RESUMO
Background Iguaçu National Park (INP) is known worldwide due to Iguaçu Waterfalls, being considered a World Natural Heritage by UNESCO. The INP is one of the last large forested extensions of inland Brazil that provides protection to the Atlantic Forest, one of the world's biodiversity hotspots. However, its Natural Heritage status has been threatened by the construction and operation of the Baixo Iguaçu dam, agricultural and urban impacts on its boundaries and the increasing interest of the Brazilian government in re-opening of the "Colono road", an old illegal road that crossed the interior of the park. Indeed, since benthic macroinvertebrates have been widely used for the environmental assessment of streams, records and abundance of their taxa under different seasonal periods may provide an additional dataset for biomonitoring of hydrographic systems in the face of current anthropogenic impacts on the INP boundaries and other similar streams on forest edges. New information In this study, we improved the sampling design of benthic macroinvertebrates and provided seasonal records covering distinct precipitation/temperature periods between 2016 and 2017 of a stream on the eastern edge of the Iguaçu National Park, Brazil. The records total 2,840 individuals distributed in 88 different taxa. The most abundant taxa were the Diptera subfamilies, Chironominae (n = 1,487) and Tanypodinae (n = 256), besides the Heterelmis genus (n = 152, Elmidae; Coleoptera). Diptera was the richest order in number of families (n = 8), while Leptophlebiidae (Ephemeroptera) was the richest taxonomic family in number of genera (n = 11). Aegla (Crustacea) and the Insecta genera, Heterelmis, Hexacylloepus, Noelmis, Phylloicus and Thraulodes, were recorded through all samplings. Twenty-five genera of Ephemeroptera, Plecoptera, Trichoptera (EPT) and Odonata were recorded during intermediate precipitation/temperature periods. Twenty-one of them were recorded in May 2016, with five genera standing out in abundance (Hydrosmilodon, Anacroneuria, Argia, Coryphaeschna, Americabaetis) and four (Needhamella, Tikuna, Simothraulopsis, Neocordulia) in December 2016. Four general taxa were exclusive of the lower precipitation/temperature period (August 2016), standing out in abundance were the Oxystigma (Odonata) and Corydalus (Megaloptera) genera. In March 2017 (higher precipitation/temperature period), four exclusive taxa were recorded, amongst them, the Chimarra (Trichoptera) genus. Furthermore, seasonal records demonstrated higher occurrences and abundance of macroinvertebrates during the intermediate and lower precipitation/temperature periods, besides a varied taxa composition throughout the year, with the presence of both sensitive and tolerant groups to environmental impacts. Our findings suggest that the number and composition of the local-stream macrobenthic fauna were influenced by the seasonal climatic regime. These changes should be considered in the limnological monitoring developed on the hydrographic systems of INP eastern edges to improve the assessment of environmental quality under different local seasonal conditions.
RESUMO
Environmental differences occur between lentic and lotic communities' establishment, especially because of water time residence. Here we used a combination of field measurements and statistical analysis to evaluate the influent factors on the aquatic macroinvertebrates' composition and structure in 15 anthropogenic lakes from Alto Iguaçu's region. Macroinvertebrates were sampled from the marginal vegetation (with or without macrophytes) and sediment. Chemical parameters ranged among the anthropogenic lakes, mainly those which are connected to the Iguaçu River, beyond the presence or absence of macrophytes, interfering on the community's structure. Lake's morphometric data were measured in each lake and its relation to community was tested. The community structure was not related to the margin development index (Ds), macrophytes and altitude. Higher equitability was associated to the macrophytes presence in more than 30% of water surface and also where the riparian vegetation was more complex. Chironomids and oligochaetes densities were associated to lakes with the water surface completely covered by macrophytes and complex riparian vegetation. We observed a close association between productivity (phosphorous and nitrogen) and the community equitability (R = 0.3; p < 0.05) and Oligochaeta dominance (R = 0.32; p < 0.05), and not to Ostracoda's (R = 0.33; p > 0.05) and Chironomidae's (R = 0.34; p > 0.05) dominances, although we had not weighty difference among analyzed biological indexes. The obtained values from the BMWP' and EPT indexes resulted in acceptable, doubtful or critical water quality, what corroborates with the macroinvertebrate's structure of the composition and with the environmental variables observed in field.
Diferenças ambientais ocorrem entre o estabelecimento de comunidades de ambientes lênticos e lóticos, especialmente por causa do tempo de residência da água. Foi usada uma combinação de métricas de campo e análise estatística para avaliar os fatores influentes sobre a composição e estrutura de macroinvertebrados aquáticos em 15 lagos antropogênicos da região do Alto Iguaçu. Os macroinvertebrados foram amostrados da vegetação marginal (com ou sem macrófitas) e sedimento. Parâmetros químicos variaram entre os lagos antrópicos, principalmente aqueles conectados ao Rio Iguaçu, além da presença ou ausência das macrófitas, interferindo na estrutura da comunidade. Dados de morfometria de lagos foram mensurados e sua relação com a comunidade foi testada. A estrutura da comunidade não foi relacionada ao índice de desenvolvimento da margem (Ds), macrófitas e altitude. Maior equitabilidade foi associada à presença de macrófitas em mais de 30% da superfície da água e também onde a vegetação ripária foi mais complexa. Densidades de quironomídeos e oligoquetas foram associadas a lagos com a superfície completamente coberta por macrófitas e complexa vegetação ripária. Foi observada associação entre a produtividade (fósforo e nitrogênio) e a equitabilidade da comunidade (R = 0.3; p < 0.05) e dominância de Oligochaeta (R = 0.32; p < 0.05) e não para a dominância de Ostracoda (R = 0.33; p > 0,05) e Chironomidae (R = 0.34; p > 0.05), apesar de não haver diferença entre os índices biológicos analisados. Os valores obtidos através do Índice BMWP' e EPT/C resultaram em ambientes de qualidade aceitável, duvidosa ou crítica, o que corrobora com a estrutura da composição de invertebrados e com as características ambientais observadas em campo.