This dataset consists of measurements of 224Ra and macronutrients in core top water, porewaters and sediments, as well as calculated 224Ra and macronutrient fluxes (via 224Ra/228Th disequilibrium) from benthic incubations of replicate mesocosms containing selected benthic macrofauna. The experiments were conducted at the Biodiversity Ecosystem Futures Facility (BEFF lab) at the National Oceanography Centre Southampton during 2022. Sediment was collected from Rame Mud, Plymouth, and benthic organisms were collected from Rame Mud and from Loch Linhe, Scotland. For each incubation, homogenised, sieved (500 µm) sediment was added to a mesocosm to 10 cm depth, overlain by approximately 15 cm (approx. 1.3 L) seawater (0.45 µm filtered, UV sterilised, salinity 33), and left to settle for 24 hours before conducting a full water exchange. After water exchange, 1 individual of either Paraleptopentacta elongata , Edwardsia claparedii, Turritellinella tricarinata, or Amphiura chiajei was weighed and morphological measurements were taken before being added to the mesocosm. 3 replicates containing 1 individual were run for each species, in addition to 3 replicate control mesocosms containing no macrofauna. All mesocosms were continually aerated and maintained in a temperature-controlled water bath for 10 days under a 12:12h on/off light cycle. On days 4 and 8, 2.5ml of a mixed Phaeodactylum tricornutum: Tetraselmis suecica phytoplankton culture was added to all mesocosms. For a subset of mesocosms (mesocosms 14 and 15 ), daily water column nutrient samples (10 ml, 0.2 µm filtered) were taken ~5 cm below the water surface and frozen at -20°C for subsequent analysis. Experiments 1 & 2 were set up in the same manner, except that in experiment 2 only one species was included, but at higher replication (8 replicate mesocosms containing 1 individual each of E. claparedii + 1 control mesocosm). Water samples for macronutrient concentrations were analysed using a QuAAtro 39 autoanalyser (Seal Analytical) and samples for Ra activity were analysed using a Radium Delayed Coincidence Counter (RaDeCC) system.The work was conducted to quantify the influence of different species and individuals of benthic macrofauna on benthic flux, using 224Ra as a naturally occurring tracer of sediment-seawater exchange. For further information, please see the associated research paper doi: 10.1002/lno.70033
