Chapter 25 Seagrass Conservation Biology
597
emphasis between terrestrial and marine protection,
indicating that an interdisciplinary and comprehensive approach to the conservation of marine biodiversity associated with the biomes like seagrasses is
a high priority (Lavery, 2000). In this chapter, we
examine the current state of seagrass science within
the viewpoint of conservation biology. We discuss
areas where seagrass science has been influenced by
a conservation biology approach, identify priority
research topics for conservation science, give examples where science and conservation biology are
being applied in the seagrass biome, and recommend
a course of action based on the principles of conservation biology to reverse the global trend of local
extinction, fragmentation, and general degradation
of the seagrass biome.
C. Seagrass Biodiversity
The sea and the coastal margins, are some the most
biodiverse regions on earth (Irish and Norse, 1996).
Seagrasses are unique because out of the estimated
two to three hundred thousand species of flowering plants they are the only angiosperms that have
adapted to life in a submarine environment (Arber,
1920; den Hartog, 1970; Hemminga and Duarte,
2000; den Hartog and Kuo, Chapter 1). With only
12 genera and 50–60 described species, seagrasses
themselves are not taxonomically diverse compared
to other benthic marine primary producers such as
seaweeds and microalgae (Fig. 2; den Hartog, 1970;
Green and Short, 2003). Yet, seagrass beds can be
long-lived and some are reportedly a 1,000 years
old (Reusch et al., 1999). Despite their own limited taxonomic diversity, seagrasses are the only
rooted organisms in the near shore region and are
the foundation for thousands of other taxa including vertebrate and invertebrate species that use the
biome for shelter, foraging sites, spawning habitat,
and nurseries (Kikuchi and Peres, 1977; Orth et al.,
1984). Protecting the few seagrasses species that
exist is essential to the biome and will safeguard
species richness, biodiversity, ecosystem structure,
and many ecological processes. A loss of just one
species of seagrass could cascade throughout an
entire coastal ecosystem with long-lasting effects
(Preen et al., 1995; Duarte, 2000; Hemminga and
Duarte, 2000).
The biodiversity supported by the seagrass
ecosystem can be appreciated by examining representative biomes from temperate and tropical regions (Duarte, 2000; Hemminga and Duarte, 2000).
In almost every comparison between submerged areas covered by seagrasses and those that are not,
species richness, abundance, and diversity of the
associated communities are greater within seagrass
beds (Howard et al., 1989; Sheridan, 1997). Many
of the organisms associated with the seagrass biome
drive important ecological processes that take place
in coastal systems. For example, invertebrates within
seagrass beds transfer energy to higher trophic levels
by transforming primary into secondary production
(Klumpp et al., 1989; Valentine and Duffy, Chapter 20). The loss of seagrasses alters the flow of organic matter, nutrient cycles, and food webs throughout coastal ecosystems where seagrasses occur and
in adjacent ecosystems where seagrasses export organic matter (Kenworthy, 1981; Bach et al., 1986;
Preen et al., 1995; also refer to Chapters 7, 8, 21,
24 and 26). The loss of these important ecological
processes eventually leads to economic disasters including the collapse of fisheries, degradation of water quality and the decline of other living resources
(De Jonge and De Jonge, 1992).
The Great Barrier Reef (GBR) region of northeastern Australia is one of the most conspicuous examples of seagrass biodiversity and bio-connectivity
known. Frequently referred to as the rainforest of
the sea, the GBR ecosystem has 15 species of seagrass including nearly 6,000 km
2 in water less than
15 m deep and as much as 40,000 km
2 of seagrass
in deeper water (Lee Long et al., 2000). The seagrass and invertebrate communities of the GBR provide water column and benthic structure for thousands of other invertebrate taxa, 1,500 species of
fish, 4,000 species of molluscs, 5 species of turtles,
250 species of birds, and one of the four remaining
large herbivorous marine mammals, the threatened
dugong. Throughout the GBR seagrasses make frequent contact with coral reefs and other live bottom
communities and the interconnectivity between the
reef and seagrass communities is ecologically very
important. The GBR region serves as a good example of the great potential for structural and functional
biodiversity in the seagrass biome that needs to be
conserved.
