Protistan cysts

Hi! I am a PhD student in Geography, researching Quaternary Paleoenvironments using lake sediments. I analyze for charcoal, XRF, stable C and N isotopes, and various other things. I need to learn more about dinoflagellates.  One of my sites has Peridinium limbatum during the oligotrophic lower portion of the core.  There is a transition with many cysts that may be P. limbatum, but I am not sure.  If I find the vegetative forms in the lower portion but mostly cysts in a transition section, is this indicative of an unfavorable environment for the mature forms?  If they never excysted, then conditions must have stayed unfavorable? Or they were buried?  What do you think?  Thanks.