Dense beds of Ophiura sarsii limited by food supply in the Sea of Japan

摘要

In the Sea of Japan, the dominant ophiuroid Ophiura sarsii forms heavily populated areas known as "dense beds" at depths between 200 and 350 m. In order to determine the factors responsible for maintainingthese dense beds, we focused on the carbon budget. The carbon consumption rate of the ophiuroid was more than 20 mg Cm~(-2) day~(-1). Another study reported that the meiobenthos consumed more than 55 mg Cm~(-2)day~(-1), and carbon flux to the bathyal zone was approximately 100 mg Cm~(-2) day~(-1) . Therefore, sinking particulate carbon alone may be inadequate to meet the food demand of 0. sarsii. Stable isotope and gut content analyses revealed that the diet of O. sarsii in the dense beds mainly comprised the krill Euphausia pacifica that transports surface organic matter to the deep sea during daily migration. The results show that food supply by the krill plays an important role in the maintenance of dense beds.