Relative influence of direct and indirect environmental effects on sestonic chlorophyll-a concentration in Cerrado streams

Abstract

Aim: Chlorophyll-a may be directly influenced by local variables and/or indirectly by land use and cover, once landscape modifications change limnological variables, which in turn affect the primary productivity of aquatic environments, e.g., streams. Therefore, the objective of this study was to determine the relative importance of the local and landscape environmental components and assess the direct and indirect effects of these variables on sestonic chlorophyll-a concentration in 30 Cerrado streams (Santa Teresa River basin). Results All aquatic environments were oligotrophic during the study period. Only the local variables were important to explain chlorophyll-a variation (R2 = 0.27; P = 0.04). In addition, the path analysis showed that all variables used in the analysis influenced chlorophyll-a concentration more directly than indirectly. Conductivity was the most important variable to directly influence chlorophyll-a, followed by turbidity. Conclusion The large amount of remnant native vegetation in the basin indicates that the region studied is well preserved, which may explain the greater importance of local variables and the low effect of the landscape in explaining chlorophyll-a variation.

Relative importance of local and landscape variables on fish assemblages in streams of Brazilian savanna

“…Such complex linkages among landscape and local factors have been recently observed in Brazil for Southern grasslands (Dala‐Corte et al., ) and the Amazon (Leitão et al., ). Nonetheless, research conducted in the same region of Cerrado studied here did not find indirect influence of landscape variables on the concentration of plankton chlorophyll a (Borges et al., ). In this sense, the type, intensity and spatial configuration of land use, as well as geomorphological characteristics of watersheds, may determine how landscape variables will affect local instream habitat.…”

“…According to metacommunity theory, headwaters may have great importance of the local environment, but this may depend on environmental heterogeneity and the overall connectivity of the watersheds (Henriques-Silva et al, 2018). The greater importance of local variables found in this study may also be explained by the relatively good conservation status of the riparian vegetation around the studied streams (Borges et al, 2015;Borges et al, 2016).…”

“…RapidEye satellite images (referring to years 2011, 2012 and 2013) with a 5-m pixel resolution were used. Methods used to process the images and to obtain data of watershed area and percentage cover of native vegetation, pasture and bare soil are described in Borges et al (2015). The land cover classes considered as native vegetation were forested areas, native grassland and shrubs; pasture lands were those areas with planted grasses for raising livestock and bare soil areas had no vegetation cover (usually areas used for agriculture during the rainy season and abandoned during the dry season, as well as degraded pastures and eroded areas).…”

Metrics derived from fish assemblages as indicators of environmental degradation in Cerrado streams

“…These streams also have good physical integrity, with high environmental complexity, and hard substrate that maintains high species richness (Dala-Corte et al 2016). On the other hand, impacted streams have more unconsolidated substrate, which is evidence of the siltation process that is currently underway in the region (Borges et al 2015). These impacts, associated with riparian forest removal and loss of native vegetation surrounding streams, cause habitat homogeneity, favoring tolerant fish species that become abundant (Lorion and Kennedy 2009).…”

“…In the studied region, the native vegetation comprises 85% of the land cover (Borges et al 2016). Impacts resulting from removal of the riparian forest contribute to a loss of physical integrity in aquatic habitats, and are among the main antropogenic impacts in local streams (Borges et al 2015). Minimally disturbed streams have streambeds with stable substrate (composed of rocks and pebbles) and forested riparian zones and catchments.…”