Spatio-Temporal Distribution of Amino Acids on the Surface Sediment of the Segara Anakan Lagoon, Java, Indonesia

Coastal lagoon sediments function as a site for mineralization and storage process of settled organic matter (OM) originating from different sources. Studying the geochemical processes in the coastal sediment would provide information related to the adjacent environmental activities and helps examining the processes occurring in the sediments in the course of degradation.

In this study, the spacio-temporal abundance and composition of total hydrolysable amino acids was determined on the mangrove-fringed coastal lagoon sediments of Segara Anakan Lagoon (SAL), Java, Indonesia. Total organic carbon (C_org), total nitrogen (TN), carbon/nitrogen ratio (C:N), stable isotopic compositions of carbon (δ¹³C) and nitrogen (δ¹⁵N), total hydrolysable amino acids (THAA) and hexosamines (THHA) were measured from the surface sediments. The surface sediment samples were collected from 11 stations during two sampling campaigns (SPICE II project) in February and September to represent the rainy and dry seasons, respectively. The sediment C_org and TN value of the stations were as high as 3.4% and 0.2% for the rainy, and 4.5% and 0.2% for the dry seasons, respectively. While the δ13C_org values showed a range between -24.83‰ and -27.9‰, the δ¹⁵N (‰) values range between 2.4‰ and 5.6‰ in the dry and rainy seasons. Correlation of the AA-C% and AA-N % contribution across the stations in the rainy and dry seasons were comparable (r² = 0.6). However, AA-C% display a slight decrease from western to eastern area of SAL. C:N ratio of rainy and dry seasons showed a range between 23.8 - 7.9 and 36.4 - 7.3, respectively. which clearly marked that the stations are getting mixtures of OM from autochthonous and allochthonous OM sources. Results from the reactivity index (RI) and production of non-protein amino acid reveals strong positive correlation of the dry and rainy seasons. The β-alanine and γ-aminobutyric acids (1.9-3.6 mol%) fits well within the coastal sediment ranges. Glycine was found to be the most abundant amino acid both in the dry and rainy seasons.