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The impact of sewage effluent on the benthic macroinvertebrate community of the upper Thredbo RiverTiller, David, n/a January 1988 (has links)
Thredbo Village is a year round alpine resort located in Kosciusko
National Park, south eastern New South Wales. Treated sewage effluent
from Thredbo Village is discharged to the upper Thredbo River. The
river is a rocky bottomed, high mountain stream (> 1,200 m altitude in
the study area) flowing predominantly through subalpine woodland, the
only major impact on the river within the study area was that of the
Thredbo Village alpine ski resort.
Nutrient concentrations were measured in the upper Thredbo River
monthly from January to September 1983 at 9 sites along the river, both
upstream and downstream of the effluent discharge. In addition,
invertebrates were collected at the same sites in January, April and July
1983.
The near pristine section of the upper Thredbo River upstream of
Thredbo Village was low in phosphorus and nitrogen (<20 mg m-3 and
<100 mg m-3 respectively). The sewage effluent discharge was high in
phosphorus and nitrogen (up to 5,000 mg m-3 and 28,000 mg m-3
respectively). Phosphorus generally returned to concentrations similar to
those measured in the pristine sections by 3.5 kilometres downstream of
the discharge. Nitrogen (mostly in the form of nitrate and nitrite)
often remained elevated down to the most downstream site, 8 kilometres
downstream of the effluent discharge.
The elevated nutrient concentrations immediately downstream of the
effluent discharge stimulated the growth of attached filamentous algae in
January when conditions for growth were most favourable. It is
concluded that this growth provided an additional food source for several
invertebrate taxa, Cricolopus sp. 12E and 160E (Diptera, Chironomidae),
Conoesucidae sp. TR6, Oxyethira columba (Trichoptera), Nais sp.,
Aeolosomatus niveum (Oligochaeta), and Austrocercella tillyardi
(Plecoptera), which occurred in higher numbers downstream of the effluent
discharge. Downstream of the effluent discharge the taxonomic
composition of the invertebrate community was not altered substantially
from that upstream, although there was a significant increase in the
abundance of the taxa which could take advantage of the increased food
resource. The changes in the invertebrate community were not evident
3.5 kilometres downstream of the effluent discharge, which corresponded
to the return of phosphorus concentrations to background levels. There
were increased abundances of several invertebrate taxa downstream of
both Thredbo Village and the rubbish tip in January which were
consistent with, but not as great as, those downstream of the sewage
effluent discharge. This was likely to be a result of increased nutrient
loads from urban runoff and tip leachate at these sites which possibly
lead to increased algal productivity. However, nutrient concentrations at
these sites were not notably higher than at the control site. The
sewage effluent discharge resulted in only small changes to the
invertebrate community in April or July 1983.
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Towards an in situ technique for investigating the role nutrients play in epilithon growth in an Australian upland streamBrown, Glen, n/a January 2001 (has links)
There is limited knowledge and understanding of the role of nutrients and effect of
herbivore grazing on epilithon production in Australian upland rivers. Before
investigating these processes, a method was required that will allow the study of factors
(physical, chemical and biological) that affect epilithon abundance and distribution in
lotic systems. The Thredbo River, Kosciusko National Park, New South Wales,
provided an opportunity to conduct this investigation because it: is relatively
undisturbed; has been intensely studied; is easily accessed; and is of appropriate width
and depth to conduct in-stream experiments.
The specific goals of this research were the: (1) validation of the nutrient-diffusing
substrate method for investigating epilithon responses to nutrients; (2) development of
experimental channels in which to investigate nutrient/epilithon dynamics in an upland
stream; (3) development of a method to inhibit macroinvertebrate grazing from in situ
experimental channels, so that epilithon responses to nutrients with and without grazing
pressure can be studied; and (4) assessment of the ecological implications of nutrient/
epilithon/macroinvertebrate interactions assessed from in-stream experiments.
Major achievements of my research, that advance the study of stream ecology, are as
follows:
· The investigation of the features of nutrient release from terracotta nutrientdiffusing
substrates showed that phosphorus does not readily diffuse through
terracotta clay, probably because terracotta contains known binding agents for
phosphorus, such as iron, and because pores are easily blocked. I concluded that
this type of substrate is inappropriate for studying nutrient dynamics and epilithon
responses to the nutrient(s) limiting growth. The outcomes of this research has
implications for future research using nutrient-diffusing substrates, and of how
nutrient limitation information is interpreted from past research using terracotta
nutrient-diffusing substrates.
