C, N, P, S content of the Chlorophyta Chaetomorpha linum (Müller) Kützing in a vast high density mat of a Mediterranean non-tidal lagoon

In a Chaetomorpha linum high density mat extending over 300 hectares, between 2017 and 2019 samples were collected for C, N, P, S tissue content determination, biomass (b) was estimated, sediment samples collected for labile organic matter (LOM) determination, and water chemical-physical variables measured. The latter showed extreme conditions with a wide range of values ​​and with zero oxygen for long periods. N-NO3:SRP atomic ratio showed extreme P-limitation. Tissue macronutrients showed very variable values, highlighting a strong P-limitation and relatively high level of S. With exception of nitrogen, no significant differences were detected for each macronutrient between the months and between the stations, neither was any correlation found between macronutrients and LOM and b data-set. The growth and survival of the mat occurred despite the scarcity of P, which probably reached with very low frequency the surface layer of the mat, the one capable of performing photosynthesis, where it was quickly re-assimilated and utilised.