Environmental conditions, intermittency, bioindicators, seasonality, Cerrado- Amazon transition

Variations in environmental conditions over space and time can affect the structure of the Caddisfly community. Studies that aim to verify seasonal and spatial fluctuations, are able to indicate changes that occur in the environment such as changes in land use, due to variations in the structure of the community, with the substitution of species. The objective of our work was to evaluate the effect of temporal / seasonal and limnological variations on the immature community of Caddisfly along a longitudinal gradient. Our hypothesis is that both the community structure and the limnological variables are affected by environmental variations. This study was carried out in the Bacaba stream, located in the municipality of Nova Xavantina-MT, in a transition area between Cerrado and the Amazon Forest. Collections were carried out over five years (2011 to 2016), with quarterly collections. We collected it in three portions of the stream continuum (nascent, intermediate and mouth) in 100 m linear transections, collecting substrate samples from the margins. The Caddisfly community was affected by both longitudinal (spring, intermediate and mouth), temporal (2011 to 2016) and seasonality (drought and rain) variations. The abundance differed between all the collection points as well as between the dry and rainy periods. The wealth presented a difference between the source and the mouth, being also different between the periods of the year. The composition was also different between the years, with 2016 being the least rich and abundant. Both wealth and abundance showed a positive relationship with dissolved oxygen and a negative relationship with ammonia. The results of this study allowed us to conclude that the immature community of Caddisfly present in Cerrado stream is sensitive to changes in the environment, climate and chemical composition of the water, indicating that they are excellent bioindicators of water quality and can be used in environmental monitoring and water quality for human populations.