Optimal filter pore size
We found 1 µm PCTE filters had the highest number of intracellular eDNA copies (mean: 970,000), with the mean number of copies descending to 937,000 for 3 µm, 801,000 for 8 µm, 762,000 for 5 µm, and the fewest copies detected with 10 µm (596,000). We found the 95% confidence intervals of all but the 10 µm filters overlapped the zero line when assessing the deviation from global mean (Figure 3 ), and there was no significant difference in copy number among different pore size categories using averaged data from qPCR technical replicates (F4,15 = 0.34, p = 0.84). We found a non-significant decrease of ~37,500 copies per µm increase in filter size when we treated filter pore size as a continuous variable (beta = 37,479, 95% CI = [-105,214, 30,257]; p = 0.26).