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Functional feeding structure of benthic macroinvertebrates in travertine barrier biotopes

In the karstic running waters of the Dinarid Mountains travertine barriers and other travertine formations covered with moss mats and filamentous algae are very common habitats. Physical aeration, the spraying of water, high O2-concentration and high current velocity, and the precipitation of calcite are the main environmental determinants of these biotopes. The earlier classification of the travertine biotopes, conducted by MATONIČKIN & PAVLETIĆ (1964), was based on types of moss and periphytic cover associated with benthic macroinvertebrate composition. From various point of view the association between vegetation cover and benthic macroinvertebrates was the objective of many recent studies (GREG & ROSE 1985, ROOKE 1984, 1986, HARGEBY 1990, DODDS 1991). This interaction has been explained by two main points of view. Firstly, bryophytes, periphytic and epiphytic algae associated with accumulated organic detritus of different size-fractions represent the basis of the trophic pyramid and serve as a food source for macroconsumers (LAMBERTI & RESH 1983, FEMINELLA & RESH 1991, RICHARDSON 1991, MIHUC 1997). Secondly, as refuge the vegetation cover, by its habitat architecture offers a certain degree of protection against current velocity (POWER 1990, RUSSEV 1991, JOWETT et al. 1991). Starting from the premise that in cascade lake systems the barrier habitats are the sites of the biological processing of alochtonous and autochthonous POM, the aim of our study was to demonstrate how the functional feeding structure of macroinvertebrates reflected ecologically the physical structure of two types of vegetation cover (moss and filamentous algae) in travertine barrier biotopes. Firstly, we hypothesized that in interaction with current velocity the degree of retention and accumulation of benthic particulate organic matter (POM) would be affected by the physical architecture of the vegetation cover. This idea was based on the fact that the compact cover of filamantous algae would have a higher degree of FPOM deposition than moss mats. Taking into consideration this standpoint we presumed that the functional feeding structure of macroinvertebrates would be depend upon the degree of POM accumulation.

macroinvertebrates; karstic water; functional feeding groups

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