Food energy supply and demand: A discrepancy between particulate organic carbon flux and sediment community oxygen consumption in the deep ocean1

Abstract

Sediment community oxygen consumption (SCOC) and particulate organic carbon (POC) flux to the benthic boundary layer were concurrently measured at five deep-sea stations on a transect across the eastern and central North Pacific at various times of year. A free vehicle grab respirometer and Alvin-manipulated grab respirometer were used to measure SCOC. Paired particle interceptor traps (PITS) were used to collect sedimenting small POC at 100 and 600 m above the bottom. SCOC decreased across the transect from the eutrophic coastal areas off southern California to the oligotrophic central Pacific gyre. These rates were generally highest in June and lowest between fall and early spring across the transect with a recurrent pattern in the magnitude of rates measured during the same months but different years. Flux of POC into the benthic boundary layer decreased across the transect from the eutrophic eastern to the oligotrophic central Pacific. No consistent temporal trends were evident in POC flux across the transect, possibly because of small sample sizes, high intra-station variability, and short-term deployments (57 d). Comparison of concurrently measured supply of POC with organic carbon demand of the sediment community as estimated from SCOC reveals a supply deficit across the transect for all seasons measured. For one nearly synoptic sampling period across the transect in June 1982, the supply-to-demand ratio is lowest at the two nearshore stations where current speeds are highest. A predictive equation for SCOC with a least-squares regression analysis and log-transformed data revealed that POC flux as the independent variable accounted for only 59% of the variability in SCOC. Direct coupling between SCOC and POC flux is not confirmed by these results, which may be attributed to the limitations of the measurements or other organic carbon sources.Sediment community oxygen consumption (SCOC) has been measured at various times of year at five deep sea stations on a transect across the eastern and central North Pacific (CNP-ENP transect) over the past 8 yr. Initial results indicated spatial variability in SCOC which increased along a gradient of increasing surface water primary productivity from the oligotrophic central gyre to the more eutrophic coastal upwelling areas off southern California . Temporal variability was also identified in SCOC at two of the transect stations and appeared related to the seasonal productivity of the overlying water (Smith and Baldwin 1984a). This result is not surprising given recent reports of seasonal fluctuations in the fluxes of small organic particles to abyssal depths (Deuser and Ross 1980; l This research was supported by NSF grants OCE 81-17661, OCE 84-09075, and OCE 84-17913 and a contract from Sandia Laboratories. Deuser et al. 198 1;Honjo 1982;Billett et al. 1983;Cole et al. 1985)-a source of food supply for deep sea benthos. The next logical step is to explore the possible coupling between this food supply from the overlying water column and the food demand of...

Deep ocean communities impacted by changing climate over 24 y in the abyssal northeast Pacific Ocean

“…Concurrently, a time-lapse camera at the bottom of the mooring photo-documented hourly changes in sedimentation events and megafaunal movements over ∼20 m 2 of the sea floor (29,30). Seasonal measurements of SCOC, used to estimate organic carbon utilization, were made with a free vehicle-grab respirometer (31). Year-round measurements of SCOC began in 2011, using an autonomous bottom-transiting vehicle (29,32) (Fig.…”

Oxygen uptake kinetics in the benthic boundary layer

“…The uptake of oxygen by sediments has reviewed by Pamatmat (1977), Bowman and been studied extensively because of the im-Delfino (1980) and Smith and Hinga (1983). portance of oxygen to benthic life and to…”

“…Hargrave 1969, measure oxygen uptake rates of sediments 1972; Pamatmat 197 1;Smith 1974Smith , 1987; consists of incubating sediment and follow- Hopkinson and Wetzel 1982). The tech-ing the decrease in the oxygen concentration niques that have been developed to measure of overlying water as a function of time.…”

Decadal Change in Sediment Community Oxygen Consumption in the Abyssal Northeast Pacific

“…The first instrument to measure SCOC at Station M was the free vehicle grab respirometer (FVGR), an autonomous tripod or tetrapod frame with attached flotation, four stainless steel respiration chambers, tandem acoustic releases and disposable steel ballast (Smith and Baldwin 1983;Smith et al 1979;Smith 1987). FVGR was deployed for 2-to 3-day incubations to yield short-term measurements of SCOC, made on a roughly seasonal basis beginning in June 1989 and ending in June 2011, with a total of 51 deployment periods (Fig.…”

“…Some of the early estimates of the balance of food supply to demand suggested that there was an unexpected deficit in food supply in the northeast Pacific (Smith 1987), which served as a motivation in developing more detailed time-series estimates. As time-series records developed, there were times when food both supply and demand seemed to balance (Smith et al 1992) and when substantial deficits of food supply persisted (Smith and Kaufmann 1999).…”