Simultaneous enumeration of protozoa and micrometazoa from marine sandy sediments

The present work addresses enumeration of marine microorganisms (nanoflagellates, ciliates, and micrometazoa) from sandy sediments. The current approaches, all of which use different principles and are specific for a given group of organisms, have been modified so as to design one technique equally suitable for all the above microorganisms. This approach provides a new means to enumerate marine sediment nanoflagellates and is the first quantitative technique to enumerate ciliates from preserved samples. Perhaps most importantly, the technique also allows for simultaneous enumeration of meiobenthos so that all proto- and micrometazoan organisms can be quickly quantified from the same sample on a single preparation. The suggested technique consists of sample preservation with glutaraldehyde, extraction of target organisms by decantation, separation of the organisms from debris by isopycnic centrifugation in non-linear silica gel gradients, concentration of organisms on polycarbonate membranes, dual fluorescent staining, and enumeration under epifluorescent illumination. For marine sandy sediments, the recovery efficacy of the technique was checked by 2 independent approaches (cumulative extraction from field sediments and recovery of test organisms from azoic sediments). Both approaches showed an efficacy close or equal to 100 %.