Search

Riparian zones mediate chemical and biological exchanges between streams and the terrestrial environment. In urban systems, these zones are often heavily modified by removal of native vegetation and bank disruption. Management agencies have made considerable investments into restoring riparian vegetation through replanting. We investigated the potential for riparian plantings to restore invertebrate communities, by comparing open and forested (replanted) reaches over winter within three urban streams in Melbourne, Australia. Clear differences in aquatic habitats, food resources and fauna were evident between reaches. Algal biomass on artificial substrates did not differ significantly between reaches. Open reaches had higher abundances of taxa reliant on autochthonous production as the primary food resources (e.g. gastropods, chironomids and oligochaetes), while forested reaches displayed a higher diversity of invertebrate taxa associated with allochthonous resources. We conclude that riparian pla...

Artificially inducedlake level fluctuations influence benthic communities in numerous lakes, but their effects are relatively poorly understood. Littoral communities were described from three habitat types in two oligotrophic lakes in New Zealand, one subject to a natural hydrological regime with limited lake level fluctuations, the other subject to >5 m fluctuations as a result of hydro‐electric management. The fluctuated lake showed evidence of littoral compression and the replacement of macrophyte beds at shallow and intermediate depths by green filamentous algae. Macroinvertebrate biomass was higher in the fluctuated lake, despite this lake having a lower standing crop of primary producers compared with the unfluctuated lake. Disturbance of the littoral zone may reduce macrophyte biomass but may maintain high levels of primary producer productivity through an increase in benthic algae such as diatoms.

The nature of benthic biofilm was assessed in four streams in New Zealand, two flowing through native tussock grassland and two through exotic Pinus radiata forest. Components of the biofilm were described using epi‐fluorescent staining (DAPI) and scanning electron microscopy (SEM) of rock and wood substrata. DAPI and SEM analyses showed significantly more bacteria and fungi on rock and wood in tussock as opposed to pine streams. This emphasises the importance of the heterotrophic community even in systems which have abundant light available for primary production. The lack of a significant heterotrophic biofilm in pine streams was unexpected, and we speculate that chemical characteristics of the water may be responsible.

We used standardised techniques to assemble 18 food‐webs in streams subject to four land uses; exotic pasture, native tussock, native forest, and pine plantation. There were clear differences in the algal productivity and standing crops of organic matter between the forested (native and pine) and grassland (tussock and pasture), but not within each grouping. Algal productivity was more than twice as high in the grassland sites, whereas the converse was true for organic matter standing crop. These differences in energy resources were correlated with differences in community composition and food‐web structure. Although all streams had a generalist core of species, certain species of algae and invertebrates were predictably associated with either forested or grassland sites. Food‐web structure in the forested and grassland sites was also distinct. Grassland food‐webs were complex, highly internally connected, and typified by a “triangular” shape. Forested food‐webs in contrast were less highly conne...