Modelling maerl habitat dynamics in response to increased storminess

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Figure 1. A. Biogenic gravel composed entirely of dead maёrl (debris) at Trá an Doilin (Carraroe) beach, County Galway. B. Individual clasts of maёrl debris on beach (photo length: 0.05m). C. Living maёrl beds in approximately 5m bathymetry (photo length: c.0.60m). D & E. Concentric patterns at Trá an Doilin suggests  maёrl has a higher mobility than quartz sediments.

An exciting new project involving field work has begun at NUI Galway School of Geography, which focuses on quantifying the impacts of storminess on maerl beach morphodynamics. Rhodolith (maerl) beds are unique, relatively rare, free-living, non-geniculate coralline red algae forming biodiverse habitats and dense biogenic debris beaches. These beds provide hard habitat for other marine algae on their surface and for invertebrates living on and in the rhodoliths. This one year field research project investigates the response of offshore maerl beds and maerl debris beaches to storminess. Specifically, the morpho-sedimentary evolution of maerl beaches over timescales of seconds (swash dynamics) to months (seasonal weather) will be measured using a suite of integrated, multi-disciplinary field and laboratory methods based on hydrodynamic modelling, bathymetric and topographic mapping, and groundwater fluxes. The experiments will utilise results from previous research. The impact of the Intergovernmental Panel on Climate Change (IPCC) scenarios on the regional hydrodynamic model will be made to quantify possible impacts of climate change on maerl. Using XBeach, an open-source numerical model with a domain size of kilometres, on the time scales of storms, outputs will be compared with nearshore-beach DEMs derived from UAV surveys (water and land), and supplemented with baseline INFOMAR LiDAR data from Greatman’s Bay. This project will integrate oceanographic observations (waves, currents, tide) to compliment habitat mapping. A poster of this work was presented at the Irish Geomorphology Group Meeting at the Geological Survey Ireland in Dublin. A0 Poster - Siddhi Joshi Poster FinalThe poster is available for download here: Siddhi Joshi Eugene Farrell Poster Final

Acknowledgements

This project is funded by the Geological Survey Ireland Short call 2017-SC-043.

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