El Niño Southern Oscillation (ENSO) enhances CO2 exchange rates in freshwater Marsh ecosystems in the Florida everglades.

Ben Bond-Lamberty,Michael G Ryan,Christina L Staudhammer,Jessica L Schedlbauer,Sparkle L Malone,Steven F Oberbauer,Henry W Loescher,Paulo Olivas,Gregory Starr

doi:10.1371/journal.pone.0115058

Abstract

This research examines the relationships between El Niño Southern Oscillation (ENSO), water level, precipitation patterns and carbon dioxide (CO2) exchange rates in the freshwater wetland ecosystems of the Florida Everglades. Data was obtained over a 5-year study period (2009–2013) from two freshwater marsh sites located in Everglades National Park that differ in hydrology. At the short-hydroperiod site (Taylor Slough; TS) and the long-hydroperiod site (Shark River Slough; SRS) fluctuations in precipitation patterns occurred with changes in ENSO phase, suggesting that extreme ENSO phases alter Everglades hydrology which is known to have a substantial influence on ecosystem carbon dynamics. Variations in both ENSO phase and annual net CO2 exchange rates co-occurred with changes in wet and dry season length and intensity. Combined with site-specific seasonality in CO2 exchanges rates, El Niño and La Niña phases magnified season intensity and CO2 exchange rates at both sites. At TS, net CO2 uptake rates were higher in the dry season, whereas SRS had greater rates of carbon sequestration during the wet season. As La Niña phases were concurrent with drought years and extended dry seasons, TS became a greater sink for CO2 on an annual basis (−11 to −110 g CO2 m−2 yr−1) compared to El Niño and neutral years (−5 to −43.5 g CO2 m−2 yr−1). SRS was a small source for CO2 annually (1.81 to 80 g CO2 m−2 yr−1) except in one exceptionally wet year that was associated with an El Niño phase (−16 g CO2 m−2 yr−1). Considering that future climate predictions suggest a higher frequency and intensity in El Niño and La Niña phases, these results indicate that changes in extreme ENSO phases will significantly alter CO2 dynamics in the Florida Everglades.

Highlights

Teleconnections from the El Nino Southern Oscillation (ENSO) are known to strongly affect climate patterns across North America [1, 2, 3, 4]
Time series analysis of long-term monthly precipitation and minimum and maximum daily temperatures versus ENSO phase showed that rain increased the month after the start of El Nino phases and declined the month following the start of La Nina (p50.7719), though not significantly (Table 1; S1 Fig.)
The goal of this research was to understand the relationship between ENSO phases and CO2 exchange rates (NEE, Reco and GEE) in Everglades freshwater marsh ecosystems

Summary

Introduction

Teleconnections from the El Nino Southern Oscillation (ENSO) are known to strongly affect climate patterns across North America [1, 2, 3, 4]. In the Florida Everglades, changes in the long-term hydrologic cycle have been linked to extreme ENSO phases (El Nino and La Nina phases) [2, 9]. Precipitation patterns in this region form wet and dry seasons, the frequency and magnitude of which fluctuate with changing climate patterns [8]. Because annual shifts in carbon dioxide (CO2) exchange rates have been linked to changes in surface hydrology in short-term studies [10, 11, 12, 13], El Nino and La Nina phases may be an important driver of seasonal-to-interannual variations in hydrology and the productivity of Everglades freshwater marsh ecosystems. Inter- and intra-annual fluctuations in CO2 exchange rates in the Everglades region may be significantly influenced by El Nino and La Nina phases

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Conclusion