SINOPSIS

This study examines the spatial and temporal variability of 6 pigments (scytonemin, β-carotene, chl. a, phycoerythrin, phyocyanin, and allophycocyanin) within calcareous cyanobacterial mats from South Florida, USA. The total pigment concentrations within the cyanobacterial mats varied spatially with deth through the mat. β-carotene, chl. a, and allophycocyanin concentrations increased significantly with mat depth. The cyanobacterial mats upper layer (0.3 cm) had a 5.57-fold increase and the middle layer (0.6 cm) had a 4.24-fold increase from 0700 to 1200 hrs, while the largest increase was in the lower layer (1 cm) a 7.23-fold increase from 1000 to 1300 hrs. The community total pigment concentration from 0800 hrs and peaked at 1300 hrs varying from 7.61 mg·cm⁻³ to 21.06 mg·cm⁻³, a 2.77-fold increase, then decreasing at 1345 hrs. Scytonemin, which shields algae from UV-radiation, was abundant throughout the mats. β-carotene, scytonemin, and chl. a contributed over 97% of the total pigment concentration. All pigment concentrations increased with time of sampling, some as much as 3-fold, from 0800 to 1300 hrs and then declined. This may represent a diurnal cycle of resource allocation to optimize light harvesting and cell growth, which has implications for timing of sampling and estimating biomass with pigment concentration.