biological monitoring using benthic organisms is one of the best and the most inexpensive methods for anthropogenic activities evaluation in aquatic ecosystems. the purpose of present investigation was biological monitoring of shahrud river that was performed in the qazvin province using by macro benthic invertebrates population. in the present investigation macro benthic invertebrate samples w...

119 Small invertebrates are functionally important in many terrestrial and aquatic ecosystems (Wilson 1992, Freckman et al. 1997, Palmer et al. 1997, Postel and Carpenter 1997). In freshwater sediments, benthic invertebrates are diverse and abundant, but they are often patchily distributed and relatively difficult to sample, especially when they live in deep subsurface sediments. Thus, the spec...

The cosmopolitanism paradigm in the biogeography of freshwater invertebrates is currently being replaced by non-cosmopolitanism or continental endemism. Benthic water fleas (Cladocera) from the family Chydoridae were the first group of freshwater invertebrates for which non-cosmopolitanism and cryptic diversity was substantiated by morphological studies. Yet, little is known about genetic diffe...

The absence of species in polluted sediments does not necessarily imply exclusion due to toxicity. Other factors, like for instance food availability and oxygen content, could also partly cause their absence. Hence, knowledge of the (combinations of) factors acting on individual organisms is essential in order to understand how populations can persist in polluted sediments. In this study specie...