NUNZIUM

As Australia transitions into September, a concerning forecast from the Bureau of Meteorology predicts a marine heatwave for the Tasman Sea. The waters off Tasmania and Victoria are expected to experience temperatures of at least 2.5C above average from September to February, with potential spikes up to 3.5C, according to oceanographer Grant Smith.

The south-east of Australia, a recognized climate change hotspot, is no stranger to such anomalies. Its waters are warming at a rate four times faster than the global average, a phenomenon largely attributed to the east Australian current and rising atmospheric temperatures, as explained by CSIRO research director Alistair Hobday.

The region still bears the scars from the record-breaking marine heatwave of 2016, which lasted 250 days. The heatwave had severe repercussions on marine life, including increased catch mortality, loss of salmon farming stock, and the emergence of tropical fish species. Additionally, an outbreak of Pacific oyster mortality syndrome posed a significant threat to the oyster population.

Hobday cautions that the upcoming summer could have similar effects, particularly on aquaculture. New species may appear in the southern south-east Australia, and the remaining kelp forest, a crucial component of the marine ecosystem, is at risk. Tasmania's giant kelp species have already seen a 95% reduction in their historical range.

In response to the impending heatwave, salmon farmers are exploring various strategies, including early harvesting, oxygen level enhancement in the water, or altering their feed mix. Hobday is also set to publish a paper in September, offering advice on how to prepare for the hotter, drier weather expected due to the probable onset of El Niño conditions.

CSIRO's Rich Little is currently leading a project to examine the changes in marine life in south-eastern waters over recent years. The project, expected to conclude by November 2024, involves a series of marine surveys. Preliminary findings point to changes in marine life composition, with increased numbers of mackerel and fur seals, and decreased populations of species such as blue warehou and red fish.

Scientists are further studying the extent to which these changes are due to climate change caused by burning fossil fuels and other local factors. The Australian Fisheries Management Authority is eagerly awaiting the results to understand the factors influencing changes in commercial fisheries.

Since the 1960s, the Tasman Sea has seen an average temperature increase of about 0.8°C, marking it as a significant indicator of global warming. Dr Edward Doddridge, an oceanographer from the University of Tasmania, underscores that a warming world will result in more frequent and intense ocean heatwaves, unless the consumption and burning of fossil fuels are reduced.

As the heatwave approaches, the Tasman Sea stands as a stark symbol of the pervasive impacts of climate change. The warming waters pose a threat to not only marine life but also the industries and communities that rely on them. The pressing challenge is to mitigate the impacts while addressing the root cause of the problem - our continued dependence on fossil fuels.