Defining quantitative stream disturbance gradients and the additive role of habitat variation to explain macroinvertebrate taxa richness
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2013-02
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Resumo
Most studies dealing with the use of ecological indicators and other applied ecological research rely on
some definition or concept of what constitutes least-, intermediate- and most-disturbed condition. Currently,
most rigorous methodologies designed to define those conditions are suited to large spatial extents
(nations, ecoregions) and many sites (hundreds to thousands). The objective of this study was to describe
a methodology to quantitatively define a disturbance gradient for 40 sites in each of two small southeastern
Brazil river basins. The assessment of anthropogenic disturbance experienced by each site was
based solely on measurements strictly related to the intensity and extent of anthropogenic pressures. We
calculated two indices: one concerned site-scale pressures and the other catchment-scale pressures. We
combined those two indices into a single integrated disturbance index (IDI) because disturbances operating
at both scales affect stream biota. The local- and catchment-scale disturbance indices were weakly
correlated in the two basins (r = 0.21 and 0.35) and both significantly (p < 0.05) reduced site EPT (insect
orders Ephemeroptera, Plecoptera, Trichoptera) richness. The IDI also performed well in explaining EPT
richness in the basin that presented the stronger disturbance gradient (R2 = 0.39, p < 0.001). Natural habitat
variability was assessed as a second source of variation in EPT richness. Stream size and microhabitats
were the key habitat characteristics not related to disturbances that enhanced the explanation of EPT
richness over that attributed to the IDI. In both basins the IDI plus habitat metrics together explained
around 50% of EPT richness variation. In the basin with the weaker disturbance gradient, natural habitat
explained more variation in EPT richness than did the IDI, a result that has implications for biomonitoring
studies.We conclude that quantitativelydefineddisturbance gradients offer a reliable andcomprehensive
characterization of anthropogenic pressure that integrates data from different spatial scales.
Descrição
v. 25, p. 45-57, fev. 2013.
Palavras-chave
Reference condition approach, Local disturbances, Catchment disturbances, Disturbance indices, Stream habitats, EPT assemblages
Citação
LIGEIRO, Raphael; HUGHES, Robert M.; KAUFMANN, Philip R.; MACEDO, Diego R.; FIRMIANO, Kele R.; FERREIRA, Wander R.; OLIVEIRA, Déborah; MELO, Adriano S.; CALLISTO, Marcos. Defining quantitative stream disturbance gradients and the additive role of habitat variation to explain macroinvertebrate taxa richness. Ecological Indicators, v. 25, p. 45-57, Feb. 2013. Disponível em: <http://www.sciencedirect.com/science/article/pii/S1470160X12003214>.