Environmental factors – spatial and temporal variation of chironomid communities in oceanic island streams (Azores archipelago)

Abstract

-Freshwater systems on volcanic oceanic islands have very particular characteristics as a result of their geological origins, relatively small size, distances from source areas for colonizers, and distinct catchment morphology. These factors result in freshwater communities that are clearly distinct from continental systems. Chironomid spatial and temporal distribution was investigated in chironomid assemblages at 21 sites across the Azores Archipelago. Results using PERMANOVA, a permutational multivariate analysis of variance, indicated significant longitudinal differences in assemblages but none between islands or over time.Links between hydromorphological and physicochemical variables and the community assemblage were assessed using DISTLM, a linear model for distance-based multivariate analysis. The percentage of variation explained by hydromorphological factors (31%) was slightly higher than that explained by physicochemical (28%) factors. Descriptors of land use (forest area, scrub area, natural area of catchment) and stream slope were found to be the best environmental predictors of chironomid assemblages in Azores. Physicochemical variables such as temperature, pH, nitrite, iron and conductivity were the principal drivers of change in chironomid composition in stream locations. Headwater sites, characterized by lower temperature, acid to neutral pH values, low conductivity, nutrient and metal concentrations were dominated by Rheocricotopus atripes. Mid-section sites, located in agricultural areas were dominated by Thienemanniella clavicornis. Urbanized lower reaches were characterized by higher temperature, pH, conductivity and nutrient levels and were dominated by Cricotopus sp. These results give essential information that allows us to predict the response of different chironomid species to hydromorphological and physicochemical gradients across the archipelago's streams contributing providing the basis for the development of tools for the implementation of the Water Frame Directive.

Leaf litter decomposition in remote oceanic island streams is driven by microbes and depends on litter quality and environmental conditions

“…The higher reaches run mostly through forests while middle and lower reaches are affected by agriculture and urbanisation (Raposeiro et al, 2011;Gonc ßalves, Marques & Raposeiro, 2015). The higher reaches run mostly through forests while middle and lower reaches are affected by agriculture and urbanisation (Raposeiro et al, 2011;Gonc ßalves, Marques & Raposeiro, 2015).…”

“…laurel forests) are composed mostly of evergreen species and are dominated by species endemic to the Macaronesia as Laurus azorica (Lauraceae), Ilex azorica (Aquifoliaceae) and Morella faya (Myricaceae) (Elias & Dias, 2009). In the highlands, large areas of native forests have been invaded by the exotic Pittosporum undulatum (Pittosporaceae) or converted into commercial plantations of the conifer Cryptomeria japonica (Cupressaceae), while in the lowlands they have been converted to agricultural land, pastures and urbanisation (Raposeiro, Costa & Hughes, 2011).…”

Leaf litter decomposition on insular lentic systems: effects of macroinvertebrate presence, leaf species, and environmental conditions

“…Environmental characterization of the seven lakes is presented in Table 1; water variables (collected in the middle of the lake) for July were compiled from the data collected as part of the European Water Framework Directive-Regional Monitoring Programme (sampled between 2003 and 2012). The macroinvertebrate community in Azorean lakes is characterized by low taxa richness, which is typical of oceanic islands (Raposeiro et al, 2011(Raposeiro et al, , 2012(Raposeiro et al, , 2013. Chironomidae, Oligochaeta, Gastropoda, and Odonata are the dominant macroinvertebrate fauna in the study lakes (Gonçalves et al, 2009(Gonçalves et al, , 2013a.…”

Ecological assessment of a southeastern Brazil reservoir

“…0.7) through use of Spearman Rank Correlation. If only two variables were correlated, the one with higher average correlation coefficient was excluded from further analysis (Feld & Hering 2007, Hughes et al 2009, Raposeiro et al 2011. We then performed an RDA (Redundancy Analysis) on the selected environmental variables standardized by Statistica 8.0 (StatSoft Inc. 2007) and biological metrics transformed as described above.…”