The Environment Ministry plans to take measures against the Seto Inland Sea becoming “too clean,” which it believes could cause harm to the local fisheries industry, sources told Jiji Press.
The inland sea in western Japan has seen the density of nutrient salts, and nitrogen and phosphorus, decline, with the lower density causing farmed seaweed to become discolored and fish hauls to shrink.
The ministry is considering introducing a new system for designating areas where nutrient salts will be increased, according to the sources.
To implement the plan, the ministry will submit a bill to revise the special measures law on the conservation of the environment of the Seto Inland Sea to the ordinary session of the Diet, to be convened early next year.
The law was introduced in 1973 after water conditions of the inland sea deteriorated due to the inflow of industrial waste water during the period of high economic growth. Under the law, the environment minister sets reduction targets for nutrient salts, which are also the cause of red tides, and each prefecture imposes restrictions on waste water from sewage treatment plants and factories based on the targets.
While the reduction of nutrient salts has led to a drastic decrease of the occurrences of red tides, it has also had a negative impact on the seaweed farming and sand lance fishing industries.
Meanwhile, some areas used for farming Japanese amberjack and sea bream still require the active reduction of nutrient salts for preventing red tides.
In order to balance the conflicting needs, the ministry plans to maintain the current legal framework while making it possible to newly designate areas for increasing nutrient salt levels, according to the sources. Prefectures and municipalities in the coastal areas along the inland sea will set nutrient salt density targets on their own, and take measures to achieve the targets.
Specifically, local governments are expected to implement special measures during the seaweed farming season between autumn and the following spring, such as increasing the amount of nutrient salts released from sewage treatment plants and releasing water from dams and reservoirs so that nutrient salt deposits can enter the sea.
Such measures are already being implemented by some municipalities, and the envisaged system is expected to make it easier for local governments to take steps tailored to an area’s specific needs.
Some lawmakers are also expected to hold discussions on measures to tackle the nutrient salt issue.
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