Finding killer
frog fungus in
the Marshes:
Joanne Ocock
2013
But it’s not really anything to worry about!
Intro…
Methods...
Chytridiomycosis is a disease that frogs get from a
fungus called Batrachochytrium dendrobatidis or
Bd for short. It has dramatically affected amphibians,
causing population declines in over 200 species
worldwide. In Australia, most populations have
disappeared in rainforests and streams along the east
Coast (Figure 1). Generally, Bd is thought to not
survive in hot, arid conditions.
We obtained samples from 271 frogs over 13 species
in Feb ‘09 and Nov ‘09 to March ’10 by swabbing
their bellies and feet, and tested them for the
presence of Bd.
Figure 1. Distribution of Bd surveys in Australia showing
localities where Bd was detected (black symbols) and not
detected (white symbols). The Macquarie Marshes, is indicated
by a star, and positive records in the arid zone (light grey
shading, <500 mm annual rainfall).
Conclusions...
Volunteer Richard Tate swabs a green tree frog (Litoria caerulea)
Results...
These were a little surprising. Seventeen individuals
from seven species tested positive. This was
unexpected, because due to the high temperatures
and dry conditions of the Marshes, Bd was not really
expected to occur at all in the area. However, all
individuals had a very low infection load, well below
what generally causes frogs to die in other areas.
The killer fungus seems to occur in the Marshes, but
it doesn’t have much killing power, which is great
news! But to really say for sure, we’d need to test
frogs again during cold months when frogs are more
vulnerable to the fungus to likely to get sick.
The study was valuable because we showed
assumptions about Bd were wrong, and that there is
a lot more to learn about how the fungus behaves
and survives in semi-arid regions in Australia.
Acknowledgments...
We thank R. Jones G & L Hall, S & K Earl, D Thornton, M
& P Simpson and R. McConichie for access to the Marshes.
Rachel V. Blakey, 2013
In this flooded river red gum forest, I recorded
over 1000 bats with one bat detector in a single
night! We recorded 4 times as many bats in wet
habitats than in dry habitats.
Bats are everywhere!
They occur on every continent except
Antarctica, and in the Macquarie
Marshes there’s at least 12 different
species!
Long-eared bats prefer to fly under
cover of trees. They prefer river
red gums but we also recorded
them foraging in the dry forest
near the school.
Freetail bats are fast flyers and not shy of
flying out in the open, these bats were most
common foraging over the open swamps
like these reed beds.
For every different type of environment in the
Macquarie Marshes there’s a type of bat that
uses it. The Little Pied bat, a threatened species,
were most common foraging over these dry open
paddocks. Since they can eat up to their
bodyweight in insects per night, just think of
what they can do for our crops!
Bats love wetlands and
rivers. They need to
drink water regularly,
especially females who
are nursing young. They
also feast on all the
insects that emerge
from watercourses and
some bats even catch
fish.
We identify bat species by catching
them or by looking at their calls. This
distinctive Little Pied bat call has an
alternating frequency.
Excerpt from Honours Project by Claire Sives, 2011
Supervisor: Dr Kim Jenkins
Co-supervisor: Dr Debashish Mazumder
How important is River Red Gum carbon as an energy
source in floodplain ecosystems?
Introduction
Carbon is the energy currency that drives floodplain foodwebs. This study
looked at carbon in three different flood regimes- high (1-3 years), medium
(4-7 years) and low frequency (8+ years between floods).
Specifically we were interested in:
- The availability of River Red Gum carbon in floodplain sediments.
- What zooplankton will emerge from sediments when flooded?
- Will the zooplankton use River Red Gum carbon as an energy source?
This research is important to determine the knock-on impacts of the
reduction of RRG due to altered flooding regimes in the Marshes.
Methods
Dry topsoils from the three different flood regimes were inundated in the
lab and sampled over time to determine carbon content and consumption by
emerging zooplankton. How do we know whether RRG carbon was there and
being consumed? Each plant (and algae) has its own carbon stable isotope
signature (a ratio of 13C/12C), this signature can be detected in plants,
water, sediment, detritus and the creatures in floodplain waters.
Ostracods - Cladocerans
Results
High flood frequency contained fresh River Red Gum, medium flood frequency
areas contained aged Red Gum and low frequency flood areas contained
chenopods and grasses. Highest diversity and abundances of zooplankton
emerged in high flood frequency areas, less in medium and few in low
flood frequency areas. Cladocerans, consumed River Red Gum where is was
available and switched to chenopods and grasses in low flood frequency
areas. Ostracods did not consume the predominant carbon resources and
were in far lower abundances than cladocerans.
1mm
Conclusion
The study indicated that
- some microinvertebrates consume
basic floodplain carbon resources
- and extended drying of floodplain
wetlands may impact carbon sources
that support floodplain foodwebs.
We also found that stable isotope
analysis is a useful tool in floodplain
management. This method can detect
changes in floodplain resources and
micro-scale linkages at a basic trophic
level. This is particularly pertinent as
changes in microinvertebrate ecology
are often early warning signs of
declining in floodplain health.
High flood frequency
- Healthy River Red Gum -
Medium flood frequency
- Unhealthy/dead RRGum -
Low flood frequency
- Chenopods/grasses -
Thanks go to Leonie and Adam Coleman at ‘Wilgara’, Garry and Leanne Hall at ‘The Mole’, Doug and Chris
Andrews at ‘Messines’ and Ray Jones, Field Officer out in the beautiful Macquarie Marshes Nature Reserve.