Life Histories, Salinity Zones, and Sublethal Contributions of Contaminants to Pelagic Fish Declines Illustrated with a Case Study of San Francisco Estuary, California, USA

Human effects on estuaries are often associated with major decreases in abundance of aquatic species. However, remediation priorities are difficult to identify when declines result from multiple stressors with interacting sublethal effects. The San Francisco Estuary offers a useful case study of the potential role of contaminants in declines of organisms because the waters of its delta chronically violate legal water quality standards; however, direct effects of contaminants on fish species are rarely observed. Lack of direct lethality in the field has prevented consensus that contaminants may be one of the major drivers of coincident but unexplained declines of fishes with differing life histories and habitats (anadromous, brackish, and freshwater). Our review of available evidence indicates that examining the effects of contaminants and other stressors on specific life stages in different seasons and salinity zones of the estuary is critical to identifying how several interacting stressors could contribute to a general syndrome of declines. Moreover, warming water temperatures of the magnitude projected by climate models increase metabolic rates of ectotherms, and can hasten elimination of some contaminants. However, for other pollutants, concurrent increases in respiratory rate or food intake result in higher doses per unit time without changes in the contaminant concentrations in the water. Food limitation and energetic costs of osmoregulating under altered salinities further limit the amount of energy available to fish; this energy must be redirected from growth and reproduction toward pollutant avoidance, enzymatic detoxification, or elimination. Because all of these processes require energy, bioenergetics methods are promising for evaluating effects of sublethal contaminants in the presence of other stressors, and for informing remediation. Predictive models that evaluate the direct and indirect effects of contaminants will be possible when data become available on energetic costs of exposure to contaminants given simultaneous exposure to non-contaminant stressors.     

Enigmatic clastic pipe swarms and implications for fluidization dynamics in aeolian deposits

Soft‐sediment deformation of contorted and massive sandstone is common throughout much of the siliciclastic record, but clastic pipes represent a distinctive class of pressurized synsedimentary features. Remarkable centimetre to metre‐scale clastic pipe exposures in the Jurassic Navajo Sandstone of Utah (USA) establish a range of pipe sizes, expressions and relationships to the host rock in an erg margin setting, traditionally thought to be just a dry desert system. In particular, the field and laboratory characterizations of cylindrical pipes show internal concentric, annular rings that imply water fluidization, with alignment of long grain axes due to shear flow along pipe margins. Central interior parts of decimetre‐scale pipes appear massive in plan view, but display weakly developed pseudobedding from post‐pressure release, gravitational settling in the cross‐sectional view. Deformation features of conjugate fractures, ring faults, hypotrochoid patterns (geometric arcs and circles) and breccia in the host material reflect both brittle and ductile behaviour in response to the fluidization and injection of the clastic pipes. The stratigraphic context of individual pipes and the stratabound intervals of pipe features imply dynamic deformation nearly coincident with deposition in this Early Jurassic aeolian system related to multiple factors of groundwater expulsion, timing and local host sediment properties that influenced pipe development. Although the pipe features might be easily overlooked as a smaller scale feature of soft‐sediment deformation in dune deposits, these are valuable environmental indications of disrupted fluid pathways within porous, reservoir quality sands, associated with possible combinations of periodic springs, high water‐table conditions and strong ground‐motion events. These pipe examples may be important analogues where exposures are not so clear, with applications to diverse modern and ancient clastic settings internationally on Earth as well as in planetary explorations such as on Mars.     

Stable and clumped isotopes in desert carbonate spring and lake deposits reveal palaeohydrology: A case study of the Lower Jurassic Navajo Sandstone,south‐western USA

Carbon, oxygen and clumped isotope (Δ₄₇) values were measured from lacustrine and tufa (spring)‐mound carbonate deposits in the Lower Jurassic Navajo Sandstone of southern Utah and northern Arizona in order to understand the palaeohydrology. These carbonate deposits are enriched in both ¹⁸O and ¹³C across the basin from east to west; neither isotope is strongly sensitive to the carbonate facies. However, ¹⁸O is enriched in lake carbonate deposits compared to the associated spring mounds. This is consistent with evaporation of the spring waters as they exited the mounds and were retained in interdune lakes. Clumped isotopes (Δ₄₇) exhibit minor systematic differences between lake and tufa‐mound temperatures, suggesting that the rate of carbonate formation under ambient conditions was moderate. These clumped isotope values imply palaeotemperature elevated beyond reasonable surface temperatures (54 to 86°C), which indicates limited bond reordering at estimated burial depths of ca 4 to 5 km, consistent with independent estimates of sediment thickness and burial depth gradients across the basin. Although clumped isotopes do not provide surface temperature information in this case, they still provide useful burial information and support interpretations of the evolution of groundwater locally. The findings of this study significantly extend the utility of combining stable isotope and clumped isotope methods into aeolian environments.     

