A major difference between the two ponds' temporal variability appeared at d63. Pond D showed a strong decrease of cyanobacteria in favour of diatoms (57%), prasinophytes 1–2 (36%) and some cryptophytes (3%), while pond C produced the same order of abundance for cyanobacteria (37%), diatoms (32%) and prasinophytes 3 (28%), with 2% of dinoflagellates instead of cryptophytes. Note that this major difference between the two ponds coincided with the first mortality period.
Within the 2–20 μm size fraction (Fig. 6), there was also a difference between the two ponds at days d37 and d43, when diatoms were clearly dominant in pond D (74%) and diatom, cyanobacteria and prasinophytes 1–2 were combined in pond C. At d49, relative biomasses of the three major taxa were similar in the two ponds. Abundance of dinophytes (3%) was low at d43 for pond C and at d49 for pond D.