Abstract
The objective of this work was to investigate the patterns of diversity and abundance of ciliates protozoa community in three tropical urban streams and verify which species can be considered bioindicators of water quality. In each stream, three regions (headwater, middle and mouth) were sampled in two years, in the rainy and dry seasons. The abiotic factors (dissolved oxygen, pH, temperature, turbidity, width, depth, flow and conductivity) and biotic factors (total coliforms, bacterioplankton, chlorophyll and flagellates) were analyzed using appropriate methods and ciliates were identified and counted through specialized literature. We identified 84 species distributed into 24 orders. Peniculida was the most representative order followed by Prorodontida. The RDA scores showed a spatial difference between streams. On the other hand, regarding the temporal variation, there was no separation of the sampled data. The Indval analysis showed ten species indicators, such as Coleps hirtus, Euplotes moebiusi and Tintinidium pusillum. The Cluster analysis per stream versus period showed a greater distinction of the streams in the dry season. On the other hand, a low similarity was observed between sections within the same stream. In summary, the results indicated that the ciliates can be used as important tools as bioindicators in lotic environments affected by different degrees of pollution, due to the fact that they have short life cycle, allowing the detection of impacts on a small time scale, as well as by having direct answers to environmental changes and high sensitivity to contaminants.
Highlights
The demand for freshwater has grown ominously worldwide, but the degradation of its quality has further reduced its availability (Kuhl et al, 2010)
This study aims to investigate the patterns of diversity and abundance of the ciliate community and the factors involved in its structuring in three tropical urban streams, as well as to determine which species can be considered bioindicators of water quality
The Redundancy Analysis (RDA) analysis showed that the intervenient factors together with the most abundant ciliate species accounted for 40% of the data variability for the three streams in the rainy and dry periods (Figure 2)
Summary
The demand for freshwater has grown ominously worldwide, but the degradation of its quality has further reduced its availability (Kuhl et al, 2010). Rural and urban watersheds suffer from undue human activities, which alter the characteristics, the balance and the dynamics of natural resources making it difficult the supply of good quality water. Along with these changes, the increase in discharge of pollutant loads into water systems and urbanization usually results in the interruption or limitation of the use of these resources given the impacts on the quality of these ecosystems (Madoni, 2005). Urban streams are usually subjected to degradation from high population density, with increased waterproofing, such as sidewalks, asphalt in street, avenues and roads To monitor these impacts, both physical and chemical factors as the biotic variables have been used considering that they respond to environmental changes and the effects of pollution (Walsh et al, 2005). The integrated assessment of these factors allows us to evaluate the replenishment ability and sustainable use of resources, providing a systematic and integrated perception of environmental reality
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