Modeling the Potential of Submarine Groundwater Discharge to Facilitate Growth of Vibrio cholerae Bacteria

Felix Vollberg,Astrid Gärdes,Nils Moosdorf,Marc Walther

doi:10.3390/hydrology6020039

Abstract

Submarine groundwater discharge (SGD), the discharge of terrestrial groundwater to the ocean, can govern the coastal benthic environment. Bacteria such as Vibrio cholerae inhabit coastal waters and sediments, whose growth can be influenced by SGD. In particular, salinity changes introduced by SGD could have a positive effect on the abundance but also virulence of non-halophilic V. cholera bacteria dwelling in coastal waters and shallow marine sediments. Here we assess potential effects of SGD on the environmental properties that favor V. cholerae in a numerical modeling study representing multiple scenarios. Approaching natural systems, simulation results reveal a high sensitivity of non-halophilic Vibrio cholerae growth to SGD and its primary driving factors. This dependency leads to highest growth potential at high groundwater inflow and low hydraulic conductivity of the aquifer as well as for steep sea-side boundary slopes. Besides its minor impact on the extent of SGD in our model, dispersion is a crucial limiting factor for V. cholerae habitat. We conclude that there is a close connection between the driving factors of SGD and low salinity zones along a coastal slope, and recommend taking these into consideration for evaluating local V. cholerae outbreaks.

Highlights

IntroductionA seaward flow of fresh groundwater requires the hydraulic potential of the onshore aquifer to be above the sea level [6]
Submarine groundwater discharge (SGD), here defined as terrestrial groundwater discharging directly to the coastal ocean, may occur along coastal interfaces of permeable sediments.Significant amounts of SGD have been reported, such as from Florida [3] and Southern Brazil [4](see [5] for a review on other available studies).A seaward flow of fresh groundwater requires the hydraulic potential of the onshore aquifer to be above the sea level [6]
Salinity changes introduced by SGD could have a positive effect on the abundance and virulence of non-halophilic V. cholera bacteria dwelling in coastal waters and shallow marine sediments

Summary

Introduction

A seaward flow of fresh groundwater requires the hydraulic potential of the onshore aquifer to be above the sea level [6]. While groundwater flow in porous media is generally controlled by aquifer permeability and inflow and the hydraulic head [7,8,9,10,11] as well as dispersion effects [12,13], SGD is influenced by drivers that are specific to the coastal situation, such as tides and waves [14]. Connections between SGD and algae blooms as well as marine biota were made in [15,16]. To assess the extent to which SGD can favor the growth of marine Vibrio bacteria, we focus on Vibrio cholerae, which finds ideal living conditions when salt concentrations reach values of

Methods

Results

Discussion

Conclusion