Epibenthic sled versus giant box corer – Comparison of sampling gears for tanaidacean species richness assessment in the abyssal benthic ecosystem

Abstract

Species richness is an important biodiversity measure that strongly relies on the sampling gear used. We have compared the efficiency of two types of sampling gears (camera-epibenthic sled – C-EBS and giant box corer – BC) for species richness assessment of Tanaidacea in the abyssal plain of the region of the Kuril-Kamchatka Trench. In terms of species richness small, benthic, brooding tanaidaceans are amongst the most highly underestimated groups of the deep-sea macrofauna and can be treated as a model group for such a study. Large numbers of singletons and doubletons (25% of species in BC, 24% of species in C-EBS) together with steep species accumulation curves suggest substantial undersampling. The total number of species and the number of unique species collected by each gear was higher in the C-EBS (77 and 44 species respectively) than in the BC (46 and 11 species respectively) but those differences seem to be low taking into account the total sampled area (5.75 m2 of seafloor for BC, and 53,709 m2 for C-EBS). Thirty-three species were collected with both gears. Therefore, efficiency of the point sampler (BC) was very high. The comparison of replicability (2 replicate stations per site) showed that only 13–60% (BC) and 22–58% (C-EBS) of species recorded at any given site can be found in both replicates, suggesting a highly patchy distribution of abyssal tanaidaceans. On the other hand many species were recorded in more than ten samples (both in BC and C-EBS). Our results indicate important gear-specific problems suggesting that it would be difficult to say if observed patterns (e.g., the level of patchiness or rarity of a particular species) are true or caused by sampling artefacts.