Assessing the suitability of EcoQS indicators to signal intertidal recreation consequences in a coastal lagoon

• Oxygen depletion was detected at sites with greatest recreational visitation. • Richness and abundance decline in response to trampling and bait harvesting. • H ’ is a robust indicator of beach EcoQS. • M−AMBI and Bentix may inflate EcoQS relative to H ’. Ecosystem quality status (EcoQS) indicators have been shown to be robust signallers of anthropogenic perturbations globally. Rarely, however, have they been used to assess recreation consequences in intertidal beach systems. Apart from computational differences, taxonomy knowledge gaps or those of taxon perturbation sensitivities challenge the use of EcoQS indicators to assess recreation repercussions in beach systems. We used a multi-metric approach incorporating sediment biogeochemical indicators, macrobenthic community metrics and widely used benthic EcoQS classification tools ( H ’, ABC, Bentix and M−AMBI) to quantify changes in status of intertidal sandflat ecosystems across a recreational gradient in a South African lagoon, where taxonomic and ecological knowledge gaps are evident. Highest recreation levels were associated with benthic oxygen depletion, and macrofaunal richness and abundance declines. H ’, Bentix and M−AMBI values were strongly correlated with sediment coloration (a proxy for sediment oxygenation) and declined with increasing recreation. Since H ’ does not require detailed knowledge of species taxonomy or perturbation sensitivities, it can robustly signal EcoQS responses to recreation in regions with limited ecological and taxonomic knowledge. M−AMBI and Bentix inflated EcoQS relative to H ’, but in the case of M−AMBI, differences were minor when sensitivities of taxa were excluded (e.g. due to coarse taxonomic resolution) or included (e.g. due to posteriori sensitivity assignment of taxa). M−AMBI and Bentix appear to be robust indicators of spatial changes induced by recreation, but ground-truthing scores against sediment oxygen indicators can refine EcoQS classification. Our findings offer valuable insights in the use of benthic EcoQS indicators to quantify recreation consequences, especially in regions experiencing limitations in ecological and taxonomic expertise.