Regionalisation is key to establishing reference conditions for neotropical savanna streams

Abstract

Areas with minimal anthropogenic influences are frequently used as reference sites and represent the best ecological state available in a region. Streams in such conditions are necessary for evaluating the conservation status of aquatic ecosystems of a region and to monitor them, taking natural environmental variability into consideration. Therefore, the aim of the present study was to analyse whether hydrological units are reliable regional units for aggregating reference sites. To this end, reference sites were studied in three different landscape units of the same hydrological unit. The study tested the hypothesis that water quality, physical habitat structure and the composition and structure of macroinvertebrate assemblages will be more similar for sites in the same landscape unit than for sites located in different landscape units in the same hydrological unit. The study showed that taxonomic richness and composition of the macroinvertebrate assemblages were negatively affected by site slope and positively affected by the presence of leaf packs on the streambed. The three landscape units supported significantly different macroinvertebrate assemblages and indicator taxa. Therefore, a hydrological unit does not constitute a homogeneous entity in terms of environmental variables and biological composition if it incorporates high landscape heterogeneity. These results should improve and facilitate the selection of reference sites for biomonitoring programs and for managing tropical headwater streams.

Beta diversity of aquatic invertebrates increases along an altitudinal gradient in a Neotropical mountain

“…Sites were sampled in May 2017. At each stream (hereafter called stream sites), a 25 m long stretch subdivided into six equidistant transects was determined (Martins, Ligeiro, Hughes, Macedo & Callisto, ). Three substrate types were sampled in each stream: leaf litter, gravel (>2–64 mm diameter), and cobbles (>64–250 mm).…”

“…Water quality was characterized by measuring temperature, electrical conductivity, pH, turbidity, and dissolved oxygen concentration (APHA ). Physical habitat characteristics were measured based on the protocol developed by the US Environmental Protection Agency (Peck et al., ; USEPA, ) as adapted and validated for streams of the Brazilian Cerrado (Callisto, Hughes, Lopes & Castro, ) and mountaintop grasslands (Martins et al., ). All site variables were calculated according to Kaufmann, Levine, Robison, Seeliger and Peck ().…”

Efeitos ecológicos sobre a ictiofauna

“…Nos últimos anos, adaptações e novos índices foram desenvolvidos e aplicados em avaliação ecológica, conservação e manejo de ecossistemas em bacias hidrográficas (Klemm et al 2003, Prudente et al 2018. Gradativamente foram incorporados critérios estatísticos de seleção de métricas (Hering et al 2006, Stoddard et al 2008, definição de sítios de referência (Johnson 2005, Whittier et al 2007b, Herlihy et al 2008, Ligeiro et al 2013, Martins et al 2018, avaliação de métodos de ranqueamento por escores (Blocksom 2003), uso de desenho amostral probabilístico (Herlihy et al 2000 e correção de métricas para variações ambientais naturais (Chen et al 2014, Pereira et al 2016.…”

“…A variabilidade de sítios em condições de referência é avaliada considerando condições abióticas que incluem aspectos geológicos, geomorfológicos, climáticos, características químicas da água, aspectos hidromorfológicos e características da vegetação ripária (p. ex. Martins et al 2018). É importante que sítios de referência estejam no "melhor cenário" em uma dada região, onde a cobertura vegetal seja predominantemente natural e as alterações nos usos do solo devido a atividades humanas sejam mínimas.…”

Índices Multimétricos para Avaliação de Integridade Biótica

“…Nos últimos anos, adaptações e novos índices foram desenvolvidos e aplicados em avaliação ecológica, conservação e manejo de ecossistemas em bacias hidrográficas (Klemm et al 2003, Prudente et al 2018. Gradativamente foram incorporados critérios estatísticos de seleção de métricas (Hering et al 2006, Stoddard et al 2008, definição de sítios de referência (Johnson 2005, Whittier et al 2007b, Herlihy et al 2008, Ligeiro et al 2013, Martins et al 2018, avaliação de métodos de ranqueamento por escores (Blocksom 2003), uso de desenho amostral probabilístico (Herlihy et al 2000, Silva et al 2018 e correção de métricas para variações ambientais naturais (Chen et al 2014, Macedo et al 2016, Pereira et al 2016, Carvalho et al 2017.…”