Tourism impacts on benthic communities of sandy beaches

This study evaluated the effect of human trampling on the benthic macrofauna of two beaches in Southeast Brazil with different levels of intensity of tourism, Grussaí (more impacted) and Manguinhos (less impacted), during periods of high and low tourism activity. The macrofauna of urbanized (U) and non‐urbanized (NU) sectors of the inter‐tidal zone was sampled and the number of visitors was recorded. General linear models revealed a decreasing in abundance of macrofauna species in the urbanized sectors of analyzed beaches, which are exposed to higher trampling impact than in non‐urbanized areas. At Manguinhos Beach, trampling did not affect the macrofauna (<1 visitors ? m^?²), except for the polychaete Scolelepis sp., which was less abundant in the U sector. Considering the benthic community, Atlantorchestoidea brasiliensis, Hemipodia californiensis and Scolelepis sp. were more sensitive to human trampling pressure and may be used as potential bioindicators of tourism impact. Management plans should consider mitigation of the effects of tourism, such as the control of the visitor number and their decentralization.     

Geochemistry and tectonic setting of Tertiary volcanism in the Güvem area, Anatolia, Turkey

Detailed field mapping in the Güvem area in the Galatia province of NW Central Anatolia, Turkey, combined with K–Ar dating, has established the existence of two discrete Miocene volcanic phases, separated by a major unconformity. The magmas were erupted in a post-collisional tectonic setting and it is possible that the younger phase could be geodynamically linked to the onset of transtensional tectonics along the North Anatolian Fault zone. The Early Miocene phase (18–20 Ma; Burdigalian) is the most voluminous, comprising of over 1500 m of potassium-rich intermediate-acid magmas. In contrast, the Late Miocene volcanic phase (ca. 10 Ma; Tortonian) comprises a single 70-m-thick flow unit of alkali basalt. The major and trace element and Sr–Nd isotope compositions of the volcanics suggest that the Late Miocene basalts and the parental mafic magmas to the Early Miocene series were derived from different mantle sources. Despite showing some similarities to high-K calc-alkaline magma series from active continental margins, the Early Miocene volcanics are clearly alkaline with higher abundances of high field strength elements (Zr, Nb, Ti, Y). Crustal contamination appears to have enhanced the effects of crystal fractionation in the petrogensis of this series and some of the most silica-rich magmas may be crustal melts. The mantle source of the most primitive mafic magmas is considered to have been an asthenospheric mantle wedge modified by crustally-derived fluids rising from a Late Cretaceous–Early Tertiary Tethyan subduction zone dipping northwards beneath the Galatia province. The Late Miocene basalts, whilst still alkaline, have a Sr–Nd isotope composition indicating partial melting of a more depleted mantle source component, which most likely represents the average composition of the asthenosphere beneath the region.     

Book reviews

AN AUSTRALIAN DICTIONARY OF ENVIRONMENT AND PLANNING by A. Gilpin. 16 × 24 cm, xvi and 271 pages. Oxford University Press: Melbourne 1990 (ISBN 0 19 554806 X) $A60.00 (hard).

CONTINENT IN CRISIS: A Natural History of Australia by D. Smith, 13 × 20 cm, xii and 201 pages. Penguin: Melbourne 1990 (ISBN 0 14 011169 7) $A14.99 (soft).

THE END OF NATURE by B. McKibben. 14 × 22 cm, xi and 212 pages. Viking: London 1990 (ISBN 0 670 82877 7) $A29.99 (hard); distributed by Penguin Books.

THE FATE OF THE FOREST: Developers, Destroyers and Defenders of the Amazon by S. Hecht and A. Cockburn. 13 × 20 cm, xiii and 349 pages. Penguin: London (ISBN 0 14 013382 8) $A16.99 (soft).

