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Climatic processes

Climate influences temperature, evaporation, humidity, and the amount and seasonality of rainfall. These factors are critical drivers for wetlands as they play a significant role in determining water quantity and wetting regime, which, in turn, affect virtually all other aspects of wetland ecosystems e.g. water quality, connections to other wetlands, nutrient cycling and animal breeding and movement.

Quick facts

The eastern long-necked turtle
(Chelodina longicollis) occurs in rivers of central Queensland[1]. It has been suggested that large numbers of females may be prompted to nest following heavy rain[3].

Climate is the synthesis of weather observations over a long period. It can be classified into zones using criteria such as rainfall, temperature, humidity and vegetation. The Climate Classification of Australia from the Bureau of Meteorology website is recommended as the base map for this layer.

Rainfall

Precipitation results in lateral run-off from the surrounding land into wetlands supplying nutrients and debris (allochthonous inputs) to the system. In a number of areas rainfall is the main source of water for wetlands. However, it is commonly exceeded by the evaporation rate. In 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 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 are successful, 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[6]. They then emerge from the mud and reproduce rapidly while conditions are favourable.

Tadpole development is influenced by temperature and 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.[6]

Temperature

Temperature and light can influence algal and water plant growth Photo by Queensland Government

Water temperature changes can impact  fish communities Photo by Queensland Government

The thermal regime of an area has a major influence on water temperature, which, in turn, influences the 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 and lower primary and secondary production. Air temperature affects the water temperature which has a direct influence on dissolved oxygen level. As water temperature rises, oxygen diffuses out of the water into the atmosphere leaving less oxygen available for aquatic organisms to breathe[7].

Water temperature is highly influential on fish individuals and their community structure. Temperature controls the metabolic rate, influences growth and the allocation of resources for reproduction and affects patterns of microhabitat use[5]. Increased temperatures can alter the tolerance of fish to stressors such as low dissolved oxygen. Additionally, fish species adapted to cool water high in dissolved oxygen cannot tolerate warm conditions[2] where dissolved oxygen is markedly lower.

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[4]. 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 are 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 the 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 and emergent vegetation influences water temperature through shading, reducing the amount of light and heat that reaches the water. Reduced cover of riparian and emergent vegetation can result in increased average summer water temperatures, decreased winter water temperatures, and an increase in the extent and rate of change of dielfluctuations of water temperature.

Water temperature is also affected by turbidity, and the temperature at different water depths is determined by the amount of mixing of water layers (e.g. top of the water and the lower depths)[8].


References

  1. ^ Cann, J 1998, Australian Freshwater Turtles, Beaumont Publishing Pty Ltd, Singapore.
  2. ^ Pearson, RG & Penridge, LK 1992, An ecological survey of selected rivers in Queensland with particular reference to the effects of sugar mill effluents, Australian Centre for Tropical Freshwater Research, James Cook University, Townsville, Australia.
  3. ^ Pritchard, PCH 1979, Encyclopedia of Turtles, p. 895, T.F.H.Publications, Inc., Neptune, New Jersey.
  4. ^ Pusey, B, Kennard, M & Arthington, AH 2004, Freshwater fishes of north-eastern Australia, CSIRO.
  5. ^ Pusey, BJ & Arthington, AH 2003, 'Importance of the riparian zone to the conservation and management of freshwater fish: a review', Marine and Freshwater Research, vol. 54, pp. 1-16, CSIRO.
  6. ^ a b Tyler, M 1989, Australian Frogs, Penguin Books, Australia.
  7. ^ Waterwatch Australia national technical manual: Module 4 - physical and chemical parameters 2002, Waterwatch Australia Steering Committee, Australian Government Department of Sustainability, Environment, Water, Population and Communities, <http://www.waterwatch.org.au/publications/module4/oxygen.html>.
  8. ^ Young, WJ 2001, Rivers as Ecological Systems: The Murray-Darling Basin, CSIRO Land and Water, Murray-Darling Basin Commission, Canberra.

Last updated: 22 March 2013

This page should be cited as:

Climatic processes, WetlandInfo, Department of Environment and Science, Queensland, viewed 11 February 2019, <https://wetlandinfo.des.qld.gov.au/wetlands/ecology/processes-systems/climate/>.

Queensland Government
WetlandInfo   —   Department of Environment and Science