370
Kenneth A. Moore and Frederick T. Short
for restoration (Williams and Orth, 1998; Olsen
et al., 2004).
III. Ecology
A. Ecological Functions
Zostera beds in general provide a wide array of ecological functions important for maintaining healthy
estuarine and coastal ecosystems, creating essential
habitat, and forming a basis of primary production
that supports ecologically and economically important fisheries (Duarte et al., in press). Zostera marina provides habitat for numerous commercially
important fish and shellfish species (Orth and Heck,
1980; Thayer et al., 1984; Orth and van Montfrans,
1987; Heck et al., 1989, 1995, 2003; Fredette et al.,
1990; Short et al., 1993a; Dean and Haldorson, 2000;
Beck et al., 2001; Short et al., 2001). In New South
Wales, Australia, areas vegetated with Z. capricorni
were found to have the greatest diversity and highest abundance of fish in shallow, marine regions,
especially during the recruitment period (West and
King, 1996). These included juveniles of many commercially important species such as the yellowfin
bream (Acanthopagrus australis) and sea mullet
(Mugil cephalus). Worthington et al. (1995) associated the great temporal and spatial variability in
juvenile species in Z. capricorni habitats to variability in recruitment as well as subsequent mortality.
Connolly (1994a,b) reports the significantly greater
abundance of fish in Z. capricorni (reported as Z.
muelleri) beds compared to unvegetated habitats and
suggests that the use of these Zostera habitats may be
related to both food availability and habitat structure
(see Gillanders, Chapter 21). Similarly, Woods and
Schiel (1997) found that the crab Macrophthalmus
hirtipes used only Z. capricorni (reported as Z. novazelandica) beds, especially along patch edges of
the seagrass, to the exclusion of other habitats as they
fed on both the seagrass and sediment in the patches.
Here, their burrows affected seagrass bed structure
as crab burrow abundance at patch edges accelerated
patch erosion. The relationships between the Zostera
habitats and organisms using these habitats are very
complex. In mixed beds of intertidal Z. capricorni
(reported as Z. muelleri) and subtidal Z. tasmanica
(reported as Heterozostera tasmanica), for example, differences in fish assemblage have been related
more to the depth zone of the habitat than to the presence or absence of vegetation (Jenkins et al., 1997).
Similarly, abundance of some gastropods was found
to be significantly different between seagrass species
in mixed beds of Z. caulescens and Z. marina (Toyohara et al., 1999).
Overall, the generally recognized value of Zostera
beds as important nursery areas for many species has
not been well quantified for most regions of the world
(Heck et al., 2003). Heck et al. (2003) suggest that
the structural component provided by seagrass beds
may be the most important attribute contributing to
their nursery function. There are, however, many recent studies continuing to confirm the greater habitat functions and secondary production of Zostera
beds compared to adjacent unvegetated areas (Fredette et al., 1990; Costa, 1994; Orth et al., 1996;
Dean and Haldorson, 2000). Yet the impacts of the
continuing loss of these of these important habitats
to fisheries is still not well quantified (Beck et al.,
2001).
Some species associated with Z. marina habitat are in decline, such as flounder, cod and
scallops. In Puget Sound, Washington juvenile
salmonids are associated with Z. marina habitat and
are listed as threatened (http://www.nwr.noaa.gov/
1salmon/salmesa/). The Z. marina limpet, Lottia
alveus, became extinct after the 1930s wasting disease (Carlton et al., 1991). The brant goose (Branta
bernicla), a species dependent on Z. marina as a primary food source, was abundant before the 1930s
and has only partially recovered. Ducks, swans, and
other species of goose use Z. marina as food and
are known to stop in Z. marina areas during migration. The Pacific black brant migration is linked
closely to the distribution of Z. marina at sites from
Baja California, Mexico to Izembek Lagoon, Alaska
(USA) (Wyllie-Echeverria and Ackerman, 2003).
Zostera beds are also important foraging habitats for
wading birds such as the heron (Matsunaga, 2000).
The abundance of Zostera and waterfowl populations have been reported to co-vary in many areas. In British Columbia, Canada, expansion of Z.
japonica habitat was associated with increases in
dabbling ducks and brant (Baldwin and Lovvorn,
1994a) and waterfowl distribution within shallow
water areas has been related to the presence of
Zostera vegetation (Baldwin and Lovvorn, 1994a;
Clausen et al., 1998). Conversely, the impacts of
waterfowl on Zostera have been quantified and birds
have been found to consume from a low percentage
to more than half of Zostera biomass in areas studied
Kenneth A. Moore and Frederick T. Short
for restoration (Williams and Orth, 1998; Olsen
et al., 2004).
