Some of the most common concerns about the Tuggerah Lakes are water quality, odour and seaweed (which is actually seagrass and macroalgae: not true seaweed). While many of these issues are part of the lakes’ natural processes, they can be made worse by pollutants and human activities.
Water quality in the estuary has improved since old septic systems were replaced with sewerage systems. In the fight to keep nutrients out of the lakes, Council is going one step further and trapping litter and sediments in stormwater before they reach the lakes. From time to time there will be algal blooms, murky water and seagrass wrack (dead seagrass leaves) in the lakes. Turbid (or dirty) water is a result of the wind blowing across the shallow muddy basins, stirring up the bottom sediments.
In fact, systems like the Tuggerah Lakes estuary often have a muddy or dirty appearance. These are all part of the natural daily and seasonal patterns in the estuary and not necessarily an indicator of poor water quality.
Photo: Joining of Spring and Wallarah Creeks – Estuarine section – looking downstream towards Pacific Hwy bridge.
The estuary performs a vital biological role and acts as a ‘sink’ for nutrients and sediments. Everything that is washed into the estuary falls to the bottom of the lakes and is devoured by the many microscopic organisms living there.
These organisms break down and recycle the organic material and contribute to chemical reactions between the sediments and the lake water. If oxygen levels in the water are low, hydrogen sulphide (rotten egg gas) is released which is the cause of the foul odour.
Seagrasses and algae
Seagrasses and macroalgae play a crucial role in the health of the lakes. They utilise nutrients and sediments that have been washed into the system and provide a home for animals. When seagrasses naturally shed their leaves, the wrack (dead leaf matter) floats to the foreshore where it is washed up onto the foreshore where it decomposes and provides a number of benefits for plants like saltmarsh.
Changes to the foreshore edge by human impacts and development have interfered in this natural process. Rather than being washed up onto the foreshore, the wrack now tends to stay in the water where it collects fine sediments and other organic and inorganic matter that smothers sediments, rots and becomes smelly. This can then contribute to the ‘black ooze’ around the shore.
Sediment and pollutant build-up
The loss of native vegetation from the banks of lakes and creeks has increased the amount of sediment and pollution that is washed into the estuary. Council is rehabilitating many streambank sites along major tributaries within the catchment to reduce this process.
Stormwater runoff is also a major contributor of sediment and pollutants to the lakes. To trap these contaminants, Council has constructed new wetlands, fitted filters and built treatment devices to stormwater drains.
Photo: Stormwater treatment works Lowana Crescent
If the lake becomes degraded even more then the scientists expect, there will be a greater shift towards algal dependency and this may have subsequent further effects on types and abundances of invertebrates and fish in the lake.
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