ABSTRACT
Marine snow is enriched in organic matter and harbors dense microbial communities at concentrations two to five orders of magnitude higher than found in the surrounding water. Thus, it can be a significant site of heterotrophic bacterial production in the water column. This production is measured by incubating samples with tritiated thymidine and measuring incorporation of the radiolabel into bacterial DNA. Cell growth rate and heterotrophic carbon production are then calculated from thymidine incorporation. Minute quantities of incorporated label may be measured, allowing determination of the bacterial production occurring on single detrital particles or even subsamples of single particles. Multi-aggregate samples may also be collected using standard disposable syringes. Aggregate-free surrounding seawater required for background seawater blanks is also collected by divers using 60-ml syringes. Aggregates have been collected individually at deeper depths from submersibles using 5- L transparent, mechanically triggered Van Dorn bottle-type samplers or hydraulically operated cylindrical samplers.
