Measurements of intraspecific variability in functional trait expression obtained from laboratory experiments conducted, between June 2021 and April 2022, on marine bioturbating benthic invertebrate macrofauna, collected between May 2021 and February 2022.

This dataset contains species mass, respiration, burial times, sediment particle analysis, redox potential depths, and water nutrient concentrations (ammonium, nitrate+nitrite, nitrite, and phosphate) data obtained from two separate laboratory experiments involving the following macroinvertebrate species held at different densities: <em>Amphiura filiformis</em>, <em>Amphiura chiajei</em>, <em>Turritellinella tricarinata</em>, <em>Edwardsia claparedii</em>, <em>Sternaspsis scutata</em>, <em>Paraleptopentacta elongata</em>, <em>Hediste diversicolor</em>, and <em>Nephtys hombergii</em>. The macroinvertebrates were collected from various locations around the UK (Plymouth, Oban, and Newcastle) on 6 occasions between May 2021 and February 2022. Subtidal species were collected using a Van Veen grab or Agassiz trawl (depths 10-42 m) whilst intertidal species were collected at low tide in mud flats by bucket and spade. The experiments were conducted at the National Oceanography Centre in Southampton from June 2021 - April 2022. One experiment tested the effects of season and geographic locality on body size, burial traits, bioirrigation, sediment oxygen penetration depth and respiration, and nutrient release with all measurements taken at the end of the 1.5-month experiment. The second experiment focused on how individual density and climate conditions impact burial traits, bioirrigation, sediment nutrient release and sediment redox discontinuity depth with all measurements being taken at the end of the 2-month experiment. Body size was measured using digital weighing scales, burial traits were measured using fluorescent sediment profile imaging and video analysis, sediment respiration was measured using optical oxygen probes and oxygen penetration depth was measured using a motorised sediment depth profiler, and nutrient release measured using a flow injection auto-analyser. Bioirrigation was measured at the end of both experiments by taking water samples at 0, 4 and 8 hours and analysed using a flow injection auto-analyser. Sediment redox discontinuity was measured using sediment profile imaging. These data were collected to investigate intraspecific variability in functional trait expression in marine bioturbating benthic invertebrate fauna. Data were generated under NERC Discovery Science project 'Implications of intraspecific trait variability across different environmental conditions for projections of marine ecosystem futures' (grant reference NE/T001577/1).