July 2023: Water Quality and Macroinvertebrate analysis

Hi everyone

Attached are the results for Water Quality Monitoring, Chemical Analysis and Macroinvertebrate Sampling for July, 2023.

In respect of those results please find the following notes:

Water quality was generally quite good across the areas sampled; the worst results were from Waterhen Lake as usual and Crane Creek at Nerang. This is due primarily to a lack of water flow and stagnation which will only be remediated by rainfall in the order of 150mm. Of particular note is the significant salinity at the Coomera River Weir, where the increased salinity was due to a greatly reduced flow of fresh water in the Coomera River, which in turn was the result of a lack of rain and water extraction by residents, probably in equal proportion.
Chemical analyses were remarkably consistent across the area sampled which was welcome news following the results from the previous month; this means that there were no sewage leaks and not more than normal phosphate levels from agricultural/garden activities.
Macroinvertebrate samples were generally in the healthy range, however we could not sample three streams due to the lack of flow. To sample where there is no flow is pointless and does damage whatever animals may be aestivating in the sediment/substrate. These streams will be sampled as soon as significant rainfall occurs. It was great to see the return of significant numbers of animals in July, as the previous sampling in April was the worst for numbers of animals that I have experienced. The benchmark for a healthy sample is 200 individual animals; back in April were fortunate if the numbers reached 50 in total in a couple of sample points.
Of potential interest to fishing people was a conversation I had with a fellow fishing under the M1 bridge at 4.30am one morning: he told me that he had been fishing in Saltwater Creek at Monterey Keys and had caught significant numbers of bream between 37 and 42cm in length, both roed up females and breeding ready males (bait was chicken hearts for those interested). This is relevant because this year, instead of bream running out to sea to spawn, it appeared they were spawning well up river. The reasons for this are not clear however it could be speculated that, with a lack of significant rainfall and higher than usual salinity levels upstream, the fish found it easier to spawn where they were and not run the gauntlet of predators – humans, dolphins and sharks.

So there you have it for the month of July.

If you have the time and energy, get out there and enjoy our great country; there is so much to see and learn.

Kind regards

Steven Gill