By Councillor Weldon
(A) Council note:
(i)
there
has been an alarming number of duck fatalities in Victoria Park’s Lake Northam.
Sydney Wildlife carers have recorded 25 fatalities over the last fortnight;
(ii)
the
observed species, the Pacific black duck and chestnut teal, are native to
Australia and play an important role in wetland ecosystems;
(iii) the City have been working with the Australian
Registry of Wildlife Health, Taronga Zoo, the NSW Environment Protection
Authority (EPA) and the Department of Primary Industries to determine the
cause;
(iv) the City expedited its routine quarterly
water testing of the Lake Northam. No risks were identified. The City is
conducting further testing for soil borne bacteria;
(v) post mortems conducted by the Australian
Registry of Wildlife Health show no injury, adequate weight and muscle mass,
indicating absence of any longer term illness;
(vi) prior to colonial incursion and
industrialisation, Lake Northam formed part of a natural watercourse that
extended from marshy headwaters at (what we now call) Glebe towards Redfern and
Waterloo to the south;
(vii) Lake Northam is now a constructed wetland,
functioning as both wildlife habitat, a recreational area and a filtration
system for stormwater run-off from King Street and the surrounding area;
(viii) in 2018, City capital works upgrades in
Victoria Park included a range of measures to restore and maintain the water
quality of Lake Northam;
(ix) over the last 12 months, there has been a
proliferation of duck weed and algae on the surface of the lake; and
(x) a Honi Soit report in September
2022 noted that the condition of Lake Northam appeared to be in dire need of
attention, with decaying plants, increasingly murky water and a slew of
semi-submerged rubbish; and
(B) the Chief Executive Officer be requested to:
(i)
provide an update to Council
regarding the City’s investigations of the cause of duck fatalities;
(ii)
subject to the findings of
investigations, implement measures to mitigate the risk of a similar
mass-fatality event from reoccurring; and
(iii) undertake a condition assessment of Lake Northam and develop an
effective and sustainable remediation strategy to improve water quality and
promote a healthy wetlands ecosystem.
Note – at the meeting of Council, the content
of the original Notice of Motion was varied by Councillor Weldon. Subsequently
it was –
Moved by Councillor Weldon, seconded by
Councillor Jarrett –
It is resolved that:
(A) Council note that all Councillors were
provided the following information about wildlife fatalities at Victoria Park’s
Lake Northam, a constructed wetland which functions as a filtration system for
stormwater runoff from King Street and the surrounding area:
(i)
City
staff were first made aware of duck fatalities at or near Lake Northam on 9
March 2023, with the City receiving additional notification from Sydney Wildlife Rescue on 10 March 2023;
(ii)
Sydney
Wildlife Rescue advised dead ducks had been sent to Taronga Zoo for autopsies;
(iii)
the
City has since been working with the Australian Registry of Wildlife Health,
Taronga Zoo, the NSW Environment Protection Authority (EPA) and the Department
of Primary Industries to determine the cause;
(iv)
working
with Taronga Zoo, the City has provided background on the wetland system, the
current ecological condition of the lake and details of the City’s quarterly
water monitoring program;
(v)
through
discussions with Taronga Zoo, City staff and volunteers, the City understands
that the carcasses of 26 Pacific Black Ducks, one Corella, one Rainbow
Lorikeet, one Flying Fox and two Ibises have since been found in or near the
lake;
(vi)
the City
has been unable to confirm if there are additional carcasses collected/disposed
of by other agencies or volunteer groups;
(vii)
it is
unlikely that the Corella, Lorikeet and Flying Fox deaths are related to that
of the duck deaths, as these species tend to have limited interactions with
standing water;
(viii)
early
correspondence between the City and the zoo indicated avian botulism as the
potential cause since a range of environmental conditions had been experienced
that can promote the bacterial outbreak. Conditions include:
(a)
shallow
water depths from low levels of stormwater inflows and surface evaporation;
(b)
high water temperature from recent heatwaves; and
(c)
high
nutrient load, organic levels and low dissolved oxygen in the water;
