Our discoveries at seamounts are quite diverse
Our expeditions to the sea floor result in biological as well as geological observations and collections. A sea star has been named after our very own Dave Clague. 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.
Our research on other topics at seamounts
Strontium/calcium ratios in deep water corals
CALIFORNIA SEAMOUNTS - A depth transect of deep-sea bamboo corals along the California margin provides evidence that coral strontium to calcium ratios (Sr/Cacoral) record seawater Sr/Ca ratios (Sr/Casw). A calibration was constructed utilizing Sr/Cacoral ratios and previously published Pacific Sr/Casw data (R2 = 0.53, n = 12, p < 0.01): Sr/Cacoral/ (mmol/mol) = 4.62*Sr/Casw (mmol/mol) − 36.64. Sr/Casw is ultimately governed by the remineralization of Sr-containing shells of surface water-derived marine organisms (e.g., Acantharia) at intermediate water depths. California margin Sr/Cacoral records from 792 and 1295 m document fluctuations in Sr/Casw that appear decadal-scale. These results suggest that Sr/Casw may not be as stable as previously assumed and may be influenced by surface productivity on short timescales.
Reference: Hill, T.M., M. LaVigne, H.J. Spero, T. Guilderson, B. Gaylord, and D. Clague (2012). Variations in seawater Sr/Ca recorded in deep-sea bamboo corals. Paleoceanography, 27(3), PA3202. doi: 10.1029/2011PA002260. [Abstract] [Article]
Rare deep sea anglerfish
DAVIDSON AND TANEY SEAMOUNTS - In situ observations and collections of Chaunacops coloratus (Garman, 1899) from seamounts in the eastern North Pacific Ocean lend new behavioral, morphological and molecular data to an under-sampled, deep-sea group of fishes in the order Lophiiformes. Seven observations were made at Davidson Seamount, 130 km southwest of Monterey, CA, and from the Taney Seamount chain, 290 km west of Moss Landing, CA, from depths ranging from 2313 to 3297 m. Specimens were collected at both locations. Morphometric and meristic analyses were performed to identify individuals to the species level. These observations of C. coloratus provide greater latitude and depth distributions in the eastern North Pacific Ocean than previously known. Detailed habitat information indicated the fish occurred near manganese-encrusted volcanic talus slopes, a highly rugose habitat. Video observations revealed possible ontogenetic color changes in which small fish were blue and large fish were red. Video recorded rapid, vertical swimming as an escape response and maneuvering, or walking, with pectoral and pelvic fins and esca deployment. Phylogenetic analyses used here verify what has been known since Garman first described C. coloratus in 1899, that Chaunax and Chaunacops are closely related; molecular tools complement previous knowledge and genetic information created has been submitted to GenBank for further use by the scientific community.
Reference: Lundsten, L., S.B. Johnson, G.M. Cailliet, A.P. DeVogelaere, D.A. Clague (2012) Morphological, molecular, and in situ behavioral observations of the rare deep-sea anglerfish Chaunacops coloratus (Garman, 1899), order Lophiiformes, in the eastern North Pacific, Deep Sea Research I, 68, 46–53, doi:10.1016/j.dsr.2012.05.012 [Article]
Palagonitization: alteration of volcanic glass to clay
DAVIDSON SEAMOUNT (AND OTHER LOCATIONS) - Palagonitized sideromelane from submarine volcaniclastic, seafloor volcanic, marine phreatomagmatic, lacustine phreatomagmatic, and subglacial volcanic settings was investigated using in situ microanalysis to test if palagonite composition and texture are related to depositional environment. Palagonitization extent varies linearly and inversely with original sample porosity, suggesting that porosity is a controlling factor of palagonitization. Water absorbance of reflected infrared light varies linearly with water content derived from electron microprobe totals. Palagonite water content has a linear, inverse relationship to palagonitization extent. REEs are immobile during palagonitization, so they can be used to construct isocon diagrams for estimating major‐element concentration changes. Major‐element and overall mass changes during palagonitization vary widely (particularly for FeO and TiO2) and indicate that palagonitization cannot be an isovolumetric process. These parameters depend strongly on original sideromelane composition, thus requiring composition to be taken into account when performing global