Structure of macroinvertebrate communities in riffles of a Neotropical karst stream in the wet and dry seasons

Abstract

Aim: Our study evaluated the effects of physical and chemical variables and seasonality on diversity and structure of the macroinvertebrate fauna in riffles of a Neotropical chalk stream; Methods: Sampling was performed during the dry (September 2003) and rainy (March 2004) seasons, in five sites. Five samples were taken at each point with a Surber sampler. Physical and chemical variables were also evaluated; Results: Temperature, pH, orthophosphate and total nitrogen were very similar for both seasons, while riffle length, conductivity, alkalinity, ammonia, phosphorus and leaf litter had different values. The total number of organisms collected was 25114 belonging to at least 50 families. Insects dominated in the samples. The highest abundance was found for the dry period. Temporary stretches were sampled in rainy season in order to complement the faunal inventory; Conclusions: The environmental seasonality was an important factor for structuring the macroinvertebrate fauna, with a significant difference between the invertebrate compositions in the sampling periods. The results of this study demonstrate the influences of seasonality on the temporal variation of communities.

Soft-bodied benthic algae in pristine Brazilian streams: from acid to karst

“…Compared with pristine karst systems around the world, where EC is generally above 400 µS cm-1 (e.g. Righi-Cavallaro et al 2010;Vilenica et al 2017), it is noticeable, however, that even the EC values in streams connected to caves were not very high. The headwaters of PETeR's streams are located in the hills of Serra Geral de Goiás.…”

“…Cerrado pristine waters generally have a slightly acidic pH, with low electrical conductivity and low nutrient concentrations (Markewitz et al 2006;. However, some limestone outcrops with karst geology are also found in the region, generally belonging to the Brazilian sedimentary unit known as the Bambuí Group (Faquim et al 2017), promoting alkaline waters and higher electrical conductivity (Righi-Cavallaro et al 2010). Variation in these chemical variables (pH and electrical conductivity) can result in marked differences in algal community structure (Mutinová et al 2016).…”

Ecomorphology and diet reflect the spatial segregation between two Siluriformes species inhabiting a stream of the Bodoquena Plateau, in Central Brazil

“…However, it is important to note that the largest amount of plant material was consumed in the rainy season. The increased frequency of this item in the feeding of P. taenioptera during rainy season is probably a response to a reduction in density of aquatic insects, which are eventually washed away by fl oods, as ascertained by riGhi- Cavallaro et al (2010). Alternatively, plant material increases during the rainy season by the input of plant debris washed into the stream, increasing the availability of this resource and, at the same time, contributing to the increase of variability in the diet of this species during that season.…”

“…The highest consumption frequencies in the diet of P. taenioptera were, in decreasing order, the insect families Leptophlebiidae (Ephemeroptera), Elmidae (Coleoptera), Chironomidae (Diptera) and Hydropsychidae (Trichoptera). According to riGhi-Cavallaro et al (2010), these four families of insects are the most abundant in the community of insects found in the Salobrinha stream, even though chironomids suffer a drastic numerical drop during the rainy season. This reinforces P. taenioptera as an opportunist species, possibly feeding on the most common items available.…”

Checklist de Ephemeroptera do Estado de Mato Grosso do Sul, Brasil

“…Algumas pesquisas referentes à Baetidae foram desenvolvidas no Mato Grosso (Salles & Batista, 2004; Salles et al, 2004b), e sobre a ecologia e distribuição do grupo (Shimano et al, 2010(Shimano et al, , 2011 Silva et al (2008;2009; e no Planalto da Bodoquena, Righi-Cavallaro et al (2010b); Dalzochio et al (2011) e Escarpinati et al (2011. Com enfoque taxonômico, uma nota de distribuição geográfica de uma espécie de Ephemeroptera no estado de MS foi publicada por Righi-Cavallaro et al (2008) Perspectivas de pesquisa para o grupo nos próximos 10 anos.…”