Community study of tubeworm-associated epizooic meiobenthos from deep-sea cold seeps and hot vents

The permanent metazoan meiofauna associated with vestimentiferan tubeworm aggregations from hydrocarbon seeps of the upper Louisiana slope in the Green Canyon (similar to 550 m) and the lower slope in Atwater Valley (similar to 2200 m) of the Gulf of Mexico was characterized. Meiofauna abundance, diversity, and community composition at genus level were compared between these seep sites, and with those of tubeworms from hydrothermal vents of the East Pacific Rise (Gollner et al. 2007; Mar Ecol Prog Ser 337: 39-49). The abundance was not significantly different between the 2 seep sites, and was also similar to those found at vents. A total of 150 meiobenthic genera were identified from the cold seep sites. While no significant difference in univariate measurements of diversity was detected, a shift in community composition between the shallow and the deep seep site was found. The hot vent communities included a total of only 17 genera and the diversity measurements were significantly lower at vents than at seeps. Also, Bray-Curtis dissimilarity was 97{%} between the meiobenthic communities from seeps and vents. The genera richness was negatively correlated with maximum temperature and maximum sulfide concentration, and positively correlated with minimum pH value. We conclude that the harsh conditions tubeworms experience at vents compared to the moderate conditions at cold seeps, as well as the longevity of cold seeps surrounded by sedimented deep-sea plains but short-lived vents on basaltic mid-ocean ridges, might explain the contrasting diversity patterns.