The Importance of Coastal Wetlands in the Age of Harmful Algal Blooms

Following a couple of wet days in August, I was in the neighbourhood of the Aldinga Washpool and stopped in for a look.

The Washpool, one of Adelaide’s last coastal lagoons, was full and spilling over the concrete weir into the outlet channel and the mouth was open. What was very striking was the difference in the turbidity of the water flowing into the Washpool compared to the water flowing out (see videos below).

It is well known that wetlands are the “kidneys of the landscape”, playing a key role in improving water quality. This is why constructed wetlands are now an integral feature of urban design.

In the case of the Washpool, we have a natural wetland, albeit somewhat degraded, playing that role and at an important location immediately adjacent to where the water discharges into a marine protected area, Encounter Marine Park.

With nutrient-rich runoff believed to be a factor contributing to the harmful algal bloom recently affecting the marine environment across SA, the case for reducing the nutrient load of freshwater flows into the sea has never been stronger. NGT’s restoration concept for the Aldinga Washpool (see our 2022 and 2025 reports) would do just that.

By returning the Washpool to something more closely resembling its original volume, depth and area, restoration would reduce the volume of water discharging to sea and more effectively improve the quality of that water. It would enhance the effectiveness of the Washpool at protecting the marine environment and it would also improve the habitat quality of the Washpool itself for wetland dependent species such as waterbirds, sadly now also imperilled by H5N1 avian influenza.

At NGT we are continuing to work towards the restoration of the Aldinga Washpool through funding applications and will keep readers updated.