Sources and implications of particulate organic matter from a small tropical river—Zuari River, India

• Published in: Acta oceanologica Sinica Vol. 39; no. 4; pp. 18 - 32
• Main Authors: Fernandes, Dearlyn, Wu, Ying, Shirodkar, Prabhaker Vasant, Pradhan, Umesh Kumar, Zhang, Jing
• Format: Journal Article
• Language: English
• Published: Beijing The Chinese Society of Oceanography 01.04.2020; Springer Nature B.V; State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China%National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa 403004, India%National Institute of Oceanography (Council of Scientific and Industrial Research), Regional Centre, 4 Bungalows, Andheri (West) 400053, Mumbai, India
• Subjects: Alanine; Amino acids; Anthropogenic factors; Aquatic ecosystems; Aspartic acid; Bacteria; Biogeochemical cycle; Biogeochemical cycles; Biogeochemistry; Biomarkers; Brackishwater environment; Carbon 13; Chlorophyll; Chlorophyll a; Climatology; Coastal waters; Detritus; Earth and Environmental Science; Earth Sciences; Ecology; Ecosystems; Enantiomers; Engineering Fluid Dynamics; Environmental Chemistry; Estuaries; Estuarine dynamics; Estuarine ecosystems; Glutamic acid; Heterotrophic bacteria; Human influences; Leucine; Marine & Freshwater Sciences; Monsoons; Oceanography; Organic carbon; Organic matter; Parameters; Particulate matter; Particulate organic carbon; Particulate organic matter; Plankton; Principal components analysis; Rivers; Seasons; Serine; Spatial variability; Spatial variations; Suspended particulate matter; Temporal variability; Temporal variations; Turbidity; Tyrosine; Variability; Wind; India; suspended particulate matter (SPM); degradation index (DI); Zuari River; estuarine turbidity maximum (ETM); organic matter (OM); amino acids (AA); organic matter(OM)
• DOI: 10.1007/s13131-020-1544-x
• ISSN: 0253-505X

Transitional ecosystems, estuaries and the coastal seas, are distinctively affected by natural and anthropogenic factors. Organic matter (OM) originating from terrestrial sources is exported by rivers and forms a key component of the global biogeochemical cycles. Most previous studies focused on the bulk biochemical and anthropogenic aspects affecting these ecosystems. In the present study, we examined the sources and fate of OM entrained within suspended particulate matter (SPM) of the Zuari River and its estuary, west coast of India. Besides using amino acid (AA) enantiomers (L- and D-forms) as biomarkers, other bulk biochemical parameters viz. particulate organic carbon (POC), δ 13 C, particulate nitrogen (PN), δ 15 N and chlorophyll a were analyzed. Surprisingly no significant temporal variations were observed in the parameters analyzed; nonetheless, salinity, POC, δ 13 C, PN, δ 15 N, glutamic acid, serine, alanine, tyrosine, leucine and D-aspartic acid exhibited significant spatial variability suggesting source differentiation. The POC content displayed weak temporal variability with low values observed during the post-monsoon season attributed to inputs from mixed sources. Estuarine samples were less depleted than the riverine samples suggesting contributions from marine plankton in addition to contributions from river plankton and terrestrial C 3 plants detritus. Labile OM was observed during the monsoon and post-monsoon seasons in the estuarine region. More degraded OM was noticed during the pre-monsoon season. Principal component analysis was used to ascertain the sources and factors influencing OM. Principally five factors were extracted explaining 84.52% of the total variance. The first component accounted for 27.10% of the variance suggesting the dominance of tidal influence whereas, the second component accounted for heterotrophic bacteria and their remnants associated with the particulate matter, contributing primarily to the AA pool. Based on this study we ascertained the role of the estuarine turbidity maximum (ETM) controlling the sources of POM and its implications to small tropical rivers. Thus, changes in temporal and regional settings are more likely to affect the natural biogeochemical cycles of small tropical rivers.