Behold, the advent of taxa diversity! Don’t worry; this Latin-sounding phrase isn’t heralding the introduction of a new tax or taxes. Rather, “taxa diversity” simply refers to a diversity of species. Aquatic macroinvertebrates (i.e., spineless animal species large enough to be seen without a microscope) comprise a wide range of organisms that are likely to respond to physical and chemical changes in their environment.
It’s a snail's life in the Murray River wetlands near Wellington and close to Lake Alexandrina in South Australia. Photo: Arthur Mostead
Even so, long-term monitoring of these is quite rare – not just in Australia, but globally.
In 1978, a long-term biological monitoring project was funded to monitor water quality and river health using insect and non-insect macroinvertebrates. The monitoring itself began in 1980 and is continuing three decades later. This study of the insect and non-insect communities in the River Murray resulted in a number of interesting findings.
Firstly, there has been an increase in the diversity and abundance of mosquitoes, flies and non-insects (excluding freshwater cray, shrimp, snails and mussels) over time. However, the number of mayflies – which are generally aquatic in nature – has decreased. Similarly, there has been reduced seasonal variability and less inter-annual variability.
The study also found that macroinvertebrate communities in the Murray are changing, with site and system variability altering over the almost 30-year period.
What does this all mean? And what are the implications on the River Murray?
Although there have been improvements in water quality, such as reduced salinity and turbidity, the system is changing in a non-cyclical way. This suggests that there could be a number of stress factors reducing system resistance and resilience, leading to continual change in the structure of the insect and non-insect communities.
The study suggested that the changes could result in a loss of some of the geographic distinctiveness in environmental and biological conditions in the Murray and Lower Darling Rivers.
Let’s cut to the chase then! What’s causing these changes to the macroinvertebrate community?
In this case, there isn’t one clear cut answer. Changes in macroinvertebrate communities were seen with seasonal and hydrological variations in electrical conductivity, water temperature, turbidity, alkalinity and flow. The recent drought along with water management, land management and climate changes are thought to be contributors to the changes observed.
If you want to find out more, including the recommendations made for possible management approaches, grab a copy of the report, “Review of the River Murray Biological Macroinvertebrate Monitoring program: Data analysis 1980-2008”, via BP-KID. The full report (with the exception of the Commonwealth Coat of Arms, the MDBA logo, all photos, graphics and trademarks), has been released under a Creative Commons Attribution 3.0 Australia Licence (CC BY).
When using the report or its material, make sure you reference us. You can use the following wording:
Title: River Murray Biological (Macroinvertebrate) Monitoring Program – Review of monitoring 1980-2009. Report prepared for the Murray–Darling Basin Authority by the Murray-Darling Freshwater Research Centre.
Source: Licensed from the Murray–Darling Basin Authority, under a Creative Commons Attribution 3.0 Australia Licence.
Authors: R Cook, W Paul, J Hawking, C Davey and P Suter
Brian
I really appreciated your answer – it would seem that you have confirmed that the proposed MDDA proposed Basin Plan is a solution in search of a problem given your answer that the primary driver of water quaility is droughts and floods and the natural variability of our river ...
... system?
Given the MDBA River Murray Water Quality Monitoring Program (WQMP)is providing data necessary for an improved understanding and better management of the water quality of the rivers in the Southern Basin, where can I find the MDBA data for salt and turbity levels for the following monitored sites; Morgan, Merbein, Red Cliffs, Euston, Kerang, Rochester, Shepparton and Balranald.
Do you have plotted graphs of the salinty and turbidity levels over the time that this data has been collected and does it show improvements in salinity and turbidity levels or is the situation currently at a ‘tipping point’ as some have claimed?
Does the MDBA’s WQMP show the similar results to the Macroinvertebrate study that there has been improvements in water quality, such as reduced salinity and turbidity over the last thirty years?
Given the tens of millions of dollars which have been spent by the MDBA on the proposed Basin Plan can you provide a simple breakdown in percentage terms of what is causing salinity and turbity issues in the Basin Rivers at the aforemention monitoring sites across the Southern Basin.
For example you say that the natural variabilty such as floods and drought play a major (primary) role and that recent water quality improvements where primarily driven by the drought and turbidity spikes by the floods; is the natural varibility responsiblity for 80%, 90% or more of the increased or decreases in salinty and turbity levels?
What percentage is driven by river regulations?
What percentage is driven by consumptive water use and diversions?
What percentage has been driven by the hundreds of millions of dollars spent on the National Salinity Plan?
What percentage is driven by human interference in the MDB (dams, weirs. levies, railway lines, roads etc?
In relation to water quality what impact are introduced species like carp and other introduced pests and weeds having in percentage terms?
What other factors are having an influence on water quailty and to what extent (please express as a percentage)?
If you don’t know or can’t answer doesn’t this just highlight the MDBA has developed a proposed Basin Plan based on the false premise that the health of the basin is at ‘tipping point’ because of human intervention when in fact that ‘primary’ driver of the Basin’s health is the natural variability of the system?
Thanks Brian
Really appreciate the feedback
Thanks makes for interesting reading.
Given the MDBA has stated above ‘… there have been improvements in water quality, such as reduced salinity and turbidity,’ to what does the MDBA attribute the improvements to water quality such as reduced salinity and turbidity?
Does this confirm the MDBA proposed Basin Plan ...
... is a solution in search of a problem?
thanks
Tom Chesson
Hi Tom,
A blog post never has room for all the detail!
The improvements referred to in water quality refer to the reductions in salinity and turbidity that occurred during the last nine years of the study (2000 – 2009), to various extents across the 7 sites. Temperature also increased – ...
... whether this is a regarded as an improvement or not depends on your viewpoint! However inflows decreased during the same period, and this is the key – these changes were driven primarily by the drought. During drought, low water tables mean decreased inflows of saline groundwater, leading to lower river salinity. Low river flows mean decreased erosion and transport of sediment, leading to lower turbidity. Since the floods of recent years, these parameters have gone in the opposite direction – in a big way! Recent peaks in turbidity for example, which appear as a dramatic degradation in water quality, are really just a reflection of the natural variability in water quality associated with droughts and floods.