Hypertrophic Reservoir Research Articles

Limnological dynamics of methane (CH4) and carbon dioxide (CO2) emissions from a tropical hypertrophic reservoir lake

ABSTRACT Methane (CH4) and carbon dioxide (CO2) emissions from tropical freshwater ecosystems have been understudied, particularly in terms of their interaction with limnological dynamics, their cycling, and the emission mechanisms of CH4. To help reduce that knowledge gap, this study addressed these processes in Valle de Bravo (VB), a tropical (19° 11. 65′ N) reservoir lake, that provides water supply to Mexico City metropolitan area. CH4 and CO2 concentrations and emissions from VB were measured during four field campaigns distributed along the annual limnological cycle of the reservoir. Dissolved CH4 concentration varied over four orders of magnitude (0.015–176.808 μmol L−1), and dissolved CO2 varied from below atmospheric saturation (15.062 μmol L−1) to 10 times that concentration (219.505 μmol L−1). CH4 fluxes ranged from 23.25 to 1220.80 μmol m−2 day−1, while CO2 fluxes ranged from −60.11 to 254.99 mmol m−2 day−1. Seasonal monitoring also allowed the assessment of the annual emissions as well as the greenhouse gas (GHG) storage during thermal stratification, which accounted for >58% of the total GHG annual emissions from VB. Overall, VB is a source of GHG, and its major contribution is the CH4 released during the autumn overturn.

It's a numbers game: inundative biological control of water hyacinth (Pontederia crassipes), using Megamelus scutellaris (Hemiptera: Delphacidae) yields success at a high elevation, hypertrophic reservoir in South Africa.

ABSTRACT Classical biological control of water hyacinth in South Africa has been constrained by cool winter temperatures that limit population growth of the biological control agents, and highly eutrophic waters which enhance plant growth. However, inundative releases of the control agent, Megamelus scutellaris (Hemiptera: Delphacidae), at the Hartbeespoort Dam, South Africa, suggest that water hyacinth can be managed successfully using biological control as a standalone intervention for the first time in the absence of herbicide operations, despite eutrophication and a temperate climate. Sentinel-2 satellite images were used to measure the reduction in water hyacinth cover from over 37% to less than 6% over two consecutive years since M. scutellaris was first released on the dam in 2018, while site surveys confirmed a corresponding increase in M. scutellaris population density from fewer than 500 insects/m2 in October 2019, to more than 6000 insects/m2 by March 2020. Inundative release strategies are recommended for the control of water hyacinth in South Africa at key stages of its invasion, particularly after winter, and flooding events.

Interaction of ciliate communities with cyanobacterial water bloom in a shallow, hypertrophic reservoir

The response of ciliate communities to cyanobacterial bloom was investigated in a shallow, hypertrophic reservoir in Slovakia, central Europe. Seasonal dynamics of ciliate communities corresponded negatively with course of water bloom formation. The highest numbers and abundances of ciliate species occurred during the spring season when cyanobacterial bloom was not fully developed, while there was an abrupt decrease in both numbers and abundances at the beginning of summer when water bloom culminated. Cyanobacterial blooming thus significantly lowered diversity and equitability of ciliate communities: many rare and sporadic species disappeared and few common taxa flourished and dominated. Nonetheless, these leading ciliates formed a functionally diverse assemblage whose members showed mostly positive contemporaneous and only rarely time-shifted interactions. There were fine filter feeders (Cinetochilum margaritaceum, Dexiotricha granulosa, Paramecium caudatum and Spirostomum teres) grazing heterotrophic bacteria and picocyanobacteria, omnivorous fine to coarse filter feeders (Frontonia leucas) as well as hunters (Coleps hirtus, Holophrya teres and Loxophyllum helus) looking for an individual prey. Also a comparatively rich, anaerobic coenosis comprising various bacterivorous armophoreans and plagiopyleans, developed at the bottom of the reservoir. Our study documents that ciliates form functionally diverse communities with potential to control cyanobacterial blooms in hypertrophic reservoirs.

