Copley, J. T. P.; Flint, H. C.; Ferrero, T. J.; Van Dover, C. L. (2007). Diversity of meiofauna and free-living nematodes in hydrothermal vant mussel beds on the northern and southern East Pacific Rise. J. Mar. Biol. Ass. U.K.
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Copley, J. T. P.; Flint, H. C.; Ferrero, T. J.; Van Dover, C. L.
2007
Diversity of meiofauna and free-living nematodes in hydrothermal vant mussel beds on the northern and southern East Pacific Rise
J. Mar. Biol. Ass. U.K.
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The ecology and biogeography of meiofauna at deep-sea hydrothermal vents have historically received less
attention than those of mega- and macrofauna. This study examines the composition of major meiofaunal taxa
in beds of the mussel Bathymodiolus thermophilus at hydrothermal vents on the northern and southern East Pacific
Rise (EPR) and presents the first comparison of species assemblages of the dominant taxon, the nematodes,
among sites spanning 27 degrees of latitude. Meiofaunal samples were collected by submersible from three
mussel beds at 9¡ÆN on the EPR and four mussel beds between 17 and 18¡ÆS in 1999. Estimated ages of the
mussel beds at the time of sampling range from 4 to >20 years, enabling investigation of the influence of mussel
bed age on meiofaunal assemblages. Overall, the meiofauna of the mussel beds was dominated by nematodes,
with copepods constituting the second most abundant meiofaunal group. There was variation in the ratio of
nematodes to copepods between sites, however, with copepods more abundant than nematodes in the youngest
mussel beds. Apart from polychaete larvae, other meiofaunal groups were generally present at very low
abundance (<1%) in the samples and restricted in diversity to gastropod larvae, acari, foraminifera, ostracoda
and turbellaria. Seventeen nematode species from 14 genera and 11 families were found in the samples, with
no evidence of endemicity to hydrothermal vents at the generic level. Four genera present were not previously
recorded at hydrothermal vents. Nematode species richness, species:genus ratios and abundances were low
compared with other deep-sea habitats, though the ecological relevance of comparisons with soft-sediment
benthos is discussed. Nematode assemblages exhibited high dominance by a few species, with one species of
Thalassomonhystera most abundant at five of the seven vent sites. Multivariate analysis of nematode assemblages
reveals similarities among sites that do not match geographical proximity. The youngest mussel beds were
most similar to each other and exhibited lower species richness than other sites, consistent with colonization
of mussel bed habitat by nematodes over time. Similarity in the composition of nematode assemblages among
sites separated by ¡3000 km indicates that they lie within a single biogeographic province, consistent with
that proposed for mussel bed macrofauna. At a generic level, samples exhibited some overlap with nematode
assemblages at vents elsewhere on the EPR, on the Mid Atlantic Ridge and in the North Fiji Basin.
