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.
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