(ix) unfortunately, duck fatalities within the Local
Government Area and surrounding councils during summer are not uncommon when
environmental conditions combine to contribute to an outbreak;
(x) there have been previous outbreaks of avian botulism in Lake Northam in the summers
of 2010 and 2012; and
(xi) botulism is caused by the release of toxins
from the Clostridium bacteria, under optimal conditions, where concentrations
in standing water can increase to a level which is harmful to wildlife,
particularly birds. It poses a low risk to humans and dogs;
(B) Councillors note that they were also
informed about the following investigations being undertaken and the outcomes
of these investigations:
(i)
quarterly
testing of water quality at Lake Northam is undertaken by an independent
environmental consultant with samples taken to an accredited laboratory and
assessed against state and national guidelines. Following initial
communications with Taronga Zoo, the City arranged for monitoring at Lake
Northam to be expedited to 16 March 2023;
(ii)
based
on the initial field inspection and measurements:
(a)
no
immediate environmental risks were identified;
(b)
field
measurements together with laboratory results indicate an elevated nutrient and
organic content combined with low dissolved oxygen;
(c)
these
conditions could encourage the production of botulinum;
(d)
to
further verify avian botulism, the City requested additional sedimentary
sampling and targeted laboratory analyses for suspect bacterium;
(e)
partial
water quality testing results have been received with the remainder due by 31
March 2023; and
(f)
all water quality results from this round of
monitoring have been provided to the NSW EPA;
(iii) on
24 March 2023, Taronga Zoo distributed preliminary pathology reports for 10
birds submitted by Sydney Wildlife Rescue;
(iv) preliminary
results indicate avian botulism remains the likely diagnosis, however other
intoxication is a possibility; and
(v) to
confirm the findings animal tissue
samples have been sent to a specialised laboratory in Western Australia for
toxicology testing. Results were due on 31 March 2023;
(C) Councillors further note the following Management Control Measures
proposed by the City:
(i)
as multiple lines of supporting evidence from both water quality and
autopsy results indicate avian botulism is the likely cause, the City is
preparing to implement controls in relation to avian botulism if it is
confirmed as the cause of the deaths; and
(ii)
the following
management strategy has been planned to mitigate the outbreak with works to
commence 3 April 2023:
(a)
remove sediment and reduce vegetation guided by an
ecologist/wetland specialist;
(b)
increased
reticulation of water in the wetland; and
(c)
additional
one-off sampling event of the water body to determine if conditions have
improved to suppress the outbreak (i.e. lower nutrient concentrations, lower
organics, higher oxygenation, etc);
(D) Councillors additionally note:
(i)
the system often experiences high nutrient levels due to stormwater flows
entering the system and the water is not considered suitable for primary
recreational contact (for example, swimming). As a result, permanent signage
exists, advising park users to:
(a) refrain from entering the lake and to be careful near the lake edge;
(b) avoid drinking the water;
(c) avoid fishing or using model boats on the lake; and
(d) prevent dogs entering the lake and keep them away from wildlife; and
(ii) the City works with a range of internal and external specialists to undertake proactive management measures to ensure the wetlands are maintained in a good condition. These include:
(a) quarterly testing of water quality by an independent environmental consultant;
(b) daily rubbish removal and litter inspections;
(c) monthly weed management of wetland reed beds and lake islands;
(d) periodic removal of silt build-up, excess vegetation and weeds (most recently undertaken in February 2023);
(e) inspections to ensure wetland is clean and in good ecological condition; and
(f) monthly check of water reticulation systems and pumps; and
(E) the Chief Executive Officer be requested to:
(i)
keep Councillors informed about
actions being taken to address duck and other wildlife fatalities at Lake
Northam;
(ii)
implement measures to mitigate the
risk of a similar mass fatality event from reoccurring; and
Carried unanimously.
X086653