Fo' > Fs Discussion

To start, I am working with Acropora and Porites corals, specifically measuring active photosynthetic yield (YII) of endosymbiotic dinoflagellates (Symbiodiniaceae). I use the DIVING-PAM-II (https://www.walz.com/products/chl_p700/diving-pam-II/introduction.html). Alongside the standard YII measurement, I also use the far-red light before non-photochemical quenching to determine minimal fluorescence yield of an illuminated sample (Fo' value). I always acquire a higher Fo' value than my initial F value (Fs), thus leading to qL and qP values slightly higher than 1. As far as I can tell, my SAT-charts and light settings are good, so I am wondering if there is some biological reason this may occur.

Am I correct in the initial assumption that I calculate this metric without dark acclimation, given my use of the far-red laser to acquire minimum fluorescence yield (Fo')? As far as I can tell, Kramer et al. (2004) state that it should be fine given their use of Fs when calculating their coefficients of photochemical quenching (qL and qP):

qL = ((1/Fs) - (1/Fm'))/((1/Fo') - (1/Fm'))

qP = (Fm'-Fs)/(Fm'-Fo')

Article New Fluorescence Parameters for the Determination of Q A Red...

Is there actually a chance that I am opening up more reaction centers after excitation? Could I be exciting another molecule in the Symbiodiniaceae photosystem? Or, do I fundamentally misunderstand how to generate these parameters and how to interpret them? Either is fine, I just would like some additional input.

Secondary discussion:

In general, I know there is a lot of discussion as to whether metrics, other than Fv/Fm, are biologically relevant for dinoflagellates, including effective quantum yield (YII). I would love to get peoples' perspectives and insights on this. Is it worth collecting non-Fv/Fm values for endosymbiotic dinoflagellates given their biologically different systems (compared to the land plants all of this stuff was developed for).

This all stems from collecting Fv/Fm being impractical (and generally uninformative) for my work. I've been working on following the response of coral microbial assemblages to transplantation, so it is not practical to repeatedly night dive to collect this metric. Additionally, I've seen some resources saying that effective photosynthetic yield (YII) is more informative for detecting acclimation responses. Fv/Fm is big in the coral community due to all of the heat-stress assays used to evaluate response to warming ocean temperatures.

Thanks in advance for your insight.