Chapter 19
Epiphytes of Seagrasses
Michael A. Borowitzka
∗
School of Biological Sciences and Biotechnology, Murdoch University,
Murdoch, WA 6150, Australia
Paul S. Lavery
School of Natural Sciences, Edith Cowan University, Joondalup, WA 6027, Australia
Mike van Keulen
School of Biological Sciences and Biotechnology, Murdoch University,
Murdoch, WA 6150, Australia
I. Introduction
In all aquatic environments, available surfaces are
rapidly colonized by a variety of organisms. If
these organisms grow on plants they are called epiphytes. Seagrasses provide an excellent substratum
for epiphytic organisms and these organisms are
an integral component of seagrass ecosystems. The
ecology and physiology of seagrass epiphytes have
been reviewed previously (Harlin, 1980; Borowitzka
and Lethbridge, 1989) and this chapter focuses primarily on new developments in our understanding
of seagrass epiphyte
1 biology and ecology that have
occurred since then.
Seagrasses grow in a wide range of habitats ranging from the intertidal to depths of over 50 m (Long
et al., 1996), from estuarine to marine environments,
and from temperate regions to the tropics. The different seagrass genera also show a diversity of morphologies ranging from the simple subulate leaves of
Syringodium and the strap-shaped leaves of Cymodocea, Posidonia, Thalassia, and Zostera, to species
∗ Author for correspondence, email: m.borowitzka@murdoch.
edu.au
1 The term epiphyte is variously defined in the literature. In this
chapter, we define an epiphyte as an organism that grows upon
plants. Periphyton are the microalgae (diatoms, dinoflagellates,
juvenile germlings of larger algae, etc.), bacteria, protozoa, etc.
on surfaces such as seagrass leaves.
with upright lignified stems with terminal strapshaped leaf bundles as in Amphibolis, providing a
structurally diverse range of habitats (refer to Kuo
and den Hartog, Chapter 3, for further details). The
above-ground parts of seagrasses provide a temporary, but continuously renewing, substratum for epiphytic organisms. The life-span of the leaves, stems,
and rhizomes upon which epiphytic organisms can
grow varies between species, habitats and with season and ranges from about 11 days for Halophila
ovalis leaves to about 130 days for Posidonia leaves
and over 2 years for stems of Amphibolis antarctica
(Fig. 1).
II. The Role of the Epiphytic Organisms
A. Primary Producers
The epiphytic algae of seagrasses are important primary producers in seagrass ecosystems and make
a significant contribution to food webs. They can
account for over 50% of the standing stock in seagrass meadows. In Florida, USA, epiphytic algae
contributed 62, 50, and 44% of primary production
for Syringodium filiforme, Thalassia testudinum, and
Halodule wrightii, respectively (Wear et al., 1999).
In Papua New Guinea, Heijs (1984) determined
that the epiphytic algae on T. hemprichii contribute
441–461.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp.
c
2006 Springer. Printed in the Netherlands.
Epiphytes of Seagrasses
Michael A. Borowitzka
∗
School of Biological Sciences and Biotechnology, Murdoch University,
Murdoch, WA 6150, Australia
Paul S. Lavery
School of Natural Sciences, Edith Cowan University, Joondalup, WA 6027, Australia
Mike van Keulen
School of Biological Sciences and Biotechnology, Murdoch University,
Murdoch, WA 6150, Australia
I. Introduction
In all aquatic environments, available surfaces are
rapidly colonized by a variety of organisms. If
these organisms grow on plants they are called epiphytes. Seagrasses provide an excellent substratum
for epiphytic organisms and these organisms are
an integral component of seagrass ecosystems. The
ecology and physiology of seagrass epiphytes have
been reviewed previously (Harlin, 1980; Borowitzka
and Lethbridge, 1989) and this chapter focuses primarily on new developments in our understanding
of seagrass epiphyte
1 biology and ecology that have
occurred since then.
Seagrasses grow in a wide range of habitats ranging from the intertidal to depths of over 50 m (Long
et al., 1996), from estuarine to marine environments,
and from temperate regions to the tropics. The different seagrass genera also show a diversity of morphologies ranging from the simple subulate leaves of
Syringodium and the strap-shaped leaves of Cymodocea, Posidonia, Thalassia, and Zostera, to species
∗ Author for correspondence, email: m.borowitzka@murdoch.
edu.au
1 The term epiphyte is variously defined in the literature. In this
chapter, we define an epiphyte as an organism that grows upon
plants. Periphyton are the microalgae (diatoms, dinoflagellates,
juvenile germlings of larger algae, etc.), bacteria, protozoa, etc.
on surfaces such as seagrass leaves.
with upright lignified stems with terminal strapshaped leaf bundles as in Amphibolis, providing a
structurally diverse range of habitats (refer to Kuo
and den Hartog, Chapter 3, for further details). The
above-ground parts of seagrasses provide a temporary, but continuously renewing, substratum for epiphytic organisms. The life-span of the leaves, stems,
and rhizomes upon which epiphytic organisms can
grow varies between species, habitats and with season and ranges from about 11 days for Halophila
ovalis leaves to about 130 days for Posidonia leaves
and over 2 years for stems of Amphibolis antarctica
(Fig. 1).
II. The Role of the Epiphytic Organisms
A. Primary Producers
The epiphytic algae of seagrasses are important primary producers in seagrass ecosystems and make
a significant contribution to food webs. They can
account for over 50% of the standing stock in seagrass meadows. In Florida, USA, epiphytic algae
contributed 62, 50, and 44% of primary production
for Syringodium filiforme, Thalassia testudinum, and
Halodule wrightii, respectively (Wear et al., 1999).
In Papua New Guinea, Heijs (1984) determined
that the epiphytic algae on T. hemprichii contribute
441–461.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp.
c
2006 Springer. Printed in the Netherlands.