ALBERT

Description:    The accurate and precise measurement of total sulfide has been of major interest for well over a century. The most commonly used method involves the formation of a methylene blue–sulfide complex and spectrophotometric measurement of its concentration. The study presented herein compares the two most commonly used methods as outlined in Standard Methods for the Examination of Water and Wastewater (in APHA, Standard methods for the examination of water and wastewater, Washington, 1960 ) and by Cline (Limnol Oceanogr 14:454–458, 1969 ). In addition, this study clarifies the existing confusion of Cline’s reagent preparation procedure, as it is apparent that various interpretations exist among research groups regarding reagent preparation. After evaluating both methods with respect to precision and accuracy, detection limit, sample storage time, and ease of use, the method outlined in Cline was determined to be superior. Furthermore, we suggest that the reagent concentration has to be optimized depending on the range of sulfide concentrations to increase the accuracy and precision of the method. Content Type Journal Article Pages 1-16 DOI 10.1007/s10498-011-9128-1 Authors Brandi Kiel Reese, Department of Oceanography, Texas A&M University, College Station, TX 77843-3146, USA David W. Finneran, Department of Natural Sciences, Miami-Dade College, Miami, FL 33132, USA Heath J. Mills, Department of Oceanography, Texas A&M University, College Station, TX 77843-3146, USA Mao-Xu Zhu, Department of Chemistry and Chemical Engineering, Ocean University of China, Qingdao, 266100 People’s Republic of China John W. Morse, Department of Oceanography, Texas A&M University, College Station, TX 77843-3146, USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165

Description:    The distributions of iodate and total inorganic iodine concentrations in the waters on the Texas–Louisiana shelf in April, June, and August 2004 are described. Iodine–salinity graphs show three-end-member mixing involving onshore and offshore surface waters and deep offshore water. The April survey showed simple mixing on the surface, but in the later surveys, iodate concentrations were often much lower than predicted by the mixing curve while those for total inorganic iodine were higher. This demonstrated both iodate reduction in the water and iodide addition, although individual samples did not show equivalent speciation changes. Hydrographically, the system consists of the estuaries of the Mississippi and Atchafalaya rivers as they spill onto the shelf. The waters are stratified seasonally by a robust halocline, leading to hypoxia in the bottom waters from the combined effect of restricted downward diffusion of oxygen and the sinking of the luxuriant growth of phytoplankton induced by riverine nutrient supply. The distributions of iodate and total inorganic iodine are, therefore, interpreted in terms of water–sediment interaction as the shelf shoals to the north. Content Type Journal Article Pages 1-25 DOI 10.1007/s10498-011-9123-6 Authors Piers Chapman, Department of Oceanography, Texas A&M University, College Station, TX 77843, USA Victor W. Truesdale, School of Life Sciences, Oxford-Brookes University, Headington, Oxford, OX3 0BP UK Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165

