Search results | Digital Commons of Moss Landing Marine Laboratories

Title: Copper complexation in the Northeast Pacific,
Description: Copper titrations were conducted at sea with differential pulse anodic stripping voltammetry to examine the degree to which copper was associated with organic ligands. Greater than 99.7% of the total dissolved copper in surface waters of the central Northeast Pacific shallower than 200 m was estimated to be associated with strong organic complexes. Below 200 m, increasing proportions of inorganic or labile copper species were observed. At middepths (1000 m), about 50-70% of the total dissolved copper was in the organically complexed form. Whereas total copper varies by a factor of only three from the surface to middepths (0.6-1.8 nM), copper complexation gives rise to extremely low cupric ion activities in surface waters ({Cu2+} = 1.4 × 10-4 M) and higher values at middepth ({Cu2+} = 10-11 M) -a variation of three orders of magnitude., Cited By (since 1996):208 Oceanography, ,
Author: Coale, Bruland
Date: 1988-01-01T00:00:00Z

Title: 234Th:238U disequilibria within the California Current
Description: Profiles of dissolved and particulate 234Th were determined at several stations within the California Current. Modeling of the disequilibria between the 234Th and 23aU within the surface waters provides for estimates of the residence time of dissolved thorium with respect to particle scavenging (TP varies from 6 to 50 days), the particle residence time (TP varies from 2 to 20 days), and the particulate 234Th flux exiting the surface layer. The model-derived, first-order scavenging rate constant for dissolved thorium is observed to be proportional to the rate of primary production. Particle residence times seem to be governed by the rate of zooplankton grazing and the types of zooplankton present. Model-derived particulate 234Th fluxes are in good agreement with direct measurements by sediment traps.
Author: Coale, Bruland
Date: 1985-01-01T00:00:00Z

Title: Analysis of seawater for dissolved cadmium, copper and lead,
Description: , , , An intercomparison study of voltammetric and atomic absorption spectrometric methods for determining cadmium, lead and copper in seawater samples was conducted. The voltammetric approach utilizes differential pulse anodic stripping voltammetry using a rotating, glassy carbon, mercury film electrode under conditions developed to minimize contamination sources and to enhance sensitivity for seawater matrices. The atomic absorption approach involves a concentration step using either an organic solvent extraction of metal dithiocarbamate chelates or a Chelex-100 column with detection by graphite furnace atomic absorption spectrometry. Similar and consistent results were obtained using both methods for the three trace metals studied on a wide range of natural seawater samples. Both methods are comparable in sensitivity for cadmium and copper, however the voltammetric method is better suited for the analysis of lead in seawater because of its enhanced sensitivity and low blank. An advantage of the voltammetric approach is its amenability towards real-time shipboard analysis., ,
Author: Bruland, Coale, Mart
Date: 1985-01-01T00:00:00Z

Title: Oceanic stratified euphotic zone as elucidated by 234Th : 238U disequilibrial,
Description: Profiles of dissolved and particulate 234Th were determined at the VERTEX 2 and 3 stations off Manzanillo, Mexico, and at the VERTEX 4 station about 900 km north of Hawaii. By modeling the disequilibria between 234Th and 238U in the dissolved and particulate form, estimates of scavenging rates for Th from the dissolved to particulate phases, particle residence times, and the flux of Th via particle removal can be obtained. 234Th: 238U activity ratio profiles indicate that the euphotic zone can be separated into two layers: An upper oligotrophic layer characterized by low new production values, low net scavenging, and long dissolved 234Th residence times; and a subsurface eutrophic layer with higher new production values, more intense scavenging, and shorter dissolved 234Th residence times. New production, rather than total primary production may determine net scavenging rates of reactive elements from oceanic surface waters. These results contribute to the emerging descriptions of the layered structure of oligotrophic euphotic zones and support the notion that this may be a general and ubiquitous feature of global stratified oligotrophic regimes. These layered systems can be structured not only in biological and nutrient parameters, but also in terms of the rates of chemical scavenging and elemental transport., , ,
Author: Coale, Bruland
Date: 1987-01-01T00:00:00Z

