Hi Melanie, I use ProDSS probe for vertical profiling in reservoirs. I also have quite experience in pigment quantification under lab conditions, mainly with HPLC technique. In my experience the results of total algae (in terms of Chl a) and PC sensor are only approximate (to be generous). The Chl a data in the field presents quite large oscillation forks so that not even the estimated average data is reliable when compared to spectrophotometry or chromatography data.

Considering the calibration issue, the supplier indicated me that it was best to maintain the factory calibration. I bought a chlorophyll standard for fluorescence measures and after the calibration I made sure that it is not advisable to make routine calibrations for this sensor. Actually, nowadays I work with the restored factory calibration.

In summary, in my case it only serves to have a rough estimate of the amount of algal biomass that I can detect in further analyses or to the effect of early warning considering the presence of cyanobacteria in the water if both ug/L and RFU units return clearly positive data. Perhaps in continuous measurements this type of sensor is more reliable (my experience with continuous profiling platforms is not too promising either) when working with huge data sets but for specific measurements, in my opinion, they only represent a first contact with the trophic state of the water mass.

I hope my answer has been helpful to you. Greetings.

Alfredo Llorente Thank you for your response. We are just interested in relative changes at this point for possible cyano detection during depth profiles in a lake. The plan is that if we see a spike in the data, that we would then take a sample for confirmation.

Hi Melanie,

I do not measure with the probe alone, but I use the measured values for the evaluation of water reservoirs. I take the data as indicative, they do not match the data measured spectrophometrically, which I prefer when evaluating, eg trophy.

the advantage is that the sampler sees the measured data right in the field and thus can take additional samples from the currently animated layer for microscopic evaluation. but the results do not always agree. At the same time, I found, especially for clean water tanks, that it is necessary to monitor even picocyanobacteria.

Regards Emil

Thank you for the input. That is what we are hoping to do with it. Get a general idea of when and where changes are occurring then sample as needed for confirmation.

This stream article for the Pac. NW may be of interest:

Preprint Microbial diversity and metabolic potential in cyanotoxin pr...

-Bob