The influence of environmental variables on bdelloid rotifers of the genus Rotaria in Thailand

This research investigates the influence of environmental parameters that are known to affect bdelloid rotifer species richness and composition in temperate zones on the genus Rotaria in tropical zone. Our study analysed species richness and composition of the genus Rotaria from 390 samples collected from several types of aquatic habitats in Thailand. Coordinates, elevation, limnological parameters such as water temperature, conductivity, total dissolved solids, salinity, dissolved oxygen and pH were measured. A total of nine species was recorded. Of these, one species, Rotaria macrura (Ehrenberg, 1832), was a new record for Thailand and new to the oriental region, and was a yet undescribed species, Rotaria sp. The species diversity of this genus increased from eight to 10 species. The presence or absence of the genus Rotaria was significantly influenced by dissolved oxygen and habitat type. For the samples where the genus occurred, species richness was not affected by any of the limnological or bioclimatic variables. Differences in species composition were affected only by habitat type. The results support former suggestions that common abiotic parameters do not seem to strongly influence diversity in bdelloids, whereas major ecological differences between habitats influence bdelloid occurrence.

Impact of Changes in Land Use and Land Cover in the Contribution Basin of Doutor João Penido Water Supply Reservoir of Juiz de Fora, MG, Brazil

Changes in the land use and land cover in areas adjacent to water reservoirs directly affect the quality of this water. This research presents a study on the water quality in the basin of one of the most important public water supply reservoirs in the city of Juiz de Fora, Minas Gerais. The main objective of this study was to analyze the behavior of limnological parameters and the correlation with land use and land cover in the contribution basin of the Doutor João Penido reservoir (CBJPR). The methodology was based on the analysis of water quality parameters, related to water samples collected from 2012 to 2015. Six sampling points were chosen from different locations: spring, medium course, main tributaries of the reservoir and the reservoir catchment. The parameters analyzed were turbidity, total solids (TS), oxygen consumed (OC), dissolved oxygen (DO), electrical conductivity, total nitrogen (TN), total phosphorus (TP), E. Coli, temperature, pH and total dissolved solids (TDS). The Kendall’s tau test was used to analyze the correlations between the parameters of water quality, land use and land cover in the CBJPR. In general, measured parameters showed better results in spring and in reservoir catchment, showing a worse quality of the water along the tributaries and the dilution power of the reservoir. The correlations pointed to the need for protection and preservation of forests in strategic locations to ensure good water quality.

Análise de atributos limnológicos em reservatórios do semiárido nordestino

Este trabalho objetiva investigar os parâmetros limnológicos: condutividade, sólidos totais, turbidez, pH, e clorofila-A, de quatro reservatórios multiuso do semiárido nordestino, sendo estes: Barreiras, Bocaina, Estreito e Piaus. Durante os anos de 2018 a 2019, tais reservatório sofreram impactos decorrentes da seca resultando em volumes inferiores a 30% da capacidade total desses reservatórios. Ao longo do período estudado, foram comparados valores obtidos in situ aos valores estabelecidos na resolução CONAMA n° 357/2005 para águas doces de classe II. A correlação linear foi aplicada para verificar as relações entre os parâmetros estudados e fatores naturais como temperatura média e precipitação. A caracterização climática, volumétrica e a ocorrência de seca, foram fatores importantes na discussão dos atributos limnológicos. Os resultados demostram que a ocorrência da seca tem relação com a redução dos volumes dos reservatórios, impactando negativamente na qualidade da água. Os sólidos em suspensão na água foram apontados como determinantes na variação de outros parâmetros, principalmente, da turbidez, da condutividade e do pH. A clorofila-A, variável de grande importância para a qualidade da água, apresentou correlação significativa positiva com precipitação e temperatura. Quanto os valores determinados pelo CONAMA, observou-se que o pH, sólidos totais, e clorofila-A encontram-se com valores superiores ao que é recomendado. A turbidez foi o único parâmetro que se enquadrou dentro do limite de aceitabilidade desta resolução. Os reservatórios Barreiras e Estreito apresentaram os piores valores médios para os parâmetros analisados. Analysis of limnological attributes in northeastern semi-arid reservoirs A B S T R A C TThis work investigates the limnological parameters: conductivity, total solids, turbidity, pH, and chlorophyll-A, from four multipurpose reservoirs in the northeastern semi-arid region of Brazil, namely: Barreiras, Bocaina, Estreito, and Piaus. During the years 2018 to 2019, these reservoirs suffered impacts due to droughts, resulting in volumes below 30% of the reservoirs' full capacity. Over the study period, values obtained in situ were compared to the values established in CONAMA resolution n° 357/2005 for class II freshwater. A linear correlation was applied to verify the relationships between the studied parameters and natural factors such as average temperature and precipitation. Climatic and volumetric characterization and the occurrence of drought were essential factors in the discussion of limnological attributes. The results show that droughts' occurrence is related to the reduction of reservoir volumes, negatively impacting water quality. Suspended solids in water were identified as determining the variation of other parameters, mainly turbidity, conductivity, and pH. Chlorophyll-A, a variable of great importance for water quality, showed a significant positive correlation with precipitation and temperature. Regarding the values determined by CONAMA, it was observed that the pH, total solids, and chlorophyll-A are higher than what is recommended. Turbidity was the only parameter that fell within the acceptability limit of this resolution. The Barreiras and Estreito reservoirs had the worst average values for the analyzed parameters.Keywords: water quality, CONAMA resolution n° 357/2005, drought, semi-arid.