· I designed and tested in-stream experimental channels that were functional and
provided near natural conditions for studying the interactions between nutrients/
epilithon/macroinvertebrates, without affecting physical variables not tested for.
The in situ method developed was successful in simulating 'real world'
complexities. Clay paving bricks were used as standardized common surface for
community development because their colour, size and surface texture are similar
to those of natural stones.
· I developed a technique for successfully inhibiting macroinvertebrate grazing from
designated areas, using electricity, without affecting flow and light. This technique
will enable in-stream herbivory studies to assess the effects of macroinvertebrate
grazing pressure on epilithon under natural conditions, including variability in
flow, temperature, light and nutrients. It will allow the vexed question of whether
epilithon biomass is controlled by bottom-up or top-down processes to be
objectively addressed.
The construction of in situ experimental channels that simulate natural conditions,
combined with the non-intrusive methods of macroinvertebrate exclusion and nutrient
addition, resulted in a study design that will facilitate the investigation of biotic
responses to nutrients in Australian upland streams. Using the method developed, I
showed that variable flows in the upper Thredbo River appear high enough to slough
epilithon, but not high enough to dislodge macroinvertebrates. This may mean that in
systems such as the Thredbo River that experience frequent low level disturbance, the
epilithon is unable to reach equilibrium. There is strong top-down control of epilithon
in this stream, with nutrients, temperature and light playing a secondary role. I
concluded that natural variability may be more important than previously considered
and perhaps this, rather than constancy, should be studied.
This thesis adds support to the continuance of multiple factor investigations, and
advocates that such studies be conducted under natural conditions so that the results
are more relevant to natural systems than from studies conducted in controlled
laboratory and outdoor artificial streams. Clearly, the in-stream channels, developed as
part of the current research, will allow research that contributes to our understanding of
community responses to the physical, chemical and biological processes operating in
lotic environments.
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The impact of sewage effluent on the relationship between periphyton and benthic macroinvertebrates of the Thredbo River and the effects of nutrient removalThurtell, Lisa, n/a January 1992 (has links)
Nutrients, periphyton and macroinvertebrates were sampled every two months
for one year to assess the effects of treated sewage effluent on the Thredbo River
and to compare changes in chemical concentrations and the invertebrate
community since the introduction of nutrient removal on the Thredbo sewage
treatment plant. Chemically, the impact of the effluent was minor and was
reduced from levels measured before the addition of nutrient removal to the
Thredbo sewage treatment plant. However, the reduction may be the result of
higher flows during the study period. Biologically there was no indication of
nutrient enrichment during June, August and October, with differences occurring
between physically dissimilar sites irrespective of position relative to the sewage
effluent inflow. Large increases in periphyton and macroinvertebrates occurred in
December, February and April at both open sites and those downstream of the
sewage outflow. Previous studies found increases in invertebrate abundance and
richness immediately downstream of the sewage inflow, but the impact was
greater and extended further downstream than found in this study.
Strong correlations between total phosphorus and periphyton biomass and
chlorophyll-a indicate phosphorus was a limiting nutrient. Higher periphyton
biomass and chlorophyll-a at all sites during the warmer months (especially at
open sites with an even cobble substratum), throughout the year, indicates light,
temperature and substratum type were as important as phosphorus in controlling
algal growth. Low algal biomass during the high flow month of October also
indicates the importance of water velocity in controlling periphyton biomass.
The structure of the macroinvertebrate community was noticeably different at
sites downstream of the effluent discharge, with the exception of the most
downstream site, when compared to the upstream sites. The occurrence of high
macroinvertebrate numbers and species richness at sites with high periphyton
growth and the strong positive correlation between invertebrate grazers and
periphyton measurements shows a dependent relationship between invertebrates
and periphyton growth. Therefore, the physical factors of light, temperature and
substratum characteristics of particular sites in the Thredbo River, may be as
important in controlling the benthic community as the levels of nutrient inputs
from sewage.
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