Planktonic rotifers and cyclopoid copepods were studied in two reservoirs of different trophic states (eutrophic and oligo/mesoeutrophic) in the south of Brazil. During a year, monthly samplings were ...carried out in three stations in each reservoir. Species richness, frequency and abundance were used to find out useful and indicatives trends of water quality based on these organisms, reinforced by literature data. Species that showed higher differences between reservoirs were chosen. For Rotifera, richness, frequency and abundance of Brachionus were higher in the eutrophic reservoir, but Plationus patulus occurred only in the oligo/mesotrophic reservoir. For copepods, Tropocyclops prasinus dominated in the eutrophic reservoir, but Thermocyclops decipiens, T. minutus, T. inversus and Microcyclops anceps were dominants in the oligo/mesotrophic reservoir. In the canonical correspondence analysis, these species were indicators of the trophic state and were related with chlorophyll-a, total phytoplankton and total phosphorus. The use of these species can be efficient in the studied regions (subtropical/temperate), but comparing with other Brazilian reservoirs of tropical climate, the results could be different. Despite the dominance of T. decipiens over T.minutus, T. inversus has been widely used in Brazil as an indicator of eutrophic waters; in those cases of excessive eutrophication, other species, more rustic, commonly dominate. In the present study, Thermocyclops was dominant in the oligo/mesotrophic reservoir. The dominance of Brachionus for rotifers and Tropocyclops prasinus and Acanthocyclops robustus for copepods were indicative of eutrophic conditions.Original Abstract: Se analizaron los rotiferos y copepodos planctonicos ciclopoides colectados en dos embalses de diferentes estados troficos (eutroficos y oligo/mesoeutroficos) en el sur de Brasil. Durante un ano, se efectuaron muestreos mensuales, en tres estaciones en cada embalse. La riqueza de especies, frecuencia y abundancia, se utilizo para determinar tendencias utiles e indicativas de la calidad del agua sobre la base de estos organismos, complementando con datos de la literatura. Se escogieron aquellas especies que presentaron las mayores diferencias. Para rotiferos, la riqueza, frecuencia y abundancia de Brachionus fueron mas altas en el embalse eutrofico, Plationus patulus se detecto solo en el embalse oligo/mesotrofico. Para los copepodos, Tropocyclops prasinus domino en el embalse eutrofico, mientras que Thermocyclops decipiens, T. minutus, T.inversus y Microcyclops anceps dominaron en el embalse oligo/mesotrofico. En el analisis de correspondencia canonica, estas especies fueron indicadoras del estado trofico y se relacionaron con la clorofila-a, fitoplancton total y fosforo total. El uso de estas especies puede ser eficaz en las regiones estudiadas (subtro- pical/templada), pero comparado con otros embalses de clima tropical del Brasil, los resultados podrian ser diferentes. A pesar de la dominancia de T. decipiens por sobre T. minutus, T. inversus ha sido ampliamente utilizado como indicador de agua eutroficas, en aquellos casos de eutroficacion excesiva, otras especies, mas rusticas, dominan comunmente. En el presente estudio, Thermocyclops fue dominante en el embalse oligo/mesotrofico. La dominancia de Brachionus para los rotiferos, y Tropocyclops prasinus y Acanthocyclops robustus para los copepodos fueron indicativos de condiciones eutroficas.
Water level fluctuation by artificial drawdown is one management activity that has the potential to control macrophyte growth, but there is little knowledge of how this operational procedure affects ...other biotic components of the ecosystem. This study investigated zooplankton dynamics in response to artificial drawdown over a short timeframe (13 days) in a Brazilian reservoir, by examining the impact on zooplankton communities in two shallow lakes (Lake Pedra Branca-LPB, and Guaritá-LG) connected to a reservoir (Salto Grande) that undergo sudden and remarkable fluctuations in their water levels. Zooplankton communities were sampled in both lakes before (pre-drawdown), during (low water), and after (post-drawdown) the artificial drawdown procedure. In LPB, drawdown resulted in an increase in zooplankton density, and temporarily changed the community in association with an increase in water conductivity and presence of non-planktonic organisms during the low water phase. In LG, drawdown had no significant effect on zooplankton community between the phases before and during the drawdown event. The results from this study suggest that artificial drawdown over a short timeframe in reservoir systems do not negatively affect the overall density, richness, and diversity of zooplankton communities in marginal shallow lakes.
