Water quality changes quickly, which can make it difficult to assess. Scientists have long relied on the biological communities of water to serve as indicators of water quality integrated over time. These are typically invertebrates or fish. But each taxa indicates different aspects of water quality and some aspects of water quality might not be well indicated by insects or fish.
Diatoms have also been used as indicators of water quality, but there utility is limited by the difficulty in counting them (it’s a skill) and knowing the environmental tolerances of each species of diatom.
Speeding up the reconstructions of assemblages of phytoplankton (green algae, diatoms…) would help immensely in providing better data on water quality. eDNA is a good candidate here, but very little work has been done on this.
Matt Cannon and colleagues at the Cleveland Clinic recently published a paper on eDNA for the Cuyahoga River. It’s an amazing paper where they report patterns of taxa such as fish, mammals, and birds all along the river.
They also measured algae and diatoms with two different primer pairs, but didn’t publish those data.
We looked at the data together and the data on algae and diatoms are actually quite informative.
Without going into details, the more pristine upper reaches are well-separated from the lower reaches by what algae and diatoms are present. Taxa like Paraphysomonas (a chrysophyte) are relatively more abundant in the upper reaches and other taxa like the dinoflagellate Peridiniopsis are more abundant in the lower reaches.
Without going into details on the results (hopefully, he’ll be able to write them up eventually), sequencing the DNA of phytoplankton has strong potential to change our ability to assess water quality in ways that just weren’t in reach earlier.
If you are interested in reconstructing phytoplankton communities with eDNA, feel free to contact us. These procedures are still in development, but should be available quite soon.