| Micro- and meiofauna are important components in benthic microbial food web. In comparison with the pelagic ecosystem, relatively less information is available on the benthic habitats. This can be partially explained by the complex in ecological functions and morphological diversities of these organisms, and methodological shortcomings, especially for the extraction of microorganisms from marine sediments for quantitative and qualitative analysis. Methodological experiments were conducted firstly and a new method-Ludox centrifugation-QPS technique -was developed. Using the protocol, ciliated protozoa and meiofauna, were studied monthly at intertidal stations during one year, meanwhile the community was analyzed with environmental factors.Currently, Ludox has been widely applied to the extraction of meiobfauna, while Percoll is the only effective silica directly used for marine microbenthos. However, the high cost and low density limitation of Percoll hamper its wide application in routine ecological studies. A new approach namely Ludox centrifugation-QPS method was developed using the very cheap Ludox replacing the rather expensive Percoll to extract ciliates from marine sediments for enumeration and identification. The protocol consists of sample preservation, desalinization by elutriation, extraction of organisms by Ludox, preparation with the QPS and enumeration and identification under a microscope. The extraction efficiency was initially tested by recovering a known number of ciliates added to azoic sand and mud and over 94% of test ciliates were obtained. Two reference ciliates and nematodes from marine natural sediments were selected for evaluation. The method showed 97.6% for marine ciliates from sand and 97% of entire abundance of nematodes from sand 96.9% from muddy sand and 97.8% from mud. The high extraction efficiencies for both ciliates and nematodes indicated the method allowed for simultaneous enumeration of micro- and meiofauna. The comparison experiments showed that the abundance of meiofauna from QPS were higher than that from routine method using sieves. Especially when a large number of nematodes with smaller size (150-200×10-15μm) occurred, the QPS method showed much quantitative advantage for the estimation of meiofaunal importance in benthic microbial food web. Furthermore the method fulfils to enumerate ciliates with good taxonomic resolution, hence the ecological importance could be conducted in community Level.Using the Ludox -QPS method, the quantitative importance of benthic ciliates and meiofauna collected from two sites (St. IIQ & St. Y) of an intertidal area was carried out monthly in one year and analyzed with the environmental factors. The average annual abundances of ciliates were 2236 inds./10 cm2 and 935 inds./10 cm2 in St. IIQ and St. Y (28 inds /ml and12 inds /ml)), and the seasonal trend was spring > autumn > summer > winter, and the pattern is also found in diversity. 57.1% of ciliates in Sta. Y were distributed in 0 - 0.5 cm, the proportion in 0.5 - 2 cm, 2 - 4 cm and 4 - 8 cm were 23.1%,11.4% and 8.5% respectively, ciliates occured in 4-8 was found in each month except for December; While in Sta. IIQ, 97% of ciliate lives in 0-0.5 cm, the proportion in deeper sediments were 2.4%,0.4% and 0.2% resoectively. The occurrence in 4-8 cm was only found in spring and autumn.Two-Way Crossed ANOSIM test that there is significant difference in ciliated community between sites and seasons. Pseudochilodonopsis sp., Chilodontopsis sp., Euplotes sp and Prorodon sp. were the main dominant species which contributed to the community difference.Meanwhile, 14 meiofaunal groups were sorted, with the average annual abundances of 4793 inds./10 cm2 and 8915 inds./10 cm2 (60 inds./ml and 111 inds./ml) in St. IIQ and St. Y, respectively. The annual average biomass were 1068.8μgC /10 cm2 and 1790μgC /10 cm2 (13.4μgC/ml and 22.4μgC/ml) The seasonal trend of abundance in St. IIQ was summer (7888 inds./10cm2) > autumn (5447 inds./10cm2) > spring (3731 inds./10cm2) > winter (2780 inds./10cm2), while the trend in St. Y was in reverse: winter (15579 inds./10cm2) > spring (10691 inds./10cm2) > autumn (6611 inds./10cm2) > summer (4667 inds./10cm2).The data suggested that the quantitative importance of benthic ciliates and meiofauna was related to the habits and seasons.The analysis between ciliates and environmental factors showed that ciliate abundance and diversity were significant related to the temperature, salinity and organic matter. The combination of temperature, organic matter and meiofaunal abundance contributed 34.5% to the ciliated community difference in abundance. The combination of salinity, Ph-a, temperature organic matter, and meiofaunal biomass accounted for 40.3% for the difference in ciliate diversity.Benthic studies concerning the pollution at Qingdao Bay in 1990s of last century showed that its environments had been improved. To learn the condition of the Bay after twenty years of developments in Qingdao, meiofauna was sampled in silt-sand and sand sediments (St-S & S) from May, 2006 to May, 2007. The annual average abundance in St-S and S were 4853±1292 inds./10 cm2 and 1528±569 inds./10 cm2 respectively, and the annual biomass were 1434.1±897.0μgC /10cm2 and 720.7±353.8μgC/10cm2. The seasonal pattern in abundance was only found in sand. There were two peaks in June and September. 48% of meiofauna were occurred at 0 - 0.5 cm in the two stations, the percentage for nematodes in St. and S were 48% and 34 % respectively in this surface layer。14 meiofauna groups were found, nematodes were contributed 95.2% and 66.4% to the total meiofauna abundance。The other dominant groups in silt sand were Polychaeta (1.5%), Nauplii (1.5%) and Copepoda (0.7%); Nauplii (12.6%), Gastrotricha (8.3%) and Copepoda (6.2%) were the dominant groups besides Nematoda in S. The similarity was about 64.01% between the meiofaunal abundance in the two stations resulted from the CLUSTER analysis. The combination of temperature, salinity, medium size and the content of silty and clay could explained the difference using the analysis of BIOENV, and the coefficient were 0.614. Some pollution was existed in St-S considering the meiofaunal abundance and composition.
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