Aquatic-terrestrial linkages
The linkage between riparian predators and aquatic insects across a stream-resource spectrum
|
Stream ecosystems are intimately linked to their adjacent riparian habitat by spatial subsidies. One particular food-web linkage is the contribution of emergent adult aquatic insects to riparian insectivores such as birds, lizards and spiders. As part of his MSc research, Frank Burdon (see Burdon 2004, pdf, 6.8mb) conducted a survey of 37 forest streams across differing environmental gradients in the central South Island, New Zealand. This survey aimed to investigate the relationship between potential aquatic prey subsidies and predatory riparian invertebrates, and the published results of this work can be viewed here (Burdon & Harding 2008, pdf, 300kb). |
 |
 |
The right branch of the Rahu River, Westland was a typical study site showing the exposed gravel-bar habitat adjacent to the stream. |
The large New Zealand fishing spider Dolomedes aquaticus dominated the arachnid biomass recorded from the exposed gravel-bars. |
Positive associations were confirmed between stream-insect biomass and riparian arachnid biomass and web densities after adjusting for the effects of confounding environmental variables. Hierarchical partitioning confirmed the importance of stream insect biomass as a statistically significant contributor to the total explained variance in analyses for arachnid biomass, abundance and web density.
A concurrent survey of spider-web densities along 20-m transects from the stream edge into the forest indicated a strong decline in web-building spider density moving away from the stream, with stream insect biomass as a significant covariate.
Riparian spiders appeared to be positively associated with stream-insect biomass, suggesting a strong linkage with emergent adult aquatic insect subsidies. This indicates that productivity gradients present in the donor system may affect the magnitude of the interaction between adjacent habitats (Burdon 2004, pdf, 6.8mb; Burdon & Harding 2008, pdf, 300kb).
People involved in this project
Frank Burdon (PhD student)
Jon Harding
Publications
Burdon 2004. Effects of stream productivity on aquatic-terrestrial linkages. MSc thesis, University of Canterbury (pdf, 6.8mb).
Burdon & Harding 2008. The linkage between riparian predators and aquatic insects across a stream-resource spectrum. Freshwater Biology 53: 330-346 (pdf, 300kb).