Estuaries on the south-east coast of Australia are warming at twice the rate of oceans and the atmosphere, a new study has found. Researchers say the apparent accelerated impact from climate change on estuaries could adversely affect economic activity and ecological biodiversity in rivers and lakes worldwide. The researchers say that changes in estuarine temperature, acidity and salinity are likely to reduce the global profitability of aquaculture and wild fisheries. Global aquaculture is worth $US243.5 billion a year and wild fisheries, much of which occurs in estuaries, is worth $US152 billion. More than 55 million people globally rely on these industries for income.
The results are based on 12 years of recording temperatures in 166 estuaries along the entire 1100-kilometre stretch of the New South Wales coast in south-eastern Australia. In that time more than 6200 temperature observations were taken. The data, which are publicly available, were taken by field officers of the NSW Department of Planning, Industry and the Environment and used in a marine research collaboration with the University of Sydney.
On average, the estuary systems experienced a 2.16-degree temperature increase, about 0.2 degrees each year. This is the world’s first long-term study that has considered a diverse range of estuary types on such a large scale. According to the Australian Bureau of Meteorology, air and sea temperatures in Australia have increased by about 1 degree since 1910. And over the past decade, air temperatures have increase 1.5 degrees as compared to the 1961 to 1990 average. “Our results highlight that air or ocean temperatures alone cannot be relied upon to estimate climate change in estuaries; rather, individual traits of any estuary need to be considered in the context of regional climate trends,” Dr Elliot Scanes said.
The study also found that acidification of estuaries was increasing by 0.09 pH units a year. There was also changes to the salinity of estuary systems: creeks and lagoons became less saline while river salinity increased. Temperature increases in estuaries were also dependent on the type, or morphology of the system, the study found. The study suggests that estuaries that remain open may also soon begin to “tropicalise”, and estuarine ecosystems could become colonised by tropical marine species and reflect a warmer environment.
Source: EurekAlert!
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