Water Quality Assessment Based on the Macroinvertebrate Fauna - the Pcinja River Case Study - page 02

 

Study Area

The Pcinja River is the left tributary of the Vardar  River and belongs to the Aegean Sea drainage basin. It originates from several streams on the western slopes of the Dukat Mountain which meet at the village of Radovnica, and flows into the Vardar River, in a section of the Vardar’s course located in the Taor Gorge, halfway between the cities of Skopje and Veles. The river’s length is 135 km, 100 km of which are in the Republic of Macedonia. Throughout its course in the territory of the Republic of Macedonia, the Pcinja River  is a recipient of water from 8 tributaries, the most significant of which are the Kumanovska River with 44 km and the Kriva River with a length of 85 km.

 

Material and Methods

A qualitative and quantitative analysis of macroinvertebrates from the Pcinja River was performed during the summer of 2009. The Macedonian and Serbian sector of the river was analysed. A total of eight locali­ties, seven on the river itself and one on the tributary, the Kumanovska River (Figure 1), were investigated: T1 - source region (1,100 m a.s.l.), T2 - the village  of Trgoviste (920 m a.s.l.), T3 – the border region between Serbia and Macedonia (420 m a.s.l), T4 - the village of Nagoricane (310 m a.s.l.), T5 - “Supli Kamen” (300 m a.s.l.), T6 - the mouth of the Kumanovska River into the Pcinja (275 m a.s.l.), T7 - downstream of the mouth of the Kumanovska River into the Pcinja (270 m a.s.l.), T8 – the mouth of the Pcinja River into the Vardar River (241 m a.s.l.). Sampling localities were determined upstream and downstream of the settlements, as well as upstream and downstream of the mouth of the tributaries.

Benthic fauna samples from different substrates were collected with a Surber sampler and hand-net with a mesh size of 500 μm, and in some cases (coarse sand and silt) with an Ekman grab, following the standard methodology for collecting bottom fauna (EN 28265:1994, EN 27828:1994, EN 9391:1995). Qualitative samples were taken with a hand net. For the purpose of preserving macrozoobenthos, 4% formaldehyde was used. Further processing of the material was conducted in the laboratory. Animals were flushed with tap water through a standard sieve (280 μm pore size). Material was divided into groups, for further determination. Identification was performed with the Olympus SZX9 binocular microscope, using the following keys: Merritt and Cummins (1984) and Williams and Feltmate (1992). The following indices based on macroinvertebrate fauna were used to assess the water status: BMWP, ASPT and EPT richness. The metrics were selected because they are among the most commonly applied biotic indices for rapid assessment (Armitage et al., 1983; Bode et al., 1997) and they are widely used in European assessment systems. In addition, the calculation of indices does not require identification on the species level, but on the family level or higher taxonomic group. The Ephemeroptera-Plecoptera-Trichoptera (EPT) taxa/family and ASPT indices were found to be a good tool for detecting the difference between sites that are under the influence of nutrient pollution and non-impacted sites. According to Sandin and Johnson (2000) the statistical power of EPT taxa/family and ASPT indices in the differentiation of non-polluted and polluted sites is >0.99 and >0.95, respectively.

Results

Macroinvertebrate community

During the investigation of the bottom fauna from the Pcinja River, 40 families from 13 animal groups were recorded (Table 1). Trichoptera (10), Ephemeroptera (6) and Diptera (5) were the most diverse groups with families. The other groups were found to be less diverse. Apart from this, cold stenothermic representatives of flatworms (Turbelaria) inhabited only the source region of the Pcinja River (T1).


 




The number of families decreased in the longitudinal direction (Table 1). The upper and middle part of the river was characterised by a higher taxa richness (16-22 families) in comparison with the lower stretch of the Pcinja River (T8, 13 families) and the Kumanovska River tributary (T6, 11 families).

The results presented in Figure 2 clearly show that EPT reach relatively high values (from 7 to 14 families) along the river course from the source region to the sampling point T7 - Iskrin Most. According to the classification given by Bode et al., (1997) such value of EPT indicates a healthy, natural or near natural water ecosystem. This general trend is disturbed in the sampling sites T2 and T6. Namely, as a result of the influence of wastewater from the town of Trgoviste, a decline of EPT family richness occurred (8 families), indicating water quality impairment. These results concur with an observation by (Wang and Kanehl, 2003) who found that the level of watershed urbanisation is negatively correlated with the number of EPT taxa. Concerning the mouth of Kumanovska River (T6), a low EPT value was detected (2 families).

Table 1: Diversity of macroinvertebrate families registered along the Pcinja River and from the mouth of the Kumanovska River