Title: Controls of temporal and spatial variation in resuspension driven inorganic nutrient exchange in UK shelf seas.
Shelf seas are highly dynamic environments, undergoing frequent resuspension events as a result of wave and current action. They are also highly valued global ecosystems, with a recognized role in biogeochemical cycling of carbon and nutrients. However, the interplay between resuspension events and biogeochemical exchange is not well understood. To address this, the relative importance of sediment type, seasonality and water depth on the flux of inorganic nutrients across the sediment water interface has been investigated in the North and Celtic Seas. Combinations of ship-board and in situ annular flume experiments were used to determine seabed stability, likelihood of resuspension, and flux of dissolved inorganic nutrients across different sediment types (ranging from mud to sands) under pre-bloom, post-bloom and later summer conditions. Data from research cruises spanning from 2008 to 2015 indicate an increase in surface bed stability with increasing median grain size, and from early spring – summer, related to bulk density and organic matter in the surface sediments. Nutrient concentration data demonstrate that resuspension can lead to increased inorganic nutrient release to the water column. However, these releases are mediated by the overall depth of erosion, bed type and season, and water depth. These findings illustrate the complex variations in resuspension driven biogeochemical cycling within shelf seas, and highlight the importance of understanding the relative importance of the controlling factors of resuspension.