Eutrophication or Rehabilitation?

Reversing the Dead-End Trend ....
The Manly Lagoon Estuary Management Study (1995) states that:

  • The water of the Lagoon is EUTROPHIC and sensitive to further increases in nutrient inputs.
  • Manly Lagoon sediment is CONTAMINATED with HEAVY METALS and, compared with Sydney Harbour and Curl Curl Lagoon, has the highest average levels of copper and lead. The concentrations of heavy metals in the muddy surface sediments of the lagoon appear to have increased significantly over the period l985 to l993. On the available data, concentrations of lead, mercury and zinc exceed overseas sediment standards (Washington, USA) over much of the lagoon.
  • There are 29 Sydney Water sewer overflows in the catchment.

A eutrophic lagoon has limited aesthetic appeal due to high turbidity and the potential for periodic blooms of planktonic algae, including in some instances blooms of toxic blue-green algae. "Apart from visual problems, algal blooms could generate other water quality problems such as production of unpleasant odours, deoxygenation and ultimately fish kills" (Cheng, 1993).


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