Meiobenthic community in tropical mangrove and seagrass bed of Chuuk Lagoon

Abstract

Meiobenthos (originally Greek) was defined by Mare as a size class of benthos (also originally in Greek) smaller (meio in Greek) than macrobenthos. Now the definition has been modified as a fraction of benthic organisms which pass through 1.0 mm mesh-size sieve and are retained on 0.032 mm sieve. In most benthic environments, nematodes are almost always the most dominant taxon in meiofauna, accounting for 80 to 90 % of the total in number and/or biomass. The community structure of meiobenthos were studied in the intertidal of Chuuk Lagoon in South Pacific Area, a series of sampling were carried out in 24 and October 20 2003 and 15 and July 19, 2004. The sediment samples for research of meiobenthos collected by the sub corer (inner-diameter 4.3cm) at each station were sliced according to the various depths (0~1cm, 1~2cm, 2~3cm, 3~4cm, 4~5cm, 5~6cm, 6~7cm, 7~8cm, 8~9cm, 9~10cm). Then, the sediment samples were fixed with the 5 % neutralized formalin mixed with the Rose Bengal. A total of 22 meiofaunal groups were found in the intertidal flat of Chuuk Lagoon in South Pacific Area. Nematodes were the most dominant among the meiofaunal groups as a whole. Polycheata, Ciliophorans, Sarcomastigophorans, which were also important components of the meiofaunal community. All of these four faunal groups comprised more than 70% of total meiofauna at every stations. The total density of meiobenthos at each stations was the highest at station MG-1C (2,032 inds./10㎠), and the lowest at station MG-3C (207 inds./10㎠). Meiobenthos in general showed the highest density in the upper 1 cm layer. this maybe associated with food and oxygen supply to subsurface. In easy penetration of oxygen, high abundance is often observed in deeper surface. The meiobenthos followed the general trends reported from other studies: densities decreased with depth in relation to the more limited supply of degradable organic matter at greater depths.