Paul R. Bartholomew

Cadmium accumulation and detoxification in a Cd-resistant population of the oligochaete Limnodrilus hoffmeisteri

Abstract It was reported earlier that the oligochaete Limnodrilus hoffmeisteri from metal-polluted Foundry Cove has evolved resistance to a combination of cadmium, nickel and cobalt (Klerks and Levinton, 1989). This paper addresses the possible physiological mechanisms by which this resistance is achieved. Exposing animals from both the control population and the resistant population to Foundry Cove sediment or to109Cd in water, shows that the resistance is not achieved by a reduced cadmium accumulation. HPLC gel-permeation of the cytosol obtained after the exposure to109Cd in water reveals that the resistant worms have significantly higher levels of a cadmium-binding, metallothionein-like protein than control worms. This elevated protein level is shown to be genetically determined and is proposed to contribute to the resistance of L. hoffmeisteri from Foundry Cove. In addition, electron microprobe anaiyses of Foundry Cove worms exposed to metal-rich sediment demonstrated the presence of Cd in granules. High levels of Cd were found in S-rich granules, possibly in the form of cadmium sulfide. These granules occurred both as individual ones and as large granular aggregates.

Pelletal black shale fabrics: their origin and significance

Abstract Recent work has demonstrated that, under certain conditions, laminated mudstones may be produced from the compaction of highly pelletized, organic-rich sediments occupied by populations of marine benthic worms. Such sediments can be found at the most developed part of the dysoxic region in many modern minimum zones. In order to reconstruct this facies accurately in the rock record, it is necessary to discern the true origin of pellets (benthic or planktonic) present in black, laminated shales. Petrographic techniques, electron microscopy and microprobe analysis were employed on modern benthic and planktonic faecal pellets in order to arrive at inorganic geochemical criteria useful for discriminating between them. Benthic pellets contained more of those elements found in the fine fraction of the sediments (Al, Mg, K) while planktonic pellets contained high amounts of those elements (Si) representing the inorganic remains of the food they consume. These criteria were successfully applied to pellets and their enclosing sedimentary matrices in ancient laminated black shales. Systematic identification of the origins of pellets found in laminated black shales should allow for detailed identification of palaeooxygen gradients within ancient depositional environments and may reveal that truly anoxic and azoic marine conditions were much less widespread than is commonly thought.

Zoltaiite, a new barium-vanadium nesosubsilicate mineral from British Columbia: Description and crystal structure

Abstract Zoltaiite, ideal formula BaV24+V123+ Si2O27, space group P3̅, a = 7.601(1), c = 9.219(1) Å, V = 461.34(1) Å3, Z = 1, is a new mineral found on the eastern edge of the Shuswap metamorphic complex of British Columbia, Canada. It is a metamorphic mineral formed under greenschist-facies P-T conditions as part of an assemblage that includes quartz, celsian, apatite, sphalerite, pyrrhotite, galena, and pyrite. Zoltaiite has a Mohs hardness of 6.7, no cleavage, an anhedral to semi-prismatic habit, and a calculated density of 4.83 g/cm3. It is opaque with reflectance and color similar to those of sphalerite. The strongest eight lines of the X-ray powder diffraction pattern [d in Å (I) (hkl)] are 3.103(78)(021), 2.934(89)(21̅2), 2.785(67)(013), 2.679(48)(022), 2.403(50)(211), 2.190(100)(212), 1.934(53)(213), and 1.438(63)(140). The empirical formula, derived from electron-microprobe analysis and the crystal structure, is Ba1.05(Ti1.31V4+0.69)Σ2.00(V3+11.06Fe3+0.49Cr0.34)Σ11.89Si2.06O27 based on O = 27. The crystal structure was solved by direct methods and refined on the basis of F02 using all unique reflections measured with MoKα Xradiation on a CCD-equipped diffractometer. The final R factor was 3.2%, calculated using 659 unique observed reflections. The unit cell contains four layers of two types parallel to (001): X, an octahedral and tetrahedral sheet, and Y, an octahedral plus barium sheet; both layers are doubled through inversion centers resulting in the sequence XXYY... Two consecutive equivalent layers are interconnected through shared octahedral edges, whereas consecutive non-equivalent layers are linked through shared corners. The high calculated density is consistent with the dense packing of the structure.