Key drivers of river and wetland food webs in Australia’s wet-dry tropics

Background/Question/Methods

Douglas et al (2005) proposed five general principles to characterise aquatic food webs in northern Australia: (i) Seasonal hydrology is a strong driver of ecosystem processes and food web structure,(ii) Hydrological connectivity is largely intact and underpins important terrestrial-aquatic food-web subsidies, (iii) River and wetland food webs are strongly dependent on algal production, (iv) Omnivory is widespread and food chains are short, and (v) A few common macroconsumer species have a strong influence on benthic food webs. We used stable isotope analysis of food sources and consumers across the region to test support for these principles.

Results/Conclusions

Three principles were generally supported: (i) Food sources varied between wet and dry seasons, (ii) Consumer-resource coupling was weaker at sites with greater hydrological connection, and (iii) Food webs were generally dependent on algal production. However, food chain lengths were similar to those in temperate systems. Although isotope surveys showed that consumer diversity was high, other experimental evidence suggests that some common macroconsumers do indeed exert strong control on benthic food webs. Seasonal hydrology and hydrological connectivity appear key drivers of aquatic food webs in northern Australia.