Do I want to know how bad the consequences of this are?
OK, I'll ask because I'm curious, but it sounds like it could be quite different from your research so feel free to ignore:
1. Do you compare at all with other comparable river systems?
2. I assume plastic levels also affect biodiversity? (though so I guess might rainfall?)
The
wasn't really about ecological impacts of rainfall not appearing to have detectable significant effect on plastics, but more so about it not being viable for me to explore what could've been an interesting analysis. It's hard to say whether there not being a clear detectable trend here is because there isn't one or if it's because of limitations in the data (e.g. maybe if there were more trawls per month there would be a discernible pattern). I'm also unsure whether strong correlation between rainfall and plastics would have a strong effect size on biodiversity or ecosystems services and if so how. If there had been a clear pattern this might have been able to inform understanding of how plastics are entering waterways but it also could suggest greater dispersal of plastic from sites of pollution potentially making management and regulation more difficult.
1. Haven't yet but I'll be looking up literature around this. This also brings in the question of what to search for. E.g. other waterways in Victoria, waterways which face similar pressures, well-monitored waterways...
2. Yeah absolutely. Probably the most classic example of plastic harming wildlife is a sea turtle choking on a plastic bag, but for example, microplastics can have negative impacts on sea turtle brains. From individual impacts this can then change species composition etc. thus influencing bigger scope ideas like biodiversity. Rainfall as you would expect substantially influences ecosystem system functioning but afaik for these waterways that would be trend-based rather than substantial fluctuations for individual weather events.
There's a clear "turning point" in the data when looking at number of pollutants (in the up direction sadly) which I'll be looking at to see if there's data on change in biodiversity indexes which correlate with that; I won't be able to show causation but it'll still be interesting to see how closely tied they are (if that information is available - this will be a literature search).