Coastal Marine Environment Sustainability - Sustainable Practices in Geoenvironmental Engineering - page 279

from the blooming of phytoplankton—with the latter event (phytoplankton blooming)
being the result of human activities.
Guidelines and/or criteria are necessary requirements in addressing environmental
problems. It is important to realize that in respect to the bioenvironment, environmen-
tal change is often irreversible, with no prospect for recovery or rehabilitation. A spe-
ciic example of adverse effects of eutrophication most likely responsible for extinction of
marine life in the bioenvironment is shown below.
Japanese sand lance ( Ammodytes personatus ), also called sand eel, is one of about 18 spe-
cies of marine ish of the family Ammodytidae (order Perciformes). Sand lances are slim,
elongated, usually silver ish that are especially abundant in northern seas. Individuals
range from about 8 to 20 cm in length. They have a forked tail, a long head, a long dorsal
in, and peculiar skin folds on the lower sides, as shown in Figure 8.5. They live in schools,
often under the sand below the surf (aestivation) in summer, which means that they can
be affected by sediment quality. They lay their eggs in sand, and the eggs hatch in winter.
The fry become a target of ishery for about 1 month in the spring.
The haul of sand lance in the Seto Inland Sea has continued to decrease since 1970.
This is considered to be mainly due to the decrease in sand beach and tideland. Sand
was harvested from the bottom of the Seto Inland Sea for use as aggregates for concrete.
This also decreased the habitat for sand lance and their egg-laying sites. According to
a report by the Ministry of Economy, Trade, and Industry and the Ministry of Land,
Infrastructure, Transport, and Tourism, about 10,000 to 20,000 m of sand were har-
vested annually from the bottom of the Seto Inland Sea from 1971 to 2004. During this
period, a large coastal area was reclaimed from the sea, as shown, for example, by the
reclamation of 16 km of coast in the Okayama and Kagawa Prefecture facing the middle
of Seto Inland Sea. This has resulted in the loss of sand lance habitat. The haul of sand
lance, which has not recovered since harvesting of sand at the bottom was prohibited,
continues to decrease, with large luctuations. There has been no explanation for this
phenomenon. Because of anthropological activities, various kinds of solutes and solids
have been discharged into the Seto Inland Sea. In particular, organic matter has caused
eutrophication. The organic matter discharged from land has spread over the areas of
the Seto Inland Sea, except for straits with a strong current. In this situation, the clean
sand of the sea bottom has changed to sand with clay or silt fractions and organic
matter.
The sedimentary rate in the Seto Inland Sea determined using the 210 Pb method var-
ies between 0.11 and 1.13 g/cm 2 (Hoshika and Shiozawa, 1987). The sedimentary rate is
FIGURE 8.5
Japanese sand lance.