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Amamo means eelgrass in Japanese, mainly Zostera marina, which is distributed
in temperate regions in the northern hemisphere. This is the most common species
of seagrass in Japan and is widely distributed from Hokkaido to the Satsuma
Peninsula in southern Kyushu, forming vast beds in shallow areas of sandy to
muddy sea bottom (Nakaoka and Aioi 2001). Around the Nansei Islands, which
have a subtropical climate, numerous other seagrass species distribute, and in temperate regions, species other than Z. marina, such as Z. japonica and Z. caulescens,
also exist. Because of its wide distribution, however, Amamo (i.e., Z. marina) is the
most representative seagrass in Japan, and in many cases seagrass beds are simply
referred to as Amamo-ba by researchers in Japan.
Garamo-ba is a bed composed of macroalgae belonging to the family
Sargassaceae, order Fucales (Phaeophyceae, brown algae). Macroalgae belonging
to Sargassaceae are widely distributed from temperate to tropical regions, and about
70 species have been described in Japan (Yoshida et al. 2015). Each species shows
slightly different physiological and ecological characteristics, and Garamo-ba has
diverse constituents, depending on differences in water depth, current flow conditions, and characteristics of the substrate where the beds are formed.
Both Kombu-ba and Arame-ba consist of various kinds of macroalgae belonging
to the order Laminariales (Phaeophyceae). The kelp forming Kombu-ba contains
many commercially important species, mainly of the genus Saccharina, and are
distributed from Hokkaido to the Pacific coast of the Tohoku region, where the cold
current affects the coastal environment (Kawashima 2004). Kelp forming Arame-ba
belong to the genera Ecklonia and Eisenia in the family Lessoniaceae. They are
mainly distributed on the coast in temperate regions affected by warm currents and
are sometimes called “warm temperate kelp.” The constituent species are limited to
two species of the genus Eisenia (E. bicyclis and E. arborea) and three species of
the genus Ecklonia (E. cava, E. kurome, and E. stolonifera), but each species forms
beds on a large scale and Arame-ba is commonly found on the rocky shores in temperate Japan, often along with Garamo-ba. Arame is a Japanese name for E. bicyclis
in a narrow sense, but species of Eisenia and Ecklonia share similar morphology
and ecological features, so they are often collectively referred to as Arame in many
local areas (Terawaki and Arai 2004).
Hereafter, Amamo-ba will be referred to as “eelgrass bed”. Garamo-ba,
Arame-ba, and Kombu-ba will be referred to as “Sargassum bed,” “warm-temperate
kelp bed,” and “cold-temperate kelp bed,” respectively.
4.2.2 Areas and Geographic Distribution Patterns of Seagrass
and Macroalgal Beds in Japan
The nationwide area and distribution of seagrass and macroalgal beds in Japan has
been surveyed in various ways such as scuba, shipboard observation or interviews,
etc., in the National Survey of Natural Environment led by the Ministry of
G. Yoshida et al.
Amamo means eelgrass in Japanese, mainly Zostera marina, which is distributed
in temperate regions in the northern hemisphere. This is the most common species
of seagrass in Japan and is widely distributed from Hokkaido to the Satsuma
Peninsula in southern Kyushu, forming vast beds in shallow areas of sandy to
muddy sea bottom (Nakaoka and Aioi 2001). Around the Nansei Islands, which
have a subtropical climate, numerous other seagrass species distribute, and in temperate regions, species other than Z. marina, such as Z. japonica and Z. caulescens,
also exist. Because of its wide distribution, however, Amamo (i.e., Z. marina) is the
most representative seagrass in Japan, and in many cases seagrass beds are simply
referred to as Amamo-ba by researchers in Japan.
Garamo-ba is a bed composed of macroalgae belonging to the family
Sargassaceae, order Fucales (Phaeophyceae, brown algae). Macroalgae belonging
to Sargassaceae are widely distributed from temperate to tropical regions, and about
70 species have been described in Japan (Yoshida et al. 2015). Each species shows
slightly different physiological and ecological characteristics, and Garamo-ba has
diverse constituents, depending on differences in water depth, current flow conditions, and characteristics of the substrate where the beds are formed.
Both Kombu-ba and Arame-ba consist of various kinds of macroalgae belonging
to the order Laminariales (Phaeophyceae). The kelp forming Kombu-ba contains
many commercially important species, mainly of the genus Saccharina, and are
distributed from Hokkaido to the Pacific coast of the Tohoku region, where the cold
current affects the coastal environment (Kawashima 2004). Kelp forming Arame-ba
belong to the genera Ecklonia and Eisenia in the family Lessoniaceae. They are
mainly distributed on the coast in temperate regions affected by warm currents and
are sometimes called “warm temperate kelp.” The constituent species are limited to
two species of the genus Eisenia (E. bicyclis and E. arborea) and three species of
the genus Ecklonia (E. cava, E. kurome, and E. stolonifera), but each species forms
beds on a large scale and Arame-ba is commonly found on the rocky shores in temperate Japan, often along with Garamo-ba. Arame is a Japanese name for E. bicyclis
in a narrow sense, but species of Eisenia and Ecklonia share similar morphology
and ecological features, so they are often collectively referred to as Arame in many
local areas (Terawaki and Arai 2004).
Hereafter, Amamo-ba will be referred to as “eelgrass bed”. Garamo-ba,
Arame-ba, and Kombu-ba will be referred to as “Sargassum bed,” “warm-temperate
kelp bed,” and “cold-temperate kelp bed,” respectively.
4.2.2 Areas and Geographic Distribution Patterns of Seagrass
and Macroalgal Beds in Japan
The nationwide area and distribution of seagrass and macroalgal beds in Japan has
been surveyed in various ways such as scuba, shipboard observation or interviews,
etc., in the National Survey of Natural Environment led by the Ministry of
G. Yoshida et al.