<p>Soft sediments cover over 75% of the marine floor and provide key functions and habitat on globally relevant scales. In contrast, they remain overlooked in coral reef research. To understand the degree to which coral reefs influence their adjacent soft sediments, we analysed sediment grain size characteristics, total organic carbon, total nitrogen and total phosphorus concentrations at various distances from 13 coral patch reefs in the One Tree Island lagoon of the southern Great Barrier Reef, Australia. For each coral patch reef, we measured reef-shape complexity, benthic cover and used fish community data to estimate nutrient deposition and tested the importance of these factors to sediment characteristics. Organic carbon and nitrogen decreased strongly with distance from patch reefs. Phosphorus was not affected by distance from a patch reef but was generally lower in the presence of high live coral cover, suggesting potential phosphorus limitation for corals. Sediments had higher grain size variability, lower mean grain size and higher rubble content close to the patch reefs. An additional spatial study of general sediment properties, including 25 sites throughout the lagoon, revealed the accumulation of finer particles and nutrients in areas associated with low water movement. Current dynamics may be the primary driver of observed trends, as the measured physical and biological attributes of reefs had only minor effect on adjacent sediment characteristics. Our results suggest that coral patch reefs are likely to support the biodiversity and ecological function of lagoons by creating structural and chemical heterogeneity within soft sedimentary habitats.</p> Graphical abstract <p></p>