Salinity cascading and predator effects on consumer and producer community structure: a mesocosm experiment

1. An observed community structure is often shaped by a combination of bottom-top and top-bottom processes, affected by biotic and abiotic factors. These factors affect community structure either directly (each species separately) or indirectly, via other species. Few studies have observed the combined effects of biotic and abiotic factors on primary producers and consumer communities composed of numerous species. 2. This study investigated the combined effects of a predatory hemipteran and water salinity on abundance and species richness of the periphyton and arthropod communities in an artificial pool experiment. 3. The abundance and species richness of both periphyton and arthropod communities were affected by the combination of salinity and predator. 4. It is suggested that the observed consumer community is composed of arthropod species that vary in salinity tolerance and response to the predator. In addition, the abundance of euryhaline species or species that are not consumed by this particular predator increases indirectly in specific treatment combinations that eventually result in reduced interspecific competition. Periphyton variables were strongly correlated to densities of larval Ochlerotatus caspius (Diptera: Culicidae), suggesting that this species may be largely responsible for structuring the producer community. 5. It is suggested that O. caspius distribution is the result of female oviposition habitat selection that is manipulated by chemical signals. Therefore, chemical signals that inform about habitat suitability also play an important role in shaping both consumer and primary producer communities.