The effect of phosphorus removal from sewage on the plankton community in a hypertrophic reservoir

When developing water quality improvement strategies for eutrophic lakes, questions may arise about the relative importance of point sources and nonpoint sources of phosphorus. For example, there is some skepticism regarding the effectiveness of partial reductions in phosphorus loading; because phosphorus concentrations are too high in hypertrophic lakes, in-lake phosphorus concentrations might still remain within typical range for eutrophic lakes even after the reduction of phosphorus loading. For this study, water quality and the phytoplankton and zooplankton communities were monitored in a hypertrophic reservoir (Lake Wangsong) before and after the reduction of phosphorus loading from a point source (a sewage treatment plant) by the installation of a chemical phosphorus-removal process. Before phosphorus removal, Lake Wangsong was classified as hypertrophic with a median phosphorus concentration of 0.232 mg L−1 and a median chlorophyll-a concentration of 112 mg L−1. The dominant phytoplankton were filamentous cyanobacteria for the most of the ice-free season. Following the installation of the advanced treatment process, phosphorus concentrations were reduced to 81 mg L−1, and the N/P atomic ratio increased from 42 to 102. Chlorophyll-a concentrations decreased to 42 μg L−1, and the duration of cyanobacterial dominance was confined to the summer season. Cyanobacteria in spring and autumn were replaced by diatoms and cryptomonads. Filamentous cyanobacteria in summer were replaced by colony-forming unicellular Microcystis spp. It was remarkable that zooplankton biomass increased despite the decrease in phytoplankton biomass, and especially cladoceran zooplankton which increased drastically. These responses to the reduction of point source P loading to Lake Wangsong imply that reducing the point source P loading can have a big impact even when nonpoint sources account for a large fraction of the total annual phosphorus loading. Our results also show that the phytoplankton community can shift to decreased cyanobacterial dominance and the zooplankton community can shift to higher cladoceran dominance, even when phosphorus concentrations remain within the typical range for eutrophic lakes following the reduction of phosphorus loading.

Using H2O2 treatments for the degradation of cyanobacteria and microcystins in a shallow hypertrophic reservoir.

Toxins produced by cyanobacteria in freshwater ecosystems constitute a serious health risk worldwide for humans that may use the affected water bodies for recreation, drinking water, and/or irrigation. Cyanotoxins have also been deemed responsible for loss of animal life in many places around the world. This paper explores the effect of H2O2 treatments on cyanobacteria and microcystins in natural samples from a hypertrophic reservoir in microcosm experiments. According to the results, cyanobacteria were more easily affected by H2O2 than by other phytoplanktonic groups. This was shown by the increase in the fractions of chlorophyll-a (a proxy for phytoplankton) and chlorophyll-b (a proxy for green algae) over total phytoplankton pigments and the decrease in the fraction of phycocyanin (a proxy for cyanobacteria) over total phytoplankton pigments. Thus, while an overall increase in phytoplankton occurred, a preferential decrease in cyanobacteria was observed with H2O2 treatments over a few hours. Moreover, significant degradation of total microcystins was observed under H2O2 treatments, while more microcystins were degraded when UV radiation was used in combination with H2O2. The combination of H2O2 and ultraviolet (UV) treatment in natural samples resulted in total microcystin concentrations that were below the World Health Organization limit for safe consumption of drinking water of 1μg/L. Although further investigation into the effects of H2O2 addition on ecosystem function must be performed, our results show that the application of H2O2 could be a promising method for the degradation of microcystins in reservoirs and the reduction of public health risks related to the occurrence of harmful algal blooms.

Interannual changes in the summer zooplankton in the lakes of the Khopyor River flood plain

By zooplankton indices, the lakes of the Khopyor River flood plain in the reserve area can be classified as eutrophic–hypertrophic reservoirs. In the years of intensive overflow of the Khopyor River, the trophic level of the flood plain lakes has been revealed to increase; the variety, numbers, biomass, and relative abundance of rotifers in the zooplankton increase. It is most evident in the coastal zone, where the total number and biomass of the zooplankton decreases. In the central parts of the lakes, the number and biomass of zooplankton increase, as does the proportion of crustaceans and the variety of rotifers. In the zooplankton of the central parts of the reservoirs with the longest term of coastal flooding after high water, the fraction of rotifers in the total number and the biomass of zooplankton communities increases. Simultaneously, the annually flooded lakes are characterized by maximum specific richness.

