314
John D. GAGE
on the deep-sea floor (e.g., Menzies, 1962; Sanders and
Hessler, 1969).
Three main pathways, or mechanisms, for input of
the various forms of particulate organic matter as a
food source for the ecosystem of the deep-sea bed have
been put forward (Fournier, 1972). These are:
(1) passively sinking detrital rain;
(2) active biological transport; and
(3) the utilization of dissolved organic carbon.
An important goal in deep-sea biology has been to
describe and quantify these organic inputs in relation
to the global distribution of deep-sea benthic biomass
(e.g., Rowe and Staresinic, 1979; Rowe, 1981). The
density of this deep-sea biomass is typically one or
two orders of magnitude less than in coastal benthic
systems (see Chapter 10 for a detailed account of this
pattern, and of the global and depth-related patterns
in biomass distribution). The traditional paradigm of
the deep sea became one of a ‘low-activity’ ecosystem
because of these very low densities in microbial and
animal biomass, and the low nutritive value of much
of the refractory organic material typically caught in
sediment traps set for short durations in the water
column. This was reinforced by the recovery of
remarkably well-preserved crew’s packed lunches left
for a year in the submersible DSV Alvin which was accidentally flooded and sank onto the deep-sea bed in the
Northwest Atlantic in 1968 (see Chapter 5, p. 154).
The modern view of the functioning of deep-ocean
ecosystem
Two linked discoveries upset the ‘low-activity’ ecosystem paradigm. The first was the unexpected discovery
of seasonal peaks in flux of organic particles in longterm sediment traps set at great depths (Deuser and
Ross, 1980). The second resulted from dramatic seabed
photographs of mass accumulations of phytodetritus
suddenly arriving on the abyssal sea floor (Billett et al.,
1983). These discoveries encouraged a new and more
dynamic view of deep-ocean processes. Furthermore,
the conventional wisdom of low microbial reactivity at
the deep-sea bed was challenged by discovery of rapid
microbial reaction to freshly deposited phytodetritus incubated under pressure (Lochte and Turley, 1988). This
showed rapid degradation of the phytodetrital material
by barophilic bacteria and other prokaryote microorganisms as opposed to the increasingly pressureinhibited activity of bacteria on material sinking down
from the surface (Suess, 1988).
Other data previously had indicated rapid utilization
of fresh planktonic detritus by microbes and metazoans,
of dead fish by scavengers (Isaacs and Schwartzlose,
1975) and of wood blocks by specialized molluscs
(Turner, 1973). These observations showed that the
deep-sea bed ecosystem was able to react rapidly and
vigorously to availability of new organic carbon. This
was linked to unexpected findings of seasonal variability in reproduction and recruitment, and indications
of relatively rapid growth rates, and seasonal growthbanding in skeletal parts, of deep-sea deposit-feeding
benthic invertebrates (Tyler et al., 1982; Gage and
Tyler, 1991; see also Chapter 12). All this challenged
the conventional view and revealed similarities to the
more familiar functioning of shallow-water benthic
ecosystems.
The view of constancy in small-particle input has
now given way to one where much of the deep
ocean is subject to pulsed intermittency in volume and
quality of organic flux (Conte et al., 1998). This view
has resulted from improved resolution of the nature
of small-particle flux, which constitutes the bulk of
organic input to the deep ocean from the euphotic
zone. Intermittency in events at the surface results
in delivery of a large portion of the most nutritious
material to the benthic community within relatively
short periods, albeit with sometimes marked spatial
variability. Important implications for deep-sea biology
of this spatial and temporal variability in organicmaterial input have yet to be clarified. But it seems
likely that such episodic, but high-quality, detrital flux,
represents a most important nutritional source for the
deep-sea bed community.
The idea of a very attenuated link between the upper
ocean and the deep-sea bed communities, where for
all intents and purposes the upper ocean could be
regarded as a closed ecosystem with no important
carbon sink except respiration, is now of limited
value in quantifying global organic carbon-flux. Instead
the complex community dynamics of the upper-ocean
ecosystem may be seen as involving major and highly
variable losses to the deep ocean, particularly after
phytoplankton blooms. The openness of the whole
system leads to benthic–pelagic coupling that may
be dynamic and highly variable, just as it is on the
continental shelf.
Furthermore, the recent advent of improved instrumentation for use on the seabed has allowed one to
appreciate the importance of flow-related dynamics
of resuspension and lateral transport of this organic
John D. GAGE
on the deep-sea floor (e.g., Menzies, 1962; Sanders and
Hessler, 1969).
