biomass, and increased light intensity at sediment surface, stimulating benthic algal development. Moreover, sediment 32P release was lower in the restored than unrestored section. Concurrently, dissolved oxygen levels in upper layers of the sediment cores were higher in the restored section. Our study indicates that the biomanipulation improved water quality and enhanced growth of benthic algae, thereby reducing sediment P release, which may be one of the main mechanisms to create successful restoration.

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

It is well established that benthivorous fish in shallow lakes can create turbid conditions that influence phytoplankton growth both positively, as a result of elevated nutrient 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 relationship 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 community structure in eutrophic shallow lakes suggests that stocking with this species causes resuspension of sediment, thereby increasing light attenuation and elevating nutrient concentrations. However, the effect of light attenuation was insufficient to offset the impact of nutrient enhancement on phytoplankton growth, and significant increases in both phytoplankton biomass and chlorophyll a concentrations 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 sedimentation 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 subtropical or tropical shallow lakes, or suspension of aquaculture, is unlikely to boost phytoplankton growth, despite the resulting improvements in light availability.

Seasonality of freshwater bacterioplankton diversity in two tropical shallow lakes from the Brazilian Atlantic Forest.

Bacteria are highly important for the cycling of organic and inorganic matter in freshwater environments; however, little is known about the diversity of bacterioplankton in tropical systems. Studies on carbon and nutrient cycling in tropical lakes suggest a very different seasonality from that of temperate climates. Here, we used 16S rRNA gene next-generation sequencing (NGS) to investigate seasonal changes in bacterioplankton communities of two tropical lakes, which differed in trophic status and mixing regime. Our findings revealed seasonally and depth-wise highly dynamic bacterioplankton communities. Differences in richness and structure appeared strongly related to the physicochemical characteristics of the water column, especially phosphate, pH and oxygen. Bacterioplankton communities were dominated by common taxonomic groups, such as Synechococcus and Actinobacteria acI, as well as rare and poorly characterized taxa such as 'Candidatus Methylacidiphilum' (Verrucomicrobia). Stratification and oxygen depletion during the rainy season promoted the occurrence of anoxygenic phototrophic and methanotrophic bacteria important for carbon and nutrient cycling. Differences in lake mixing regime were associated with seasonal beta diversity. Our study is the first attempt to use NGS for cataloging the diversity of bacterioplankton communities in Brazilian lakes and thus contributes to the ongoing worldwide endeavor to characterize freshwater lake bacterioplankton signatures.

Spatial and temporal distribution of gerrid (Heteroptera) and predation on microcrustaceans from a tropical shallow lake.

Predator-prey interactions involving an aquatic insect and zooplanktonic prey of different sizes were investigated to quantify prey mortality exposed to predators. Laboratory experiments were undertaken with the young and adult gerrid Rheumatobates crassifemur to test predation and size selectivity on the cladocerans Daphnia gessneri, Ceriodaphnia richardi, and Bosmina tubicen. Population fluctuations and spatial distribution of the gerrid were also evaluated in a small and shallow Brazilian lake throughout 12 months in fortnightly samples. The insects were more abundant in the littoral (mean density 7.0 ± 1.2 ind.m-2) compared to the limnetic zone. The period with the highest densities was late January to June, in both zones. Predation by young instars on Daphnia and Ceriodaphnia was significant (mean ingestion rate of 1.3 ± 0.1 D. gessneri and 0.7 ± 0.1 C. richardi per predator per hour). Adult insect fed only the large-sized prey (mean ingestion rate of 1.0 ± 0.1 D. gessneri per predator per hour). Young gerrids have greater potential to prey on cladocerans than adults, and size selectivity occurred for both predators. Preference of adults by the larger prey is probably related to difficulties in manipulating smaller planktonic prey, such as Ceriodaphnia. Due to higher densities of insects in the littoral, higher predation on zooplankton in this zone is expected. This study does contribute to a better understanding of trophic interactions in tropical shallow lakes and is the first to investigate predation of a gerrid on cladocerans in laboratory experiments.

Benthic-pelagic coupling drives non-seasonal zooplankton blooms and restructures energy flows in shallow tropical lakes.

