Academic journal article Estonian Journal of Ecology

Macroinvertebrates in Estonian Streams: The Effects of Habitat, Season, and Sampling Effort on Some Common Metrics of Biological quality/Elupaiga, Aastaaja Ja Proovimeetodi Moju Bioloogilise Kvaliteedi Kolmele Tavalisele Hindamistunnusele Suurselgrootute Jargi Eesti Vooluvetes

Academic journal article Estonian Journal of Ecology

Macroinvertebrates in Estonian Streams: The Effects of Habitat, Season, and Sampling Effort on Some Common Metrics of Biological quality/Elupaiga, Aastaaja Ja Proovimeetodi Moju Bioloogilise Kvaliteedi Kolmele Tavalisele Hindamistunnusele Suurselgrootute Jargi Eesti Vooluvetes

Article excerpt

INTRODUCTION

The Water Framework Directive (2002) established a framework for the European Community.s action in the field of water policy. The benthic macroinvertebrate fauna is considered a biological quality element required for typology and classification of the ecological status of surface waterbodies. According to the Directive, the obligatory typological factors for streams are ecoregion, altitude, latitude, longitude, size (based on the catchment area), and geology, to which several optional factors may be added (e.g. velocity and bottom substrate).

The effect of the catchment or the ecoregion on macroinvertebrate characteristics usually complements local habitat features (Feminella, 2000; Newall & Wells, 2000; Parsons et al., 2003; Weigel et al., 2003). Rabeni & Doisy (2000) found that subregionalization reduces unexplained variability

and can therefore be recommended for use. Presumably, a tiered classification based on both reach-level and larger-scale landscape features is needed to accurately predict the composition of the freshwater fauna (Hawkins et al., 2000).

As altitude in the wide sense is not a significant factor for macroinvertebrates in Estonia (most of the territory belongs to the lowest altitude class, < 200 m a.s.l.), we will not discuss its influence in detail.

Stream size has a high classification strength for habitat and water chemistry classifications (Waite et al., 2000). The highest species richness on stony bottom was observed for mid-order streams, while lower species richness was recorded for headwaters and for high-order streams (Minshall et al., 1985; Crunkilton & Duchrow, 1991; Grubaugh et al., 1996; Reyjol et al., 2003), or species richness was found to increase with increasing watershed size (Klemm et al., 2002; Heino et al., 2003). Furse (2000) reported significantly lower richness values for headwaters compared with larger streams, the mean sensitivity of their taxa being approximately similar.

The geological factor is seldom primary and exerts influence in combination with ecoregion, stream size, etc. (Feld, 2004; Moog et al., 2004). The effect of bedrock on macroinvertebrates usually depends on its alkalinity.

Significant variation in the macroinvertebrate community is attributable to local physical conditions (Rabeni, 2000; Dovciak & Perry, 2002). Likewise, the number of substrate types found in a reach is an important variable (Olsen & Friberg, 1999). Although the riffle habitat (having high velocity) is usually considered a standard biotope for biological quality studies, the margin habitat in slow-flowing streams (where riffles do not occur) proved a representative substrate for the entire macroinvertebrate diversity at a site (Turak et al., 1999; Newall & Wells, 2000; Linke & Norris, 2003). Sampling of submerged wood or plant roots has a far higher influence on the estimation of biological quality in slow-flowing than in fast-flowing reaches (Speth & Boettger, 1994; Rader & McArthur, 1995).

Although summer is a favourable time for many macroinvertebrate taxa (particularly phytophiles), several heterotopic insects (most Plecoptera, many Ephemeroptera and Trichoptera) leave waterbodies in this period or occur as unidentified forms (eggs, very young larvae). Hence spring and/or autumn are considered the most advantageous seasons to estimate biological quality (Johnson, 1999; Turak et al., 1999; Hewlett, 2000; Heino et al., 2003).

In Estonia the influence of none of the above factors, recommended by the Directive, on the estimation of stream quality has been sufficiently studied.

Recently, several macroinvertebrate projects for intercalibration of different geographical areas and assessment methods, such as AQEM and STAR, were executed in Europe (Hering et al., 2003; Furse et al., 2006). Consequently, a modern, acceptable sampling technique should (1) be standardized, (2) include a wide variety of taxa at the studied site, and (3) incorporate a measure of abundance. …

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