EFFECTIVENESS OF VARIOUS TREATMENTS IN RETARDING MICROBIAL ACTIVITY IN SEDIMENT TRAP MATERIAL AND THEIR EFFECTS ON THE COLLECTION OF SWIMMERS

Laboratory and field experiments were conducted to determine the effectiveness of various poison, preservative, and antibiotic treatments currently in common use in sediment trap work. Our results agree with previous reports that most biological activity in sediment traps can be inhibited by appropriate concentrations of formaldehyde, chloroform, or mercuric chloride. Sodium azide appears to be less effective at inhibiting biological activity, while antibiotics and salt alone are probably too ineffective for long-term deployments. On the basis of laboratory experiments. effective concentrations when sustained throughout the deployment are 50% saturated chloroform, 37 mM formaldehyde, or 180-mu-M HgCl2. Our results also indicate, however, that the weight of swimmers (zooplankton which swim into the trap and die there from contact with the poison) collected in sediment traps is higher when more effective treatments are used. The presence of large numbers of swimmers can greatly affect the flux and composition of particulate organic matter collected in sediment traps and may decrease the effectiveness of the various treatments in inhibiting microbial activity in the traps.