ENVIRONMENT, AID AND REGIONALISM IN THE SOUTH PACIFIC (Pacific Research Monograph No. 22) by J. Carew‐Reid. 17 × 25 cm, xii and 185 pages. National Centre for Development Studies, Australian National University: Canberra 1989 (ISBN 0 7315 0673 1) $A25.00 (soft).

NEW SEEDS AND POOR PEOPLE by M. Lipton with R. Longhurst. 14 × 21 cm, xiv and 473 pages, Unwin Hyman: London 1989 (ISBN 0 04 45326 4) $A39.95 (soft).

CLIMATE CHANGE AND WORLD AGRICULTURE by M. Parry. 15 × 23 cm, xv and 157 pages. Earthscan: London 1990 (ISBN 1 85383 065 8) £9.95 (soft).

INTRODUCTION TO WORLD VEGETATION (Second Edition) by A. S. Collinson. 14 × 21 cm, x and 325 pages. Unwin Hyman: London 1988 (ISBN 0 04 581 030 3) $A95.00 (hard); (ISBN 0 04 581 031 1) $A39.95 (soft).

OCEANS OF LIFE OFF SOUTHERN AFRICA edited by A. I. L. Payne and R. J. M. Crawford. 22 × 29 cm, xii and 380 pages. Vlaeberg: Cape Town 1989 (ISBN 0 947461 01 9) $US30.00 plus $US5.00 postage (hard).

KARST GEOMORPHOLOGY AND HYDROLOGY by D. Ford and P. Williams. 15 × 23 cm, xv and 601 pages. Unwin Hyman: London 1989 (ISBN 0 04 551106 3) $A79.95 (soft).

ENVISIONING INFORMATION by E. R. TUFTE. 22 × 78 cm, 126 pages. Graphics Press: Cheshire, CT 1990 $US48.00 (hard). Available from Graphics Press, Box 430, Cheshire, Connecticut, 06410, USA.

A GUIDE TO REMOTE SENSING: Interpreting Images of the Earth by S. A. Drury. 22 × 27 cm, viii and 199 pages. Oxford University Press: Oxford 1991 (ISBN 0 19 854495 2) $A44.95 (soft).

THE CAINOZOIC IN AUSTRALIA: A Re‐appraisal of the Evidence (Special Publication No. 18) edited by M. A. J. William, P. De Deckker and A. P. Kershaw. 17 × 25 cm, x and 346 pages. Geological Society of Australia Inc: Sydney 1991 (ISBN 0 909869 76 6) $A60.00 (non‐members), $A40.00 (members) (soft).

MONSOONAL AUSTRALIA: Landscape, Ecology and Man in the Northern Lowlands edited by C. D. Haynes, M. G. Ridpath and M. A. J. Williams. 20 × 29 cm, xii and 231 pages. Balkema: Rotterdam 1991 (ISBN 90 6191 638 0) $A85.25 (hard).

SOILS: THEIR PROPERTIES AND MANAGEMENT: A Soil Conservation Handbook for New South Wales edited by P. E. V. Charman and B. W. Murphy. 21 × 27 cm, xix and 363 pages. Sydney University Press: Sydney 1991 (ISBN 0 424 00183 7) $A39.95 (soft).

VEGETATION (Atlas of Australian Resources, Third Series, Volume 6) by Australian Surveying and Land Information Group. 30 × 43 cm, 64 pages. Australian Surveying and Land Information Group: Canberra 1990 (ISBN 0 642 14993 3) $A39.95 (soft).

THE ATLAS OF NEPAL IN THE MODERN WORLD by M. Sill and J. Kirkby. 27 × 22 cm, 160 pages. Earthscan: London 1991 (ISBN 1 85383 032 1) £37.50 (hard).

DEVELOPMENT IN PRACTICE: Paved With Good Intentions by D. Porter, B. Allen and G. Thompson. 15 × 23 cm. Routledge: London 1990 (ISBN 0 415 16626 3) $A27.95 (soft); distributed by The Law Book Co.

CHINA'S SPATIAL ECONOMY: Recent Developments and Reforms edited by G. J. R. Linge and D. K. Forbes. 15 × 22 cm, xiii and 225 pages. Oxford University Press: Hong Kong 1991 (ISBN 0 19 585296 6) $A29.95 (hard).     

