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

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),δ13C,particulate nitrogen(PN),δ15N and chlorophyll a were analyzed.Surprisingly no significant temporal variations were observed in the parameters analyzed;nonetheless,salinity,POC,δ13C,PN,δ15N,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 C3 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.

Assessment of the Impact of Developmental Activities on the Estuarine Environments of Mandovi and Zuari Rivers of Goa along the West Coast of India

Physico-chemical and biological data on water and sediments were collected from Mandovi and Zuari Rivers of Goa along the central west coast of India from 2007 to 2008 to understand the impact of developmental activities on the riverine environments. Factor analysis of the data segregated over high and low tides indicated a total of 6 factors each explaining 91% of variance during high tide and 84% of variance during low tide in Mandovi River. In Zuari River, a total of 6 factors explained 83% of variance during high tide and 4 factors explained 78% of variance during low tide. Factor analyses showed the dominance of nitrite and nitrate in Mandovi and of lead and mercury in Zuari. Higher inputs of anthropogenic ammonia and phenols associated with some phosphate were found in both these rivers. Water quality index （WQI） studies showed increasing overall index of pollution （OIP） values especially in the upstream of Zuari River, suggesting slightly polluted water. Increasing developmental activities along the banks of these rivers introduce domestic and anthropogenic nutrients and trace metals in their estuarine region, which flush out to the sea as per tidal currents, which otherwise can hamper the natural environments of these two rivers.