engleski

Mayfly (Ephemeroptera, Insecta) community of the regulated Mediterranean river, Cetina, Croatia

The damming considerably alters the river flow and the consequences on biota are insufficiently investigated. Cetina River (Croatia) is one of the longest perennial Mediterranean rivers and is highly regulated. We aimed to assess the level of ecological disturbance of the mayfly communities through the damming and flow alterations of the Cetina and Ruda Rivers. Our study encompassed nine sites along Cetina River’s course and two on Ruda River. Mayfly larvae were sampled monthly between August 2004 and August 2005. A total of 22 mayfly taxa were recorded in this study including some rare, insufficiently investigated species such as Nigrobaetis niger, Procloeon bifidum and Ecdyonurus insignis. Contrary to our hypotheses, species richness, abundance of specimens and diversity of mayflies recorded in the Cetina River follow a general trend, i.e. all these values increase downstream. Multidimensional scaling analysis (MDS) reveals grouping of sites according to their position in particular river section. The pH value and water temperature were the most important environmental variables influencing mayfly community. Regarding the functional feeding guilds, general trend was the shift from the grazer to detritivore dominance following the upstream to downstream gradient. The communities were generally dominated by the species typical for the rhithral zone, with proportion of crenal and potamal species, decreasing and increasing downstream, respectively. No obvious influence of the river regulation on the mayfly communities was detected in our study. However, this is most likely due to specific karst hydrology, i.e. the presence of lateral springs along the course of the river. Hence, the interplay of surface and groundwater ecosystem properties should be thoroughly investigated in permanent Mediterranean rivers of karstic regions, in order to properly assess vulnerability of such systems to flow regulations.

karstic river / river regulations / functional feeding guilds / longitudinal zonation / diversity

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