Revenge of the Algae

It’s day three of the algae treatment of my pond. The data are not that encouraging if you were rooting for algaecide as a quick fix for my swampy green problem. Here are the results:

Visible spectra of pond water over 3 days

The absorption spectrum looks fairly consistent over the three days. We have had temperature fluctuations of about 10-15 degrees in addition to rain, so there are many variables that can impact subtle variations in the shape of the spectrum. The water has not altered from its turbid, green characteristics, and the spectra support the claim that little has changed in terms of algae content.

Fluorescence spectra (excitation wavelength of 405 nm) of pond water over 3 days. The spectra have been normalized by setting the height of the peak at 405 nm to 1.

The fluorescence spectra are displayed slightly differently from the previous articles in that they have been normalized. Assuming that the excitation peak stays roughly the same regardless of conditions, normalizing the spectra allows for a better comparison of the peak at 690 nm. It looks like there was a big change between days 1 and 2; however there is little change, and possibly an increase, in the peak from day 2 to day 3.

The instructions on the algaecide bottle say to repeat the treatment every 3 days until the pond has cleared. I will do one more treatment of 15 mL and if I do not see any meaningful change in the water quality, I will bite the bullet and replace the water.

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