Three main pathways, or mechanisms, for input of
the various forms of particulate organic matter as a
food source for the ecosystem of the deep-sea bed have
been put forward (Fournier, 1972). These are:
(1) passively sinking detrital rain;
(2) active biological transport; and
(3) the utilization of dissolved organic carbon.
An important goal in deep-sea biology has been to
describe and quantify these organic inputs in relation
to the global distribution of deep-sea benthic biomass
(e.g., Rowe and Staresinic, 1979; Rowe, 1981). The
density of this deep-sea biomass is typically one or
two orders of magnitude less than in coastal benthic
systems (see Chapter 10 for a detailed account of this
pattern, and of the global and depth-related patterns
in biomass distribution). The traditional paradigm of
the deep sea became one of a ‘low-activity’ ecosystem
because of these very low densities in microbial and
animal biomass, and the low nutritive value of much
of the refractory organic material typically caught in
sediment traps set for short durations in the water
column. This was reinforced by the recovery of
remarkably well-preserved crew’s packed lunches left
for a year in the submersible DSV Alvin which was accidentally flooded and sank onto the deep-sea bed in the
Northwest Atlantic in 1968 (see Chapter 5, p. 154).
The modern view of the functioning of deep-ocean
ecosystem
Two linked discoveries upset the ‘low-activity’ ecosystem paradigm. The first was the unexpected discovery
of seasonal peaks in flux of organic particles in longterm sediment traps set at great depths (Deuser and
Ross, 1980). The second resulted from dramatic seabed
photographs of mass accumulations of phytodetritus
suddenly arriving on the abyssal sea floor (Billett et al.,
1983). These discoveries encouraged a new and more
dynamic view of deep-ocean processes. Furthermore,
the conventional wisdom of low microbial reactivity at
the deep-sea bed was challenged by discovery of rapid
microbial reaction to freshly deposited phytodetritus incubated under pressure (Lochte and Turley, 1988). This
showed rapid degradation of the phytodetrital material
by barophilic bacteria and other prokaryote microorganisms as opposed to the increasingly pressureinhibited activity of bacteria on material sinking down
from the surface (Suess, 1988).
Other data previously had indicated rapid utilization
of fresh planktonic detritus by microbes and metazoans,
of dead fish by scavengers (Isaacs and Schwartzlose,
1975) and of wood blocks by specialized molluscs
(Turner, 1973). These observations showed that the
deep-sea bed ecosystem was able to react rapidly and
vigorously to availability of new organic carbon. This
was linked to unexpected findings of seasonal variability in reproduction and recruitment, and indications
of relatively rapid growth rates, and seasonal growthbanding in skeletal parts, of deep-sea deposit-feeding
benthic invertebrates (Tyler et al., 1982; Gage and
Tyler, 1991; see also Chapter 12). All this challenged
the conventional view and revealed similarities to the
more familiar functioning of shallow-water benthic
ecosystems.
The view of constancy in small-particle input has
now given way to one where much of the deep
ocean is subject to pulsed intermittency in volume and
quality of organic flux (Conte et al., 1998). This view
has resulted from improved resolution of the nature
of small-particle flux, which constitutes the bulk of
organic input to the deep ocean from the euphotic
zone. Intermittency in events at the surface results
in delivery of a large portion of the most nutritious
material to the benthic community within relatively
short periods, albeit with sometimes marked spatial
variability. Important implications for deep-sea biology
of this spatial and temporal variability in organicmaterial input have yet to be clarified. But it seems
likely that such episodic, but high-quality, detrital flux,
represents a most important nutritional source for the
deep-sea bed community.
The idea of a very attenuated link between the upper
ocean and the deep-sea bed communities, where for
all intents and purposes the upper ocean could be
regarded as a closed ecosystem with no important
carbon sink except respiration, is now of limited
value in quantifying global organic carbon-flux. Instead
the complex community dynamics of the upper-ocean
ecosystem may be seen as involving major and highly
variable losses to the deep ocean, particularly after
phytoplankton blooms. The openness of the whole
system leads to benthic–pelagic coupling that may
be dynamic and highly variable, just as it is on the
continental shelf.
Furthermore, the recent advent of improved instrumentation for use on the seabed has allowed one to
appreciate the importance of flow-related dynamics
of resuspension and lateral transport of this organic