Can sediment trap-collected zooplankton be used for ecological studies?

Abstract

The absence of quantitative comparisons of sediment trap-collected zooplankton (TCZ) and plankton net-collected zooplankton (NCZ) prevents the effective use of TCZ for ecological studies. We compared 24 TCZ time-series at 200 m with 19 vertical NCZ casts and recorded various environmental variables in Franklin Bay, Canadian Arctic during 2003–2004. While 30 taxonomic groups were commonly found in both the TCZ and NCZ assemblages, their taxonomic composition and seasonal variation differed. Based on the multiple regression analysis, we divided zooplankton taxa into three groups; Group 1: it was significantly correlated with NCZ abundance, Group 2: it was significantly correlated with environmental variables but not with NCZ abundance, and Group 3: no significant correlations were found. Pteropods (mostly Limacina helicina) and two copepods (Heterorhabdus norvegicus and Metridia longa) were found in Group 1, suggesting that their entrapment activity were relatively constant throughout the year, and therefore their NCZ abundance can be estimated from that of TCZ using the trap settings in this study. Conversely, in Group 2, Calanus hyperboreus had no significant relationship with the NCZ abundance (C. hyperboreus). This is likely the result of a winter peak in TCZ abundance during their reproductive season; the co-occurrence of high suspended particulate organic matter with low C/N ratio around the trap probably indicated the presence of C. hyperboreus eggs and nauplii. Therefore, monitoring interannual changes in C. hyperboreus reproductive succession by TCZ abundance might be possible in the future studies. In conclusion, Group 1 taxa are potential candidates for ecological monitoring using TCZs.