Project Title
Ecological responses to seasonally inundated leaf litter in billabongs of the Murray River
Abstract
The floodplains of the Murray River, a large regulated river in
south-eastern Australia, are dominated by river red gums (Eucalyptus
camaldulensis). These tall eucalypts are common throughout flood prone
areas of Australia where they form extensive forests and dominate the
margins of rivers and associated floodplain wetlands. River red gum
leaf litter provides a substantial quantity of carbon to the aquatic
ecosystem and is an important contributor to the aquatic food chain in
floodplain wetlands.
River red gum leaf fall peaks in the Australian summer, historically a
time of minimum flows in southern Australian rivers. Thus prior to
regulation, peak litter fall would have coincided with wetland dry
phases, with leaf litter being inundated in spring after exposure on the
dry floodplain. River regulation now results in high flows (and
consequently wetland inundation) during summer, resulting in leaf litter
directly entering the aquatic phase of the floodplain cycle. Fresh
river red gum leaves directly entering the aquatic phase are thought to
contain more bioavailable dissolved organic matter than leaves which
have remained exposed on the dry floodplain. Therefore, the flow regime
of a river may have an impact on the amount of bioavailable dissolved
organic matter entering the aquatic ecosystem.
The role of river red gum leaf litter in floodplain wetlands, and
whether this role changes depending on the seasonality of flooding, was
investigated in experimental mesocosms using sediment collected from
Murray River floodplain wetlands and river red gum leaf litter.
Microinvertebrates, macroinvertebrates and water quality parameters were
measured during summer and spring experiments. Changes in water quality
(particularly oxygen and dissolved organic carbon) as a consequence of
the presence of leaf litter affected the abundance and community
structure of aquatic biota. The pattern and extent of these effects
changed from summer to spring suggesting that ecological responses of
floodplain wetlands to a delivery of carbon in the form of leaf litter
depends on the timing of flooding.
Supervisors
- Ralph MacNally
- Gerry Quinn
- Ben Gawne
See also
Murray-Darling Freshwater Research Centre
