Chironomidae assemblage structure in relation to organic enrichment of an aquatic environment

Abstract

Estrutura da Assembléia de Chironomidae em Relação ao Enriquecimento Orgânico de um Ambiente AquáticoRESUMO -A diversidade taxonômica da comunidade de Chironomidae em ambientes aquáticos poluídos e não-poluídos foi estudada na área de influência do Distrito Agroindustrial de Anápolis, Anápolis, GO, avaliando-se a distribuição lognormal como indicador da integridade biótica desses sistemas. Larvas de Chironomidae foram coletadas em três pontos a montante e jusante do lançamento do efluente da estação de tratamento de esgoto desse distrito industrial. O ajuste do modelo de distribuição foi realizado utilizando-se o modelo de regressão não-linear, adotando procedimento iterativo quasi-Newton. Foram amostrados 21.498 indivíduos de 24 gêneros de Chironomidae. Chironomus, Polypedilum, Rheotanytarsus e Thienemanniella foram os mais abundantes, visto que são geralmente considerados resistentes à poluição orgânica. A assembléia do ponto a montante do lançamento foi bem descrita pelo modelo de distribuição lognormal truncada. O grande aumento da abundância de alguns gêneros no primeiro ponto a jusante impossibilitou o ajuste da distribuição lognormal truncada. O segundo a jusante, no entanto, possibilitou bom ajuste, possivelmente devido à diminuição na abundância dos grupos dominantes. Esses dados corroboram a hipótese de que as assembléias de chironomideos em ambientes não alterados são bem descritas por uma distribuição lognormal, o que não pode ser observado em ambientes degradados. Desta forma, evidenciou-se que a poluição orgânica causa desestruturação das comunidades aquáticas desse sistema, com perda das espécies sensíveis e dominância das tolerantes a esse tipo de impacto. Além disso, fica evidente que a distribuição lognormal pode ser considerada uma valiosa abordagem para avaliação de impactos ambientais. PALAVRAS-CHAVE: Distúrbio ambiental, modelo lognormal, bioindicadorABSTRACT -In this study we determined the taxonomic diversity of larval Chironomidae upstream and downstream to discharges of the sewage treatment plant (STP) from Agro-industrial District of Anápolis, State of Goiás, Brazil. Additionally, we evaluated the use of the lognormal distribution as a measure of biotic integrity of this system. The Chironomidae communities were sampled in three sites, upstream and downstream of the discharge of the sewage treatment plant (STP). We fitted the truncate lognormal distribution based on a nonlinear regression of the datasets using least squares as loss function in an iterative quasi-Newton procedure. The total of 21,498 individuals were sampled, from 24 Chironomidae genera, Chironomus, Polypedilum, Rheotanytarsus e Thienemanniella,w ith 73.9%, 14.4%, 7.1% and 4.5%, respectively, of all analyzed community; they are generally considered resistant to organic pollution. The assemblage of the site upstream was described for a truncate lognormal distribution. The extreme increase in abundance of some genera in the first site downstream produced a distribution not fitted to lognormal. The second site downstream h...

Relationship between space distribution of the benthic macroinvertebrates community and trophic state in a Neotropical reservoir (Itupararanga, Brazil)

“…High densities of them followed by the decrease of the diversity of other taxa may be seen as an organic enrichment indicator to continental water bodies (Dornfeld et al 2006, Martins et al 2008). In the same way, some studies pointed out the Chironomus genera as one of the most resistant benthic organisms to organic pollution (Adriansens et al 2004, Simião-Ferreira et al 2009). B. sowerbyi was reported in impacted environments (Suriani et al 2007).…”

“…The high density from the group I species is generally correlated to the water eutrophication (Martins et al 2008, Simião-Ferreira et al 2009). Shostell & Williams (2007) analyzed the benthic macroinvertebrates community patterns in relation to the physical and chemical parameters in a shallow eutrophic reservoir (Lake Conway, AR, USA).…”

Spatial and temporal heterogeneity in a subtropical reservoir and their effects over the benthic macroinvertebrate community

“…Once that high temperatures and depths as also low turbulence are factors that diminish instead of to increasing the dissolved oxygen concentrations in the bottom, the observed pattern must be understood as a consequence of the eutrophication process (Rixen et al, 2010;Wildsmith et al, 2011). These data could be related to higher densities and the community composition dominated by tolerant taxa as L. hoffmeisteri and Chironomus calligraphus (Goeldi) in the riverine zone (Martins et al, 2008;Simião-Ferreira et al, 2009), resulting in high dominance values that were significantly different from that recorded in the other two zones. These results indicate that the dominance values could represent better the longitudinal pattern observed in the environment than diversity or richness.…”

The rainy season increases the abundance and richness of the aquatic insect community in a Neotropical reservoir

“…Regardless, it is important to note that the majority of the individuals collected belonged to the Chironomidae family. This result can be attributed to their ability to colonize, as most of the species of this family can tolerate low water-quality conditions, such as polluted environments (Simião-Ferreira et al, 2009), and low oxygen concentrations (Lee et al, 2006). Moreover, these insects live in high densities (Piedras et al, 2006), increasing their numerical abundance.…”