Can fresh submarine groundwater discharge initiate pathogenicity in Vibrio sp. settled in marine sediments?

Felix Vollberg1, Marc Walther2, Nils Moosdorf3
1 Universität Bremen, Bremen
2 Helmholtz-Zentrum für Umweltforschung – UFZ, Leipzig; Technische Universität Dresden, Dresden
3 Leibniz Zentrum für Marine Tropenforschung – ZMT, Bremen

P 19.9 in Young Hydrogeologists forum

Fresh submarine groundwater discharge (SGD), i.e. the direct discharge of terrestrial groundwater to the ocean, contributes significantly to hydrological and matter cycling in coastal areas and thus directly affects biogeochemical processes. Following the hydraulic potential, groundwater discharges out of a coastal aquifer, which influences nutrient budgets and salinities within a coastal area, both on terrestrial and marine compartments. While total SGD according to its definition encompasses a recirculated seawater component in addition to the fresh groundwater discharge, here, only the fresh component is addressed.

Brackish benthic zones of SGD have a direct effect on the living conditions of individual organisms dwelling in coastal waters and shallow marine sediments (mud) respectively. That includes pathogenic Vibrio bacteria whose growth is strongly dependent on water temperature, nutrient supply and salinity. The quantity of non-halophile Vibrios should grow if the influence of fresh groundwater increases. To what extend SGD is able to sustain favorable living conditions for Vibrio is an open question, which will be assessed in a first approach in this study.

A suite of 2D FeFlow models will represent multiple scenarios through a relevant geological and hydrological parameter space. Starting with a simple stationary homogeneous landmass we put a focus on density driven water movements in coastal areas. Increasing complexity of this setup by implementing heterogeneity and varying geometrical shapes (e.g. coastal slope) allows to approach natural conditions, thus creating a suitable base for further case-related investigations. We expect the permeability and heterogeneous distribution of flow paths to be the main controlling factors of the SGD and formation of low salinity zones in the benthic sediment. Besides building a flexible analytic model setup, the main goal of this work is a sensitivity analysis for the relevant parameters to specify the possible impact of SGD on Vibrio bacterial growth.