III. Ecology
A. Ecological Functions
Zostera beds in general provide a wide array of ecological functions important for maintaining healthy
estuarine and coastal ecosystems, creating essential
habitat, and forming a basis of primary production
that supports ecologically and economically important fisheries (Duarte et al., in press). Zostera marina provides habitat for numerous commercially
important fish and shellfish species (Orth and Heck,
1980; Thayer et al., 1984; Orth and van Montfrans,
1987; Heck et al., 1989, 1995, 2003; Fredette et al.,
1990; Short et al., 1993a; Dean and Haldorson, 2000;
Beck et al., 2001; Short et al., 2001). In New South
Wales, Australia, areas vegetated with Z. capricorni
were found to have the greatest diversity and highest abundance of fish in shallow, marine regions,
especially during the recruitment period (West and
King, 1996). These included juveniles of many commercially important species such as the yellowfin
bream (Acanthopagrus australis) and sea mullet
(Mugil cephalus). Worthington et al. (1995) associated the great temporal and spatial variability in
juvenile species in Z. capricorni habitats to variability in recruitment as well as subsequent mortality.
Connolly (1994a,b) reports the significantly greater
abundance of fish in Z. capricorni (reported as Z.
muelleri) beds compared to unvegetated habitats and
suggests that the use of these Zostera habitats may be
related to both food availability and habitat structure
(see Gillanders, Chapter 21). Similarly, Woods and
Schiel (1997) found that the crab Macrophthalmus
hirtipes used only Z. capricorni (reported as Z. novazelandica) beds, especially along patch edges of
the seagrass, to the exclusion of other habitats as they
fed on both the seagrass and sediment in the patches.
Here, their burrows affected seagrass bed structure
as crab burrow abundance at patch edges accelerated
patch erosion. The relationships between the Zostera
habitats and organisms using these habitats are very
complex. In mixed beds of intertidal Z. capricorni
(reported as Z. muelleri) and subtidal Z. tasmanica
(reported as Heterozostera tasmanica), for example, differences in fish assemblage have been related
more to the depth zone of the habitat than to the presence or absence of vegetation (Jenkins et al., 1997).
Similarly, abundance of some gastropods was found
to be significantly different between seagrass species
in mixed beds of Z. caulescens and Z. marina (Toyohara et al., 1999).
Overall, the generally recognized value of Zostera
beds as important nursery areas for many species has
not been well quantified for most regions of the world
(Heck et al., 2003). Heck et al. (2003) suggest that
the structural component provided by seagrass beds
may be the most important attribute contributing to
their nursery function. There are, however, many recent studies continuing to confirm the greater habitat functions and secondary production of Zostera
beds compared to adjacent unvegetated areas (Fredette et al., 1990; Costa, 1994; Orth et al., 1996;
Dean and Haldorson, 2000). Yet the impacts of the
continuing loss of these of these important habitats
to fisheries is still not well quantified (Beck et al.,
2001).
Some species associated with Z. marina habitat are in decline, such as flounder, cod and
scallops. In Puget Sound, Washington juvenile
salmonids are associated with Z. marina habitat and
are listed as threatened (http://www.nwr.noaa.gov/
1salmon/salmesa/). The Z. marina limpet, Lottia
alveus, became extinct after the 1930s wasting disease (Carlton et al., 1991). The brant goose (Branta
bernicla), a species dependent on Z. marina as a primary food source, was abundant before the 1930s
and has only partially recovered. Ducks, swans, and
other species of goose use Z. marina as food and
are known to stop in Z. marina areas during migration. The Pacific black brant migration is linked
closely to the distribution of Z. marina at sites from
Baja California, Mexico to Izembek Lagoon, Alaska
(USA) (Wyllie-Echeverria and Ackerman, 2003).
Zostera beds are also important foraging habitats for
wading birds such as the heron (Matsunaga, 2000).
The abundance of Zostera and waterfowl populations have been reported to co-vary in many areas. In British Columbia, Canada, expansion of Z.
japonica habitat was associated with increases in
dabbling ducks and brant (Baldwin and Lovvorn,
1994a) and waterfowl distribution within shallow
water areas has been related to the presence of
Zostera vegetation (Baldwin and Lovvorn, 1994a;
Clausen et al., 1998). Conversely, the impacts of
waterfowl on Zostera have been quantified and birds
have been found to consume from a low percentage
to more than half of Zostera biomass in areas studied