Seamounts eclectic topics

Our discoveries at seamounts are quite diverse

Our expeditions to the sea floor result in biological as well as geological observations and collections. An enteropneust worm found at the President Jackson Seamounts is of a new family, genus, and species, and we have observed others like it at Rodriguez Seamount and off Hawaii. In another study, deep sea coral distributions on Davidson Seamount were examined with video and GIS.

On all our dives to seamounts, we have found that erratic rocks are surprisingly abundant and can be from the continent and even from other seamounts. The erratics were probably transported by biological means, rather than icebergs or turbidity flows.

Enteropneust worm off Hawaii. The dome-shaped proboscis and lobed collar are about 2cm in length.
Image © MBARI 2001

Our research on other topics at seamounts

The discussions below are paraphrased from abstracts of papers published by the Submarine Volcanism group.

Erratic rocks are abundant at seamounts

SEAMOUNTS OFF CALIFORNIA, OREGON, AND WASHINGTON STATES - Sampling of volcanic seamounts with dredges and the remotely operated vehicle Tiburon recovered erratic rocks in surprising abundance as far as 500km offshore of the US West coast. The erratics usually have continental lithologies and appear to have been weathered in nearshore environments. They are probably transported by kelp holdfasts, drift logs, and pinnipeds to the seamounts, where they accumulate over time. The erratics are concentrated as lag deposits and kept from becoming buried in sediment by currents that sweep the seamounts. The erratics often have thinner manganese-oxide crusts than rocks of the seamounts because they were delivered to the seafloor more recently and manganese-oxide crusts precipitate over time. The thinner crusts make erratics easier to collect. While most of the erratics clearly did not originate by the volcanic processes that formed the seamounts, careful evaluation of some is necessary to distinguish them as erratics. Failure to recognize the presence of erratics may result in unrealistically complex interpretations of regional geology.

Reference: Paduan, J.B., D.A. Clague, A.S. Davis (2007) Erratic continental rocks on volcanic seamounts off the US west coast, Marine Geology, 246: 1-8, doi:10.1016/j.margeo.2007.07.007 [Abstract]

Enteropneusts refute previous assumptions

PRESIDENT JACKSON SEAMOUNTS – The deep ocean is home to a group of broad-collared hemichordate worms—the so-called 'lophenteropneusts'—that have been photographed gliding on the sea floor but have not previously been collected. It has been claimed that these worms have collar tentacles and blend morphological features of the two main hemichordate body plans: the tentacle-less enteropneusts and the tentacle-bearing pterobranchs. Consequently, lophenteropneusts have been invoked as missing links to suggest that the former evolved into the latter. The most significant aspect of the lophenteropneust hypothesis is its prediction that the fundamental body plan within a basal phylum of deuterostomes was enteropneust-like. The assumption of such an ancestral state influences ideas about the evolution of the vertebrates from the invertebrates. Here we report on the first collected specimen of a broad-collared, deep-sea enteropneust and describe it as a new family, genus and species. The collar, although disproportionately broad, lacks tentacles. In addition, we find no evidence of tentacles in the available deep-sea photographs (published and unpublished) of broad-collared enteropneusts, including those formerly designated as lophenteropneusts. Thus, the lophenteropneust hypothesis was based on misinterpretation of deep-sea photographs of low quality and should no longer be used to support the idea that the enteropneust body plan is basal within the phylum Hemichordata.

Reference: Holland, N.D., D.A. Clague, D. P. Gordon, A. Gebruk, D.L. Pawson, M. Vecchione (2005) 'Lophenteropneust' hypothesis refuted by collection and photos of new deep-sea hemichordates, Nature, 434, 374-376. [Abstract] [Article]

Coral resource protection

CALIFORNIA CONTINENTAL MARGIN -The Davidson Seamount is located 120 km to the southwest of Monterey. It is 2,400 m tall, yet it is still 1,250 m below the sea surface. In May 2002, 90 hours of digital video was recorded from all depths of the Davidson Seamount, using a remotely operated vehicle, and deep-sea coral specimens were collected. Preliminary analyses indicate that 20 coral taxa were found, often in dense and expansive patches, and almost exclusively in high relief, ridge areas. Other species were noted on or adjacent to the corals. Because of its pristine nature, as well as human threats and great potential for education, the Davidson Seamount is under consideration for protection as part of the Monterey Bay National Marine Sanctuary.

Reference: DeVogelaere, A.P., E.J. Burton, T. Trejo, C.E. King, D.A. Clague, M.N. Tamburri, G.M. Cailliet, R.E. Kochevar, W.J. Douros (2005) Deep-sea corals and resource protection at the Davidson Seamount, California, U.S.A., in: A. Freiwald and J.M. Roberts (eds), Cold-water Corals and Ecosystems, Springer-Verlag, Berlin, Heidelberg, 1189-1198.

Back to: Seamounts top page

Questions? Comments? Please contact Jenny Paduan
Last updated: Jan. 24, 2008