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RESULTS

Experimental Site 2

Site: Dodson Lake 

Water Test

Result

June 2005

September

2006

February 2007

April 2007

Nitrate mg/L

0.484

-

-

1.055

Phosphate mg/L

0.300

-

-

0.58

Ammonia mg/L

0.144

-

-

0.096

pH

7.7

7.99

-

7.38

Salinity ppk

0.55

0.64

-

0.57

Conductivity ms/cm 3

1.13

0.67

-

1.01

Turbidity

10

20

-

10

Water Temperature

-

16 °c 19° c

-

17 ° c

  • readings from sludge near railway bridge

 

 

Conductivity levels varied according to seasonal changes so are not a concern. In April, the reading was taken before winter rains so high conductivity levels reflect low water levels with concentrated ions In June the water is stirred by rainfall, September water levels are high and sediments settled for spring.

 

Site: Dodson Lake

We identified the green algae, Cladophera as forming part of the sludge. This is harmless by itself and breaks down to add nutrient to the sediment.

The bottleneck under a rail bridge showing a build up of algal sludge.
The same location after a clean up and first rain.

 

A warning sign to swimmers was erected 12 years ago after an outbreak of a blue-green algae Anabaena cecinalis, during summer. Concern was for livestock as paddocks surrounded this area up to the early 1990’s.

A sign indicating the Habitat Program was placed at Dodson Lake in April 2007.

 

Macro Invertebrate Sampling in Water Sites in Bunbury City

Site: Dodson Lake

 

Species sampled

Sensitivity Rating

June 2005

September 2006

February 2007

Dragonfly larvae

6

-

6

Damselfly larvae

-

6

-

Caddisfly larvae

-

-

-

Water mites

-

-

-

Beetle larvae

-

4

-

Beetle coleoptera

-

3

-

Bugs (water boatmen)

3

3

3

Daphnia/ water fleas

3

3

-

Cyclops

3

-

-

Freshwater shrimp

-

3

3

Flatworm

-

-

-

Ostracods

-

-

3

Water Snails

3

3

3

Midgie larvae

1

1

1

Aquatic earthworms

1

-

-

Macroinvertebrate Water condition

20 Fair

26 Fair

19 Poor

Vertebrates

Swan River Goby

Tadpoles

Gambusia

Gambusia

Gambusia

Ducks

Ducks

Ducks

Swan River Goby

-

Western Pygmy Perch

-

-

Swan River Goby

-

-

Mussel

-

 

Water Index Rating for Test Sites

Site: Dodson Lake

Date

 

Water Index Rating

Star Rating Guide

June 2005

× × × Gambusia

Wetland is in reasonable condition now. Keep monitoring it

September 2006

× × × Gambusia

Wetland is in reasonable condition now. Keep monitoring it

February 2007

× × Gambusia

Wetland needs some assistance. Continue restoration.

 

Angus and Hannah releasing Western Pygmy Perch into Dodson Lake in September 2006

 

Conclusion

Western Pygmy Perch were released here in 2005 and in 2006. It was a positive result to find a Western Pygmy Perch in September 2006.

The lake narrows into a bottleneck under a rail bridge. Here we identified a build up of algal sludge in September 2006. The City Council was notified and the scum removed. The Health Department placed a “No Swimming Blue Green Algae Alert” sign at this location twelve years ago. The sediment of this lake is very thick (up to 30 cm), black and muddy. It forms the original flood plain of the Preston River which flows less than 500m away.

Our sampling has indicated a fair level of water quality that is able to support a native fish species. The sedges and emergent grasses around parts of the pond perimeter will provide protection and attachment of the developing fish eggs.

 

 

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