Macroinvertebrate community structure in a regulated river segment with different flow conditions

Abstract

Two types of modification of the hydrological system are present in the same regulated segment of the Lima River (NW Portugal): (a) a reduced and constant flow from hypolimnetic release; (b) an intense irregular flow (daily and seasonal). Using multivariate techniques it was possible to compare the effects of these two kinds of disturbance on the macroinvertebrate communities. The communities colonizing both sites exhibited a higher variation in composition and diversity when compared to undisturbed sites. However, such variability was even more evident in the first case, in spite of the stability of the environmental conditions. Such temporal replacement of species is linked to the dominance of tolerant taxa with short life cycles. In the regulated segment the poor water quality and the lack of litter input impacted mainly on the shredders group. This work shows the failure of the practice of releasing constant flows as an attempt to mitigate regulation impacts.

Diversity of Odonata (Insecta) in lotic systems from Serra da Bodoquena, Mato Grosso do Sul State, Brazil

“…The pattern of species richness found in our study is probably due to the physical characteristics of the studied rivers and the degree of surrounding landscape heterogeneity. Within some of the factors cited as influencing Odonata species richness (see Vannote et al 1980;Minshall 1984;Townsend 1989;Ward 1992;Clenaghan et al 1998;Jonsen & Taylor 2000;Puth & Wilson 2001;Cortes et al 2002;Wiens 2002), certainly the amount and diversity of microhabitat within a given stretch of the river seem to be important. The immature stages of many species of Odonata inhabit various types of aquatic environments, but in most cases, exhibit preferences for specific types of habitats and substrates (Carvalho 1999), moreover, most adults exhibit territorial behavior, while remaining near the streams from which they emerged.…”

Using oligochaeta assemblages as an indicator of environmental changes

“…The flow regulation and stratification patterns developed in reservoirs frequently impact the biota downstream in four ways (Cortes et al 2002): i) alteration of physical and chemical characteristics associated with the release of water and sediment derived from the hypolimnion, that affect life history and density of macroinvertebrates (Cortes et al 2002); ii) alteration of available food resources to aquatic biota, specially through changes in the particulate organic matter (McAllister et al 2001); iii) creation of unstable environment due to daily changes in water level, increasing invertebrate drift (Hansen and Closs 2007); and iv) reduction of water released downstream, which modify abundance and diversity of benthic fauna (Bunn and Arthington, 2002). These effects have been demonstrated in several regulated rivers, where alterations in discharge have caused changes in the structure of the aquatic community (Pardo et al, 1998;Rosin et al, 2009).…”

Factors Affecting Macroinvertebrate Richness and Diversity in Portuguese Streams: a Two‐Scale Analysis

“…At a stream reach scale, invertebrates have, in general, a clumped distribution, which is assumed to be related to the mosaic of interchanging conditions in substratum, flow conditions, depth and many others (TOWNSEND, 1989;CORTES et al, 2002). These conditions are likely to change at a scale of only a few metres or centimetres.…”

“…Benthic macroinvertebrates are an important component of the river biota. At a large scale, diversity of invertebrates along and among rivers is affected by factors such as longitudinal zonation of river abiotic conditions (VANNOTE et al, 1980;CLENAGHAN et al, 1998), channel width and catchment size (MALMQVIST and HOFFSTEN, 2000), discharge (CORTES et al, 2002), temperature and pH (TOWNSEND et al, 1983;CLARKE and SCRUTON, 1997).At a stream reach scale, invertebrates have, in general, a clumped distribution, which is assumed to be related to the mosaic of interchanging conditions in substratum, flow conditions, depth and many others (TOWNSEND, 1989;CORTES et al, 2002). These conditions are likely to change at a scale of only a few metres or centimetres.…”