It is widely accepted that fish farms (FF) have important contribution to input of nutrients into water, however fundamental knowledge regarding the influence of land use and land cover (LULC) on the ...water quality of fish farms is still lacking. The aim of this study was to assess the linkages between the LULC types and the water quality parameters in FFs. Three specific objectives were set: (1) to characterize the current water quality standards in four FFs (FF1, FF2, FF3, FF4) installed in the Ilha Solteira reservoir; (2) to delineate and analyze the LULC changes in sub-basins of tributaries where FFs are installed; (3) to elucidate the interactions between LULC and water quality in FFs. Results indicated signs of eutrophication in FF2 in both the dry and wet seasons. The mainly LULC was decrease of pasture and increase of sugarcane crops were observed in the four FFs' sub-basins between 2005 and 2018. Sugarcane land uses showed a significant positive correlation with SO4, Mg and K (r > 0.95, p < 0.005). The most likely source of these highlighted parameters may come from mineral fertilization, decomposition of the plinth in sugarcane and the application of vinasse to irrigate and fertilize crops. Concentrations of SO4, Mg and K observed in this present study do not cause direct toxic effects to Nile tilapia in fish farms. However, indirect impacts to water quality should be expected due to enhance primary production and promotes water eutrophication, as observed in FF2. Based on our results, we suggest that the criteria “basin characteristics”, including future sugarcane expansions, should be adopted to gather information in identifying areas more suitable for aquaculture parks that the Brazilian government intends to install in the large reservoirs.
•We investigated the effects of LULC on FFs.•Pastureland to sugarcane field conversion reduced the water quality.•LULC should be analyzed to identifying areas suitable for aquaculture in reservoirs
The study of the structure and dynamics of cladoceran egg banks in South America began only 15 years ago and the amount of knowledge, in addition to being scarce, is widely spread over partially ...national journals, theses, and books, and thus partially unavailable. We conducted a review of the literature published for this region, focusing mainly on the methodological approaches that have been applied and describe the main findings already published. The different methodological approaches make data comparability difficult. However, a total of 77 egg morphotypes were identified in the published studies. Among the variety of methods used, we suggest to adopt as the standard procedure: 1) pre isolation of eggs from the sediments by the “Sugar Flotation Method;” 2) identification, enumeration, and sorting of egg morphotypes present in the sample; 3) individual hatching of each egg morphotype; 4) adult individual identification to the species level according to available keys; and 5) linking identified eggs to identified species’ adults. The absence of identification keys constitutes a challenge. Therefore, collaborative research with the aim of generating pictorial taxonomical support for Neotropical resting eggs are encouraged. We believe the adoption of the suggested protocol might facilitate this issue. An extremely low hatching success was reported for most studies and the factors triggering the break of dormancy in the resting eggs coming from permanent systems remain unknown. In conclusion, resting egg studies are a novel and promising field in South America, but with many challenges that need to be addressed.
The aim of this study is to present APOIA-Aquaculture, an indicator system for assessing Best Management Practices (BMPs) in tilapia cage farming. Two specific objectives were set: (1) to detail the ...construction and operation of APOIA-Aquaculture; and (2) to attest to its analytical feasibility for BMP assessment in six fish farms selected as contrasting ventures at the Furnas and the Ilha Solteira reservoirs, important production sites in Southeastern Brazil. The proposed APOIA-Aquaculture comprises 68 integrated indicators, grouped into a set of four managerial dimensions: Spatial Organization (22 indicators), Management and Nutrition (23), Water Quality (14), and Quality of Sediment (9). The indicators were devised as to express fish farm compliance to predefined environmental standards, selected legislation requirements, and BMP effectiveness. Results of farm assessments indicate common deficiencies in the indicators of the Spatial Organization dimension, such as those related to the lack of equipment for water quality monitoring, fish cage positioning, improper storage of feed and supplements, inadequate control of fish disease symptoms, lack of appropriate records of the use of therapeutic and prophylactic products, and conflicts related to multiple water uses. In the Management and Nutrition dimension, indicators stressed the absence of biometric checks, inadequate procedures for residue disposal, and deficient control and records of fish losses (escapes). Overall, interactions were observed among indicators of the Management and Nutrition dimension and signs of deterioration in Water and Sediment Quality, as a consequence of inadequate feeding practices. Based on our results, we demonstrate the efficacy of APOIA-Aquaculture as an analytical tool for assessment of BMPs in tilapia cage farming. Aggregate information from indicators facilitates the adoption of measures to promote specific local infrastructure and monitoring needs according to proposed BMPs, towards improving the sustainability of the fish farms.
