Carbon Sequestration and Sedimentation in Mangrove Swamps Influenced by Hydrogeomorphic Conditions and Urbanization in Southwest Florida

Daniel Marchio,Brian Bovard,William Mitsch,Michael Savarese

doi:10.3390/f7060116

Abstract

This study compares carbon sequestration rates along two independent tidal mangrove creeks near Naples Bay in Southwest Florida, USA. One tidal creek is hydrologically disturbed due to upstream land use changes; the other is an undisturbed reference creek. Soil cores were collected in basin, fringe, and riverine hydrogeomorphic settings along each of the two tidal creeks and analyzed for bulk density, total organic carbon profiles, and sediment accretion. Radionuclides 137Cs and 210Pb were used to estimate recent sediment accretion and carbon sequestration rates. Carbon sequestration rates (mean ± standard error) for seven sites in the two tidal creeks on the Naples Bay (98 ± 12 g-C m−2·year−1 (n = 18)) are lower than published global means for mangrove wetlands, but consistent with other estimates from the same region. Mean carbon sequestration rates in the reference riverine setting were highest (162 ± 5 g-C m−2·year−1), followed by rates in the reference fringe and disturbed riverine settings (127 ± 6 and 125 ± 5 g-C m−2·year−1, respectively). The disturbed fringe sequestered 73 ± 10 g-C m−2·year−1, while rates within the basin settings were 50 ± 4 g-C m−2·year−1 and 47 ± 4 g-C m−2·year−1 for the reference and disturbed creeks, respectively. These data support our hypothesis that mangroves along a hydrologically disturbed tidal creek sequestered less carbon than did mangroves along an adjacent undisturbed reference creek.

Highlights

IntroductionIncreasing the potential for carbon sequestration by terrestrial and aquatic ecosystems has been proposed as a solution to mitigating increased greenhouse gas (GHG) concentrations in the atmosphere
Increasing the potential for carbon sequestration by terrestrial and aquatic ecosystems has been proposed as a solution to mitigating increased greenhouse gas (GHG) concentrations in the atmosphere.Many studies have shown that wetlands play a dominant role in the global cycling of carbon as a result of anaerobic substrates and high primary productivity [1,2]
This study investigated the recent sedimentation and carbon sequestration of four distinct mangrove hydrogeomorphic settings in two Southwest Florida tidal creeks

Summary

Introduction

Increasing the potential for carbon sequestration by terrestrial and aquatic ecosystems has been proposed as a solution to mitigating increased greenhouse gas (GHG) concentrations in the atmosphere. Many studies have shown that wetlands play a dominant role in the global cycling of carbon as a result of anaerobic substrates and high primary productivity [1,2]. 20%–30% of the terrestrial total organic carbon (TOC) storage is in wetland environments [3,4]. This paper compares rates of carbon sequestration in disturbed and reference mangrove tidal creeks in southern Florida USA and whether that disturbance affects a mangrove ecosystem’s ability to mitigate human emissions of greenhouse gases to the atmosphere. We compare sedimentation rates in these tidal creeks as important indicators of whether mangroves in this region will be able to keep up with projected sea level rise

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