Comparison of sampling methods for deep-sea infauna

Sampling methods for benthic meiofauna and macrofauna assessments on the northern Gulf of Mexico continental slope and deep sea were compared. For meiofauna, a core with an inner diameter of 5.1 cm is recommended for yielding an appropriate sample size. Meiofauna are concentrated in the uppermost 2 cm sediment layer, so the top 3 cm are sufficient to sample. Macrofauna penetrate deeper and the top 10 cm are sufficient. Smaller sieves capture more organisms so 45 μm for meiofauna, and 300 μm for macrofauna, is recommended. On average, 88% of meiofauna were extracted in the Ludox fraction compared to the total of both Ludox and the sediment pellet. Box corers and multiple corers were compared for estimating macrofauna and meiofauna metrics. Multicorers are recommended for quantitative assessments, but box corers are useful for qualitative studies that require capturing more diversity. Box cores underestimate macrofauna abundance by 2.9 times. While the larger box core captures more species resulting in higher diversity estimates, it is low relative to the 24 times larger area sampled. The multicorer preserves vertical distribution. Because meiofauna are sampled from subcores, there is little difference between the two devices for estimating meiofauna metrics. Replicate multicore samples (i.e., deployments) do not add substantially to our understanding of the variance of species richness or abundance, thus to describe the spatial footprint of macrofauna community structure, it is recommended that resources should be used to sample more stations over a larger area rather than multiple replicates at fewer stations.