Impacts of fish on phosphorus budget dynamics of some SA reservoirs: evaluating prospects of ‘bottom up’ phosphorus reduction in eutrophic systems through fish removal (biomanipulation)

Data on fish standing stocks in 7 South African reservoirs were used to assess prospects of reducing in-lake amounts of total phosphorus (TP) through remedial biomanipulation – the removal of fish to deplete internal stocks of biomass-incorporated TP and especially to restrict enhancement of TP availability through internal ‘bottom up’ recycling by fish. Literature-derived conversion functions were used to estimate the quantity of TP stored in fish biomass, recycled by fish through excretion, and released from bottom sediments through carp and catfish bioturbation. This provided a quasi mass-balance assessment of these contributory influences of fish on TP budgets of reservoirs ranging from mesotrophy to hypertrophy in trophic status (annual mean TP levels of 0.04–0.51 mg/ℓ). Absolute contributions of fish were inevitably related directly to reservoir-specific fish stock abundance, both total-fish and coarse-fish biomass levels which increased with trophic status, generating parallel absolute increases in TP sinks and internal TP loading fluxes. On overall average, total fish stock sequestered 2.2 kg TP/ha in biomass, recycled 13.8 kg TP/ha/yr through excretion, and mobilized 8.0 kg TP/ha/yr through sediment bioturbation. Average values relative to external loadings in 5 reservoirs amounted to 3.8% (biomass), 22.8% (excretion) and 11.8% (bioturbation), totalling 38.4%. Most pertinently, the relative importance of fish in reservoir TP budgets declined progressively with rising trophic status, with corresponding averages less than half (1.4, 8.7 and 5.4%, total = 15.4%) in 3 hypertrophic reservoirs (> 0.10 mg TP/ℓ). While total fish eradication plausibly reduces average internal phosphorus by some 40% relative to external load, the corresponding average reduction in hypertrophic reservoirs in greatest need of nutrient reduction is far less (~ 15%). ‘Bottom-up’ bioremediation accordingly offers little help in the management of nutrient-enriched reservoirs, and is essentially futile where high external nutrient loading persists.Keywords: biomanipulation, biomass sinks, bioturbation, eutrophication management, excretion, fish, phosphorus, recycling, reservoir ecosystems

Influence of changeable hydro‐meteorological conditions on dissolved organic carbon and bacterioplankton abundance in a hypertrophic reservoir and downstream river

AbstractThe variability of dissolved organic carbon (DOC) and bacterioplankton abundance (BA) in a lowland humic reservoir and downstream river were studied in an attempt to find out whether meteorological and hydrological parameters influenced the studied factors during drier and wetter conditions. The study was carried out in two consecutive years (from June to October) that significantly differed in precipitation and hydrological parameters. Despite the observed consistently high values of DOC concentration in the studied waters (on average >20 mg l−1), DOC concentration range and dynamics differed significantly between the two compared periods; in the period of 20% lower accumulated precipitation, concentrations of DOC on all the analysed sites were 30% lower, on average. The observed hydrological changes caused by meteorological differences between the two studied periods significantly influenced DOC concentration, both in the dam and the downstream river. BA was much less variable and less dependent on meteorological factors; however, our study demonstrated that hydrological conditions exerted an important influence on DOC concentration, mostly in river. The other finding is the greater influence of hydrological conditions on BA in the reservoir than in the river, regardless of the period. No evident relations between DOC concentration and BA were observed. Water quality, together with hydrology, influences both DOC and BA changes. Copyright © 2015 John Wiley & Sons, Ltd.

Long‐term changes in the fish assemblage structure of a shallow eutrophic reservoir (Lake Hídvégi, Hungary), with special reference to the exotic Carassius gibelio

European reservoirs are considered to be well characterized from many aspects. However, the description of long‐term sequence of events in the fish fauna is restricted and mostly limited to deep, oligomictic reservoirs. Lake Hídvégi is a shallow hypertrophic reservoir (average depth = 1.14 m), which started to operate in 1985. The main function of this reservoir has been to retain nutrients carried by the River Zala in order to protect the water quality of Lake Balaton. The changes in the fish fauna of Lake Hídvégi was monitored in selected localities using standard method (electrofishing). Species composition and assemblage structure changed significantly during the study period, between 1986 and 2011. Following the inundation, the rapid expansion of gibel carp (Carassius gibelio BLOCH, 1782) occurred, but after a peak this tendency turned. Surprisingly, based on the among‐years variance of the relative abundances, most of the species were not affected seriously by the invasion. By the end of the studied period, the native generalist roach (Rutilus rutilus L. 1758) became the most abundant species, amounting to more than 50% of the stock. By analyzing functional guilds, we identified an increasing trend in omnivore abundance, in parallel with the disappearance of planktivores. Our results suggest that the fish assemblage structure can be considered as metastable, disturbance tolerant and is mostly composed of generalist cyprinid species still after 29 years of operation.

