Quantification of Environmental Changes by Benthic Animals

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To realize in situ environments in laboratory, a specific aquarium (limorium) was developed. Requirements for the aim were (1) to be taken intact sediments in the aquarium, (2) to be able to observe from outside of aquarium by an enlarging video camera, (3) to be able to control water temperature and water flow velocity, and monitor them, etc. These requirements have not been satisfied in aquaria as known as far. Thus, new special aquaria was developed.To measure food intake rate of suspension feeders, a micro-sensored thermo-flow meter for measurement of fine distribution of water flow velocity and a micro-hi-scope system for fine observation of betnos movements were constructed. A observation system available for more than 24 hours to watch and for controlling food concentrations and flow velocity was also constructed, because of suspension feeding would be affected not only by food concentration and but also water flow velocity. The observation of a suspension-feding bivalve, Tapes phillippinarum, which were taken more than 160 hours, made possible to estimate feeding rate from mesurements of point flow velocities.On a deposit-feeder and a tube-dweller, Maldane sp., defecation rate could be estimated by the system with long time observation more than 50 hours of defecation and fecal pellets. As known that feeding and defecation rates in non-selective deposit feeders are almost similar, it was appeared that the feeding rate of Maldane sp.was positively correlated to body weight. Mean defecation rate per capita was estimated as 360 mm^3 day^<-1>. If existence of 100 worms in a m^2 sea bottom were assumed, that sublayr sediments of 0.036 mm^2 day^<-1> was reworked by this species and resedimentated on the surface of sea bottom, was estimated.