Spatial and temporal variations in nematode assemblages in tropical seagrass sediments

Abstract

The changes in the community dynamics of infaunal nematodes associated with tropical Australian intertidal seagrasses at 4 estuarine sites were investigated through 3 seasons (autumn, winter and spring). Nematode densities were highest in winter in all but one of the sites, ranging from 1971 to 3084 inds./10 cm2, with one site showing a highest density of 3411 inds./10 cm2 in spring. Multiple regression revealed significant correlations between nematode density peaks and seasonal changes in temperature, salinity and surface seagrass cover. Non-metric Multi-Dimensional Scaling revealed that the communities were characterised by relatively low within-site spatial variability but relatively high temporal variability through the three seasons. This temporal variability was largely due to significant increases in abundance of epistrate-feeding species in winter and spring. An investigation of the dominant epistrate-feeding nematodes revealed that predominantly infaunal species were responsible for overall winter and spring density increases. This study provides further evidence of the role played by temperature in regulating tropical, intertidal meiobenthic communities but also indirectly provides evidence of micro-scale seagrass canopy effects (micro-algal supply and availability) that may further enhance the impacts of these larger-scale seasonal environmental changes on the infaunal nematode community.