Zooplankton blooms are a frequent phenomenon in tropical systems. However, drivers of bloom formation and the contribution of emerging resting eggs are largely unexplored. We investigated the dynamics and the triggers of rotifer blooms in African soda‐lakes and assessed their impact on other trophic levels. A meta‐analysis of rotifer peak densities including abundances of up to 6 × 105 individuals L−1 demonstrated that rotifer bloom formation was uncoupled from the food environment and the seasonality of climatic conditions. A time series with weekly sampling intervals from Lake Nakuru (Kenya) revealed that intrinsic growth factors (food quality and the physicochemical environment) significantly affected rotifer population fluctuations, but were of minor importance for bloom formation. Instead, rotifer bloom formation was linked to sediment resuspension, a prerequisite for hatching of resting‐eggs. Population growth rates exceed pelagic birth rates and simulations of rotifer dynamics confirmed the quantitative importance of rotifer emergence from the sediment egg‐bank and signifying a decoupling of bloom formation from pelagic reproduction. Rotifer blooms led to a top‐down control of small‐sized algae and facilitated a switch to more grazing‐resistant, filamentous cyanobacteria. This shift in phytoplankton composition cascaded up the food chain and triggered the return of filter‐feeding flamingos. Calculations of consequent changes in the lake's energy budget and export of aquatic primary production to terrestrial ecosystems demonstrated the large potential impact of nonseasonal disturbances on the functioning of shallow tropical lakes.

Modeling common trends of zooplankton, atherinopsid, and barred splitfin time series in a shallow tropical lake

Abstract Dynamic factor analysis was used to discern underlying common trends and the effect of physicochemical variables on time series of zooplankton, fish density, and biomass of barred splitfin (Chapalichthys encaustus) and atherinopsids (Chirostoma spp.) from Lake Chapala, Mexico. Strongly coherent trends were identified for the zooplankton and atherinopsid time series. Weakly coherent trends were detected for the barred splitfin time series.

Detecting causation on Zooplankton, atherinopsid, and barred splitfin time-series in a shallow tropical lake

Abstract We used Multispatial Convergent Cross Mapping analysis to detect causality on monthly differences of zooplankton volume and fish density and biomass time-series of atherinopsids (Chirostoma species) and barred splitfin (Chapalichthys encaustus) from Lake Chapala, Mexico. The dynamics of monthly differences of zooplankton volume were causally influenced by monthly differences in pH. The dynamics of the monthly differences of atherinopsid and barred splitfin density, and atherinopsid biomass, were not causally influenced by monthly differences of any of the measured physicochemical variables. The dynamics of the monthly differences of the barred splitfin biomass were due to monthly differences in water temperature and alkalinity. The dynamics of monthly differences of zooplankton volume did not show any significant causal forcing on the dynamics of monthly differences of density and biomass of atherinopsid and barred splitfin density. The dynamics of monthly differences of atherinopsids showed sign...

Response of metazoan zooplankton communities to ecological restoration in a tropical shallow lake

The metazoan zooplankton communities were dominated by small cladocerans and rotifers,often lack of large-sized zooplankton in tropical lakes and the controlling factors are not clear. Thus it has been questioned if eutrophic lakes can be restored by reducing fish,increasing large-sized metazoan zooplankton,and the top-down control on phytoplankton in the tropics. South Lake from Jinan University,Guangzhou,is a tropic eutrophic shallow lake. The lake was restored via fish removal and plantation of submerged macrophytes in order to improve water quality. We monitored the water quality,metazoan zooplankton communities and fish before and after restoration in order to study the response of metazoan zooplankton communities to the restoration. The results showed that total nitrogen,total phosphorus and chlorophyll-a concentrations decreased significantly and the transparency increased. The abundance and biomass of cladoceran increased,and high numbers of large-sized cladoceran Daphnia pulex were observed shortly after the restoration. The abundance and biomass of copepods had no significant changes. The density of rotifers decreased,but biomass increased. The sizes of metazoan zooplankton and biodiversity increased. The abundance of Daphnia pulex decreased quickly when fish biomass increased,and increased again when fish biomass was reduced later. Therefore,this study suggests that fish is a key factor controlling the population of large-sized zooplankton in tropical shallow lakes. As controlling fish to maintain high densities of large-sized zooplankton is difficult,it is unlikely to achieve a significant improvement in the restoration of tropical lakes using only biomanipulation.