Senior’s Sundowners

This is an opportunity for the “mature” people in the area to socialize. There is no age limit (high or low) but there are no children’s activities.
BYO nibbles and drinks

For dates and  times please phone Judy or Graeme 9739 1484

FRAGYLE MEETING REPORT

The FRAGYLE meeting at Preston Beach on Tuesday November 15, was interesting beyond my expectations. There were four speakers not including the President of FRAGYLE, Hilary Wheater who gave an overview of the Yalgorup Lake systems, a brief description of how the lakes were formed and the values of the system, the Ramsar listing and the thromoblites. Here is a summary of her overview:

In the 1990’s two events took place that may have had an effect on the Yalgorup Lake Systems

  • the Dawesville Cut 1992-3
  • subdivision along the eastern side of Lake Clifton

At this time Lake Clifton became hyper saline and nitrate and phosphate levels rose dramatically.

Were the two events linked to the change in Lake Clifton or was the change in the Lake at that time merely a coincidence?

Hilary also mentioned that pyrethrin, used in dog wash is lethal to aquatic animals. It kills fish and smaller creatures. If you use pyrethrin in the dog wash and then pour it out onto the ground, the pyrethrin could enter the ground water and then enter water bodies such as Lake Clifton and kill essential life there.

The second speaker was Craig Olejnik from DEC. DEC has been doing various research and on the ground work in and around the Lake Clifton area including

  • Research on the Tuart decline and its effect on animals in the Yalgorup National park. They had two trial areas: one where baiting was used and one where it was not. Native animal numbers were better in areas where baiting had been carried out.
  • Cotton Bush Management is being carried out in the southern end of the Yalgorup National Park. Cotton Bush is a declared weed.
  • Perscribed burns are being carried out in conjunction with Murdoch University to try and regenerate the Tuart population. They find that hot burns that create ash beds are the best for regeneration of Tuart seedlings.
  • Cat and Fox poisoning and trapping are being carried out in the Park. It is interesting to note that cats were released in the late 1800s and early 1900s to control rabbits and mice. The cats they are trapping now are descendants of these cats and are therefore feral.

The third speaker was Tony France who had made up a list of shorebirds seen in and around the Yalgorup Lakes which I intended to pick up and include in this report but forgot to do so. I can get my hands on this list and include it at a later date if anyone is interested. He also spoke about how volunteers were really important to help protect the area, lobby government departments and help with collecting data.

 

The fourth speaker was Philip Commander who spoke on the hydrogeology of the Yalgorup Lakes which are relative new being only 4,000 years old. He worked for the Department of Water but is now retired. When he worked for the Department of Water he monitored bores set up on the southern end of Lake Preston.

  • In the 1970s there was an increase in bore salinity, many becoming twice as saline as sea water.
  • He mentioned that when pumping for irrigation is carried out there is a risk of raising salt water.
  • It is interesting to note that coastal rain has a higher salt content due to ocean spray.
  • The salinity of the Yalgorup Lakes has increased over time. The water in the lakes of the system is 2/3rd rain water and 1/3rd hypersaline water coming from beneath the lakes.
  • In Lake Clifton salinity has steadily increased since 1980 as rainfall decreased. Very low rainfall years were 1993, 2001, 2006 and 2010.
  • He spoke of a mound of fresh water ion dunes west of Lake Preston coming from a deep fresh aquifer which provides numerous fresh water soaks entering the lake from the west.
  • He also pointed out that low rainfall in 1993 coincided with the Cut and subdivision spoken about by Hilary and believed that this was the real cause of the sudden jump in salinity as it also jumped again in 2001 and 2006 according to DEC records.

The final speaker was Mike White,Chairman of the Leschenault Catchment Council.

He first spoke about the Primary produceres at the base of the food chain that help to feed the thousands and thousands of migratory birds that visit the Yalgorup Lakes every year.

  • Photoautotrophs – organisms that carry out photosynthesis to acquire energy
  • chemoautotrophs-organisms that obtain energy by the oxidation of electron donors in their environments
  • Healthy ecosystems will adapt to small changes in the system and will recuperate quickly.
  • However if one feature of the system dies out, there can be a cascade collapse of the whole system which raises the question: can you define the limit of acceptable change?
  • Diversity increases resilience.

He then talked about the unique aspects of Lake Preston. It is actually divisibleble into four distinct sections

  • The section north of the causeway and
  • the northern end south of the causeway
  • the middle section and
  • the southern section at the extreme southern end of Lake Preston

Each of the southern sections is distinct and has a small channel that connects each section. The lake flows from south to north when water levels are high enough. The southern end may reflect the water table. It is surrounded by a freshwater wetland and is surrounded by freshwater flora. It has 970 mg/L salt

The north and the middle section of the lake are hyper saline and rich in carbonate.

The most interesting part of his talk was about the organisms that live in Lake Preston. He called them extremophiles because the can live in conditions that most organisms can’t. In this case it is high salinity. The food chain works like this:

  • there are cyanobacteria. The ones living in the top zone are phototrophic. The ones living below are chemoautotrophic that for a mat in the brackish area between the freshwater soaks and the lake.
  • The above are the food source for the “bugs” the birds eat.
  • There are five species that live in hyper saline water and three that live in the brackish water of Lake Preston (ephydrella marshalli which live in the whole lake; cullicoides waringi’ artemia species; tabanus townsvilli which are both predators and good food for birds; and finally odontomyia amyris which are not native and probably came in on bird feathers from North America in their cyst stage.
  • It takes 30,000 tonnes of bugs to feed the migratory birds each pre-breeding season at Lake Preston. The birds remain for 3 ½ months in the area. They must depend on food in all of the Yalgorup lakes as there is not enough solely in Lake Preston.
  • Mr. Whitehead also found Archea species in Lake Preston. This is a unique find. These creatures are not bacteria. They are a very old form of life dating back 3.4 billion years. They are a rare relic of an ancient ecosystem still living in our modern environment and provide the opportunity to study the beginning of life on our planet. To protect this amazing find, and the Lake as it is, it is best to leave it alone, rebuild wetlands through revegetation where clearing and degradation has occurred.

And finally the threats to the balanced ecosystems that enable all the migratory birds to fill up on their long journey to the Arctic are:

  • reduced water leading to increased salinity. If the salinity becomes too high the mat of cyanobacteria will die
  • The dunes on the west side of Lake Preston provide fresh water to the lake. Over extraction (caused by development) would lead to a cascade collapse. So maintaining the dunes just as they are is important.
  • Climate change could also cause such a collapse due to lack of rain. The bugs will die if the salinity levels become too high for too long.
  • Too much nutrient could also cause a collapse.

Nancy Fardin

PHOTOGRAPHY COMPETITION

DISCOVER PEEL PROJECT

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Mandurah and Peel are about to launch a brand new website showcasing the whole Peel region’s fabulous features to potential visitors.

 

Send us your best picture to be a part of our website– and you could be in the running for the chance to win

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We need the best possible picture you can take that portrays the Region at its best. Let your imagination not be limited as we are looking for images that depict family time, Water & Outdoor activities, Naturel & Wildlife, Arts & Culture and/or other attractions/events/places of interest in the Peel Region.

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  • visit www.mandurahandpeel.com
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GOOD LUCK

This is a Peel Chamber of Commerce and Industry project funded by Royalties for Regions Peel Region Grant Scheme, administered by the Peel Development Commission.

 

*Terms and conditions apply – see website for details

Regards

Tracey