Hydroperiod and Salinity Interactions Control Mangrove Root Dynamics in a Karstic Oceanic Island in the Caribbean Sea (San Andres, Colombia)

Jairo Humberto Medina-Calderón,José Ernesto Mancera-Pineda,Víctor H Rivera-Monroy,Edward Castañeda-Moya

doi:10.3389/fmars.2020.598132

Jairo Humberto Medina-Calderón, José Ernesto Mancera-Pineda + Show 2 more

Open Access

https://doi.org/10.3389/fmars.2020.598132

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Abstract

Mangroves sustain high soil accretion and carbon sequestration rates, yet it is still unknown if they can keep pace with increasing sea level rise (SLR) across a wider range of coastal geomorphic settings. Because accretion rates are controlled by mineral sediment inputs and organic matter accumulation, it is paramount to assess the relative contribution of root productivity to soil formation. Here, we evaluated root biomass, production, and turnover in three mangrove ecotypes to evaluate the role of soil nutrient limitation, stressors, and hydroperiod in controlling root dynamics in San Andres Island (SAI), a karstic oceanic island in the Caribbean Sea. Root production was modulated by soil stress conditions and not by nutrient availability as it has been reported for other karstic environments. The lowest root biomass allocation, and both production and turnover of fine roots were measured under low flooding duration, and low salinity (&lt;20 PSU) and sulfide concentrations (0.84 ± 0.4 mM). Yet, when soil stress conditions increased during high flooding duration (6207 h y–1) and low oxygen conditions (Eh), root tissues reached the highest biomass and production values, including a relative fast turnover of fine roots (&lt;2 mm; 0.75 y–1). Our results follow the predictions of the plant root longevity cost-benefit hypothesis where plants maintain roots only until the efficiency of resource acquisition is maximized by water and nutrient acquisition. Because of the importance of groundwater in controlling porewater salinity and mangrove root productivity in karstic oceanic islands such as SAI, water use and coastal development should be regulated in the short term to avoid the loss of mangrove area and concomitant ecosystem services.

Highlights

The provision of ecosystem services by coastal wetlands is recognized worldwide, yet most of these services are under increasing threat due to the combined impacts of natural and human disturbances and accelerating sea level rise (SLR) as result of climate change (McLeod et al, 2011; Murdiyarso et al, 2015; Lovelock et al, 2017)
Our results show that under minimum stress conditions caused by regulators and hydroperiod, root biomass and production rates in the inland mangrove forest are very low compared to the fringe and basin forests
This study revealed that the interaction between hydroperiod and salinity have a major control on root productivity in different mangrove ecotypes in the oceanic island of San Andres, Colombia

Summary

Introduction

The provision of ecosystem services by coastal wetlands is recognized worldwide, yet most of these services are under increasing threat due to the combined impacts of natural and human disturbances and accelerating sea level rise (SLR) as result of climate change (McLeod et al, 2011; Murdiyarso et al, 2015; Lovelock et al, 2017). The quantification of mangrove belowground biomass and productivity have advanced during the last 20 years, there is still a lack of understanding about the magnitude of this production and root dynamics across ecogeomorphic settings and latitudinal gradients (Saintilan, 1997; Komiyama et al, 2000; Gleason and Ewel, 2002; McKee et al, 2007; Tamooh et al, 2008; Castañeda-Moya et al, 2011; Adame et al, 2014; Cormier et al, 2015) This is the case of oceanic islands (Cormier et al, 2015) and semi-arid and arid coastal regions (Ochoa-Gomez et al, 2019; Saderne et al, 2019) in the Atlantic East Pacific (AEP) mangrove biogeographic region (Duke, 2017; Rivera-Monroy et al, 2017a)

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