The Effect of Small River Fragmentation on the Biodiversity and Structure of Macroinvertebrate Communities - Page 03

The group with the highest diversity from the 2011-2013 research was Trichoptera. This group was represented with a total of nineteen taxa. The second most diverse insect group is Ephemeroptera with 12 taxa determined, followed by Diptera (10), Plecoptera (9) and Coleoptera (6). Mollusks are represented with 5 taxa, Crustacea with 3, while Odonata and hirudinea had two representatives. Lepidoptera, Turbellaria and Nematoda are represented with a single taxon.

According to the 1973 data, the group with the highest diversity was Ephemeroptera with 18 taxa, with Trichoptera as the second most diverse with a total of 17 taxa. Diptera, Coleoptera and Plecoptera had 9 representative taxa, Oligochaeta were represented with 4, and mollusks and crustaceans with 3. Two taxa were recorded from Hirudinea and Hydracarina groups respectively, and the samples had noted one representative of Hydrozoa, Collembola and Odonata (Table 3).

 

Tab03

 

The presence of various macroinvertebrate groups, and their species and genera varies between sampling points, depending of the environmental factors and the adaptability of organisms to the potential habitat alteration. Species recorded at every sampling point and present along the entire river course of the Grošnica River are: Gammarus balcanicus (Crustacea), Baetis rhodani (Ephemeroptera), Elmis aenea (Coleoptera) and Hydropsyche fulvipes (Trichoptera).

We calculated the Sorensen similarity index (Sörensen, 1948) for the 1973 data and 2011-2013 data (Table 4), as well as similarity percentages between the most diverse groups. Similarity was calculated for 7 sampling points, 5 of which were located in the upper part of the flow and two were in the lower part.

Based on the results acquired from calculating the total similarity of the macrozoobenthic communities, the highest similarity of 40% was between the fourth sampling point from our research and the fifth sampling point from the 1973 research, while the lowest similarity was noted between the first (2011-2013) and seventh (1973) sampling point. Overall similarity between the communities was 26,99%.

Total similarity of Ephemeroptera taxa between the two studies was 46,66%, with 7 species in common.

Similarity percent differs depending on the location from 25% to 58,88%. Common species for both studies are: Ecdyonurus venosus, Rhithrogena semicolorata, Paraleptophlebia submarginata, Baetis rhodani, Caenis macrura, Ephemerella ignita and Ephemera danica.

A total of 16 representatives of Plecoptera were determined for both studies, with two common species; Perla burmeisteriana and Leuctra hippopus. Overall similarity was 22,22%. Common species appear from sampling point 1 to 5. The highest similarity was recorded from point 3 to point 5 and it is 50%. The least similar samples were from point 1 and 5 (2011-13) and 2 (1973). Samples from the lower part of the river had no common species.

Diptera were represented by total of 15 taxa in both studies, with Simulium sp., Tipula sp. and Chironomidae as common. The highest similarity was between the first (2011-13) and the third point (1973), and the lowest between the first and the fifth sampling point. Overall Diptera similarity between the two studies was 31,57%.

There were three crustacean species determined, all three common for both studies. They were Asellus aquaticus, Gammarus balcanicus and Austropotamobius torrentium. Gammarus was present along the entire course of the river in both of the studies, while the presence of Asellus and stone crayfish differed depending on the sampling points.

 

Tab04 

 

Discussion and Conclusion

According to Jackson (2003), rivers and streams as long, linear ecosystems, are particularly sensitive to fragmentation. Increased human activity could disturb river and stream ecosystem continuity. One of the activities that has a strong negative influence is dam building.

Qualitative analysis of the Grošnica River macroinvertebrate fauna has determined a reduction of the total number of taxa by 4 during a time period from 1973 (80 taxa) to 2011-2013 (76 taxa). Likewise, differences in diversity of some macroinvertebrate groups was noted, as well as changes in their longitudinal distribution. The majority of the taxa are eurobionts with a wide geographic distribution.

Studies of the Jablanica River (Stefanović et al., 2009), Svrljiški and Trgoviški Timok (Simić, 1993), Golijska Moravica (Đikanović et al., 2008), and Pusta Reka (Živić et al., 2001) have shown similar diversity of the macroinvertebrate communities as the Grošnica River community, regardless of the high fragmentation.

The Grošnica River similarity index analysis determined the highest similarity for the crustacean species of 100%. Changes were detected only in the species distribution, but not in their number. High similarity was determined for the Ephemeroptera (46,66%) and Diptera (31,57%), followed by Plecoptera (22,22%), Trichoptera (21,05%) and Coleoptera (14,28%).

Based on the results from this study and compared with the other research it can be said that the macroinvertebrate community structure of the Grošnica River is typical for the highland streams in this region.

Analysis of the obtained results showed that there were no large scale changes in qualitative composition of the Grošnica River macrozoobenthos community subsequent to a 40 year time period. Possible reasons for this may be a decrease in anthropogenic influence to the upper course of the river, as well as macroinvertebrate dispersion possibility in different stadiums of their development, despite the existence of the weirs.