報告書番号

U86029

タイトル（和文）

ムラサキイガイの付着生態

タイトル（英文）

RECRUITMENT FROM LARAVAE TO FOULING COMMUNITY OF MARINE MUSSEL

概要 （図表や脚注は「報告書全文」に掲載しております）

冷却水路に付着するムラサキイガイの付着期の生態を把握する目的で東京湾湾口部で調査を実施した。ムラサキイガイ前期浮遊幼生のＤ型幼生は４月上旬，後期浮遊幼生の殻頂期幼生はこの１週間後に出現個体数のピークが見られた。付着ロープへの幼貝の付着は４月中旬に最も多かった。岸壁に付着しているムラサキイガイ群集中に１０ｍｍ未満の幼貝が増加し始めるのは４月下旬以後で，５月上旬には全個体数の約４０％を占めるようになり，浮遊幼生出現ピークから幼貝着生のピークまで約１カ月を要した。Ｄ型幼生の出現ピークから１週間で殻頂期幼生となり，ロープへの付着を始めるので，付着を防止するためにはＤ型幼生の出現ピークの１週間後から対策を講ずれば有効である。また，水中ロボットなどにより付着幼貝を処理する場合には，Ｄ型幼生出現ピークから１カ月後に処理を行えば効果的である。

概要 （英文）

MUSSEL FOULING OF THE COOLING WATER CONDUITSOF THERMAL AND NUCLEAR POWER PLANTS CAN RESULT IN REDUCTION OF WATER INTAKE,INCREASED PUMPING COSTS,PLUGGING OF CONDENSER TUBES,AND OTHER EFFECTS ON THE OPERATION OF POWER PLANTS. IN ORDER TO EFFECTIVELY CONTROL MUSSEL FOULING,THIS WORK WAS CONDUCTED WITH THE OBJECTIVE OF IMPROVING UNDERSTANDING OF ENVIRONMENTAL CONDITIONS DURING PERIODS OF MUSSEL FOULING. 1.THE SETTLEMENT OF MUSSEL LARVAE IN MUSSEL BEDS DEVELOPING ON PIERS IN KURIHAMA BAY NEAR THE MOUTH OF TOKYO BAY WAS OBSERVED FROM MARCH TO MAY. SETTLEMENT DEPTH WAS INVESTIGATED AT COAST OF HIRATUKA USING FOULING ROPES SUSPENDED AT SELECTED DEPTHS. WATER TEMPERATURE DURING THE STUDY PERIOD WAS 12 DEGREES,ON MARCH 22,15 DEGREES,ON APRIL 22 AND 17 DEGREES C ON MAY 13. 2.NUMBER OF SETTLING D-SHAPED EARLY LARVAE AND VELICONCHA LATE LARVAE PEAKED ON APRIL 5 AND 12 RESPECTIVELY. NUMBER OF LARVAE SETTLING ON FOULING ROPES WAS HIGHEST DURING THE APRIL 10-17 PERIOD. NUMBERS OF MUSSELS SETTLING IN THE MUSSEL BEDS ON THE PIERS IN THE LESS THAN 10 MM SIZE CLASS BEGAN TO INCREASE AFTER APRIL 23 AND REACHED 40% OF THE TOTAL IN THE BEDS ON MAY 8. 3.SETTLEMENT WAS OBSERVED AT ALL REVELS OF A FOULING ROPE ARRAY SUBMERGED FOR A MONTH FROM THE END OF APRIL FROM 19 METERS (1 METER ABOVE THE BOTTOM) IN DEPTH TO THE SURFACE. SETTLEMENT WAS MOST ABUNDANT IN THE MIDDLE LEVELS. 4.PERIODIC MONITORING OF MUSSEL LARVAE AND SETTLEMENT WILL ENABLE INFERENCE OF TIMES OF SETTLEMENT AND AMOUNT OF MUSSEL FOULING ON THE WALLS OF COOLING WATER CONDUITS. IF THE TIMES AND AMOUNTS OF MUSSEL FOULING CAN BE INFERRED,THEN BIOFOULING CONTROL MEASURES SUCH AS CHLORINATION,ROBOT CLEANING,ETC. CANBE MORE EFFECTIVELY APPLIED.

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