Exploratory analysis of chitosan in marine seston samples from a temperate estuary (Argentina)

Abstract

Chitosan is a linear polysaccharide composed of randomly distributed chains of β-(1,4)-d-glucosamine (deacetylated units) and N-acetyl-d-glucosamine. It can be found in the cell walls of some fungi and is a product of the deacetylation of chitin, which is produced in large quantities by crustaceans. Chitosan was quantified in seston size fractions (F) (suspended par- ticulate matter-SPM, ≤ 20, 20–60 μm, 60–200, and ≥ 200 μm) to establish a range of importance in the contribution of this polymer to a water column in the Bahía Blanca Estuary (BBE). Sampling was conducted in the BBE inner zone (Puerto Cuatreros) between February 2014 and February 2015. Physicochemical and biological variables were also obtained. Chi- tosan concentration was highest in F ≤ 20 μm (0.19 ± 0.02 mg/L) and FSPM (0.13 ± 0.06 mg/L) during winter and spring. Highly significant differences were found between the F ≤ 20 and the rest of the seston fractions. Differences in seasonality, particularly between warm and cold seasons, were also found, corroborated by the principal component analysis in which seasonal variation was highlighted. Microdetritus and planktonic organisms (fungi, diatoms and copepods) at F ≤ 20 μm represent a chitinaceous source, which produces chitosan through the degradation process carried out by the same organisms. It is deduced that the chitosan concentrations follow the sestonic dynamics from the BBE, being this polymer a substantial component of organic matter, with great potential as a biogeochemical indicator of this system.