Spring production of mycosporine-like amino acids and other UV-absorbing compounds in sea ice-associated algae communities in the Canadian Arctic

Marine phytoplankton are known to produce mycosporine-like amino acids (MAAs) for protection against UV radiation. To assess whether the same strategy applies to sea ice-associated communities, MAAs were measured in algal communities associated with surface melt ponds, sea ice (bottom 3 cm), sea ice-water interface below melt ponds, and underlying seawater in a coastal bay of the Canadian Arctic Archipelago during the spring melt transition from snow-covered to melt pond-covered sea ice. Six UV-absorbing compounds (UVACs) were detected as the spring melt progressed, 3 of which are identified to be shinorine, palythine, and porphyra-334. A fourth UVAC (U1) is most likely palythene. The molecular identities of the other 2 UVACs, U2 and U3, which have an absorption maximum of 363 and 300 nm, respectively, remain to be structurally elucidated. The highest UVAC nominal concentrations were observed in the 3 cm bottom ice under thin snow-covered sites just prior to complete snowmelt. Normalization to chlorophyll a content revealed that the greatest contribution to UV absorption from biota was associated with melt ponds that are exposed to the highest light intensity. These results confirm that Arctic sea ice-associated communities are capable of producing photoprotectants and that spatial and temporal variations in MAA and other UVAC synthesis are affected by snow cover and UV radiation exposure.