The objective of this study was to determine the effects of land-use patterns on both diatom community composition and water quality in tropical streams during the dry season. Benthic diatom collections and water quality sampling were done 4 times at 10 sites. A suite of environmental variables that varied with human land-use pattern was assessed to find the combination of variables that best explained patterns of diatom community composition. Canonical Correspondence Analysis (CCA) was used to determine environmental gradients along which species were distributed. A clear relationship between both benthic diatom communities and water quality and land-use pattern was observed with species richness, diversity and evenness, decreasing significantly from the agricultural and forest area to the urban area. Upstream, forested, agricultural sites, with good water quality (BOD5 = 0.9 to 2.6 mg·ℓ-1, DO = 6.8 to 8.2 mg·ℓ-1, phosphate = >2 to 4.7 µg·ℓ-1), were characterised by Thalassiosira weissflogii, Orthoseira dentroteres, Meridion anceps, Melosira varians, Diatoma spp, Diadesmis contenta, Eunotia papillo, E. bilunaris, E. intermedia, E. sudetica, Aulacoseira alpigena, A. ambigua, Cymbopleura naviculiformis and Stauroneis phoenicenteron. Urban sites, with medium to bad water quality (BOD5 = ~7 mg·ℓ-1, DO = ~7 mg·ℓ-1, phosphate = 12.6 to 83.1 µg·ℓ-1), were characterised by Diadesmis dissimilis, Frustulia rhomboids, Nitzschia scalaris, Nitzschia linearis, Cyclotella pseudostelligera Neidium ampliatum, N. affine, Encyonema silesiacum, E. neomesianum, Aulacoseira granulata, Navicula cryptotenella, Pinnularia legumen, P. gibba, P. divergens, Surirella linearis, S. robusta, and Achnanthidium minutissimum. Downstream urban sites, with very bad water quality (BOD5 = 19.5 to 26.2 mg·ℓ-1, DO = 0.4 to 1.9 mg·ℓ-1, phosphate = 142.5 to 248.7 µg·ℓ-1), were characterised by Gomphonema parvulum, G. accuminatum, Nitzschia palea, Nupela praecipua, Sellaphora pupula, Planotidium lanceolata, Fallacia monoculata and Pinnularia subcapitata. Diatom communities demonstrated potential for acting as indicators of changes in water quality due to changes in catchment land-use patterns.

Diatomáceas epipsâmicas têm implicações importantes para os processos em ecossistemas em ambientes lóticos. A maioria dos estudos sobre diatomáceas bentônicas concentra-se em diatomáceas epilíticas e muito pouco se sabe sobre diatomáceas epipsâmicas. O objetivo deste estudo foi avaliar comunidades de diatomáceas epipsâmicas nos córregos em relação às condições ambientais. Amostragens de diatomáceas epipsâmicas e de água para determinação da qualidade foram feitas em sete locais durante o verão do ano de 2008. As análises de regressão múltipla passo a passo e análise de correspondência canônica (CCA) foram usadas para determinar quais espécies ao longo dos gradientes ambientais variam de acordo com as variáveis físicas e químicas da água. Um total de 112 espécies de diatomáceas distribuídas entre 44 gêneros foi registrado. A altitude e o processo de eutrofização exerceram um papel significativo na estruturação das comunidades de diatomáceas na região de estudo.

Epipsammic diatoms have important implications for ecosystem processes in lotic environments. Most of the studies on benthic diatoms concentrate on epilithic diatoms and very little is known about epipsammic diatoms. The objective of this study was to assess epipsammic diatom communities in streams in relation to environmental conditions. Epipsammic diatoms and water quality sampling was done at 7 sites during summer base flow period (2008). Forward stepwise multiple regression and canonical correspondence analysis (CCA) were used to determine environmental gradients along which species vary with physical and chemical variables. A total of 112 diatom species distributed among 44 genera were recorded. Altitude and the process of eutrophication played a significant role in structuring diatom communities in the study region.

O aumento da influência antropogênica sobre ambientes lóticos como resultado da civilização conquistou o interesse público por causa de problemas relacionados com a consequente deterioração da qualidade da água. Vários métodos de biomonitoramento que fornecem uma medida direta da integridade ecológica usando a resposta da biota a alterações ambientais têm sido desenvolvidos para monitorar o estado ecológico de ecossistemas lóticos. Diatomáceas têm sido amplamente utilizadas e esta revisão tenta resumir os conceitos básicos associados ao monitoramento biológico utilizando diatomáceas bentônicas. Sempre que possível, exemplos de trabalhos realizados no Brasil serão utilizados.

Increasing anthropogenic influence on lotic environments as a result of civilisation has captured public interest because of the consequent problems associated with deterioration of water quality. Various biological monitoring methods that provide a direct measure of ecological integrity by using the response of biota to environmental changes have been developed to monitor the ecological status of lotic environments. Diatoms have been used extensively in this regard and this review attempts to summarise the basic concepts associated with biological monitoring using benthic diatoms. Where possible, examples from work carried out in Brazil are used.