•An assessment system for aquaculture best management practices is presented.•Management performances were assessed in fish cage farms with different typologies, in contrasting contexts of large hydroelectric reservoirs.•Specific deficiencies in performance indices are related to environmental impairment and implied management recommendations.•Improved management practices can be properly reported to farmers based on the integrated assessment of indicators.
The aim of this study was to assess the abundance and richness of microcrustacean, and water physical and chemical characteristics of a high-altitude pond in the Serra do Mar at State of Paraná. ...Water samples were collected quarterly between August 2015 and August 2016. Environmental conditions of pond were characterized by small pond size and depth, cold and well oxygenated water, and neutral or slightly acid pH. Mean total microcrustacean density was 945.0 ind m-3, whereas total taxon richness was 3.40. The most abundant species was Tropocyclops prasinus. The small size and the isolament of the pond, and the low temperatures were related to the low species richness and abundance. This study is unprecedented to the State of Paraná. Future studies attempt to understand the environmental conditions and distribution of microcrustaceans from high-altitude ponds.
We studied the interactions between microcrustaceans and phytoplankton in storage and run-of-river tropical cascade reservoirs in Brazil by performing comparisons on a spatial-temporal scale and ...non-parametric correlations. Samples of zooplankton and phytoplankton were obtained quarterly over a period of two years from four sites at each reservoir. Cladocerans, such as Daphniidae and Sididae in addition to adult copepods, increased in response to seasonal phytoplankton density peaks in the storage reservoir and also in the areas close to the dam zone of the run-of-river reservoir. The abundances of filter-feeding microcrustaceans and of Cryptophyceae, Chrysophyceae, Cyanophyceae, Chlorophyceae and total phytoplankton were positively correlated. Adult cyclopoids with raptorial feeding habits were particularly correlated with Bacillariophyceae, Chlamydophyceae, Cryptophyceae and Dinophyceae. As expected, fluctuations in the abundances of the phytoplankton classes in both reservoirs could be associated with the differing responses of the filter feeders and raptorial microcrustaceans, with differences observed among the taxonomic groups.
Drought is an important driver of change in aquatic ecosystems and generally acts as a filter to select biological traits capable of persisting under severe environmental circumstances. Drylands are ...highly vulnerable to climate change and increases in climate variability. Consequently, an increase in the processes of eutrophication, salinization, and habitat desiccation may be observed in response to the loss of the hydrological connectivity. The International Network on Limnology of Drylands (INLD) was created with the overall goal of understanding the functioning and conservation status of aquatic ecosystems in drylands globally. INLD was made official in 2016 through the International Society of Limnology. Its objectives are to (1) assess the current state of biological diversity in dryland aquatic ecosystems, (2) evaluate the multiple environmental stressors acting in drylands, and (3) develop models to predict effects of global change on drylands. This special issue, Limnology of Drylands, consists of 10 manuscripts focused on the effects of environmental pressures, including global warming, on the biodiversity and distribution of aquatic communities in drylands.
To contribute to the knowledge of lotic zooplankton from dammed and free stretches, we tested the hypothesis that the ecological attributes are different between these environments, which are ...subjected to several effects caused by different hydrological conditions. The study was carried out in the low Iguacu river, a large hydrographic basin in the south of Brasil. Two samplings were performed, one in the dry period (April/04) and the other in the atypical rainy period (July/04), in five stations downstream a large reservoir, and other 12 stations in four tributaries representing the upper, intermediate and low regions of each river. The observations suggest a clear spatial distribution of zooplankton in lotic stretches subjected or not to damming, mainly due to the effects of physical, chemical and biological variables. Furthermore, the atypical rainfall promoted alterations in community structure when compared to the dry period.
Temporary aquatic environments are dependent on the rainfall distribution and form after extended periods of drought. The occurrence of groups of the cladoceran Moina micrura Kurz, 1874 was recorded ...in a temporary pool studied is located in the municipality of Monte Alegre de Sergipe, Sergipe State, Brazil. The mean abundance for each group was of 2,670 ± 2,089 individuals. Compared to other studies, we found a higher numbers of males (26 ± 6 individuals) and of ephippial females (30 ± 20 individuals). Therefore, the presence of males and ephippial females points to reproductive function of these groups, due to the dryness processes of these small pools.
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