HETEROTROPHIC ACTIVITY ON APPENDICULARIAN (TUNICATA, APPENDICULARIA) HOUSES IN MESOPELAGIC REGIONS AND THEIR POTENTIAL CONTRIBUTION TO PARTICLE-FLUX

Repeated observations and collections of appendicularian houses (ca 1-10 cm dia.) from Johnson-Sea-Link submersibles indicate these conspicuous mucoid aggregates (0.08-0.49 houses m-3) were a common component of the biodetritus at midwater depths (490-760 m) in Bermuda and the Bahamas during May and November 1984, respectively. Microorganisms and olive-green bodies found on these houses were 1-3 orders of magnitude more numerous than in an equal volume of surrounding seawater. The production rates of bacteria on aggregates varied from 0.01 to 10.83 ng C house-1 h-1 and accounted for 0.01-4.0% of total bacterial production in the water column. The potential carbon flux from these large particles amounted to 0.83 mg C m-2 day-1 (=8% of total carbon flux). © 1990.