FOOD INPUTS, UTILIZATION, CARBON FLOW AND ENERGETICS
349
Available data have been summarized by Mahaut
et al. (1995), who fitted a weight-dependent relationship to all deep-sea data available in the literature.
These data show, as might be expected, that weightspecific respiratory demand declines rapidly with
increasing size, and that, while obvious in terms
of visibility in photographs and biomass, the largest
organisms, the megafauna, may account for a relatively
small percentage of total organic-carbon mineralization
in the benthic boundary layer community. This is in
agreement with the estimates reached by K.L. Smith
(1992) and K.L. Smith et al. (1993) from calculating
uptake of particulate organic carbon by megafaunal
deposit feeders. An integrated value covering the full
size range of the deep-sea bed biota, from bacteria to
megafauna, was obtained for the biomass size classes
sampled from a site in the Northeast Atlantic and
compared to one measured directly in situ. The good
agreement obtained will allow investigators to estimate
sediment oxygen demand from size-classified biomass.
Data, when available in quantity, will provide a timeand space-integrated relationship, which will not be
subject to the scaling constraints of estimates from
benthic chambers or sediment pore-water profiling (see
above).
Growth rates and secondary production of larger
size classes
There has been, until recently, a perception that
population rates, such as growth of individuals and
rates of population expansion, are very slow, with rates
of population turnover one or two orders of magnitude
slower than in shallow water (Thiel, 1975). This view
was much influenced by early observations of low rates
of organic degradation (e.g., Jannasch et al., 1971)
and results of a study using radiometric dating which
were interpreted to show extremely low rates of shell
growth in a deep-sea protobranch bivalve (Turekian
et al., 1975). If this is true, then the diversion of energy
into growth and reproduction could be disregarded;
seabed recycling could be considered as virtually
totally expressed by respiratory demand measured by
sediment community oxygen consumption.
Against this viewpoint of low rates of turnover
there emerged scattered observations from seabed
recolonization experiments in the 1970s and 1980s that
some deep-sea sediment-dwelling macrofauna, such
as the protobranch Deminucula atacellana and the
aplacophoran Prochaetoderma yongei, are able to grow
rapidly, at least as young individuals (Grassle, 1977;
Grassle and Morse-Porteous, 1987; Scheltema, 1987).
However, information on the response at the population level, as somatic and reproductive production,
of organisms other than bacteria to organic input
is still sparse. This is because of the difficulty in
undertaking the necessary monitoring of populations
with the precision needed to distinguish change from
background noise (Gage, 1991). Nevertheless, solid
indications of rapid rates of secondary production in
larger metazoans have come from a study of a sample
time series in the Rockall Trough (Gage et al., 1980).
One of the initially most noteworthy results was the
marked increase in benthic larval and young stages in
samples taken in summer after the presumed peak in
organic-particle flux to the bottom (see summary in
Gage, 1994). Summertime increases in populations of
peracarids, such as cumaceans, have also been observed
(Cartes and Sorbe, 1996). In some cases this could
be linked to seasonal reproduction (Tyler et al., 1982).
However, a seasonal influx of postlarvae seems to occur
in other species lacking seasonal reproduction (e.g.,
Gage and Tyler, 1982); release of brooded young in
the peracarid cumacean crustacean Leucon profundus
peaks in late spring/early summer (Bishop and Shalla,
1994). Modelling studies applied to samples of the
population changes observed among several species
indicate rates equivalent to those for closely related
species in coastal soft-sediment habitats (Gage, 1991,
1994, 1995). The apparent increase may then merely
reflect growth, stimulated by the temporary increase
in food, from a pool of non-growing or very slowly
growing postlarvae which exists year-round.
Time-lapse photography has recorded rapid rates
of individual growth in the barnacle Poecilasma
kaempferi (Lampitt, 1990) and in the xenophyophore
Reticulammina labyrinthica, the latter occurring in
distinct episodes lasting 2–3 days separated by about
two months (Gooday et al., 1993). Other rapid rates
have emerged from use of the time-dependent change
(racemization) of aspartic acid in the shell. This is
used as a time marker to age the gastropod mollusc
Entemnotrochus adansonianus (Goodfriend et al.,
1995). Changes in population abundance indicate rapid
growth in deep-sea Foraminifera (Gooday and Turley,
1990; Corliss and Silva, 1993). In contrast, radiometric
study of a deep-sea coral Corallium using
210 Pb and
other natural isotopes (Druffel et al., 1990) indicates a
very slow growth rate, in line with low rates estimated
for other deep-water species such as Lophelia pertusa
349
Available data have been summarized by Mahaut
et al. (1995), who fitted a weight-dependent relationship to all deep-sea data available in the literature.
