Bacterial growth in deep-sea sediment trap and boxcore samples

Abstract

This study was to determine whether heterotrophic bacteria associated with deep-sea particulates are adapted more to the moderate temperatures and pressures of surface waters or to the extremes of the deep sea, and how such microorganisms respond to substrate enrichment. Samples of sinking particulates, fecal pellets, and deposited sediments were collected in bottom-moored sediment traps and boxcores at station depths of 1850, 4120, and 4715 m in the North Atlantic. Homogenized seawater suspensions of samples were incubated for 2 to 7 d under both shallow and deep-sea temperatures and pressures, with and without substrate enrichment (yeast extract or chitin). Increases in total bacterial number or percent dividing cells were measured by epifluorescence microscopy. Probable origins of bacteria in a given sample were evaluated according to temperature and pressure regimes affording bacterial growth. With a few exceptions, results indicated a predominance of shallow water bacteria in sediment-trap, but not boxcore, samples and an increasingly significant fraction of deep-sea bactena, adapted to low temperature and elevated pressure, in fecal pellet samples trapped at increasing depth. Under deep-sea conditions, bacterial doubling times in sediment core samples were weeks or months, regardless of substrate enrichment, while in some trap samples were days (>1.5) without enrichment, and hours (7.4 to 14) with enrichment. Doubling times of barophilic bacteria, isolated in pure culture from the deeper trap and core samples, ranged from 6 to 13 h under in situ temperature and pressure. These findings suggest that particulate organic matter, prior to its burial in abyssal sediments, is altered by indigenous, deep-sea bacteria, some of which are capable of rapid activity at low temperature and elevated pressure.

Global bathymetric patterns of standing stock and body size in the deep-sea benthos

“…Bacterial standing stock does not necessarily correlate with metabolic activity. There is ample evidence for distinctive barophilic microbiota that rapidly degrade sinking phytoplankton (Deming 1985, Lochte & Turley 1988, but an unknown fraction of bacteria in deep-sea sediments originates in surface waters and is transported to the seafloor attached to sinking phytodetritus (Lochte & Turley 1988). Many of these appear to be dormant, either because they lack labile organic material or because of inhibitory physical conditions at great depths (Deming & Baross 2000).…”

Bacterial distribution and activity at the water-sediment boundary layer on NW Mediterranean continental margin

“…Bacterial communities in the upper layer of the ocean act as a filter, rapidly using the labile organic compounds produced by photosynthesis. During their sinking period the small size particles are subject to microbial attack (Deming 1985, Hoppe et al 1993, Poremba 1994, Turley & Mackie 1994. Conversely, the rapidly sinking larger particles or aggregates pass through this biological filter and provide the seafloor with energy-rich material.…”

“…Rowe & Deming 1985, Cahet et al 1990, Turley & Lochte 1990, Deming & Baross 1993. A critical point is the actual contribution of deep sea bacterial consortia to the coupling between pelagic and benthic activities (Deming 1985, Deming & Baross 1993, Poremba 1994, Smith et al 1994, Poremba & Hoppe 1995, Ritzrau et al 1997. Bacterial communities in the upper layer of the ocean act as a filter, rapidly using the labile organic compounds produced by photosynthesis.…”

Response of benthic microbial communities to chitin enrichment: an in situ study in the deep Arctic Ocean

“…More speciWcally, Boetius and Lochte (1996) detected an increase in chitobiase activity 10 days after chitin addition. Investigations of Deming (1985) with deep-sea sediments amended with chitin showed that bacterial doubling time were in the order of weeks or months. Thus, bacterial growth is suYciently slow to preclude detection of signiWcant increases in cell number after 7 days of incubation.…”

“…North Atlantic (Deming 1985); Arctic continental slope (Boetius and Lochte 1996); Arabian Sea (Christiansen and Boetius 2000)]. These studies indicated that chitin supplies induced the synthesis of speciWc enzymes and that indigenous deep-sea bacteria were able to decompose even high amounts.…”