| Nutrient cycle in Wilson Inlet investigated
|
In October 2008 the Department of
Water employed Geoscience Australia
to investigate nutrient fluxes
between sediments and the water
column at a number of South Coast
estuaries including Walpole/
Nornalup, Irwin Inlet, Parry Inlet
and Wilson Inlet to assess the impacts
of sediment-water interactions
on water quality. The study
was a part of a broader investigation
being conducted by the Department
of Water (Water Science
Branch) to develop resource condition
indicators in estuaries.
A number of sites were chosen in
each inlet where benthic chambers
(see picture) were deployed and
sediment pore water was extracted
to measure ammonia (NH4+), nitrate
and nitrite (NOx), phosphate
(PO4-3), silicate (SIO44-) and total
carbon dioxide (TCO2). Oxygen
and carbon dioxide fluxes within
the chambers were also calculated
to determine the respiration and
photosynthetic activities of benthic
organisms and plants or algae. Bottom
and surface water nutrients
were also collected at each site for
comparison. Complimentary to the
nutrient flux investigations sediment
cores were also taken where nutrients
and porosity (measure of air
spaces in the sediment) were analysed.
In conjunction to the nutrient investigation,
an underwater video camera
was deployed over the side of a boat
to video submerged aquatic vegetation
including seagrass and macroalgae.
The video was slowly moved
along transects in each Inlet and the
benthic characteristics filmed and
described. In future this method may
assist in rapidly accessing the condition
and changes in aquatic vegetation
and used as a means of mapping
submerged vegetation.
The report on the findings will be
due out soon. If you would like further
details on this project please
contact the Department of Water on
(08) 98425 760.
| The Ecological Value of Denmark's Rivers
|
An ecological study of rivers and
creeks across the south coast was
recently completed by the Centre
for Excellence in Natural Resource
Management (University of Western
Australia), on behalf of the Department
of Water and South Coast
NRM.
The western south coast area, from
Albany westward, encompassed 18
river systems including the Denmark,
Hay and Sleeman Rivers.
The project aimed to determine the
'ecological value' of 33 river systems
and rank them in order of
value. The ecological value of the
systems was determined by the
degree of naturalnessere ranked
6th, 10th and 16th in their degree of
ecological value, respectively.
The study highlighted several interesting
facts such as:
- Hay River appeared to be a
'hotspot' for total species
richness and endemism.
- A new species of macro invertebrate
was discovered in
the Quickup and Mitchell
Rivers.
The Balston's Pygmy Perch, which
is listed as 'vulnerable' under the
Environment Protection Band Biodiversity
Act 1999 (EPBC Act), was
found in the Denmark River. This
species is regarded as the rarest of
all the endemic freshwater fishes
of south-west Australia. The perch
inhabits areas of shallow water
with tall sedge thickets and inundated
riparian vegetation as is
found through out the Denmark
River.
The Hay River, was found to be
home to the Mud Minnow, which
is
listed as 'restricted' by the Australian
Society for Fish Biology, and was
only found in three other river systems.
The species occurs in swift
flowing streams within karri forests
and is typically
found
near submerged
vegetation,
occasionally
in
the still water
of
ponds, swamps and roadside drains,
and often inhabiting darkly tannin-stained
water.
The report 'Ecological Values of Waters
in the South Coast Region' has
been drafted and will be published
in the coming weeks. For further information
please contact DoW Rivercare
Officer Kirsten Murray on (08)
98410 120.
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