oceanic cation flux calculations. Subalkaline sideromelane dissolves much more rapidly than alkaline sideromelane during palagonitization. Two styles of palagonitization, burial‐diagenesis (relatively long‐duration, low water/rock; passive fluid circulation) and hydrothermal (relatively short‐duration, high water/rock; hydrothermal fluid circulation), are recognized. Observed palagonite REE concentration gradients indicate that sideromelane dissolution must continue in the zone behind the advancing palagonitization front. MgO was found to be highly mobile during palagonitization. Observed palagonite MgO gradients are not developed during sideromelane dissolution, but instead record initiation of syn‐ and/or post‐palagonitization conversion of the gel‐palagonite layer to a phyllosillicate layer, consistent with evolution of sideromelane alteration layers toward equilibrium with the solution.Reference: Pauly, B.D., P. Schiffman, R.A. Zierenberg, D.A. Clague (2011) Environmental and chemical controls on palagonitization, Geochem. Geophys. Geosyst., 12, Q12017, doi:10.1029/2011GC003639. [Article]
Genetic exchange between clam populations
CALIFORNIA MARGIN - Genetic connectivity and habitat characteristics were examined in two species of Acesta clams (Bivalvia: Limidae) from submarine seamounts and continental slopes along the western North America margin. Two species were identified from dive videos obtained with submarine remotely operated vehicles that surveyed a 2200-km range between 27° and 46° N latitude. Acesta sphoni was only found at shallower habitats (545–860 m depth) in the southern part of this range, whereas Acesta mori was more abundant and widely distributed in deeper habitats (1029–1996 m). Both species occurred on seamounts and on the walls of submarine canyons and continental slopes. Segregation of these species by depth exposes them to correlated differences in water temperatures and dissolved oxygen concentrations. Ninety-eight individuals sampled from seven seamounts and one escarpment locality were characterized with DNA-barcodes based on 643 base pairs of mitochondrial cytochrome-c-oxidase subunit I (COI). Further analysis of these sequences revealed no significant geographical subdivision across the sampled range. This lack of differentiation suggests ongoing genetic exchange between the seamount populations and those possibly distributed along the continental margins. Examination of regional bathymetric profiles suggested that an abundance of suitable habitat might exist along these margins.
Reference: Clague, G.E., W.J. Jones, J.B. Paduan, D.A. Clague, R.C. Vrijenhoek (2012) Phylogeography of Acesta clams from submarine seamounts and escarpments along the western margin of North America. Marine Ecology, 33, 75-87, doi:10.1111/j.1439-0485.2011.00458.x.
Isotopes in deep-sea corals record growth history and paleoclimate
Deep-sea bamboo corals hold promise as long-term climatic archives, yet little information exists linking bamboo coral geochemistry to measured environmental parameters. This study focuses on a suite of 10 bamboo corals collected from the Pacific and Atlantic basins (250–2136 m water depth) to investigate coral longevity, growth rates, and isotopic signatures. Calcite samples for stable isotopes and radiocarbon were collected from the base the corals, where the entire history of growth is recorded. In three of the coral specimens, samples were also taken from an upper branch for comparison. Radiocarbon and growth band width analyses indicate that the skeletal calcite precipitates from ambient dissolved inorganic carbon and that the corals live for 150–300 years, with extension rates of 9–128 mm/yr. A linear relationship between coral calcite δ18O and δ13C indicates that the isotopic composition is influenced by vital effects (δ18O:δ13C slope of 0.17–0.47). As with scleractinian deep-sea corals, the intercept from a linear regression of δ18O versus δ13C is a function of temperature, such that a reliable paleotemperature proxy can be obtained, using the "lines method." Although the coral calcite δ18O:δ13C slope is maintained throughout the coral base ontogeny, the branches and central cores of the bases exhibit δ18O:δ13C values that are shifted far from equilibrium. We find that a reliable intercept value can be derived from the δ18O:δ13C regression of multiple samples distributed throughout one specimen or from multiple samples within individual growth bands.
