How drought and better sewage transformed Port Phillip Bay

Embargoed until: Publicly released: 2024-10-01 00:01

Australia; VIC

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Improvements to sewage treatment that coincided with one of the worst droughts in Australian recorded history transformed Melbourne's Port Phillip Bay, according to Australian researchers who say the changes weren't necessarily for the better. A major environmental study in the 1990s found too much nitrogen was entering the bay via sewage, leading to changes in sewage treatment aimed at avoiding environmental harm from too many nutrients entering the bay. These changes coincided with the Millenium Drought in the 2000s, and researchers say sampling from the bay over that time period shows the drought combined with the sewage changes saw the bay's nitrogen input halve rapidly. Looking at studies of the bay from that time period, the researchers say this drop in nitrogen coincided with declines in seagrass, kelp and groundfish. They say this shows that while setting conservative limits on nitrogen output can help avoid water quality issues, we need to consider the potential trade-offs with fewer nutrients leading to lower productivity.