Description:    The marine shelf areas in subtropical and tropical regions represent only 35% of the total shelf areas globally, but receive a disproportionately large amount of water (65%) and sediment (58%) discharges that enter such environments. Small rivers and/or streams that drain the mountainous areas in these climatic zones deliver the majority of the sediment and nutrient inputs to these narrow shelf environments; such inputs often occur as discrete, episodic introductions associated with storm events. To gain insight into the linked biogeochemical behavior of subtropical/tropical mountainous watershed-coastal ocean ecosystems, this work describes the use of a buoy system to monitor autonomously water quality responses to land-derived nutrient inputs and physical forcing associated with local storm events in the coastal ocean of southern Kaneohe Bay, Oahu, Hawaii, USA. The data represent 2.5 years of near-real time observations at a fixed station, collected concurrently with spatially distributed synoptic sampling over larger sections of Kaneohe Bay. Storm events cause most of the fluvial nutrient, particulate, and dissolved organic carbon inputs to Kaneohe Bay. Nutrient loadings from direct rainfall and/or terrestrial runoff produce an immediate increase in the N:P ratio of bay waters up to values of 48 and drive phytoplankton biomass growth. Rapid uptake of such nutrient subsidies by phytoplankton causes rapid declines of N levels, return to N-limited conditions, and subsequent decline of phytoplankton biomass over timescales ranging from a few days to several weeks, depending on conditions and proximity to the sources of runoff. The enhanced productivity may promote the drawing down of pCO 2 and lowering of surface water column carbonate saturation states, and in some events, a temporary shift from N to P limitation. The productivity-driven CO 2 drawdown may temporarily lead to air-to-sea transfer of atmospheric CO 2 in a system that is on an annual basis a source of CO 2 to the atmosphere due to calcification and perhaps heterotrophy. Storms may also strongly affect proximal coastal zone pCO 2 and hence carbonate saturation state due to river runoff flushing out high pCO 2 soil and ground waters. Mixing of the CO 2 -charged water with seawater causes a salting out effect that releases CO 2 to the atmosphere. Many subtropical and tropical systems throughout the Pacific region are similar to Kaneohe Bay, and our work provides an important indication of the variability and range of CO 2 dynamics that are likely to exist elsewhere. Such variability must be taken into account in any analysis of the direction and magnitude of the air–sea CO 2 exchange for the integrated coastal ocean, proximal and distal. It cannot be overemphasized that this research illustrates several examples of how high frequency sampling by a moored autonomous system can provide details about ecosystem responses to stochastic atmospheric forcing that are commonly missed by traditional synoptic observational approaches. Finally, the work exemplifies the utility of combining synoptic sampling and real-time autonomous observations to elucidate the biogeochemical and physical responses of coastal subtropical/tropical coral reef ecosystems to climatic perturbations. Content Type Journal Article Pages 1-26 DOI 10.1007/s10498-010-9115-y Authors Patrick Drupp, Department of Oceanography, University of Hawaii at Manoa, Honolulu, HI 96822, USA Eric Heinen De Carlo, Department of Oceanography, University of Hawaii at Manoa, Honolulu, HI 96822, USA Fred T. Mackenzie, Department of Oceanography, University of Hawaii at Manoa, Honolulu, HI 96822, USA Paul Bienfang, Department of Oceanography, University of Hawaii at Manoa, Honolulu, HI 96822, USA Christopher L. Sabine, NOAA/PMEL, 7600 Sand Point Way, Seattle, WA 98115, USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165

Description:    Comparison of results for the original burial rate of carbonate sediments over Phanerozoic time, as calculated using the GEOCARBSULFvolc model, with their rate of preservation to the present (survival rate) shows a considerable loss of mass, partly by subduction of oceanic crust, during the past 250 million years. Before that time, despite the evidence that preserved Paleozoic carbonates appear to have been deposited only in shallow water, we contend that there was also inorganic deposition of carbonates in the Paleozoic deep sea with subsequent loss by subduction. Inorganic carbonate deposition may have been abetted by the vastly different seawater and atmospheric composition for most of the Paleozoic than those of post-Cretaceous and end Paleozoic–early Mesozoic times. The hypothesis helps to explain the loss of mass greater than that predicted for shallow-water carbonates prior to 250 Ma. Content Type Journal Article Pages 1-7 DOI 10.1007/s10498-010-9113-0 Authors Robert A. Berner, Department of Geology and Geophysics, Yale University, New Haven, CT 06520-8109, USA Fred T. Mackenzie, Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI 96822, USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165

Description:    High sedimentation rates along river-dominated margins make these systems important repositories for organic carbon derived from both allochthonous and autochthonous sources. Using elemental carbon/nitrogen ratios, molecular biomarker (lignin phenol), and stable carbon isotopic (bulk and compound-specific) analyses, this study examined the sources of organic carbon to the Louisiana shelf within one of the primary dispersive pathways of the Mississippi River. Surface sediment samples were collected from stations across the inner, mid, and outer Louisiana shelf, within the Mississippi River plume region, during two cruises in the spring and fall of 2000. Lignin biomarker data showed spatial patterns in terrestrial source plant materials within the river plume, such that sediments near the mouth of the Mississippi River were comparatively less degraded and richer in C 4 plant carbon than those found at mid-depth regions of the shelf. A molecular and stable isotope-based mixing model defining riverine, marsh, and marine organic carbon suggested that the highest organic carbon inputs to the shelf in spring were from marine sources (55–61% marine organic carbon), while riverine organic carbon was the highest (63%) in fall, likely due to lower inputs of marine organic carbon at this time compared with the spring season. This model also indicated that marsh inputs, ranging from 19 to 34% and 3–15% of the organic carbon in spring and fall, respectively, were significantly more important sources of organic carbon on the inner Louisiana shelf than previously suggested. Finally, we propose that the decomposition of terrestrial-derived organic carbon (from the river and local wetlands sources) in mobile muds may serve as a largely unexplored additional source of oxygen-consuming organic carbon in hypoxic bottom waters of the Louisiana shelf. Content Type Journal Article Pages 1-26 DOI 10.1007/s10498-010-9110-3 Authors Thomas S. Bianchi, Department of Oceanography, Texas A&M University, College Station, TX 77843-3146, USA Laura A. Wysocki, Department of Earth and Environmental Sciences, Tulane University, New Orleans, LA 70118, USA Kathryn M. Schreiner, Department of Oceanography, Texas A&M University, College Station, TX 77843-3146, USA Timothy R. Filley, Department of Earth and Atmospheric Sciences and the Purdue Climate Change Research Center, Purdue University, West Lafayette, IN 47907, USA D. Reide Corbett, Department of Geological Sciences, Institute for Coastal Science and Policy, East Carolina University, Greenville, NC 27858, USA Alexander S. Kolker, Louisiana University Marine Consortium (LUMCON), 8124, Highway 56, Chauvin, LA 70344, USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165

