Assessment of Temporary Streams: The Robustness of Metric and Multimetric Indices under Different Hydrological Conditions

Abstract

The generalization of ecological results from temporary streams needs the study of those ecosystems across a broad scale of running waters, covering the geographical ecological constraints involved (e.g., precipitation, temperature and geology). For the particular situation of Mediterranean streams in Southern Europe, high changes in water level, with unpredicting flood events, represent an important factor determining the structure and function of Mediterranean streams. This variability, inducing accentuated changes in the macroinvertebrate community, tends to influence the assessment methodologies. A set of metrics commonly used in Europe to assess organic degradation (Shannon-Wiener index, evenness, richness, BBI, IBE, BMWP , ASPT , DSFI, EPT, number of Trichoptera families, percentage of Gasteropoda, Oligochaeta and Diptera) and a multimetric index (IM9) developed to assess organic degradation in southern siliceous Portuguese basins were tested to evaluate quality at two contrasting sites (one unimpaired and another impaired by an identified point source of pollution). The multimetric index (IM9) composed by: ASPT (average score per taxon); GOLD (one minus percentage of Gasteropoda, Oligochaeta and Diptera); and TRICF (number of Trichoptera families), was the most suitable assessment methodology. IM9 presented a quite stable temporal pattern from February in late winter until June in early summer, even under the effect of episodic floods. A stepwise regression showed that most of tested metrics were significantly related to environmental variables (soluble reactive phosphorous, dissolved inorganic nitrogen and dissolved oxygen). Only richness, IBE and BMWP were not significantly influenced by environmental variables. Future research must be done covering the complete gradient of organic degradation, including the extension of multimetric assessment methodologies to temporary streams located in other regions under different geological and climatic conditions.

An integrative assessment of environmental degradation of Caveira abandoned mine area (Southern Portugal)

“…Another important watercourse in this site is the Grândola stream that like other small streams in the region is temporary, with a medium flow rate of 1.44 m 3 ·s −1 , ranging from 0 to 123 m 3 ·s −1 among driest and wettest periods, respectively (source: STREAMES). This situation may cause the fragmentation of channel during summer into a series of isolated pools (Morais et al, 2004).…”

An eco-hydrological assessment method for temporary rivers. The Celone and Salsola rivers case study (SE, Italy)

“…Temporary rivers are characterized by high variability of the flow which often causes a long period of extreme low flow and the reduction of the water surface into isolated pools along the river when the flow ceases (Argyroudi et al, 2009). This results in an intermittent flow in many rivers with a shift between lotic and lentic conditions during the year which influences biotic composition (Morais et al, 2004;Buffagni et al, 2009). As a consequence biological communities may be temporally poorer in taxa and diversity than perennial rivers (Munne`and Prat, 2011).…”

Diversity and distribution of Chironomidae (Insecta: Diptera) of protected areas in North Tunisia

“…The hydrological conditions, strongly variant among seasons with many rivers and streams (known in North Africa as wadi) having intermittent flows, cause a strong shift between lotic and lentic conditions through the year (Pinto, 1994;Morais et al, 2004). Up till now, North African streams or wadis have been scantily studied; particularly their ecological aspects are scarcely known (e.g.…”