606
W. Judson Kenworthy et al.
of resource management is high (e.g. Fonseca et al.,
2000a).
B. Priority Research Topics for Seagrass
Conservation Science
1. Habitat Fragmentation and
Disturbance Dynamics
Seagrass biomes often occur as an assembly of small,
fragmented populations in a patchy distribution but
may also be distributed in distinct zonation patterns
across the seascape (Fonseca et al., 2000b; Fonseca
et al. 2002b; Bell et al., Chapter 26). The existence
of patchy seagrass biomes occurs naturally in many
ecosystems and may be the equilibrium condition for
a particular set of environmental conditions (Marb` a
and Duarte, 1995; Fonseca and Bell, 1998; Fonseca
et al., 2000b; Duarte et al., Chapter 11). While much
has been learned about the physical and biological
formation of these fragmented populations (den Hartog, 1971; Patriquin, 1975; Fonseca and Bell, 1998;
Rose et al., 1999), we know little about the species
level mechanisms that maintain patch configuration
(Fonseca and Bell, 1998; Marb` a and Duarte, 1998;
Fonseca et al. 2000b). However, transformation of
seagrass beds from continuous cover to a fragmented
landscape may increase the vulnerability of these
systems to further biophysical degradation. Practices
related to aquaculture, commercial fishing, motor
vessels, docks, and channel dredging endanger the
physical integrity and structure of seagrass meadows
leading to fragmentation and altering species abundance and richness (Peterson et al., 1987; Dimech
et al., 2000; Ruiz et al., 2001; Kenworthy et al., 2002;
Orth et al., 2002; Uhrin and Holmquist, 2003). Practices associated with access to the coastal zone, navigation and the economic incentives related to the
harvest of resources in the short-term, may impair
the stability of the biome and compromise sustainability over time.
The transformation of the seagrass biome from
continuous cover to a patchy, fragmented landscape
is not limited to harvest practices but extends to
a wide variety of recreational and industrial use
of our waterways and the desire for people to live
near coastal resources. Aerial photographs reveal
scars left by propeller rotation in the soft sediment matrix that supports seagrass growth (Sargent
et al., 1995; Whitfield et al., 2002; Kenworthy et al.,
2002). Circular patterns of unvegetated areas within
continuous seagrass cover are created by the swing
of anchor chains, mooring lines, shellfish harvesting, and trawling practices (Walker et al., 1989;
Pasqualini et al., 1999; Orth et al., 2002). Over-water
structures, providing easy access for recreational
boats and commercial ferries, shade the bottom and
eliminate seagrass cover (Thom et al., 1998; Burdick
and Short, 1999; Shafer, 1999). These activities are
fragmenting the landscape and cumulatively impacting the seagrass biome. Examples from landscapelevel ecological studies of seagrasses illustrate the
relevance of the contiguity of seagrass beds and
patch dynamics to bed structure (den Hartog, 1971;
Marb` a and Duarte, 1995; Bell et al., Chapter 26), seagrass distribution (Fonseca et al., 2002b), survival
(Fonseca et al., 2000b), response to natural energy
regimes (Patriquin, 1975; Marb` a and Duarte, 1995;
Fonseca and Bell, 1998; Fonseca et al., 2000b), and
community composition (Zieman, 1972; Uhrin and
Holmquist, 2003).
The fragmentation and degradation of the seagrass biome become especially perilous in developing nations, as coastal states attempt to increase
revenue through activities that elevate stress levels
in seagrass ecosystems (e.g. Wu et al., 1998; Cloern,
2001). A conservation biology perspective that recognizes the interdependence of ecosystem function
and societal need can help prevent fragmentation
and degradation of seagrass biomes in developing
nations.
Fragmentation can threaten biodiversity and the
structure and function of the seagrass biome. With
so few seagrass species locally and globally and numerous examples of endemism, the loss of a single species is potentially catastrophic to hundreds or
thousands of other organisms, as well as the degradation of many important ecosystem processes. Because it is difficult to separate the signal (human disturbance vectors) from the noise (natural variability
of disturbance), the role of disturbance and the response of seagrass species to a particular disturbance
should be a major focus of long- and short-term research programs. Disturbance ecology should not be
limited to just mapping and cataloging changes associated with natural and human events, but should
also include detailed ecological studies identifying
the direction of change and the mechanistic processes involved in controlling response and recovery
dynamics in order to predict their ecological consequences (Fourqurean et al., 1995; Whitfield et al.,
2002; Kenworthy et al., 2002; Peterson et al., 2002).
