Water Quality Assessment Based on Diatom Indices – Small Hilly Streams Case Study - Page 03

Results and Discussion

Qualitative analysis of benthic diatoms resulted with a total of 52 identified taxa, belonging to 25 genera. The greatest taxa richness in the assessed streams was recorded within genera Navicula Bory sp. (7), Nitzschia Hassall sp. (7) and Gomphonema Ehrenberg sp. (5). Besides these, Achnanthidium Kützing sp. was also diverse in the Bigar River.

Samples from the Jagnjilo River had the highest diversity of benthic diatoms – 29 taxa, of which 21 were recorded in the Jagnjilo upper stretch and 18 in the Jagnjilo lower stretch. In material from the Bigar River 19 taxa were identified. In the Tisnica River altogether 17 taxa were recorded – 13 taxa at the Tisnica lower stretch, and 15 taxa at the Tisnica upstream of the Crna Reka confluence. At the Crna Reka lower stretch 23 taxa were identified.

According to the frequency of the taxa, species Achnanthidium pyrenaicum (Hustedt) Kobayasi, Encyonema ventricosum (C. Agardh) Grunow, Gomphonema olivaceum (Horn) Brébisson, G. micropus Kützing, Meridion circulare (Greville) C. Agardh, Navicula cryptotenella Lange-Bertalot, N. tripunctata (O.F. Müller) Bory, and Nitzchia dissipata (Kützing) Grunow, stand out as permanent members of the diatom community, present in most of the sampling sites.

Quantitative analysis showed that Gomphonema olivaceum is dominant or subdominant at each locality, except the Bigar River, where Achnanthidium pyrenaicum and Encyonema ventricosum dominate. Also, different representatives of Achnanthidium genus are dominant constituents of the benthic diatom community at the Jagnjilo upper stretch and the Tisnica upstream of the Crna Reka confluence. At the Jagnjilo lower stretch the dominant species is Navicula cryptotenella, and at Crna Reka lower stretch N. lanceolata (C. Agardh) Ehrenberg, with Reimeria sinuata (Greg.) Kociolek et Stoermer and Rhoicosphenia abbreviata (C. Agardh) Lange-Bertalot.

Bigar, Jagnjilo, Tisnica and Crna Reka are rivers that belong to water body type six, described as small streams flowing beyond the Pannonian Plain, with a surface area of less than 100 km2, and with the larger fraction of flow in bottom substrates (cobbles, stones and large stones). According to calculated values of the diatom index IPS, water quality classes (Official Gazette of the Republic of Serbia 74/2011) for this group of watercourses are determined (Table 1). Values of IPS for Bigar, the Crna Reka lower stretch, the Tisnica lower stretch and the Tisnica upstream of the Crna Reka confluence denote I water class. Results for the Jagnjilo upper stretch and Jagnjilo lower stretch indicate II water class.

In order to illustrate the use of EPI-D and CEE (national legislative provides CEE boundary values for 1-5 water bodies type), water classification is performed for the group of Carpathian small watercourses at the 200-500m altitude, according to the Slovakian methodology (available at http://www.vuvh.sk/rsv2/index.php?option=com_content&view=article&id=59&Itemid=68&lang=en). Calculated values of EPI-D were in a range from 14.0 to 16.7, according to which all localities belong to I water class. The same result was attained using the CEE index, where values varied from 13.7 to 17.5 (Table 1).

The eutrophication level was also evaluated using the TDI index (ranges provided in Rakowska and Szczepocka, 2011). According to TDI values, the Bigar and Tisnica upstream of the Crna Reka confluence are oligo-mesotrophic, with relatively low nutrient concentrations, which indicates good ecological status, and corresponds to II water class. The Jagnjilo upper stretch is eutrophic, denoting poor ecological status (IV class). The Jagnjilo lower stretch, the Crna Reka lower stretch and the Tisnica lower stretch are eutrophic with very high nutrient concentration (bad ecological status, V class), in relation to calculated TDI values. Results are presented in Table 1.

 

Table 1: Water quality assessment for the rivers in the study area based on selected diatom indices – IPS, EPI-D, CEE and TDI
Tab01

 

IPS, EPI-D and CEE, as well as many indices which can be computed in OMNIDIA (IBD (Lenoir and Coste, 1996), DI-CH (Hürlimann and Niederhauser, 2002), IDP (Gómez and Licursi, 2001), IDAP (Prygiel et al., 1996), LOBO (Lobo et al., 2002), DESCY (Descy, 1979), IDSE/5 (Leclercq and Maquet, 1987) and GENRE (Rumeau and Coste, 1988)), were developed for estimation of general pollution. Attained results based on selected indices are expected, due to the fact that the rivers Bigar, Tisnica, Crna Reka and Jagnjilo are located in areas where small surfaces of agricultural land are mosaically distributed with a significant portion of semi-natural vegetation cover. This indicates a generally low intensity of anthropogenic pressure. Small agricultural lots are used for extensive agriculture and mainly located around the Jagnjilo River. The TDI index shows floristic changes as a response to enlarged nutrient concentrations, especially phosphates. According to the presented results, eutrophication level is considerable at most of the sampling sites. The assessed localities are positioned in the area which is slightly or not populated at all. The rivers Bigar, Tisnica, Crna Reka and Jagnjilo are small, surrounded by broad-lived forests.

These watercourses lie on limestone, with frequent changes in water level, some of them often dry out. For that reason, applicability of TDI for these types of watercourses should be further investigated on a larger number of sampling sites.

Benthic diatom community characteristics are widely used in estimation of ecological integrity of watercourses. Indices based on this group of organisms are a proven tool in determining the degradation level and the experience of many countries in this field is a valuable base for further work. Testing of IPS, CEE, EPI-D, TDI and other diatom indices applicability is needed to benefit their full potential in water quality assessment for different water types in Serbia.

 

Acknowledgements

We would like to thank "Avala Resources" Ltd, Belgrade for their support in field work and data processing. The preparation of this paper is supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia, Projects No. TR 37009 and No. III 43002.