Description:    To test the hypothesis that manganese- and iron-reducing bacteria in marine sediments respond rapidly to seasonal pulses of fresh organic carbon settling to the sea floor, we amended wet metal oxide–rich and metal oxide–poor sediments from the Beaufort Sea, Canadian Arctic, with organic carbon in the form of shrimp powder and incubated them at room temperature. Neither Mn nor Fe was released to the aqueous phase from unamended metal oxide–rich sediment during a 41-day incubation, but both elements were released from sediment aliquots amended with organic carbon. Dissolved Mn appeared in the aqueous phase after a lag period of 2 days or less and reached levels as high as 600 μmol l −1 before levelling out. The release of dissolved Mn was accompanied by a decrease in the concentration of solid-phase reducible Mn. Dissolved Fe did not appear until 2 weeks into the incubation and only after the concentration of dissolved Mn had levelled out. For low concentrations of amended organic carbon (0.3%), the kinetics of Mn reduction fit a second-order rate law with a rate constant k  = 2 × 10 −3  g μmol −1  day −1 , but at intermediate and high organic carbon concentrations (0.7 and 1.3%), the reduction kinetics was better described by a pseudo-first-order rate law with a rate constant k ′ = 1.6 × 10 −1  day −1 . A pulse of organic carbon settling to the sea floor can trigger reduction of Mn and Fe oxides within a few days in strongly seasonal sedimentary environments, such as in the Arctic. Content Type Journal Article Pages 1-15 DOI 10.1007/s10498-010-9117-9 Authors Cédric Magen, Department of Earth and Planetary Sciences, McGill University, Montréal, QC H3A 2A7, Canada Alfonso Mucci, Department of Earth and Planetary Sciences, McGill University, Montréal, QC H3A 2A7, Canada Bjorn Sundby, Department of Earth and Planetary Sciences, McGill University, Montréal, QC H3A 2A7, Canada Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165

