The flood pulse exerts a major influence on the structure and function of floodplain river systems However, the flood pulse has been, and continues to be, altered by water resource development (WRD) and climate change. These changes include changes to flood frequency, magnitude, duration and seasonality. However, there have been relatively few studies that have quantified the biotic responses to flow changes arising from WRD and climate change.
In this study, we use relationships between the duration and temperature of flooding and microcrustacean hatching established in laboratory trials to estimate how climate changes and ongoing WRD affect microcrustacean hatching. Daily hatching rates over time as well as temperature effects, were established for all microcrustaceans, for ostracods and non-ostracods and for anabranches grouped according to commence-to-fill (CTF) thresholds. Hydrological modelling and climate models were used to derive hydrographs for a 30-year period (1970-2000) for four scenarios: actual flow data (S1); modelled flow data with no WRD and no climate change (S2); modelled flow data with WRD but no climate change (S3); and modelled flow data with both WRD and climate change. Both temperature and hydrological modelling were based on RCP 8.5 and centred on 2030.
The results show the number of microcrustaceans hatched per m2 area differed among the four different flow-climate scenarios and among the CTF groups. In general, hatching rates per m2 declined with increased CTF, reflecting the declining frequency and durations of flooding with increased CTF under all scenarios. Water resource development has a greater individual impact on microcrustaceans hatching than climate change. However, the combination of WRD and climate change has the strongest impact on microcrustacean hatching.
This study suggests that water resource development and climate change have had and will continue to have impacts on the number and composition of microcrustaceans hatching from flooded anabranches.