Trophic status and condition of Hyalinoecia longibranchiata from two regions of contrasting oceanic productivity

The Chatham Rise and Challenger Plateau are 2 regions of New Zealand's Exclusive Economic Zone with very different levels of productivity. The Chatham Rise is a physically dynamic region that sustains one of New Zealand's largest mid-deep water fisheries, whilst the Challenger Plateau is a region of low hydrodynamic activity and productivity. These contrasting regions of pelagic productivity are likely to influence the trophic status of their benthic communities, where downward coupling of pelagic resources to the benthos occurs. Populations of the benthic quill worm Hyalinoecia longibranchiata (Onuphidae) were sampled at a range of depths on the Chatham Rise and the Challenger Plateau. Stable isotope signatures, ï¤13C and ï¤15N, and nutritional condition indices (DNA:dry weight, protein:DNA, RNA:DNA and C:N) of the quill worms were measured to: (1) determine whether regional-scale differences in surface productivity are reflected in the trophic status and condition of the quill worms; and (2) ascertain the extent to which other factors (e.g. depth, distance from the mainland) may affect this. Analysis revealed that H. longibranchiata collected on the Chatham Rise were more enriched in ï¤13C and in better condition than those collected on the Challenger Plateau. The isotopic enrichment observed at the Chatham Rise is likely to arise from differences in the quality and quantity of the organic inputs to the benthos. Overall, regional productivity had a much greater influence on the trophic status and condition, reflective of the degree of pelagic-benthic coupling, rather than any depth or spatial considerations.