|The ecology of marine microbenthos I. The quantitative importance of ciliates as compared with metazoans in various types of sediment|In: Ophelia: International Journal of Marine Biology. Ophelia Publications: Helsingør. ISSN 0078-5326, more
Ecology; Ciliata Couch, 1832 [WoRMS]; Marine
An investigation of the quantitative importance of protozoans — especially ciliates — has been undertaken in Scandinavian waters. Ciliates were found in numbers from 106 to 4 × 107 individuals per m2 representing 0.03–2.3 grammes wet weight per m2. Highest numbers were found in fine sand and in localities with a rich growth of sulphur-bacteria. In these sediments ciliates are 10 to 100 times more numerous than the total number of metazoans, and their biomass is of the same order or sometimes larger than the biomass of the micro-metazoans (nematodes, turbellarians, gastrotrichs etc.). In coarser sand ciliates are fewer, and micro-metazoans play a larger quantitative role. This distribution is explained by the small size and other morphological adaptations making ciliates able to inhabit the small interstitia of fine sand, and also their ability to endure reducing and anaerobic conditions. In the detritus layers which cover clayey and muddy sediments ciliates are few in number and play a small role compared with metazoan groups, such as nematodes, which may sometimes be as numerous as ciliates.A comparison with the enumeration of the benthic metazoans in Nivå Bay carried out by Muus (1967) shows that 93% of all animals in the bay are ciliates which, however, only comprise 0.4 %of the total animal biomass.Large dinofiagellates were found in numbers of 105 to 1.5 × 107 per m2. Euglenoids are less numerous, normally fewer than 5 × 105 per m2. Naked amoebae seem also to play a small quantitative role; more than 105 per m2 were rarely found.Ciliates show a maximum population size in summer, but this maximum may be obscured by other factors in more exposed localities. Large populations of active animals are found throughout the year.The importance of ciliates in community respiration is discussed. It is concluded that in localities with fine sand and in sulphureta the ciliates account for a larger part than the micro-metazoa, and that the ciliates contribute significantly to the energetics of these communities.