Chapter 5
Ecology of Seagrass Seeds and Seagrass
Dispersal Processes
Robert J. Orth*
School of Marine Science, College of William and Mary, Virginia Institute of Marine Science,
Gloucester Point, VA 23062, USA
Matthew C. Harwell
A. R. M. Loxahatchee National Wildlife Refuge, United States Fish and Wildlife Service,
Boynton Beach, FL 33437, USA
Graeme J. Inglis
National Institute of Water and Atmospheric Research, P.O. Box 8602, Christchurch,
New Zealand
I. Introduction
Seagrasses began colonizing the marine environment 100 million years ago in the Cretaceaous (den
Hartog, 1970) and, like their terrestrial, wetland, and
freshwater angiosperm counterparts, established a
highly effective method of dispersal - seeds. While
the terrestrial plant literature is replete with studies
on all aspects of seed ecology, ranging from the importance of seed size and storage reserves, morphology, to dispersal and recruitment strategies (see reviews by Baskin and Baskin, 1998; Clark et al., 1998;
Nathan and Muller-Landau, 2000; Higgins et al.,
2003; Levin et al., 2003) research on the ecology of
seagrass seeds has been remarkably sparse. These
processes are integral to understanding the demography of natural plant populations and the absence of
this information for seagrasses led to the historical
paradigm that seeds were unimportant in seagrass
bed dynamics. However, recent studies demonstrating higher than expected genetic diversity (Waycott,
1995; Reusch, 2002), patch development due to seed
recruitment (Duarte and Sand-Jensen, 1990; Ole∗ Author for correspondence, email: jjorth@vims.edu
sen and Sand-Jensen, 1994; Frederiksen et al., 2004;
Meehan and West, 2004; Olesen et al., 2004; Duarte
et al., Chapter 11), and more rapid recovery of disturbed stands than expected from vegetative propagation alone (Preen et al., 1995; Cambridge et al.,
2002; Plus et al., 2003; Whitfield et al., 2004; Greve
et al., 2005) have focused attention to seeds, seed
production and the fate of seeds, dispersal and recruitment strategies, and the potential role of seeds
in seagrass restoration projects (Williams and Davis,
1996; Harwell and Orth, 1999; Kenworthy, 2000;
Orth et al., 2000; Inglis, 2000a; Orth et al., 2003;
Balestri and Bertini, 2003; van Katwijk and Wijgergangs, 2004).
The objectives of this chapter are:
1. To review basic aspects of what is known about
seeds and the seed ecology of seagrasses, in particular processes important in their dispersal and
recruitment,
2. to provide the conceptual basis for emerging
paradigms in this field, and
3. to highlight the relevance of sexual propagules
for the restoration and conservation of seagrass
meadows.
111–133.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp.
c
2006 Springer. Printed in the Netherlands.
Ecology of Seagrass Seeds and Seagrass
Dispersal Processes
Robert J. Orth*
School of Marine Science, College of William and Mary, Virginia Institute of Marine Science,
Gloucester Point, VA 23062, USA
Matthew C. Harwell
A. R. M. Loxahatchee National Wildlife Refuge, United States Fish and Wildlife Service,
Boynton Beach, FL 33437, USA
Graeme J. Inglis
National Institute of Water and Atmospheric Research, P.O. Box 8602, Christchurch,
New Zealand
I. Introduction
Seagrasses began colonizing the marine environment 100 million years ago in the Cretaceaous (den
Hartog, 1970) and, like their terrestrial, wetland, and
freshwater angiosperm counterparts, established a
highly effective method of dispersal - seeds. While
the terrestrial plant literature is replete with studies
on all aspects of seed ecology, ranging from the importance of seed size and storage reserves, morphology, to dispersal and recruitment strategies (see reviews by Baskin and Baskin, 1998; Clark et al., 1998;
Nathan and Muller-Landau, 2000; Higgins et al.,
2003; Levin et al., 2003) research on the ecology of
seagrass seeds has been remarkably sparse. These
processes are integral to understanding the demography of natural plant populations and the absence of
this information for seagrasses led to the historical
paradigm that seeds were unimportant in seagrass
bed dynamics. However, recent studies demonstrating higher than expected genetic diversity (Waycott,
1995; Reusch, 2002), patch development due to seed
recruitment (Duarte and Sand-Jensen, 1990; Ole∗ Author for correspondence, email: jjorth@vims.edu
sen and Sand-Jensen, 1994; Frederiksen et al., 2004;
Meehan and West, 2004; Olesen et al., 2004; Duarte
et al., Chapter 11), and more rapid recovery of disturbed stands than expected from vegetative propagation alone (Preen et al., 1995; Cambridge et al.,
2002; Plus et al., 2003; Whitfield et al., 2004; Greve
et al., 2005) have focused attention to seeds, seed
production and the fate of seeds, dispersal and recruitment strategies, and the potential role of seeds
in seagrass restoration projects (Williams and Davis,
1996; Harwell and Orth, 1999; Kenworthy, 2000;
Orth et al., 2000; Inglis, 2000a; Orth et al., 2003;
Balestri and Bertini, 2003; van Katwijk and Wijgergangs, 2004).
The objectives of this chapter are:
1. To review basic aspects of what is known about
seeds and the seed ecology of seagrasses, in particular processes important in their dispersal and
recruitment,
2. to provide the conceptual basis for emerging
paradigms in this field, and
3. to highlight the relevance of sexual propagules
for the restoration and conservation of seagrass
meadows.
111–133.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp.
c
2006 Springer. Printed in the Netherlands.