Food-web structure in the hypertrophic Rietvlei Dam based on stable isotope analysis: Specific and general implications for reservoir biomanipulation

Fish predation on zooplankton is the basic foundation for top-down biomanipulation of lacustrine ecosystems. To test this premise, we determined stable isotope (SI) values (δC and δN) of representative samples of major planktonic (phytoplankton, zooplankton), benthic (submerged macrophytes and associated epiphytes, benthic macro-invertebrates) and nektonic (fish) food-web components, collected from 3 to 7 shallow inshore locations (with additional plankton samples at 1 or 2 deep offshore sites) in Rietvlei Dam over a period of 30 months. The resulting δC values did not indicate significant consumption of zooplankton by fish, while the δN values for fish confirmed their wide trophic separation from zooplankton. Instead, SI values indicated that fish relied mostly on food resources of benthic origin (through direct consumption or piscivory). The SI signatures of individual fish species were consistent with their known feeding habits. The lack of trophic couplings between zooplankton and fish accords with previous gut content analyses of fish and analyses of zooplankton abundance and size structure in hypertrophic reservoirs. Marginal utilisation of zooplankton by indigenous reservoir fish is attributable to their native origin as riverine species unaccustomed to feeding on zooplankton. These findings indicate that top-down biomanipulation is unlikely to be effective as a management tool in eutrophic South African reservoirs. Primary producer components exhibited surprisingly wide and unsystematic temporal fluctuations in both δC and δN values; some potential contributory factors are considered. Changes in phytoplankton δC values were broadly tracked by zooplankton – their nominal consumers. Some questions arising from the study, and some apparently anomalous findings are identified and discussed. Keywords : δC, δN, trophic structure, plankton, benthos, fish, warm-water ecosystems, South Africa

Distributions of trace metals in sediment cores from a hypertrophic reservoir in northeast Brazil

Distributions of trace metals in sediment cores from a hypertrophic reservoir in northeast Brazil

Distributions of Trace Metals in Sediment Cores from a Hypertrophic Reservoir in Northeast Brazil

The distributions of Al, Cu, Co, Cr, Fe, Mn, Ni, Pb and Zn were measured in two sediment cores obtained from the Macela Reservoir in Northeast Brazil. Principal component analysis (PCA) clearly separated both the cores and the sections corresponding to different depths. The concentrations of Cu, Cr, Mn and Zn were highest in the upper sections (0-20 cm), and were significantly correlated with the total organic carbon (Corg) content. The concentrations of Co, Pb and Ni were highest in the lower sections (25-45 cm), and showed strong correlations with aluminum. Cu, Cr, Mn and Zn were derived from anthropogenic sources, while Co, Ni and Pb were of natural origin. Toxicity assessment based on the threshold effect level (TEL) and probable effect level (PEL) values listed in the Canadian Sediment Quality Guidelines (SQG) showed that Cu, Pb and Zn rarely cause any adverse effects, while Ni was likely to cause frequent effects in the biota of the reservoir. The toxicity of Cr was uncertain.

Rehabilitation and management of a moderately deep-stratifying reservoir by the use of nutrient reduction and food-web management

