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2018
Vargas, JA, Hilton DR, Ramirez C, Molina J.  2018.  Metals in bivalve mollusks from the Jaco Scar seep, Pacific, Costa Rica. Revista De Biologia Tropical. 66:S269-S279. AbstractWebsite

Deep sea-research has made significant discoveries thanks to the availability of high resolution bathymetric mapping and vehicles able to reach hydrothermal vents and cold seeps. The Pacific continental margin of Costa Rica includes cold seeps that are inhabited by vesicomyid clams, which are expected to accumulate metals. Data on metals from cold seep clams are scarce. Thus, the objective of this study is to present the concentrations of Al, Cd, Cu, Fe, Pb, Mn, Ni, Sb and Zn in samples from seven clams, a mussel, sediment, and a rock, together with clam morphometric data. The bivalves (Archivesica sp.?) were collected in 2005 at a depth of 1888 m on the Jaco Scar (09 degrees 06' N - 84 degrees 50' W) during DSRV Alvin dive 4129. Metals were analyzed by Flame Atomic Absorption Spectrometry (FAAS) and Graphite Furnace (GFAAS). Concentrations are in mu g/g dry weight. The order of decreasing maximm concentrations and range in tissues of seven clams, were: Zn (43.4 - 266.3) > Fe (27.2 - 100.0) > Al (5.0 - 69.9) > Cd (0.1 - 12.2) > Sn (2.8 - 9.5) > Cu (4.0 - 7.3) > Mn (1.1 - 2.2) > Pb (0.2 - 0.8) > Ni (0.19 - 0.58 ). The gills had the maximum concentrations of Fe and Al. Maximum concentrations in the only mussel specimen collected, were: Zn (80.4 - gills), Fe (70.6 - gills). Cu (31.0 - gills). Al (26.6 - gills), Sn (4.8 - mantle), Mn (1.7 - mantle). Ni (0.97 - muscle), Pb (0.7 - muscle), Cd (0.57 - gills). The sediment sample had: Al (40 800), Fe (26 500), Mn (72.0), Zn (64.7), Cu (29.4), Ni (19.3), Sn (15.5). Pb (2.98), Cd (0.16). A rock fragment had: Fe (15 650), Al (9 240), Mn (170), Sn (99.5), Zn (36.5), Ni (20.4), Cu (13.4), Pb (1.6), Cd (traces). Clam gills concentrated metals such as Fe and Al. Fe was below the range reported for hydrothermal vent clams. while concentrations of other metals were near the lower range. Fe, Cd, Mn, and Pb in mussel tissues were lower than those in mussels from hydrothermal vent sites, while Cu and Zn were within the range. Metals in the sediment and rock samples appeared very rich in certain metals like Al and Fe and very poor in others, such as Cd. There is a paucity of information on metals and pollutants in clams and other macrofaunal species from Costa Rican cold seeps. Data presented herein must be complemented with future studies conducted jointly on the geochemistry, biology. and management of these deep-sea systems.

2012
Tryon, MD, Henry P, Hilton DR.  2012.  Quantifying submarine fluid seep activity along the North Anatolian Fault Zone in the Sea of Marmara. Marine Geology. 315:15-28.   10.1016/j.margeo.2012.05.004   AbstractWebsite

The Sea of Marmara presents the rare case where active seafloor venting sites are found on the surface trace of a major plate boundary fault: the North Anatolian Fault Zone. The objective of the 2007 MarNaut project was to quantify the level of activity of these venting sites, and the source of the fluids emitted, with the goal of understanding the processes involved and setting a baseline for long-term studies of the relationship between seismic activity and fluid migration/expulsion processes. Sites for flow meter and fluid sampler deployment and coring included basin bounding transtensional faults and strike-slip faults cutting through the topographic highs. Significant fluid flow appears to be primarily an episodic phenomenon at all sites. with background rates on the order of mm/yr to cm/yr except at or very near rare focused vents. Basin bounding faults expel primarily shallow sourced fluid with a strong influence of brackish Pleistocene Lake Marmara water, with the notable exception of the main active fault along the northern edge of the Cinarcik Basin. Expulsion sites where the main fault crosses topographic highs are more complex with evidence for deep-sourced fluids including thermogenic gas. One site on the Western High displayed two mound structures that appear to be chemoherms atop a deep-seated fluid conduit. The fluids being expelled are brines with an exotic fluid chemistry along with thermogenic gas and oil. Our work shows that submerged continental transform plate boundaries can be hydrologically active and exhibit a diversity of sources and processes. (C) 2012 Elsevier B.V. All rights reserved.

2009
Furi, E, Hilton DR, Brown KM, Tryon MD.  2009.  Helium systematics of cold seep fluids at Monterey Bay, California, USA: Temporal variations and mantle contributions. Geochemistry Geophysics Geosystems. 10   10.1029/2009gc002557   AbstractWebsite

We report helium isotope ratios ((3)He/(4)He) as well as helium and neon abundance results for submarine cold seep fluids from Extrovert Cliff in Monterey Bay, California. Samples were collected in copper tubing attached to submarine flux meters operating in continuous pumping mode. Following instrumentation recovery, the tubing was sectioned to produce for the first time a high-resolution time series of dissolved He and Ne variations over a time span of several days. Noble gas concentrations are variable and appear affected by interaction with a hydrocarbon phase within the aquifer. However, it is still possible to resolve the He signal into components associated with air equilibration, excess air entrainment, and terrigenic fluxes (both crustal and mantle-derived). The mantle He contribution reaches similar to 25-30% in some samples (up to 2.3 R(A), where R(A) = air (3)He/(4)He). Our quasi-continuous He-Ne record shows remarkable fluctuations over time scales of only a few hours and reflects the combined effects of gas stripping by hydrocarbons and an episodic input of mantle- derived fluids.