ENUMERATION OF PROTOZOA AND BACTERIA IN MUDDY SEDIMENT

Improved enumeration methods were developed for marine bacteria and pr otozoa in muddy sediment containing large amounts of organic detritus. In sediment from polluted and nonpolluted sites, total bacterial coun ts ranged from 6.2 x 10(9) to 15 x 10(9) g(-1) dry sediment and were s ignificantly higher in nonpolluted sediment. Ciliates were restricted to the top I cm where they reached abundances of similar to 1000 cm(-3 ). Nanoflagellate populations were high to a depth of 5 cm and reached higher populations in nonpolluted sediment (1.7 x 10(7) cm(-3)) than in polluted sediment (0.5 x 10(7) cm(-3)). For enumeration of protozoa , direct counts of fixed, unstained cells by phase-contrast microscopy was more accurate than counting using epifluorescent microscopy of fu :ed, DAPI-stained cells. The Percoll-sorbitol method for separating pr otists from sediment was effective for sandy sediment but much less ef fective (35-64% recovery efficiency) for muddy, detritus-rich sediment .