Nematode morphometry and biomass patterns in relation to community characteristics and environmental variables in the Mekong Delta, Vietnam

Nematode morphometry and biomass were investigated in the dry season of 2009 at the mouth of eight Mekong estuaries in Vietnam. We investigated how morphometry and biomass of nematodes were related to community characteristics and environmental gradients. Mean nematode lengths were significantly greater along the Co Chien estuary. In contrast, there were no significant differences in nematode width, length/width ratio, individual biomass and total biomass between stations at the estuarine mouth and along the Co Chien estuary. This study further confirmed that nematode morphometry and biomass distribution reflect specific modes of life in terms of feeding strategies, life history, and diversity. There were also particular morphotypes associated with specific environmental conditions. Over the whole area and especially along the mouth stations, nematodes were especially longer in sandy substrates where chlorophyll a concentrations were low, possibly due to the presence of predators and an associated reduction in the density of small opportunistic deposit feeders. An increase in the silt fraction together with pigment concentrations, especially along the Co Chien estuary, was positively correlated with the number, total biomass and abundances of small opportunistic genera resulting in a low maturity index and a high number of nematode genera