The Quantitative Importance of the Benthic Microfauna of an Arctic Tundra Pond

The microfauna (protozoa and micrometazoa) and bacteria and microalgae of the sediment of an arctic tundrapond at Barrow, Alaska were quantified through the summer. Very small protozoans (i.e. zooflagellates) and burrowing micrometazoans were found to be the most important components of the microfauna, whereas ciliates play a smaller role. This composition of microfauna is attributed to the mechanical property of the detrital sediment.Through a combination of laboratory experiments and field observations the grazing rates of protozoa for bacteria and microalgae in the field were estimated; protozoa were found to be important as bacterial grazers, but they consume only a modest fraction of the microalgae. An estimate of the grazing activity of the micrometazoans, based on indirect considerations, is also offered. It is of the same magnitude as that of protozoans but microalgae play a relatively larger role for the former. Based on previous studies on the pond it is estimated that microfaunal grazing constitutes about 30% of that of the detritus feeding macrofauna and that all categories of grazers together do not consume the total microbial production. The reasons for this results and the fate of this surplus production of algae and bacteria are discussed.