Chapter 10
LARGE-SCALE SPATIAL AND TEMPORAL PATTERNS OF
DEEP-SEA BENTHIC SPECIES DIVERSITY
Carol T. STUART, Michael A. REX and Ron J. ETTER
INTRODUCTION
The discovery of high species diversity in the deepsea benthos by Hessler and Sanders (1967) required
fundamental changes in the understanding of marine
biodiversity. Sanders (1968) synthesized patterns of
diversity among coastal and deep-sea communities,
and proposed the stability–time hypothesis as a new
unifying explanation. This very influential idea is the
principal paradigm that shaped the course of modern
deep-sea ecology, and represents the logical starting
point for a consideration of deep-sea biodiversity. Two
key assumptions of the theory are that the deepsea environment is ecologically stable, allowing a
high level of coexistence through competitive niche
partitioning, and that this condition has persisted
over a geological time span sufficient for extensive
evolutionary diversification. Much of contemporary
deep-sea research has been directed at evaluating
these assumptions, and identifying the scales at which
ecological factors and historical processes operate to
control diversity.
The assumption of environmental stability in the
deep sea has been greatly modified by recent exploration. Species diversity and composition have
been shown to vary locally (Grassle and Maciolek,
1992), regionally (Cosson-Sarradin et al., 1998) and
globally (Rex et al., 1993, 2001; Wilson, 1998),
suggesting changes in the environmental factors determining community structure at all spatial scales.
The benthic landscape, far from being monotonous
as once assumed, is revealed to be a topographically
complex patchwork of distinctive habitats (MacDonald
et al., 1988; Van Dover, 1990; Mellor and Paull,
1994). Population fluctuations and reproductive cycles
in the deep benthos are linked to seasonal changes
in surface production, mediated through surface–
benthic coupling (Gage and Tyler, 1991; Young and
Eckelbarger, 1994). Catastrophic submarine landslides
(Rothwell et al., 1998) and ash from volcanic eruptions
(Hess and Kuhnt, 1996) can obliterate huge areas
of the seafloor. Current-driven “benthic storms” that
resuspend sediments are regular features of some deep
regions (Gage, 1997). The deep sea is a complicated,
dynamic environment, and one that functions as an
integral part of the global biosphere.
New advances in paleoceanography are changing
the assumption of a long history of stability or even
continuous occupancy of the deep sea. The deep sea
experienced a global mass-extinction event as recently
as the Paleocene (Kennett and Stott, 1991), and developed large-scale gradients of diversity as the planet
cooled during the Cenozoic (Thomas and Gooday,
1996). Much of the vast deep-sea environment may
be relatively new compared to terrestrial and shallowwater ecosystems, and may have changed substantially
during the last 50-million-year “ice-house” era. During
the Pliocene and Pleistocene, the deep-sea environment
is now known to have fluctuated dramatically in
temperature, in nutrient input, and in the position and
intensity of the deep thermohaline circulation, with the
waxing and waning of polar ice sheets (Raymo et al.,
1998). These oscillations are reflected in microfossil
communities recovered in seabed cores (Cronin and
Raymo, 1997).
In this chapter, we review the basic features of largescale geographic patterns of diversity documented
during the last thirty years of exploration, and the
changes of environment and community structure
through geological time that are emerging from
paleoceanographic studies of the last decade. They
295
LARGE-SCALE SPATIAL AND TEMPORAL PATTERNS OF
DEEP-SEA BENTHIC SPECIES DIVERSITY
Carol T. STUART, Michael A. REX and Ron J. ETTER
INTRODUCTION
The discovery of high species diversity in the deepsea benthos by Hessler and Sanders (1967) required
fundamental changes in the understanding of marine
biodiversity. Sanders (1968) synthesized patterns of
diversity among coastal and deep-sea communities,
and proposed the stability–time hypothesis as a new
unifying explanation. This very influential idea is the
principal paradigm that shaped the course of modern
deep-sea ecology, and represents the logical starting
point for a consideration of deep-sea biodiversity. Two
key assumptions of the theory are that the deepsea environment is ecologically stable, allowing a
high level of coexistence through competitive niche
partitioning, and that this condition has persisted
over a geological time span sufficient for extensive
evolutionary diversification. Much of contemporary
deep-sea research has been directed at evaluating
these assumptions, and identifying the scales at which
ecological factors and historical processes operate to
control diversity.
The assumption of environmental stability in the
deep sea has been greatly modified by recent exploration. Species diversity and composition have
been shown to vary locally (Grassle and Maciolek,
1992), regionally (Cosson-Sarradin et al., 1998) and
globally (Rex et al., 1993, 2001; Wilson, 1998),
suggesting changes in the environmental factors determining community structure at all spatial scales.
The benthic landscape, far from being monotonous
as once assumed, is revealed to be a topographically
complex patchwork of distinctive habitats (MacDonald
et al., 1988; Van Dover, 1990; Mellor and Paull,
1994). Population fluctuations and reproductive cycles
in the deep benthos are linked to seasonal changes
in surface production, mediated through surface–
benthic coupling (Gage and Tyler, 1991; Young and
Eckelbarger, 1994). Catastrophic submarine landslides
(Rothwell et al., 1998) and ash from volcanic eruptions
(Hess and Kuhnt, 1996) can obliterate huge areas
of the seafloor. Current-driven “benthic storms” that
resuspend sediments are regular features of some deep
regions (Gage, 1997). The deep sea is a complicated,
dynamic environment, and one that functions as an
integral part of the global biosphere.
New advances in paleoceanography are changing
the assumption of a long history of stability or even
continuous occupancy of the deep sea. The deep sea
experienced a global mass-extinction event as recently
as the Paleocene (Kennett and Stott, 1991), and developed large-scale gradients of diversity as the planet
cooled during the Cenozoic (Thomas and Gooday,
1996). Much of the vast deep-sea environment may
be relatively new compared to terrestrial and shallowwater ecosystems, and may have changed substantially
during the last 50-million-year “ice-house” era. During
the Pliocene and Pleistocene, the deep-sea environment
is now known to have fluctuated dramatically in
temperature, in nutrient input, and in the position and
intensity of the deep thermohaline circulation, with the
waxing and waning of polar ice sheets (Raymo et al.,
1998). These oscillations are reflected in microfossil
communities recovered in seabed cores (Cronin and
Raymo, 1997).
In this chapter, we review the basic features of largescale geographic patterns of diversity documented
during the last thirty years of exploration, and the
changes of environment and community structure
through geological time that are emerging from
paleoceanographic studies of the last decade. They
295