Reference: Hill, T. M., H. J. Spero, T. Guilderson, M. LaVigne, D. Clague, S. Macalello, and N. Jang (2011), Temperature and vital effect controls on bamboo coral (Isididae) isotope geochemistry: A test of the "lines method", Geochem. Geophys. Geosyst., 12, Q04008, doi:10.1029/2010GC003443. [Article]
Geological evolution of seamounts and their influences
The geological evolution of seamounts has distinct influence on their interactions with the ocean, their hydrology, geochemical fluxes, biology, resources, and geohazards. There are six geological evolutionary stages of seamounts: (1) small seamounts (100–1000-m height), (2) mid-sized seamounts (>1000-m height, > 700-m eruption depth), (3) explosive seamounts (< 700-m eruption depth), (4) ocean islands, (5) extinct seamounts, and (6) subducting seamounts. Throughout their lifetimes, seamounts offer major passageways for fluid circulation that promotes geochemical exchange between seawater and the volcanic oceanic crust, and seamounts likely host significant microbial communities. Water circulation may be promoted by hydrothermal siphons in conjunction with the underlying oceanic crust, or it may be driven by intrusions inside seamounts from Stage 2 onward. Geochemical fluxes are likely to be very large, primarily because of the very large number of Stage 1 seamounts. Intrusive growth of seamounts also initiates internal deformation that ultimately may trigger volcano sector collapse that likely peaks at the end of the main volcanic activity at large seamounts or islands. Explosive activity at seamounts may begin at abyssal depth, but it is most pronounced at eruption depths shallower than 700 m. Wave erosion inhibits the emergence of islands and shortens their lifespans before they subside due to lithosphere cooling. Once volcanism ends and a seamount is submerged, seamounts are largely unaffected by collapse or erosion. Throughout their histories, seamounts offer habitats for diverse micro- and macrobiological communities, culminating with the formation of coral reefs in tropical latitudes. Geological hazards associated with seamounts are responsible for some of the largest natural disasters recorded in history and include major explosive eruptions and largescale landslides that may trigger tsunamis.
Reference: Staudigal, H., Clague, D.A. (2010) The geological history of deep-sea volcanoes: biosphere, hydrosphere, and lithosphere interactions. Oceanography 23(1): 58–71. [Article]
Fish communities similar at three seamounts
DAVIDSON, PIONEER, AND RODRIGUEZ SEAMOUNTS - In many regions of the world, commercial fisheries for seamount-aggregating species have collapsed. Most are trawl fisheries, which have been implicated in the destruction and loss of fragile coral and sponge habitat and potentially endemic seamount species. Even with the intense fishing effort over seamounts, our understanding of processes regulating the distribution and abundance of seamount fish assemblages, which is vital to conservation policy, is weak. Here, we describe the abundance and distribution of demersal fishes found on 3 seamounts off central and southern California. Video observations were taken during 27 dives of a remotely operated vehicle (ROV), and were annotated in detail using the Monterey Bay Aquarium Research Institute’s (MBARI) Video Annotation Reference System (VARS). Video analysis yielded 2151 observations of 36 identified taxa. No aggregations of fishes were observed during the surveys. Video transects were analyzed to quantify organism density. Similarity among seamounts was compared using Bray-Curtis similarity estimates. Our results indicate high similarity among seamount faunas at similar depths, a shift from provincial to abyssal/cosmopolitan species with increased depth, and no evidence of seamount endemism.
Reference: Lundsten, L., McClain, C.R., Barry, J.P., Cailliet, G.M., Clague, D.A., DeVogelaere, A.P. (2009) Ichthyofauna on Three Seamounts off Southern and Central California, USA. Marine Ecology Progress Series 389:223-232. [Abstract] [Article]
No evidence for species endemism
DAVIDSON, PIONEER, AND RODRIGUEZ SEAMOUNTS - Seamounts are unique and biologically productive deep-sea habitats that have often been described as having high levels of endemism, highly productive fisheries, and benthic communities vulnerable to trawl fishing. We describe the abundance and distribution of benthic megafaunal invertebrates found on 3 seamounts off central and southern California. Video observations were taken during 27 dives of a remotely operated vehicle (ROV) and were annotated in detail using the Monterey Bay Aquarium Research Institute’s (MBARI) video annotation reference system (VARS, http://vars.sourceforge.net/). Video analysis yielded 134,477 observations of 202 identified invertebrate taxa. Video transects were analyzed to quantify organism density. Thirteen new species were observed and collected. Invertebrate communities at Davidson and Pioneer Seamounts were dominated by passive suspension-feeding cnidarians (mostly corals), but at Rodriguez Seamount, a guyot, the invertebrate community was dominated by holothurian echinoderms. We found no evidence of endemism among the megafauna at these 3 seamounts, which are all in close proximity to each other and the continental margin.
Reference: Lundsten, L., J.P. Barry, G.M. Cailliet, D.A. Clague, A.P. DeVogelaere, J.B. Geller (2009) Benthic invertebrate communities on three seamounts off southern and central California, USA, Marine Ecology Progress Series, 374: 23-32. [Abstract] [Article]
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
Enteropneusts refute previous assumptionsPRESIDENT 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.
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