Species composition and structure of macroinvertebrate communities in Arda River

A study on the species composition and contemporary analysis of the structure of macroinvertebrate communities in the upper- and middle course of Arda River (South Bulgaria) in 2002 and 2003 were carried out. Totally 125 taxa, belonging to 17 macroinvertebrate systematic groups (75 genera and 46 families) were found, as a considerable enrichment of benthic fauna in comparison with previous periods is established. Twenty three species and 6 genera from all determined taxa are reported for the first time for the river fauna. The results of the dominant analysis confirm that the studied river section is inhabited by species with different ecological plasticity. A general characteristic of the sites based on the structural parameters is made. A tendency towards a permanent improving and stabilizing of the benthic communities in the bigger part of the studied section of Arda River, corresponding to beta -mesosaprobe state is observed. A successive change in the composition of the macroinvertebrate communities downstream the first reservoir and a secondary modifi cation both in the composition and the communities structure downstream the second reservoir is found.Original Abstract: Izsledvan e vidoviyat sustav i e napraven suvremenen analiz na strouktourata na zoobentnosnite tsenozi na 6 pounkta v gornoto i sredno techenie na reka Arda (Yuzhna Bulgariya) prez 2002 i 2003 g. Oustanoveni sa 125 taksona ot 17 bentnosni sistematichni groupi (75 roda i 46 semeistva), kato se otchita znachitelno obogatyavane na bentnosnata faouna v sravnenie s predishni periodi. Dvadeset i tri vida i 6 roda ot oustanovenite bezgrubnachni se suobshtavat za purvi put za faounata na rekata. Rezoultatite ot dominantniya analiz potvurzhdavat, che izsledvaniyat ouchastuk se naselyava ot vidove s razlichna ekologichna plastichnost. Napravena e obobshtena kharakteristika na pounktovete na bazata na izsledvanite strouktourni parametri. Nablyudava se tendentsiya za stabilizirane na zootsenozite v po-golyamata chast na izsledvaniya ouchastuk ot reka Arda, suotvetstvashto na beta -mezosaprobnoto sustoyanie. Oustanovyava se souktsesivno izmenenie na sustava na zoobentnosnite tsenozi v ouchastuka pod purviya yazovir, kakto i vtorichno izmeneie na sustava i stroukourata na tsenozite v ouchastuka pod vtoriya yazovir.