Analysis of sampling methods of estuarine benthic macrofaunal assemblages: sampling gear, mesh size, and taxonomic resolution

Benthic estuarine studies are usually very time-consuming. Therefore, it is critical to optimize procedures ensuring efficiency with low cost. The present study aimed to assess the cost/benefit ratio of different sampling procedures and analyze its effect on the description of spatial pattern of benthic assemblages along an estuarine gradient. Six methodological combinations (sampling gear: van Veen grab or corer; mesh sizes: 0.5, 0.7 or 1.0 mm) were applied at 11 sampling stations. The van Veen grab captured 1,219 individuals and 59 taxa, while the corer captured 967 individuals and 53 taxa. Increasing the mesh size caused a decrease in the number of specimens retained and in the time needed to sort samples. However, no significant differences were observed among the analyzed sampling methods (sampling gear and mesh size). Spearman rank correlationcoefficient showed that there was little ‘information loss’ when aggregating datato genus and family taxonomic levels. A cost/benefit index is introduced which reveals that the van Veen grab + 1.0 mm sieve + family level was the best combination to achieve the best balance between cost and precision of the results. However, choice of sampling procedure must consider estuary characteristics, target fauna, and research infrastructure, resources and objectives.