FOOD INPUTS, UTILIZATION, CARBON FLOW AND ENERGETICS
315
Fig. 11.1. Categories of food inputs to the deep-sea bed ecosystem.
flux on the deep-sea bed. These advective processes
mainly take place in the layer of water immediately
above the bottom that is mixed by turbulent shear
with the bottom, the benthic boundary layer (benthic
boundary layer). In physical terms there are sublayers or gradients in many parameters, including flow,
potential temperature and particulate and chemical
concentrations (see Chapter 2). The importance of
these in determining the nature and biological response
to organic input to the deep-sea processes (which
are particularly intense on the continental margin)
have previously been under-appreciated. Taking these
into account on the slope, supply and demand, which
previously seemed enigmatically unbalanced from measurement of input from vertically sinking particle flux,
now seem roughly in equilibrium.
However, such processes operate on the ecological
time scale. Overwhelming fluxes of organic carbon may
occur from episodic events over a longer time scale
triggered by earthquakes, for example (Thunell et al.,
1999). These may transfer large quantities of organic
carbon to the deep ocean from turbidity flows and slides
down the continental slope. The associated smothering
effect caused by displaced sediment will certainly cause
extinction of the benthic ecosystem in the immediate
vicinity. While such turbidites may be conveniently
preserved in the sediment biogenic structure and trace
fossils as ‘ichnofabric’ (Wetzel and Uchman, 1998),
there may be enhanced sedimentation of organic carbon
associated with resuspended sediment from shallow
depths over large adjacent areas of the deep ocean (e.g.,
Thunell et al., 1999). To what extent the living benthic
communities are able to utilize this bonanza before it
is buried is unknown.
Scope of chapter
Because of the openness of the oceanic ecosystem
in terms of carbon export, it is appropriate to track
from source all significant organic fluxes to the deepsea ecosystem (Fig. 11.1). In order to understand
the variability in response shown by the benthic
boundary layer (BBL) ecosystem, one now needs to
understand these sources better than was previously
thought necessary in deep-sea biology. These sources
will be described in turn, starting with active biological
transport, followed by the various size categories
of passive transports. The first and most important
315
Fig. 11.1. Categories of food inputs to the deep-sea bed ecosystem.
flux on the deep-sea bed. These advective processes
mainly take place in the layer of water immediately
above the bottom that is mixed by turbulent shear
with the bottom, the benthic boundary layer (benthic
boundary layer). In physical terms there are sublayers or gradients in many parameters, including flow,
potential temperature and particulate and chemical
concentrations (see Chapter 2). The importance of
these in determining the nature and biological response
to organic input to the deep-sea processes (which
are particularly intense on the continental margin)
have previously been under-appreciated. Taking these
into account on the slope, supply and demand, which
previously seemed enigmatically unbalanced from measurement of input from vertically sinking particle flux,
now seem roughly in equilibrium.
However, such processes operate on the ecological
time scale. Overwhelming fluxes of organic carbon may
occur from episodic events over a longer time scale
triggered by earthquakes, for example (Thunell et al.,
1999). These may transfer large quantities of organic
carbon to the deep ocean from turbidity flows and slides
down the continental slope. The associated smothering
effect caused by displaced sediment will certainly cause
extinction of the benthic ecosystem in the immediate
vicinity. While such turbidites may be conveniently
preserved in the sediment biogenic structure and trace
fossils as ‘ichnofabric’ (Wetzel and Uchman, 1998),
there may be enhanced sedimentation of organic carbon
associated with resuspended sediment from shallow
depths over large adjacent areas of the deep ocean (e.g.,
Thunell et al., 1999). To what extent the living benthic
communities are able to utilize this bonanza before it
is buried is unknown.
Scope of chapter
Because of the openness of the oceanic ecosystem
in terms of carbon export, it is appropriate to track
from source all significant organic fluxes to the deepsea ecosystem (Fig. 11.1). In order to understand
the variability in response shown by the benthic
boundary layer (BBL) ecosystem, one now needs to
understand these sources better than was previously
thought necessary in deep-sea biology. These sources
will be described in turn, starting with active biological
transport, followed by the various size categories
of passive transports. The first and most important