Physical pollution: effects of gully erosion on benthic invertebrates in a tropical clear‐water stream

Abstract

1. Many tropical streams are situated in geologically old, weathered landscapes that are prone to erosion. Permanent or seasonally pulsing inputs of eroded material into the streams may have significant effects on benthos and habitats, even if chemical water quality remains unaltered. 2. This study presents data from the Cerrado Region, Brazil, where the semideciduous forests have been largely converted into agricultural areas with considerable erosion problems. In order to quantify impacts of erosion on the benthic community, a simple, inexpensive, standardized artificial substrate was exposed on the stream bed above and below the mouth of an erosion gully in two experiments at the beginning and at the end of the rainy season. 3. While the abundance and biomass of most of the biota in the reference sites did not change during the rainy season, it decreased significantly at the impact sites below the mouth of the erosion gully. It was the combination of rainfall-driven flood pulses and increased load of suspended particles from erosion which caused the decline of the benthic colonization in these streams rather than the hydrological disturbance alone. 4. Site-to-site comparisons revealed a highly significant reduction in density, biomass and taxon richness of the benthic invertebrates caused by siltation. All benthic insect taxa studied showed the same pattern, indicating a general impact of erosion on habitat quality and food sources. Semi-aquatic insects adapted to shifting habitat conditions, terrestrial food sources and aerial respiration were the most resistant invertebrate group. 5. Restoration schemes for the stream catchments are urgently needed to reduce local population extinctions due to impassable stream sections

Distribution, Composition, and Abiotic Environment of Silver Rasbora (Rasbora argyrotaenia Blkr) Fish in Upstream Areas of Barito Watershed, South Kalimantan

“…In dry season, the water is blackish brown-colored, and when rainy season comes, it is brownish yellow-colored. The phenomenon is triggered by occurrence of soil erosion along riparian areas, and then it drifts along to river (Wantzen, 2006). Naughton (1996) explains that turbidity comes about because of mud and precipitative particle, and it is like bounding factor in open water.…”

Automated identification of stream-channel geomorphic features from high‑resolution digital elevation models in West Tennessee watersheds

“…For example, locating sites of erosion is vital for enhancing water quality and preserving aquatic habitat, because eroded sediment transported by streams is a leading cause of habitat impairment in lotic ecosystems (Ribaudo, 1986;Wood and Armitage, 1997;Henley and others, 2000) and in downstream estuaries (Thrush and others, 2004). Erosion has been linked to reduced biomass and diversity of benthic invertebrates in downstream reaches (Wantzen, 2006) and has negatively affected amphibian diversity and abundance (Smiley and others, 2009). Identifying erosional features within stream-channel networks is also important in efforts to mitigate potential threats to economically valuable resources, such as agricultural land and urban infrastructure.…”

Biological traits and community patterns of Trichoptera at two Patagonian headwater streams affected by volcanic ash deposition

“…Additionally, high loads of suspended solids may increase turbidity, reducing stream primary production and interfering predator-prey relationships (e.g., optical orientation of dragonfly larvae). Moreover, allochtonous material, such as leaves and detritus may be covered by slow sand movement and become inaccessible for epibenthic detritivorous animals, consequently modifying the trophic structure (Wantzen 1998(Wantzen , 2006. Following a natural disturbance like an ashfall phenomenon, the recolonization process will depend on species showing selected traits that maximize their survival rates, arrival of new colonizers, and the presence of resources as well as appropriate habitat for organisms to establish.…”