Reproductive functions of biological resources can be quantified by fisheries landing tatistics.
To understand biological purification unctions, we must be able to quantify the removal of sestinas by the filter feeders in aerobic situations. digestive degradation of organic mud by bottom feeders. uptake and decomposition of organic matter by bacterial growth. and transfer of nutrients to larger animal.
Physical purification consists mainly of disposal of nutrient-rich water into outer ocean. and creation of aerobic environment through flushing and renewal.
Quantification of the functions of various man-made marine habitats such as artificial mud-flats, artificial kelp forests. artificial rock beds, and artificial reefs.
Amenity functions may vary widely by location, as they are sensitive to specific types of environments such as urban, rural. etc.
6. Compensation of environmental impacts are possible only through enhancement and creation of environmental functions.
Quantitative standards enforced by our environment regulation are effectively dealing with environmental impacts associated with air and water pollution.
Negative environmental impacts associated with the loss and degradation of marine habitats shall be compensated for through artificial creation of the lost functions with equivalent ecological value.
Example: Creation of a clam fishing ground an artificial tidal flat leads to improved filtration and removal of suspended organic matter in the nearshore water. resulting in on-land removal of nitrogen and phosphorous loading.
In Central Japan. facing the Pacific Ocean. there is a semienclosed bay called Mikawa Bay. 601 square kilometer body of water with excessive loading of nutrients. within this bay is a small inlet called Fukue Bay. At the entrance to this small bay is a sand spit. This sand spit was graded to costruct a 70-hectare clam farm on artificial tidal flat. The project gave rise to a thriving new fishery with annual harvests of as much as 4900 tons of clam, more than enough to pay the construction. Additionally, the farm provided the water purification functions. as follows:
・ Filtration and removal of organic suspensions including red-tide micro-organisms
.... 3.36 million m3/day
・ Decomposition of organic detritus (BOD)
.... 1.01 O2 tons/day
Nitrogen retrieval by clam harvesting
.... 0. 67 tons/day
In order to understand economic implications of this clam farm, one may compare it with that of a modern sewage treatment plant. The water purification functions of this clam farm equal that of a sewage treatment plant capable of handling 1. 01 Ｏ2 ton/day by active sludge. The clam farm's capacity to remove 3.36 million m3 of organic suspensions is comparable to that of a sewage treatment plant capable of servicing a population of approximately 20. 000.
7. conclusions
The ecosystems in the marine environment are destined to become a system which is impacted and manipulated by the man. I fear, however, that the man is still far from understanding the functions of the natural environment. Our ignorance of the functions of the natural environment could lead us to manipulation of the natural ecosystems by trial and error - a serious mistake which must be avoided by all means. Let us hope that it is not yet too late to begin a serious effort to understand the ecosystem.
It is my sincere hope that this conference would become a part of this important effort. contributing to achieving the man's most critical goal in the 21st century: a sustainable development with preserved environments.
