Could Sydney’s creaking sewerage system be linked to the spate of shark attacks?
Experts say dirty waters can attract more sharks – but there are many other factors at play
TL;DR
- Four shark attacks occurred in New South Wales between January 18-20, prompting unusual warnings from authorities.
- Experts suggest a 'perfect storm' of factors contributed, including more people in the water, warmer ocean temperatures due to global heating, and murky waters after storms.
- Heavy rainfall is identified as a key factor, flushing brackish water and nutrients from estuaries and storm/sewage overflows into the ocean, which attracts plankton, small fish, and then sharks.
- Sydney's sewage management system uses only 'primary treatment,' releasing effluent directly into the ocean, unlike other cities using secondary treatment.
- Aging infrastructure in Sydney's sewage system is unable to keep up with population growth, increasing the risk of contamination during extreme rain events.
- Experts debate the direct link between the sewage system and the shark attacks, with some suggesting it indirectly contributes to attracting sharks by affecting water quality.
- Deepwater ocean outfalls, a unique feature of Sydney's system, are also discussed, but some experts believe they push nutrient-rich water further offshore.