These data show, as might be expected, that weightspecific respiratory demand declines rapidly with
increasing size, and that, while obvious in terms
of visibility in photographs and biomass, the largest
organisms, the megafauna, may account for a relatively
small percentage of total organic-carbon mineralization
in the benthic boundary layer community. This is in
agreement with the estimates reached by K.L. Smith
(1992) and K.L. Smith et al. (1993) from calculating
uptake of particulate organic carbon by megafaunal
deposit feeders. An integrated value covering the full
size range of the deep-sea bed biota, from bacteria to
megafauna, was obtained for the biomass size classes
sampled from a site in the Northeast Atlantic and
compared to one measured directly in situ. The good
agreement obtained will allow investigators to estimate
sediment oxygen demand from size-classified biomass.
Data, when available in quantity, will provide a timeand space-integrated relationship, which will not be
subject to the scaling constraints of estimates from
benthic chambers or sediment pore-water profiling (see
above).
Growth rates and secondary production of larger
size classes
There has been, until recently, a perception that
population rates, such as growth of individuals and
rates of population expansion, are very slow, with rates
of population turnover one or two orders of magnitude
slower than in shallow water (Thiel, 1975). This view
was much influenced by early observations of low rates
of organic degradation (e.g., Jannasch et al., 1971)
and results of a study using radiometric dating which
were interpreted to show extremely low rates of shell
growth in a deep-sea protobranch bivalve (Turekian
et al., 1975). If this is true, then the diversion of energy
into growth and reproduction could be disregarded;
seabed recycling could be considered as virtually
totally expressed by respiratory demand measured by
sediment community oxygen consumption.
Against this viewpoint of low rates of turnover
there emerged scattered observations from seabed
recolonization experiments in the 1970s and 1980s that
some deep-sea sediment-dwelling macrofauna, such
as the protobranch Deminucula atacellana and the
aplacophoran Prochaetoderma yongei, are able to grow
rapidly, at least as young individuals (Grassle, 1977;
Grassle and Morse-Porteous, 1987; Scheltema, 1987).
However, information on the response at the population level, as somatic and reproductive production,
of organisms other than bacteria to organic input
is still sparse. This is because of the difficulty in
undertaking the necessary monitoring of populations
with the precision needed to distinguish change from
background noise (Gage, 1991). Nevertheless, solid
indications of rapid rates of secondary production in
larger metazoans have come from a study of a sample
time series in the Rockall Trough (Gage et al., 1980).
One of the initially most noteworthy results was the
marked increase in benthic larval and young stages in
samples taken in summer after the presumed peak in
organic-particle flux to the bottom (see summary in
Gage, 1994). Summertime increases in populations of
peracarids, such as cumaceans, have also been observed
(Cartes and Sorbe, 1996). In some cases this could
be linked to seasonal reproduction (Tyler et al., 1982).
However, a seasonal influx of postlarvae seems to occur
in other species lacking seasonal reproduction (e.g.,
Gage and Tyler, 1982); release of brooded young in
the peracarid cumacean crustacean Leucon profundus
peaks in late spring/early summer (Bishop and Shalla,
1994). Modelling studies applied to samples of the
population changes observed among several species
indicate rates equivalent to those for closely related
species in coastal soft-sediment habitats (Gage, 1991,
1994, 1995). The apparent increase may then merely
reflect growth, stimulated by the temporary increase
in food, from a pool of non-growing or very slowly
growing postlarvae which exists year-round.
Time-lapse photography has recorded rapid rates
of individual growth in the barnacle Poecilasma
kaempferi (Lampitt, 1990) and in the xenophyophore
Reticulammina labyrinthica, the latter occurring in
distinct episodes lasting 2–3 days separated by about
two months (Gooday et al., 1993). Other rapid rates
have emerged from use of the time-dependent change
(racemization) of aspartic acid in the shell. This is
used as a time marker to age the gastropod mollusc
Entemnotrochus adansonianus (Goodfriend et al.,
1995). Changes in population abundance indicate rapid
growth in deep-sea Foraminifera (Gooday and Turley,
1990; Corliss and Silva, 1993). In contrast, radiometric
study of a deep-sea coral Corallium using
210 Pb and
other natural isotopes (Druffel et al., 1990) indicates a
very slow growth rate, in line with low rates estimated
for other deep-water species such as Lophelia pertusa