MEPS 425:79-90 (2011)  -  DOI: https://doi.org/10.3354/meps09014

ABSTRACT: The present study examined the partitioning of carbon between benthic meio- and macrofauna at sites between 350 and 3100 m water depth across Chatham Rise, Southwest Pacific Ocean. Biomass declined with increasing depth on both sides of the crest, but showed different patterns for each faunal size grouping at the deepest sites. Meiofaunal biomass was highest on the crest and lowest at 2800 m, south of the rise (76 and 8 mg C m^–2, respectively), whereas macrofaunal biomass peaked on the southern slope (1169 mg C m^–2), with lowest values at the deep northern sites (88 and 116 mg C m^–2). Macrofauna dominated total faunal biomass (>80%), although the relative importance of meiofauna increased with increasing depth on the northern side. The meiofauna:macrofauna carbon ratio was correspondingly low across all sites (0.04 to 0.10), except at the deep 3100 and 2300 m northern sites (0.16). These biomass patterns were significantly related to sediment chlorophyll a concentration, indicating greater availability of high-quality (labile) organic carbon. The lack of a shift towards the smaller benthic size class with decreasing food supply at the deep southern site (2800 m depth) appeared to be related to relatively high sediment particulate organic carbon and high calcium carbonate contents, which also influenced meio- and macrofaunal biomass. These findings reveal the close link between faunal biomass and food availability in deep-sea habitats and highlight the importance of phytodetritus in structuring benthic assemblages in the Chatham Rise/Subtropical Front region.

KEY WORDS: Metazoan · Sediment characteristics · Phytopigment · Deep sea · Regression models