Amino acids in biofilm material on aluminium panels immersed in marine waters

Abstract

Suspended particulate matter (SPM) and the biofilm material on aluminium panels immersed in the surface waters (∼ 1m) of Dona Paula Bay over a period of 10 d were analysed for their organic carbon (OC), organic nitrogen; (ON) and total hydrolyzable amino acids (THAA) concentrations; and for their composition. The OC, ON and THAA concentrations of the SPM did not vary much during the sampling period. As compared to this, on the aluminium panels the biofilm biomass (measured as OC and ON) and the biofilm THAA showed a non‐linear increase over the period of immersion. Carbon and nitrogen in the THAA varied from 6.61 to 23.52% of the total OC and 23.90 to 35.04% of the total ON of the biofilm material, and from 16.10 to 18.90% of the total OC and 36.63 to 52.04% of the total ON of the SPM. Aspartic acid, glycine, alanine, serine, leucine and lysine and glutamic acid were the most abundant individual amino acids in both the biofilm material and the SPM. The distribution of individual amino acids was very similar to that observed in the two major sources of organic matter, viz. terrestrial vascular plants and marine bacteria and microalgae. The mole fractions of most amino acids did not show variation over the period of observation, especially in the case of the SPM samples. However, the mole fractions of glycine and serine in the biofilm samples generally decreased during the period of observation. These changes are attributed to the increasing abundance of cells of diatoms and/or bacteria, as compared to the structural constituents of diatom cell walls and/or detrital material.