Climate

Temperature

The thermal regime of the province has a major influence upon water temperature, which in turn influences in-stream ecology. Species assemblages from high altitude sections of a province (e.g. Eungella National Park in the Central province) may differ from lower altitude ones. Cooler temperatures reduce growth rates, lowering primary and secondary production.

It follows that water temperature is highly influential on fish individuals and their community structure. Temperature controls metabolic rate, therefore influencing growth and the allocation of resources for reproduction, and water temperature also affects patterns of microhabitat use (Pusey and Arthington, 2003). Increased temperatures can alter the tolerance of fish to stresses such as low dissolved oxygen. Additionally, fish species adapted to cool stream water high in dissolved oxygen cannot tolerate such conditions (Pearson and Penridge, 1992). A seasonal change in water temperature is a cue for migration and spawning in some fish species. For example, yellowbelly (Macquaria ambigua) requires a rise in water level in conjunction with a rise in temperature above 23°C as a spawning trigger (Pusey et al, 2004). Reproduction in some fish may be associated with warmer temperatures to ensure higher food availability for their larvae and juveniles. Larval and juvenile food sources would be more abundant during these times, as high production is associated with higher temperatures. Recruitment occurring in cooler periods would result in larvae and juveniles entering the system with little or no food to sustain them. Diversity of temperature conditions may result in higher species richness as thermal requirements of more species may be met. Pusey and Arthington (2003) suggest that increased rates of transfer of thermal energy between the atmosphere and stream in the absence of an intact riparian zone may disrupt reproduction of fish, and have direct effects on mortality rates, body morphology, and disease resistance.

Riparian vegetation influences stream water temperature through shading, reducing the amount of light and heat that reaches the water. Reduced cover of riparian vegetation can result in increased average summer water temperatures, decreased winter water temperatures, and an increase in the extent and rate of change of diel fluctuations of water temperature (see Pusey and Arthington, 2003 for references).

Water temperature is affected by turbidity, and the temperature at different water depths is determined by the amount of mixing (Young, 2001).

Rainfall

Precipitation results in lateral runoff from the surrounding floodplains into rivers, supplying nutrients and debris (allochthonous inputs) to the system.  In a number of FBPs rainfall is the main source of water for the riverine systems, however, it is commonly exceeded by the evaporation rate.  In these cases, where flow is inextricably tied to rainfall, the occurrence and timing of wet/dry seasons may have important implications for the ecology of the flora and fauna of the region.

Examples

Some animals have evolved reproductive strategies to take advantage of wet seasons. The red kangaroo (Macropus rufus) stops breeding during prolonged periods of drought. Rainfall triggers an immediate hormonal response in the kangaroos, allowing breeding to recommence (Hodson, 1979).

For many turtle species, nesting behaviour occurs during or shortly after rainfall. Rainfall softens the ground, making nest excavation easier and thus faster, therefore minimising the time that turtles spend on land and are exposed to predators. The eastern long-necked turtle (Chelodina longicollis) occurs in rivers of central Queensland (Cann, 1998), and it has been suggested that large numbers of females may be prompted to nest following heavy rain (Pritchard, 1979).

Some frog species require precipitation, rather than floodplain inundation, to spawn. Such species have a limited window of opportunity to spawn in this province, but as long as spawning and the subsequent recruitment of juveniles is successful, then the species may persist. Thus many species of frogs within dry provinces are 'burrowing frogs' which dig into floodplain mud when it is soft, and enter a state of drastically reduced metabolism for long periods until rainfall re-wets the mud (Tyler, 1989). They then emerge from the mud and reproduce rapidly while conditions are favourable. Tadpole development is influenced by temperature, development is accelerated with higher temperatures, allowing tadpoles to become adults before the spawning sites dry out.  The adult frogs have morphological adaptations for burrowing, such as metatarsal tubercles for scraping soil, and they generally have a broad head, bulbous body, and short limbs (Tyler, 1989).