W. Judson Kenworthy et al.
of resource management is high (e.g. Fonseca et al.,
2000a).
B. Priority Research Topics for Seagrass
Conservation Science
1. Habitat Fragmentation and
Disturbance Dynamics
Seagrass biomes often occur as an assembly of small,
fragmented populations in a patchy distribution but
may also be distributed in distinct zonation patterns
across the seascape (Fonseca et al., 2000b; Fonseca
et al. 2002b; Bell et al., Chapter 26). The existence
of patchy seagrass biomes occurs naturally in many
ecosystems and may be the equilibrium condition for
a particular set of environmental conditions (Marb` a
and Duarte, 1995; Fonseca and Bell, 1998; Fonseca
et al., 2000b; Duarte et al., Chapter 11). While much
has been learned about the physical and biological
formation of these fragmented populations (den Hartog, 1971; Patriquin, 1975; Fonseca and Bell, 1998;
Rose et al., 1999), we know little about the species
level mechanisms that maintain patch configuration
(Fonseca and Bell, 1998; Marb` a and Duarte, 1998;
Fonseca et al. 2000b). However, transformation of
seagrass beds from continuous cover to a fragmented
landscape may increase the vulnerability of these
systems to further biophysical degradation. Practices
related to aquaculture, commercial fishing, motor
vessels, docks, and channel dredging endanger the
physical integrity and structure of seagrass meadows
leading to fragmentation and altering species abundance and richness (Peterson et al., 1987; Dimech
et al., 2000; Ruiz et al., 2001; Kenworthy et al., 2002;
Orth et al., 2002; Uhrin and Holmquist, 2003). Practices associated with access to the coastal zone, navigation and the economic incentives related to the
harvest of resources in the short-term, may impair
the stability of the biome and compromise sustainability over time.
The transformation of the seagrass biome from
continuous cover to a patchy, fragmented landscape
is not limited to harvest practices but extends to
a wide variety of recreational and industrial use
of our waterways and the desire for people to live
near coastal resources. Aerial photographs reveal
scars left by propeller rotation in the soft sediment matrix that supports seagrass growth (Sargent
et al., 1995; Whitfield et al., 2002; Kenworthy et al.,
2002). Circular patterns of unvegetated areas within
continuous seagrass cover are created by the swing
of anchor chains, mooring lines, shellfish harvesting, and trawling practices (Walker et al., 1989;
Pasqualini et al., 1999; Orth et al., 2002). Over-water
structures, providing easy access for recreational
boats and commercial ferries, shade the bottom and
eliminate seagrass cover (Thom et al., 1998; Burdick
and Short, 1999; Shafer, 1999). These activities are
fragmenting the landscape and cumulatively impacting the seagrass biome. Examples from landscapelevel ecological studies of seagrasses illustrate the
relevance of the contiguity of seagrass beds and
patch dynamics to bed structure (den Hartog, 1971;
Marb` a and Duarte, 1995; Bell et al., Chapter 26), seagrass distribution (Fonseca et al., 2002b), survival
(Fonseca et al., 2000b), response to natural energy
regimes (Patriquin, 1975; Marb` a and Duarte, 1995;
Fonseca and Bell, 1998; Fonseca et al., 2000b), and
community composition (Zieman, 1972; Uhrin and
Holmquist, 2003).
The fragmentation and degradation of the seagrass biome become especially perilous in developing nations, as coastal states attempt to increase
revenue through activities that elevate stress levels
in seagrass ecosystems (e.g. Wu et al., 1998; Cloern,
2001). A conservation biology perspective that recognizes the interdependence of ecosystem function
and societal need can help prevent fragmentation
and degradation of seagrass biomes in developing
nations.
Fragmentation can threaten biodiversity and the
structure and function of the seagrass biome. With
so few seagrass species locally and globally and numerous examples of endemism, the loss of a single species is potentially catastrophic to hundreds or
thousands of other organisms, as well as the degradation of many important ecosystem processes. Because it is difficult to separate the signal (human disturbance vectors) from the noise (natural variability
of disturbance), the role of disturbance and the response of seagrass species to a particular disturbance
should be a major focus of long- and short-term research programs. Disturbance ecology should not be
limited to just mapping and cataloging changes associated with natural and human events, but should
also include detailed ecological studies identifying
the direction of change and the mechanistic processes involved in controlling response and recovery
dynamics in order to predict their ecological consequences (Fourqurean et al., 1995; Whitfield et al.,
2002; Kenworthy et al., 2002; Peterson et al., 2002).