The distribution of Spartina anglica on estuarine mudflats in relation to wave-related hydrodynamic parameters.

Abstract

Spartina anglica is an invasive alien plant species whose spread threatens the biodiversity of Irish estuarine mudflats, sandflats and saltmarshes. Models have been developed to predict its distribution to facilitate population control and conservation management, but a more precise definition of the wave-related model parameters is required. This study investigates the distribution of established Spartina anglica in Strangford Lough, Northern Ireland, in relation to wave-related hydrodynamic parameters, generated using a numerical computer model for wave generation and propagation in shallow water.The distribution of S. anglica was statistically associated with shorter waves. Longer waves are indicative of deeper water, affect a larger and deeper volume of water and travel at faster speeds than shorter waves. They are, therefore, more likely to disrupt Lough sediment surfaces and uproot S. anglica seedlings, thus limiting establishment. Other simulated wave-related hydrodynamic parameters showed little variation between sites with and without S. anglica.Although input wave parameters were taken for storm conditions, the simulated wave parameters generated by the study did not pass recognised thresholds for initiating sediment transport. To further investigate the linkages between wave-related hydrodynamic parameters and S. anglica establishment, therefore, it may be necessary to re-assimilate the wave model using higher input waves (i.e. exceptional storm waves). This study forms a preliminary basis for understanding interactions between wave-related hydrodynamics and S. anglica establishment and for developing a predictive model of S. anglica distribution patterns.