As expected from its short renewal time, the hypertrophic Lingese Reservoir responded rapidly but incompletely to external nutrient reduction in 1993. Although there was a sudden decline in lake phosphorus and chlorophyll concentrations, the ‘turbid regime’ revealed resistance in this weakly stratified reservoir of intermediate depth. Draining the reservoir in autumn 1995 provided an unprecedented opportunity for sediment treatment—the phosphorus-rich surface layer was inverted and covered with deeper nutrient-poor layers—and removal of the dense cyprinid fish stock which had not responded to sewage diversion, at least in the short term. Commencing with refilling in 1999, a new fish stock was built up from 2000 by only stocking predators (fingerlings of pike, pike-perch and larger specimens of rainbow-trout in the first years) in combination with catch restrictions. Concomitantly, with the appearance of daphnids in 1999, a ‘clear water regime’ was established and lake water phosphorus concentrations decreased at unchanged external loading. Reduced zooplanktivory as well as reduced fish-mediated phosphorus release from the sediments were driving mechanisms behind successful reduction of internal loading and achievement of a ‘clear water regime’. Hence, phosphorus concentrations were revealed to be a response variable not only to input management but also to food-web management. As the development of cyprinid dominance was prevented in the long-term, there is ample evidence that the fish community responded to the applied management measures as expected featuring successful food-web management. Overall, the biological structure was revealed to be of major importance for lake phosphorus availability and turbidity as in shallow lakes, without, however, the establishment of macrophyte dominance.

Morphological Plasticity of Dominant Species in Response to Nutrients Dynamics in Bidighinzu Reservoir of Sardinia, Italy

The aim of this study was to describe the effect of environmental factors on the variation in population structure of phytoplankton in a hypertrophic reservoir and to analyse the size variability of dominant species, and finally to try to find a linkage between environmental factors and phytoplankton size structure. Species composition and dynamics of phytoplankton were typical of highly trophic conditions and were frequently characterized by the dominance of cyanobacteria, Microcystis, Anabaena, Aphanizomenon. Some environmental parameters play an important role in determining the phytoplankton community succession and their size structure, favouring or limiting the growth of the different groups of the phytoplankton. The results indicate that overall nutrient concentrations in Bidighinzu Lake were not limiting the phytoplankton growth in general. On the contrary, concentrations of nutrient were always above the required levels for phytoplankton growth. The results show that phytoplankton community succession and their seasonal variability of size structure (consequently cell surface area, cell volume and surface area to volume ratio) were mostly influenced by the temperature and nutrients. However, these affecting factors (especially nutrients) on seasonal variability of size structure of common species in Lake Bidighinzu showed difference among the species.

Temporal changes of phytoplankton community at different depths of a shallow hypertrophic reservoir in relation to environmental variables

We characterized phytoplankton community succession at different depths of a shallow hypertrophic reservoir in relation to physical and chemical environmental variables. The phytoplankton community was sampled biweekly at three different water depths (surface, middle and bottom) in the reservoir from November 2002 to February 2004. A range of 18 environmental variables including temperature, electrical conductivity (EC), total phosphorus (TP) and total nitrogen (TN) were measured to assess their influence on phytoplankton community succession. As well, combined multivariate analyses with a cluster analysis and a nonmetric multidimensional scale (NMDS) were conducted. Microcystis aeruginosa was the dominant species in all seasons except spring. Thus, Cyanophyceae was a dominant taxonomic group. In spring, Bacillariophyceae dominated, followed by Cryptophyceae and Chlorophyceae. The succession was relatively delayed at the middle and bottom layers compared with at the surface layer. Abundance and species richness of phytoplankton were also higher in the surface layer than in the bottom layer. Cluster analysis classified the phytoplankton community into four clusters at each depth, and the changes were also well reflected in the NMDS ordination. Each cluster showed seasonal patterns characterized by indicator species, as well as environmental variables such as temperature, conductivity, and nutrients including N and P. Seasonal dynamics of the phytoplankton community was the strongest at the surface layer and weakest at the bottom layer. These depth-variable environmental variables are likely to be the key factors driving changes in the phytoplankton community composition.

Implications of seston settling on phosphorus dynamics in three reservoirs of contrasting trophic state