Description:    To investigate controls on phytoplankton production along the Louisiana coastal shelf, we mapped salinity, nutrient concentrations (dissolved inorganic nitrogen (DIN) and phosphorus (P i ), silicate (Si)), nutrient ratios (DIN/P i ), alkaline phosphatase activity, chlorophyll and 14 C primary productivity on fine spatial scales during cruises in March, May, and July 2004. Additionally, resource limitation assays were undertaken in a range of salinity and nutrient regimes reflecting gradients typical of this region. Of these, seven showed P i limitation, five revealed nitrogen (N) limitation, three exhibited light (L) limitation, and one bioassay had no growth. We found the phytoplankton community to shift from being predominately N limited in the early spring (March) to P limited in late spring and summer (May and July). Light limitation of phytoplankton production was recorded in several bioassays in July in water samples collected after peak annual flows from both the Mississippi and Atchafalaya Rivers. We also found that organic phosphorus, as glucose-6-phosphate, alleviated P limitation while phosphono-acetic acid had no effect. Whereas DIN/P i and DIN/Si ratios in the initial water samples were good predictors of the outcome of phytoplankton production in response to inorganic nutrients, alkaline phosphatase activity was the best predictor when examining organic forms of phosphorus. We measured the rates of integrated primary production (0.33–7.01 g C m −2 d −1 ), finding the highest rates within the Mississippi River delta and across Atchafalaya Bay at intermediate salinities. The lowest rates were measured along the outer shelf at the highest salinities and lowest nutrient concentrations (〈0.1 μM DIN and Pi). The results of this study indicate that P i limitation of phytoplankton delays the assimilation of riverine DIN in the summer as the plume spreads across the shelf, pushing primary production over a larger region. Findings from water samples, taken adjacent the Atchafalaya River discharge, highlighted the importance of this riverine system to the overall production along the Louisiana coast. Content Type Journal Article Pages 1-26 DOI 10.1007/s10498-011-9134-3 Authors Antonietta Quigg, Department of Marine Biology, Texas A&M University at Galveston, 200 Seawolf Parkway, Galveston, TX 77553, USA Jason B. Sylvan, Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08540, USA Anne B. Gustafson, Horn Point Laboratory, Center for Environmental Science, University of Maryland, 2020 Horn Point Road, Cambridge, MD 21613, USA Thomas R. Fisher, Horn Point Laboratory, Center for Environmental Science, University of Maryland, 2020 Horn Point Road, Cambridge, MD 21613, USA Rod L. Oliver, Catchment Biogeochemistry and Aquatic Ecology, CSIRO Land and Water, Waite Campus, Urrbrae, SA 5064, Australia Sasha Tozzi, Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08540, USA James W. Ammerman, Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08540, USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165

Description:    Aragonite was synthesized inorganically using a seeded-growth technique to characterize precipitation kinetics for the heterogeneous growth of solid from dilute solutions (ionic strength: 0.05–0.07 mol l −1 ). The concentration of all aqueous constituents, including Ca (~5–15 mmol l −1 ), Na (~10–35 mmol l −1 ), Cl (~30–35 mmol l −1 ), and carbon (as total alkalinity: ~10 to 17 meq l −1 ), was held constant by the addition of titrants that contained excess solute concentrations to balance the growth of solid phase during the precipitation reaction, and a CO 2 /N 2 gas mixture (0.009–0.178) was bubbled through each solution to facilitate mass exchange between gaseous and aqueous carbon species. Forty-three experiments were conducted at 10° ( n  = 13), 25° ( n  = 21), and 40°C ( n  = 9), over a range of average saturation states with respect to aragonite from 8.3 to 28.5, 2.9 to 19.6 and 2.0 to 12.2, and average precipitation rates from 10 2.8 to 10 3.8 , 10 2.3 to 10 4.0 , and 10 2.5 to 10 4.1 micromol m −2 h −1 , respectively. Reaction orders averaged 1.7 ± 0.10 at 10°, 1.7 ± 0.07 at 25° and 1.5 ± 0.06 at 40°, and they were independent of temperature while rate constants averaged 10 1.3  ± 0.12, 10 1.9  ± 0.06, and 10 2.6  ± 0.04 micromol m −2  h −1 , respectively, increasing one-half order of magnitude for each 15°C rise in temperature. From these data, an Arrhenius activation energy of 71.2 kJ mol −1 is calculated for the heterogeneous precipitation of aragonite. This value is comparable to a sole independent measurement of 80.7 kJ mol −1 reported for the solid-solution recrystallization of monohydrocalcite to aragonite (Munemoto and Fukushi in J Mineral Petrol Sci 103: 345–349, 2008 ). Content Type Journal Article Pages 1-18 DOI 10.1007/s10498-011-9127-2 Authors Christopher S. Romanek, NASA Astrobiology Institute and Department of Earth and Environmental Sciences, University of Kentucky, Lexington, KY 40506, USA John W. Morse, Department of Oceanography, Texas A&M University, College Station, TX 77843, USA Ethan L. Grossman, Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843, USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165

