Energy transfer through the shelf benthos off the west coast of South Island, New Zealand

Abstract

Carbon‐flow pathways are proposed for the muddy‐shelf benthos off the coast of West‐land and north‐west Nelson, New Zealand (southeastern Tasman Sea). They are largely from bio‐mass estimates of sediment bacteria (adenosine triphosphate assay), meiofauna, macrofauna, and demersal fish, and literature values of production/ biomass ratios and energy transfer efficiencies. It is assumed that benthic secondary production (deposit‐feeder dominated) is mediated largely by microbial production, estimated for the upper 2 cm of sediment, as 39 gC m^‐2 y^‐1. About half this production may be required by benthic invertebrates: meiofaunal production, provisionally estimated as 3.6 gC m^‐2 y^‐1 consuming 12 gC m^‐2 y^‐1 and macrofaunal production, at 1.8 gC m^‐2y^‐1 using 6 gC m^‐2y^‐1. Bottom‐feeding fish, with a production of at least 0.05 gC m^‐2 y^‐1 are estimated to consume 0.5 gC m^‐2 y^‐1. The dominant source of energy for the benthos is pelagic primary production, estimated to average 182 gC m^‐2 y^‐1 on the shelf, and supplying some 76 gC m^‐2 y^‐1 to the benthos. Although the study area receives a major riverine input (at least 4.5 × 10¹⁰ m³ y^‐1), this appears to be a relatively minor source of assimilable carbon for the shelf benthos. Primary production appears high in relation to benthic secondary production and mechanisms that may account for this are discussed.

Keywords:

• micro‐organisms
• benthos
• demersal fisheries
• primary production
• secondary production
• biomass
• carbon
• energy flow
• continental shelf
• sediment
• Tasman Sea
• New Zealand

Notes

Present address: Group Environmental Services, BP International Limited, Britannic House, Moor Lane, London EC2Y 9BU, United Kingdom