We performed a comparative study in three reservoirs based on field measurements and laboratory experiments determine the impact of seston sedimentation on phosphorus dynamics. While we found a strong relationship between the trophic state and the settling flux of dry material in the study reservoirs, an increase in the trophic state did not lead to an increase in the export ratio (fraction of the primary production lost by sinking). In laboratory experiments, the analysis of biotic and abiotic contributions to phosphate (PO 4 3- ) regeneration/uptake by the sinking particles showed that an increase in the trophic state led to a significant vertical segregation in the observed patterns. Settled matter collected in both upper and lower sediment traps exhibited similar temporal patterns in the oligotrophic reservoir (Quentar), while clear spatial differences occurred in the more eutrophic systems (Cubillas and Beznar) as result of the vertical distribution of PO 4 3- characterizing warm monomictic eutrophic systems during summer thermal stratification. Chemical analysis of the settling matter in the oligotrophic reservoir (Quentar) showed that the sinking particles became richer in phosphorus during sedimentation, especially in the organic P pools. In contrast, P content in settling matter decreased with depth in the hypertrophic reservoir (Beznar), especially the org-P at the thermocline. This indicates that the mineralization of settling organic matter is important for maintaining high concentration of PO 4 3- in the deeper layers. However, no significant vertical differences in P content in settled matter were detected during the whole study period.

Effects of limiting nutrients and N:P ratios on the phytoplankton growth in a shallow hypertrophic reservoir

Effects of limiting nutrients and N:P ratios on the phytoplankton growth in a shallow hypertrophic reservoir

Effects of limiting nutrients and N:P ratios on the phytoplankton growth in a shallow hypertrophic reservoir

Effects of limiting nutrients and N:P ratios on the phytoplankton growth in a shallow hypertrophic reservoir

The zooplankton community in a small, hypertrophic mediterranean reservoir (Foix reservoir, NE Spain)

A small hypertrophic reservoir (Foix Reservoir, Spain) was sampled from March 1997 to January 2000 to document the composition and spatial and temporal variability of the zooplankton assemblage. Twenty five species of Rotifera, 10 of Cladocera, and one species of copepod (Acanthocyclops robustus (Sars)) were collected. The most abundant rotifer species were Brachionus angularis (Gosse) and Polyarthra spp. Daphnia galeata Sars, Ceriodaphnia quadrangula (Muller), and Chydorus sphaericus (Muller) were the main cladocerans. For each species, brief information is given on ecology, distribution, and occurrence in Spain and in the Foix Reservoir. The zooplankton community of the Foix Reservoir was characterized by the abundance of heleoplanktonic species, which accounted for 50 % of the taxa. Remarkable changes over time in species’ composition and occurrence were found for Rotifera and Cladocera during the study period. A. robustus showed high density and biomass values throughout the sampling period. In the summer of 1999, copepods avoided deep layers, whereas some Rotifera (Polyarthra spp,, Filinia spp,, Brachionus angularis) and Chydorus sphaericus were found near the anoxic bottom. A rare rotifer in the Iberian Peninsula, Itura aurita aurita (Ehrenberg), was also found in lotic sections of the reservoir.

Physical and chemical features of a tropical hypertrophic reservoir permanently stratified

Physical and chemical parameters of Pao-Cachinche reservoir (Venezuela) were measured in four stations (S1-S4) during an eighteen months period from September 1997 to February 1999. The tributaries of this reservoir introduce high amounts of nutrients from domestic wastewaters and from poultry and pig farms located in the basin. Thermal stratification was well established throughout the study period. Mountainous topography protects the water surface from mechanical action of wind, preventing water mixing. Hypoxic/anoxic conditions prevailed from 6–7 m depth down to the bottom in the limnetic stations. A strong smell of H2S was detected below the 10 m level. The low water transparency (max. 1.5 m) may be mainly attributed to a high biogenic turbidity. Water salinity was low, as the maximum conductivity measured (260 μS cm−1) suggests. The water was alkaline in the upper layers during the day time (pH >8.0), due to the high phytoplanktonic productivity, whereas in deeper layers, where decomposition processes predominate, pH was acidic (close to 6.0). Orthophosphate concentrations were high, reaching maximal concentrations in the deeper part of the reservoir (greater than 800 μg l−1). Total phosphorus exceeded 1000 μg l−1 in the hypolimnion during the dry season. Ammonia was the dominant inorganic nitrogen species, and its values were greater than 4000 μg l−1 in the hypolimnetic layer during the dry season. Nitrates and nitrites were present in relatively low concentrations, except for the Paito stream entrance, where nitrate concentrations remained above 260 μg l−1. Pao–Cachinche reservoir can be considered hypertrophic, according to Salas & Martino’s criteria for tropical warm lakes, and could be classified as meromictic and warm monomictic, according to Lewis tropical lake types.