Benthic boundary layer communities and carbon cycling at abyssal depths in the central North Pacific

Abstract

Cycling of carbon through the benthic boundary layer (BBL) community in the deep sea is poorly understood. Until now, attempts to summarize the flow of organic C in these communities have relied primarily on data collected from various deep-sea areas. The one BBL community where the organic C pools and fluxes are best defined is in the central North Pacific, north of the Hawaiian Islands. This data base was combined with new estimates of standing stocks and organic C fluxes to construct an organic C budget for the bottom 600 m of the water column and the sediments, using net input from sinking particulate organic C (POC) and exchanges between 12 compartments. The largest standing stocks of C (dissolved organic C, suspended POC, and POC) were in the water and surface sediments (9.1 x lo8 g C km-2), exceeding that in the 10 consumer groups by almost four orders of magnitude. Of the consumer groups, the sediment nanobiota, meiofauna, and epibenthic megafauna had the most organic C and the macrofauna had the least. Fluxes into the consumer groups, as estimated from respiration rates, were highest in the sediment community, bacterioplankton, and epibenthic megafauna. The net flux of POC into the BBL (supply) ranged from -74 to + 1,268 g C km 2 d-l, which was generally insufficient to match the combined fluxes into the BBL consumer groups (demand) of 998-3,3 15 g C krnm2 d I. Other sources of organic C to fuel the demand of the BBL community are analyzed, including active transport by migrating abyssopelagic animals which might significantly augment the POC flux into the BBL at this oligotrophic midgyre station.