Manly Lagoon - Manly Environment Centre - Manly Environment Centre

Vegetation

mec@mec.org.au (Super Admin) — Thu, 28 May 2009 20:01:18 +1000

The indigenous vegetation communities originally associated with Manly lagoon and its tributaries have been heavily altered by urban development. There has been widespread introduction of ornamental exotic species such as Coral Trees which seasonally contribute very substantial amounts of leaf matter into the tributaries and the lagoon to the detriment of water quality. Weed infestations are common throughout the area, particularly where maintenance is less intensive, detracting from the water quality, habitat value and recreational amenity of the waterways.

A recent Survey of the vegetation around Manly Lagoon found that:

Indigenous Species 67
Noxious Weeds 26
Exotic species l40
Total number of species 222

Endangered plant species: Tetratecha grandulosa (community of endangered Duffy's forest vegetation) found at the top of the catchment

Aquatic Flora and Fauna

mec@mec.org.au (Super Admin) — Thu, 28 May 2009 19:57:58 +1000

There is little habitat for aquatic life because:

The natural vegetation of the lagoon has been greatly modified by urban development and the spread of introduced plant species.
There are no saltmarshes or mangroves and only very small amounts of seagrass which fringe the shoreline in the lower reaches of the lagoon.

Fish species that can be found are:

Mullet
Bream
Flathead
Whiting

Tropical fish species that have been found in the Lagoon are:

Mangrove Jack
Giant Herring
Big-eyed Trevally
Australian Bass

A Gondwanan fish in Manly Lagoon Catchment!

In the creeks above Manly Dam, there is a Gondwanan fish species called Galaxias Brevipinnis, commonly called the Climbing Galaxias. This Gondwanan fish, which lives in Curl Curl creek is also found in New Zealand, another fragment of the great southern continent Gondwana. This fish is reputed to be the first fish to conquer the New Zealand Glacial lakes because of its phenonmenal climbing ability. It is a threatened species in Manly Dam.

Macrobenthic infauna :

The diversity and abundance of these is relatively low and particularly poor in the middle and upstream locations of the lagoon. This is indicative of poor bottom water quality and sediment contamination.

Frogs

The Red-Crowned Toadlet (Pseudophryne australis) is restricted to Hawkebury Sandstone areas in the Manly Dam area. It is also a threatened species.

Environmental Flows and Water Extraction

mec@mec.org.au (Super Admin) — Thu, 28 May 2009 19:55:03 +1000

Weirs:

on Manly Creek to water Warringah Golf Course
on Burnt Bridge Creek to water Balgowlah Golf Course

Bore: to water Manly Golf Course

Manly Dam: to water Wakehurst Golf Course

Eutrophication or Rehabilitation?

mec@mec.org.au (Super Admin) — Thu, 28 May 2009 19:50:24 +1000

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).

Physical Changes

mec@mec.org.au (Super Admin) — Thu, 28 May 2009 18:56:30 +1000

Development within the Manly area became rapid following completion of the Sydney Harbour Bridge in l932. All suitable residential areas were quickly taken up and market gardens sprang up along the creeks, which fed into the lagoon in North Manly and Brookvale.

The waterways of Manly Lagoon and its tributary creeks have been the subject of significant man-made changes over at least the past sixty years or so. Of particular interest is that Hinkler Park was an island up until the l950s when the former southern channel, some l3 to l5m wide, was artificially closed during bridge and roadworks and replaced by a small 600mm diameter pipe culvert.

Only 10% of the original wetlands in the lagoon catchment remain, 90% having been landfilled and/or reclaimed, for:

Lagoon Park as far south as the present Stella Maris School; Aitken Avenue; Manly Golf Course; Hinkler Park; Warringah Golf Course (south of Kentwell Road); District Park (now Nolan Reserve); Warringah Mall shopping centre; Playing fields off Aquatic Drive; Passmore Reserve; Addiscombe Road; T.S. Condamine; Wakehurst Golf Course.

Former Tip Sites:

Addiscombe Road; Lagoon Park (eastern end); Playing fields off Aquatic Drive.

Foreshore Former Market Garden Sites:

Along the southern side of the waterway from Manly Creek downstream to the eastern end of Campbell Parade.

Source: Mcinnes, H. Problems and Principles in Estuarine Management.

Land Use

mec@mec.org.au (Super Admin) — Thu, 28 May 2009 18:54:47 +1000

Table of Land use in Manly Lagoon Catchment

Type of Land Use	Area (km2)	Area (%)
Residential - low density	6.62	37
- low-medium density	2.31	13
	8.93	50

Industrial	1.22	7
Business	0.24	1
Open Spaces - Recreation	2.67	20.3
Bushland	3.7	14.7
Education & Technical Facilities	11.7	7

TOTAL	17.9	100

The open space generally lies adjacent to the lagoon and its tributaries. Approximately half of the open space is linked to Manly Dam, which ceased operating as a water supply source in 1942 and is now a recreational resource.

Source: Manly Lagoon Estuary Management Study 1995

Water Quality Monitoring and Rehabilitation

mec@mec.org.au (Super Admin) — Thu, 28 May 2009 18:46:07 +1000

The Water Quality Monitoring & Rehabilitation of Manly Lagoon Catchment Project

A National Landcare Grant to the Manly Environment Centre (MEC) has funded the continued employment of a Catchment Liaison Officer (CLO) whose role is to work with the community, industry, golf courses, students and other stakeholders to enhance the Manly Lagoon Catchment.

Acting as a central point of contact, the CLO continues to be based at the MEC's Waterwatch Centre and will co-ordinate the following projects:

WATERWATCH - Water quality monitoring lagoon & creeks
Community education and awareness
Lagoon clean-ups
Golf-course best practise management plans
Industry education programs
Regeneration and revegetation