A 1900 Year Sediment Record Suggests Recent Establishment of Black Mangrove (Avicennia Germinans) Stands within a Salt Marsh in St. Augustine, Florida, USA

Jessica Chamberlin,Jason Evans,Camryn Soehnlein,Benjamin Tanner

doi:10.3390/quat5010002

Abstract

Salt marshes and mangroves are currently being affected by rising temperatures. Mangroves thrive below −29° N latitude in Florida, USA, and have a low tolerance for extreme cold events, whereas salt marshes dominate further north. One potential effect of climate change is a reduction in the frequency of extreme cold events, which may lead to mangrove expansion into salt marsh systems. Our research identified sediment proxy indicators of salt marsh and mangrove environments. These indicators were applied to soil cores from intertidal wetlands near the current northern limit of mangrove presence on the east coast of Florida, to determine if mangrove expansion into salt marsh environments has precedence in the deeper past. Our findings suggest that mangrove and salt marsh sediments can be distinguished using a combination of stable carbon isotope ratios of sedimentary organic matter and macroscopic plant fragments, and our results showed that a mangrove stand that we cored established only recently. This result is consistent with other work in the southeastern United States that suggests that mangroves established at the current boreal limit only recently after the end of the Little Ice Age, and that the current mangrove expansion may be fueled by anthropogenic climate change.

Highlights

IntroductionCurrent climate change, caused largely by anthropogenic increases in greenhouse gas concentration, is affecting Earth’s temperatures, weather patterns, and ecosystems
Current climate change, caused largely by anthropogenic increases in greenhouse gas concentration, is affecting Earth’s temperatures, weather patterns, and ecosystems.Increasing levels of greenhouse gasses in the atmosphere have led to increases in global temperatures and decreases in extreme cold events [1]
Thirty surface samples were recovered from Spartina alterniflora dominated salt marsh and 30 surface samples were recovered from mangrove at Ponce Inlet, FL

Summary

Introduction

Current climate change, caused largely by anthropogenic increases in greenhouse gas concentration, is affecting Earth’s temperatures, weather patterns, and ecosystems. Increasing levels of greenhouse gasses in the atmosphere have led to increases in global temperatures and decreases in extreme cold events [1]. These climate changes have resulted in impacts on different ecosystems and the services they provide. The mangrove/saltmarsh ecotone position may result from elevation changes, hurricanes, increased predation, or rising sea levels [5,6,7,8,9]

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