In this study,the distribution pattern of meiofauna from nine sandy beaches at six latitudinal gradients along Chinese coast between 18 and 40?N was studied on their meiofauna abundance to examine the effect of latitudinal gradients.In general,meiofauna abundance was lower in four subtropical beaches in Xiamen(24?N) and Zhoushan(29?N) than that in other beaches.Meiofauna abundance differed little between tropical and temperate beaches.The taxonomic structure of meiofauna showed a dominance of nematode in colder area.The relative composition of turbellarians and polychaetes increased in warmer area.In addition to latitudinal gradient,salinity,oxygenation,sediment grain size affect also the meiofauna latitudinal distribution.As for horizontal distribution,the highest meiofauna abundance was found in low tidal zone at tropical beaches,and in middle tidal zone at temperate beaches.The horizontal distribution of meiofauna was controlled by both physical and biotic factors including feeding and anthropogenic activities.Although meiofauna abundance exhibited a horizontal difference,the composition of meiofaunal main taxa was unanimous horizontally at all beaches at the same sampling latitude.
We investigated the diversity and structure of free-living marine nematode communities at three sandy beaches representing typical intertidal environments of a temperate zone in Qingdao,Shandong Province,China.Average nematode abundance ranged from 1006 to 2170 ind.10 cm-2,and a total of 34 nematode genera were recorded,of which only 8 were common in all the studied beaches.Pielou's evenness and Shannon-Wiener diversity index were the lowest at the second beach where nematode abundance was the highest.The highest species diversity index coincided with the lowest nematode abundance at Shilaoren beach.Sediment median grain size,sorting coefficient,and chlorophyll-a content were essential for differentiation in nematode abundance and species diversity,whereas taxonomic diversity of nematode was homogeneous across the three beaches.In 0–20 cm sediment profile,nematode abundance declined abruptly with depth,whereas nematode diversity changed gently with obvious difference in 16–20 cm layer.Sediment granulometry and chlorophyll-a content were the two foremost factors which influenced the vertical distribution pattern of nematode generic diversity.Non-selective deposit feeders constituted the most dominant trophic group,followed by epistratum feeders.Bathylaimus(family:Tripyloididae) dominated at the second and Yangkou beach,while Theristus(family:Xyalidae) prevailed at Shilaoren beach.Omnivores and predators became important at Shilaoren beach because of the high proportion of Enoplolaimus.Even though,nematode community of the studied beaches did not differ significantly from each other.
To assess the recovery rate of meiofaunal and nematode communities upon abatement of sewage pollution, a field transplantation experiment was conducted in Tat Tam, which is a non-polluted, shallow subtidal habitat on the southern portion of Hong Kong Island. The sediments used were from one site located in Victoria Harbour that was heavily influenced by sewage pollution, and one site in the outside-harbor area, which was relatively clean. In addition, sediments from Tat Tam were used as a control. Fresh sediments with meiofauna were collected from the aforementioned sites, placed in plastic trays and transplanted to Tat Tam. Sediments were retrieved at the beginning of the experiment and at 1-, 3-, and 8-weeks after transplantation for analysis of the meiofaunal and nematode communities as well as the sediment characteristics. The results showed that the meiofaunal and nematode communities in the control sediments were consistent at the four sampling periods, while it took three and eight weeks, respectively, for the nematode communities from the outside-harbor and inside-harbor sites to become similar to the control. These findings indicated that the relatively poor habitat quality and the nematode community composition in the sewage polluted inside-harbor sediments required a longer time for recovery than samples from the better habitat quality and the nematode community composition in the outside-harbor sediments.
