Comparison of granulometric methods and sampling strategies used in marine habitat classification and Ecological Status assessment

► Best PSA method to explain faunal distribution is combined laser and sieve analysis. ► Pre-treatment with peroxide reduces multivariate faunal variance explained by PSA. ► EUNIS sediment classification and IQI outputs are robust to changes in PSA method. ► Independent PSA samples explain faunal pattern better than faunal grab subsamples. Sediment particle size analysis (PSA) is routinely used to support benthic macrofaunal community distribution data in habitat mapping and Ecological Status (ES) assessment. No optimal PSA Method to explain variability in multivariate macrofaunal distribution has been identified nor have the effects of changing sampling strategy been examined. Here, we use benthic macrofaunal and PSA grabs from two embayments in the south of Ireland. Four frequently used PSA Methods and two common sampling strategies are applied. A combination of laser particle sizing and wet/dry sieving without peroxide pre-treatment to remove organics was identified as the optimal Method for explaining macrofaunal distributions. ES classifications and EUNIS sediment classification were robust to changes in PSA Method. Fauna and PSA samples returned from the same grab sample significantly decreased macrofaunal variance explained by PSA and caused ES to be classified as lower. Employing the optimal PSA Method and sampling strategy will improve benthic monitoring.