Sulfide Inhibition of Nitrate Removal in Coastal Sediments

Microbial nitrate (NO₃⁻) removal via denitrification (DNF) at high sulfide (H₂S) concentrations was compared in sediment from a coastal freshwater pond in a developed area that receives salt-water influx during storm events, and a saline pond proximal to an undeveloped estuary. Sediments were incubated with added SO₄²⁻ (1,000 μg per gram dry weight basis (gdw)) to determine whether acid volatile sulfides (AVS) were formed. DNF in the sediments was measured with NO₃–N (300 μg gdw⁻¹) alone, and with NO₃–N and H₂S (1,000 μg S²⁻ gdw⁻¹). SO₄²⁻ addition to the freshwater sediments resulted in AVS formation (970 ± 307 μg S gdw⁻¹) similar to the wetland with no added SO₄²⁻ (986 ± 156 μg S gdw⁻¹). DNF rates measured with no added H₂S were greater in the freshwater than the wetland site (10.6 ± 0.6 vs. 6.4 ± 0.1 μg N₂O–N gdw⁻¹ h⁻¹, respectively). High H₂S concentrations retained NH₄–N in the undeveloped wetland and retained NO₃–N in the developed freshwater site, suggesting that potential salt-water influx may reduce the ability of the freshwater sediments to remove NO₃–N.     

Chemical weathering of a marine terrace chronosequence, Santa Cruz, California. Part II: Solute profiles, gradients and the comparisons of contemporary and long-term weathering rates

The spatial and temporal changes in hydrology and pore water elemental and ⁸⁷Sr/⁸⁶Sr compositions are used to determine contemporary weathering rates in a 65- to 226-kyr-old soil chronosequence formed from granitic sediments deposited on marine terraces along coastal California. Soil moisture, tension and saturation exhibit large seasonal variations in shallow soils in response to a Mediterranean climate. These climate effects are dampened in underlying argillic horizons that progressively developed in older soils, and reached steady-state conditions in unsaturated horizons extending to depths in excess of 15 m. Hydraulic fluxes (q_h), based on Cl mass balances, vary from 0.06 to 0.22 m yr⁻¹, resulting in fluid residence times in the terraces of 10-24 yrs.As expected for a coastal environment, the order of cation abundances in soil pore waters is comparable to sea water, i.e., Na > Mg > Ca > K > Sr, while the anion sequence Cl > NO₃ > HCO₃ > SO₄ reflects modifying effects of nutrient cycling in the grassland vegetation. Net Cl-corrected solute Na, K and Si increase with depth, denoting inputs from feldspar weathering. Solute ⁸⁷Sr/⁸⁶Sr ratios exhibit progressive mixing of sea water-dominated precipitation with inputs from less radiogenic plagioclase. While net Sr and Ca concentrations are anomalously high in shallow soils due to biological cycling, they decline with depth to low and/or negative net concentrations. Ca/Mg, Sr/Mg and ⁸⁷Sr/⁸⁶Sr solute and exchange ratios are similar in all the terraces, denoting active exchange equilibration with selectivities close to unity for both detrital smectite and secondary kaolinite. Large differences in the magnitudes of the pore waters and exchange reservoirs result in short-term buffering of the solute Ca, Sr, and Mg. Such buffering over geologic time scales can not be sustained due to declining inputs from residual plagioclase and smectite, implying periodic resetting of the exchange reservoir such as by past vegetational changes and/or climate.Pore waters approach thermodynamic saturation with respect to albite at depth in the younger terraces, indicating that weathering rates ultimately become transport-limited and dependent on hydrologic flux. Contemporary rates R_solute are estimated from linear Na and Si pore weathering gradients b_solute such that

     

Dévitrification et altération supergène d'une rhyolite (bassin du Paraná, Brésil) : mécanismes et bilans géochimiques

The weathering of a rhyolitic lava flow of the Paraná Basin (Brazil) developed, on few centimeters only, simplified petrographic features. The initial meteoric fluid pass-way is marked by celadonite-to-nontronite transformation. The second step is the complete dissolution of plagioclases, and the last one is the massive precipitation of halloysite. The geochemical mass balances according to the alteration features demonstrate the progressive leaching of major and trace elements fractionated by plagioclases, glass and opaques, and the sorption of Cu>As>Sb in the halloysite matrix. To cite this article: M. Bernard et al., C. R. Geoscience 336 (2004).