Carbon and Nitrogen Contents Driven by Organic Matter Source within Pichavaram Wetland Sediments

Sathy A Naidu,Alexander Pérez,Thanumalaya Subramoniam,Kandasamy Kathiresan,Raj A Naidu,Rajendran Narender,Ruth M Post,Arny L Blanchard,Jeffrey H Simonson,Christian J Sanders

doi:10.3390/jmse10010053

Abstract

Differences in grain size, total organic carbon (OC), total nitrogen (TN), OC/TN ratios, and stable isotope (δ13C and δ15N) were assessed in sediments from areas covered by mangrove and saltmarsh vegetation within Pichavaram estuary (Southeast India). The mean percentage contents of silt and clays (70 vs. 19%), OC (5.7 vs. 2.0%), and TN (0.39 vs. 0.14%) were consistently higher in the mangrove as compared to those observed in the saltmarsh tidal zone. These differences may obey the higher deposition and retention of fine particles in the presence of a mangrove root system that may facilitate the accumulation and preservation of organic matter within these sedimentary systems. Further, higher OC and TN contents were associated to higher terrestrial or mangrove-derived organic matter contribution with lighter δ13C signatures (−26.0‰) in both sedimentary tidal zones, whereas lower OC and TN contents were associated to heavier δ13C signatures. This study is in agreement with previous studies which indicate that the presence of wetland vegetation may increase the carbon and nutrient storage capacity within estuarine ecosystems, highly relevant information for the establishment of further conservation strategies for blue carbon ecosystems at global scales.

Highlights

There is growing global interest in vegetated coastal wetlands zones, as they are known for their significant role in providing invaluable ecosystem services including supporting high biological diversity [1,2]
This study aims to determine differences in grain size, total organic carbon (OC), total nitrogen (TN), OC/TN ratios, and stable isotope (δ13C and δ15N) within mangrove and saltmarsh sediments of Pichavaram estuary, to gain a better understanding of the blue carbon dynamics along intertidal vegetated ecotones
The organic matter content and fine particles found in mangrove sediments as compared to the adjacent saltmarsh sediments may obey the differences in the transport and deposition processes between the two sedimentary environments [10,30]

Summary

Introduction

There is growing global interest in vegetated coastal wetlands zones, as they are known for their significant role in providing invaluable ecosystem services including supporting high biological diversity [1,2]. These ecosystems protect coastal regions against environmental impacts (e.g., storms, tsunamis and hydrological) [3,4] as well as anthropogenic pressures (e.g., sewage effluents and eutrophication) [5,6]. Those factors may produce changes in the sedimentary organic matter sources and blue carbon accumulation capacity within these ecosystems, which are typically assessed using isotopic and elemental compositions, e.g., organic carbon (OC), total nitrogen (TN) and carbon isotopic signatures

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