The role of habitat heterogeneity on the spatial distribution of meiofaunal communities in the NE Pacific

Bioturbation of the sediment may influence substantially both its physical and chemical properties, thus affecting its suitability for colonisation and exploitation by other organisms. In the present study, the effects of different biogenic structures, such as bioturbation mounts or tracks produced by larger organisms, on the meiofaunal community were investigated at a long term monitoring site in the NE Pacific. For this reason, a series of dives with the submersible ALVIN were undertaken at Station M (4100 m) in August 2009 to investigate the relationships between meiofauna and 12 different microhabitats which were: a) one control site, b) within the track of Echinocrepis urchin, c) outside the track of Echinocrepis urchin, d) within the track of Cystocrepis urchin, e) outside the track of Cystocrepis urchin, f) on a bioturbation mound, g) along the periphery of the bioturbation mound, h) away from the bioturbation mound, i) away from a sponge, k) near the stalk of a sponge, l) near a decomposing kelp holdfast and m) away from the kelp holdfast. Total meiofaunal densities ranged from 244 to 1203 individuals 10 cm-2. The station away from the sponge exhibited the highest values while the bioturbation mound had the lowest densities. Nematodes were the dominant group in all samples, ranging from 71 to 89% and were followed by harpacticoid copepods and polychaetes. The other groups were represented on average with less than 6%. The effects of habitat heterogeneity on the diversity and spatial distribution of nematodes will be discussed