D. Diversity of Seagrass
Ecosystem Services
The seagrass biome provides a diversity of
ecosystem services sometimes difficult to quantify
597
emphasis between terrestrial and marine protection,
indicating that an interdisciplinary and comprehensive approach to the conservation of marine biodiversity associated with the biomes like seagrasses is
a high priority (Lavery, 2000). In this chapter, we
examine the current state of seagrass science within
the viewpoint of conservation biology. We discuss
areas where seagrass science has been influenced by
a conservation biology approach, identify priority
research topics for conservation science, give examples where science and conservation biology are
being applied in the seagrass biome, and recommend
a course of action based on the principles of conservation biology to reverse the global trend of local
extinction, fragmentation, and general degradation
of the seagrass biome.
C. Seagrass Biodiversity
The sea and the coastal margins, are some the most
biodiverse regions on earth (Irish and Norse, 1996).
Seagrasses are unique because out of the estimated
two to three hundred thousand species of flowering plants they are the only angiosperms that have
adapted to life in a submarine environment (Arber,
1920; den Hartog, 1970; Hemminga and Duarte,
2000; den Hartog and Kuo, Chapter 1). With only
12 genera and 50–60 described species, seagrasses
themselves are not taxonomically diverse compared
to other benthic marine primary producers such as
seaweeds and microalgae (Fig. 2; den Hartog, 1970;
Green and Short, 2003). Yet, seagrass beds can be
long-lived and some are reportedly a 1,000 years
old (Reusch et al., 1999). Despite their own limited taxonomic diversity, seagrasses are the only
rooted organisms in the near shore region and are
the foundation for thousands of other taxa including vertebrate and invertebrate species that use the
biome for shelter, foraging sites, spawning habitat,
and nurseries (Kikuchi and Peres, 1977; Orth et al.,
1984). Protecting the few seagrasses species that
exist is essential to the biome and will safeguard
species richness, biodiversity, ecosystem structure,
and many ecological processes. A loss of just one
species of seagrass could cascade throughout an
entire coastal ecosystem with long-lasting effects
(Preen et al., 1995; Duarte, 2000; Hemminga and
Duarte, 2000).
The biodiversity supported by the seagrass
ecosystem can be appreciated by examining representative biomes from temperate and tropical regions (Duarte, 2000; Hemminga and Duarte, 2000).
In almost every comparison between submerged areas covered by seagrasses and those that are not,
species richness, abundance, and diversity of the
associated communities are greater within seagrass
beds (Howard et al., 1989; Sheridan, 1997). Many
of the organisms associated with the seagrass biome
drive important ecological processes that take place
in coastal systems. For example, invertebrates within
seagrass beds transfer energy to higher trophic levels
by transforming primary into secondary production
(Klumpp et al., 1989; Valentine and Duffy, Chapter 20). The loss of seagrasses alters the flow of organic matter, nutrient cycles, and food webs throughout coastal ecosystems where seagrasses occur and
in adjacent ecosystems where seagrasses export organic matter (Kenworthy, 1981; Bach et al., 1986;
Preen et al., 1995; also refer to Chapters 7, 8, 21,
24 and 26). The loss of these important ecological
processes eventually leads to economic disasters including the collapse of fisheries, degradation of water quality and the decline of other living resources
(De Jonge and De Jonge, 1992).
The Great Barrier Reef (GBR) region of northeastern Australia is one of the most conspicuous examples of seagrass biodiversity and bio-connectivity
known. Frequently referred to as the rainforest of
the sea, the GBR ecosystem has 15 species of seagrass including nearly 6,000 km
2 in water less than
15 m deep and as much as 40,000 km
2 of seagrass
in deeper water (Lee Long et al., 2000). The seagrass and invertebrate communities of the GBR provide water column and benthic structure for thousands of other invertebrate taxa, 1,500 species of
fish, 4,000 species of molluscs, 5 species of turtles,
250 species of birds, and one of the four remaining
large herbivorous marine mammals, the threatened
dugong. Throughout the GBR seagrasses make frequent contact with coral reefs and other live bottom
communities and the interconnectivity between the
reef and seagrass communities is ecologically very
important. The GBR region serves as a good example of the great potential for structural and functional
biodiversity in the seagrass biome that needs to be
conserved.
D. Diversity of Seagrass
Ecosystem Services
The seagrass biome provides a diversity of
ecosystem services sometimes difficult to quantify