Description:    Great Salt Lake (GSL) is one of the largest and most saline lakes in the world. In order to accurately model limnological processes in GSL, hydrodynamic calculations require the precise estimation of water density ( ρ ) under a variety of environmental conditions. An equation of state was developed with water samples collected from GSL to estimate density as a function of salinity and water temperature. The ρ of water samples from the south arm of GSL was measured as a function of temperature ranging from 278 to 323 degrees Kelvin ( o K) and conductivity salinities ranging from 23 to 182 g L −1 using an Anton Paar density meter. These results have been used to develop the following equation of state for GSL (σ = ± 0.32 kg m −3 ): r - r 0 = 184.0 10 6 2 + 1.0 4 70 8*\text S - 1. 2 10 6 1*\text T + 3. 1 4 7 2 1 \text E - 4*\text S 2 +  0.00 1 9 9 \text T 2 - 0.00 1 1 2*\text S *\text T , where ρ 0 is the density of pure water in kg m −3 , S is conductivity salinity g L −1 , and T is water temperature in degrees Kelvin. Content Type Journal Article Pages 1-12 DOI 10.1007/s10498-011-9138-z Authors David L. Naftz, U.S. Geological Survey, 2329 W. Orton Circle, Salt Lake City, UT 84119, USA Frank J. Millero, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA Blair F. Jones, U.S. Geological Survey, 432 National Center, 12201 Sunrise Valley Dr, Reston, VA 20192, USA W. Reed Green, U.S. Geological Survey, 401 Hardin Road, Little Rock, AR 72211, USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165

Description:    Arsenic (As) and antimony (Sb) concentrations and speciation were determined along flow paths in three groundwater flow systems, the Carrizo Sand aquifer in southeastern Texas, the Upper Floridan aquifer in south-central Florida, and the Aquia aquifer of coastal Maryland, and subsequently compared and contrasted. Previously reported hydrogeochemical parameters for all three aquifer were used to demonstrate how changes in oxidation–reduction conditions and solution chemistry along the flow paths in each of the aquifers affected the concentrations of As and Sb. Total Sb concentrations (Sb T ) of groundwaters from the Carrizo Sand aquifer range from 16 to 198 pmol kg −1 ; in the Upper Floridan aquifer, Sb T concentrations range from 8.1 to 1,462 pmol kg −1 ; and for the Aquia aquifer, Sb T concentrations range between 23 and 512 pmol kg −1 . In each aquifer, As and Sb (except for the Carrizo Sand aquifer) concentrations are highest in the regions where Fe(III) reduction predominates and lower where SO 4 reduction buffers redox conditions. Groundwater data and sequential analysis of the aquifer sediments indicate that reductive dissolution of Fe(III) oxides/oxyhydroxides and subsequent release of sorbed As and Sb are the principal mechanism by which these metalloids are mobilized. Increases in pH along the flow path in the Carrizo Sand and Aquia aquifer also likely promote desorption of As and Sb from mineral surfaces, whereas pyrite oxidation mobilizes As and Sb within oxic groundwaters from the recharge zone of the Upper Floridan aquifer. Both metalloids are subsequently removed from solution by readsorption and/or coprecipitation onto Fe(III) oxides/oxyhydroxides and mixed Fe(II)/Fe(III) oxides, clay minerals, and pyrite. Speciation modeling using measured and computed Eh values predicts that Sb(III) predominate in Carrizo Sand and Upper Floridan aquifer groundwaters, occurring as the Sb(OH) 3 0 species in solution. In oxic groundwaters from the recharge zones of these aquifers, the speciation model suggests that Sb(V) occurs as the negatively charged Sb(OH) 6 − species, whereas in sufidic groundwaters from both aquifers, the thioantimonite species, HSb 2 S 4 − and Sb 2 S 4 2− , are predicted to be important dissolved forms of Sb. The measured As and Sb speciation in the Aquia aquifer indicates that As(III) and Sb(III) predominate. Comparison of the speciation model results based on measured Eh values, and those computed with the Fe(II)/Fe(III), S(-II)/SO 4 , As(III)/As(V), and Sb(III)/Sb(V) couples, to the analytically determined As and Sb speciation suggests that the Fe(II)/Fe(III), S(-II)/SO 4 couples exert more control on the in situ redox condition of these groundwaters than either metalloid redox couple. Content Type Journal Article Pages 1-33 DOI 10.1007/s10498-011-9131-6 Authors Stephanie S. Willis, Department of Earth and Environmental Sciences, The University of Texas at Arlington, Arlington, TX 76019, USA Shama E. Haque, Department of Earth and Ocean Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada Karen H. Johannesson, Department of Earth and Environmental Sciences, Tulane University, New Orleans, LA 70118, USA Journal Aquatic Geochemistry Online ISSN 1573-1421 Print ISSN 1380-6165