9 Common Structures and Properties of Seagrass
Beds Fringing the Coasts of the World
C. DEN HARTOG and R.C. PHILLIPS
9.1 Introduction
Seagrasses are aquatic angiosperms which are completely confined to the
marine environment. The name refers to a superficial resemblance to grasses,
because of the linear leaves of most of the approximate 60 species (Den
Hartog 1970). They are of paramount importance in the coastal environment
as, when they occur, they generally form dense beds that may cover extensive
areas. One of the most conspicuous ecological functions of the seagrass beds
is their capacity to stabilize and to modify the unconsolidated substrates in
which they are rooted. By their dense growth, they protect the substrate to a
considerable extent from erosion, but they also trap floating coarse and
suspended fine materials. Further, they produce litter. The accompanying
organisms contribute to the alteration of the substrate by contributing fecal
material, shells or other protective structures. Part of this material leaves the
system, and may be washed up onto the beach, or may be deposited on the
bottom of adjacent systems in deeper waters. There are even records of seagrass remains from depths of thousands of metres (Wolff 1976). Another
function is that the seagrass beds offer a substrate to many algae and animals
which otherwise could not establish themselves on the sandy and muddy
bottoms. Furthermore, the seagrass beds serve as a nursery for many fish,
crustaceans, and other invertebrates, providing food not only for these
animals, but also for a considerable number of migrating birds, sirenians,
turtles, and many organisms from neighbouring habitats.
9.2 Distribution and Zonation
Seagrasses have a wide geographical distribution along the coasts of most
continents, extending from above the Arctic Circle southward through the
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001
Beds Fringing the Coasts of the World
C. DEN HARTOG and R.C. PHILLIPS
9.1 Introduction
Seagrasses are aquatic angiosperms which are completely confined to the
marine environment. The name refers to a superficial resemblance to grasses,
because of the linear leaves of most of the approximate 60 species (Den
Hartog 1970). They are of paramount importance in the coastal environment
as, when they occur, they generally form dense beds that may cover extensive
areas. One of the most conspicuous ecological functions of the seagrass beds
is their capacity to stabilize and to modify the unconsolidated substrates in
which they are rooted. By their dense growth, they protect the substrate to a
considerable extent from erosion, but they also trap floating coarse and
suspended fine materials. Further, they produce litter. The accompanying
organisms contribute to the alteration of the substrate by contributing fecal
material, shells or other protective structures. Part of this material leaves the
system, and may be washed up onto the beach, or may be deposited on the
bottom of adjacent systems in deeper waters. There are even records of seagrass remains from depths of thousands of metres (Wolff 1976). Another
function is that the seagrass beds offer a substrate to many algae and animals
which otherwise could not establish themselves on the sandy and muddy
bottoms. Furthermore, the seagrass beds serve as a nursery for many fish,
crustaceans, and other invertebrates, providing food not only for these
animals, but also for a considerable number of migrating birds, sirenians,
turtles, and many organisms from neighbouring habitats.
9.2 Distribution and Zonation
Seagrasses have a wide geographical distribution along the coasts of most
continents, extending from above the Arctic Circle southward through the
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001