Common Structures and Properties of Seagrass Beds Fringing the Coasts of the World 199
Halophila species in the region. However, Halophila can extend to great
depths. Halodule species also occur in the sublittoral, occasionally in unispecific stands in water deeper than Thalassia. Along the coast of Brazil,
Thalassia and Syringodium are absent, while sublittoral beds of H. wrightii
or H. emarginata are present (De Oliveira et al. 1983). Halophila is represented by two species, but these are too rare to be of significance.
Along the tropical Atlantic coast of Africa, the occurrence of H. wrightii has
been recorded, but nothing is known about its habitat in that region.
The seagrass communities of the Indo-Pacific have many common traits.
In the intertidal, narrow-leaved Halodule and Halophila species have been
found over the entire area. H. uninervis is common in most of these communities, while H. pinifolia is restricted to the western Pacific and the eastern
part of the Indian Ocean. H. wrightii is found along the coast of East Africa.
Narrow-leaved morphs of Halophila ovalis often co-exist with Halodule species. Other Halophila species in the intertidal zone are generally restricted to
specific habitats. H. beccarii is found on muddy flats and creeks in mangrove
areas. In the sublittoral, larger seagrasses form dense beds, often consisting of
a mixture of several species. The dominant species of these 'mixed lawns' are
Thalassia hemprichii, Cymodocea serrulata, C. rotundata, the wide-leaved
morph of Halodule uninervis, Syringodium isoetifolium, Enhalus acoroides,
the robust morph of Halophila ova lis, and other species with a less wide area
of distribution. In habitats exposed to ocean swell, Thalassodendron ciliatum
beds may be found in unispecific stands. Where large seagrasses are absent,
their place is taken by the small species, as in the Persian Gulf.
9.3 Structure of the Seagrass Community
The structure of seagrass beds is usually regarded as quite simple, as they
consist of one or a few plant species of a rather similar morphology. However, they show differences when inspected more closely. At least six growth
forms have been recognized (Den Hartog 1977). The frame element is the
seagrass itself. As a consequence of its dominance and seasonal rhythm, it
determines, to a considerable degree, which algae and aquatic animals can
accompany it.
In Table 9.2, a survey is given of the various structural elements that can be
distinguished. The term structure comprises at least the following components: (1) floristic and faunistic composition in a qualitative and a quantitative sense, (2) the arrangement of the organisms in space and time, and (3) the
relationships between the organisms within the community and their relationships with the surrounding biotic and abiotic environment (Den Hartog
and Van derVelde 1988).
Halophila species in the region. However, Halophila can extend to great
depths. Halodule species also occur in the sublittoral, occasionally in unispecific stands in water deeper than Thalassia. Along the coast of Brazil,
Thalassia and Syringodium are absent, while sublittoral beds of H. wrightii
or H. emarginata are present (De Oliveira et al. 1983). Halophila is represented by two species, but these are too rare to be of significance.
Along the tropical Atlantic coast of Africa, the occurrence of H. wrightii has
been recorded, but nothing is known about its habitat in that region.
The seagrass communities of the Indo-Pacific have many common traits.
In the intertidal, narrow-leaved Halodule and Halophila species have been
found over the entire area. H. uninervis is common in most of these communities, while H. pinifolia is restricted to the western Pacific and the eastern
part of the Indian Ocean. H. wrightii is found along the coast of East Africa.
Narrow-leaved morphs of Halophila ovalis often co-exist with Halodule species. Other Halophila species in the intertidal zone are generally restricted to
specific habitats. H. beccarii is found on muddy flats and creeks in mangrove
areas. In the sublittoral, larger seagrasses form dense beds, often consisting of
a mixture of several species. The dominant species of these 'mixed lawns' are
Thalassia hemprichii, Cymodocea serrulata, C. rotundata, the wide-leaved
morph of Halodule uninervis, Syringodium isoetifolium, Enhalus acoroides,
the robust morph of Halophila ova lis, and other species with a less wide area
of distribution. In habitats exposed to ocean swell, Thalassodendron ciliatum
beds may be found in unispecific stands. Where large seagrasses are absent,
their place is taken by the small species, as in the Persian Gulf.
9.3 Structure of the Seagrass Community
The structure of seagrass beds is usually regarded as quite simple, as they
consist of one or a few plant species of a rather similar morphology. However, they show differences when inspected more closely. At least six growth
forms have been recognized (Den Hartog 1977). The frame element is the
seagrass itself. As a consequence of its dominance and seasonal rhythm, it
determines, to a considerable degree, which algae and aquatic animals can
accompany it.
In Table 9.2, a survey is given of the various structural elements that can be
distinguished. The term structure comprises at least the following components: (1) floristic and faunistic composition in a qualitative and a quantitative sense, (2) the arrangement of the organisms in space and time, and (3) the
relationships between the organisms within the community and their relationships with the surrounding biotic and abiotic environment (Den Hartog
and Van derVelde 1988).