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Discussion
The reliance upon video and still images to supplement the ecological and biogeographical information of single species (Harbison et al., 2001; Matsumoto et al., 2003; Haddock, 2004; Cairns, 2007; Reiswig & Lee, 2007) and, also, to characterize whole faunas (Braby et al., 2007; Lundsten et al., 2009) has become more accepted recently, particularly when describing habitats such as the deep-sea. Here we have used video observations to add to our knowledge of the biogeography and ecology of this new species, with the aim of more accurately characterizing this octocoral.
The known depth and latitudinal ranges of Gersemia juliepackardae is large. Mean depth for collected specimens and video observations, when combined, is 1039 m (± 8.36 SE, n = 235 range 520-2034 m). Video observations also expand the latitudinal range of collected specimens by approximately 100 km to 1686 km (33.10472°N - 47.85686°N). We are confident that the combined latitudinal range of collected specimens and those observed in ROV video only are accurate, however, we suggest that the true latitudinal range may be larger than our data currently show, as this trend has been observed for other organisms found upon the continental slope and at seamounts along the west coast of the USA (Lundsten et al., 2009). Our estimate of organism density was relatively low, however, the video transects were quite long and this tends to lower the estimate for patchily distributed organisms. Localized density was often greater than our estimates indicate, as we did observe G. juliepackardae in densely clustered groups of four to eight individuals.
Surprisingly, the new species described here was often observed living upon dead and live sponges. The second author has observed zoanthid anemones and hydrozoan’s living upon both dead and living corals and sponges, however, in a recent analysis of invertebrate community composition at three seamounts off California (Lundsten et al., 2009), no octocorals, aside from this species, were seen living upon any other organisms. This may represent the first account of a deep-sea octocoral living upon sponges. Other individuals of the new species were in this study were found living upon hard-rock substrata.