Climate Change-Enhanced Cyanobacteria Domination in Lake Kinneret: A Retrospective Overview

The objective of this study is re-evaluation of the long-term record of limnological parameters in Lake Kinneret (1970–2018) and its drainage basin (1940–2018) aimed at an indication of the possible impact of climate change on water quality in Lake Kinneret. The methodological approach is based on indication of significant changes, of temperature increase, decline in rainfall, causing a reduction in river discharges, and lake water inflows. These climatological changes were accompanied by a reduction in nitrogen and a slight increase in phosphorus in the lake Epilimnion. The outcome was Epilimnetic Nitrogen deficiency and Phosphorus sufficiency, which enhanced domination replacement of Peridinium spp. by Cyanobacterial. We concluded sequel suggested climate change affected water quality deterioration in Lake Kinneret.

Phytoplankton succession of the Valaam archipelago lakes

The paper presents long-term material on the succession of phytoplankton collected on the lakes of the Valaam archipelago. The work was carried out on 11 lakes about Valaam archipelago, maintaining a natural mode of functioning. The lakes differed in the shape of the basin, depth, and features of the hydrochemical regime. Phytoplankton samples were taken once a month from May to October 1998–2019. In parallel with sampling, studies of the main limnological parameters were carried out. For lakes, a wide range of limnological parameters was revealed, such as transparency (0,3–4,6 m), active reaction of the environment (4,0–8,6), water color (27–296о according to Pt-Co scale), the content of total organic matter (10,8–63,8 mgO/dm3) and mineral phosphorus (0,001–0,646 mg/dm3). The phytoplankton structure varied significantly from lake to lake. In terms of abundance in most small lakes, cyanobacteria (in abundance) and rafidophyte (in biomass) algae dominated. Abundance of phytoplankton and biomass varied from 0.1 to 676.6 million cells/dm3 and from 0.1 to 105.2 mg/dm3, accordingly. In acidic polyhumous lakes, a simplification of the phytoplankton structure was noted. Representatives of the department of green algae (chlorococcal, volvox, ulotrix) dominated in these lakes throughout the season. In the seasonal dynamics of phytoplankton, one or two peaks were noted, which occurred in different years in different months, most often in June or September. It was shown that the variation in the structural parameters of the phytoplankton of lakes was determined by the specific catchment area, the depth of the reservoir, water transparency, color, electrical conductivity and nutrient content. To a large extent, the level of phytoplankton vegetation was also determined by the active reaction of the environment.

A Recent Taxonomic Study of the Fish from the Jinam River in Dima Hasao Biodiversity Hotspot Region of Assam (India)

The Jinam River habitats inventory revealed the presence of alluvial valley, cascades, riffle-pools, boulders, cobbles, and gravel as types of substrata. The limnological parameters portrayed average values of air and water temperature, turbidity, pH, dissolved oxygen, free carbon di-oxide, total alkalinity, and conductivity. This recent pioneering study on the fish of the Jinam River in the Dima Hasao District of Assam revealed the presence of 18 species belonging to 15 genera, five families, and three orders, which are reported for the first time through this paper. Worth highlighting is the abundance of Barilius bendelisis and Devario aequipinnatus, and the fewer numbers of Chanda nama, these warranting proper management and conservation of the fish for this river.