Title: Developing standards for dissolved iron in seawater
Description: Cited By (since 1996):114
Author: Johnson, Boyle, Bruland, Coale, Measures, Moffett, Aguilar-Islas, Barbeau, Bergquist, Bowie, Buck, Cai, Chase, Cullen, Doi, Elrod, Fitzwater, Gordon, King, Laan, Laglera-Baquer, Landing, Lohan, Mendez, Milne, Obata, Ossiander, Plant, Sarthou, Sedwick, Smith, Sohst, Tanner, Van den Berg, Wu
Date: 2007-01-01T00:00:00Z

Title: Lead speciation in surface waters of the eastern North Pacific,
Description: , , , Titrations using differential pulse anodic stripping voltammetry (DPASV) to detect electroactive lead were carried out on fresh seawater samples and on samples stored acidified to determine the extent of lead complexation in the eastern North Pacific. Results of these analyses on surface water samples indicate total dissolved lead concentrations between 17 and 49 pM. The inorganic or DPASV labile fraction is 30–50%. Titration with lead yielded data consistent with one class of organic ligand(s), present at low concentration (between 0.2 and 0.5 nM) with a mean value for a conditional stability constant with respect to inorganic lead of log K′cond=9.7. The presence of this ligand, together with the various inorganic ligands in seawater, gives rise to a concentration of free ionic lead of ∼ 0.4 pM., ,
Author: Capodaglio, Coale, Bruland
Date: 1990-01-01T00:00:00Z

Title: Toxic diatoms and domoic acid in natural and iron enriched waters of the oceanic Pacific
Description: Near-surface waters ranging from the Pacific subarctic (58°N) to the Southern Ocean (66°S) contain the neurotoxin domoic acid (DA), associated with the diatom Pseudo-nitzschia. Of the 35 stations sampled, including ones from historic iron fertilization experiments (SOFeX, IronEx II), we found Pseudo-nitzschia at 34 stations and DA measurable at 14 of the 26 stations analyzed for DA. Toxin ranged from 0.3 fg·cell -1 to 2 pg·cell -1, comparable with levels found in similar-sized cells from coastal waters. In the western subarctic, descent of intact Pseudo-nitzschia likely delivered significant amounts of toxin (up to 4 μg of DA·m -2·d -1) to underlying mesopelagic waters (150-500 m). By reexamining phytoplankton samples from SOFeX and IronEx II, we found substantial amounts of DA associated with Pseudo-nitzschia. Indeed, at SOFeX in the Antarctic Pacific, DA reached 220 ng·L -1, levels at which animal mortalities have occurred on continental shelves. Iron ocean fertilization also occurs naturally and may have promoted blooms of these ubiquitous algae over previous glacial cycles during deposition of ironrich aerosols. Thus, the neurotoxin DA occurs both in coastal and oceanic waters, and its concentration, associated with changes in Pseudo-nitzschia abundance, likely varies naturally with climate cycles, as well as with artificial iron fertilization. Given that iron fertilization in iron-depleted regions of the sea has been proposed to enhance phytoplankton growth and, thereby, both reduce atmospheric CO 2 and moderate ocean acidification in surface waters, consideration of the potentially serious ecosystem impacts associated with DA is prudent., Cited By (since 1996):9, CODEN: PNASA
Author: Silver, Bargu, Coale, Benitez-Nelson, Garcia, Roberts, Sekula-Wood, Bruland, Coale
Date: 2010-01-01T00:00:00Z

Title: Spatial and temporal variability in copper complexation in the North Pacific,
Description: The complexation of trace metals by organic ligands has long been proposed to play a significant role in determining trace metal speciation in seawater. However, analytical methodologies with sufficient specificity and sensitivity only recently have been developed to enable us to address questions of trace metal/organic complexation. In this study copper titrations were conducted at sea using differential pulse anodic stripping voltammetry on North Pacific samples to determine the extent of copper complexation with organic ligands. This study includes data from a transect from 33°N, 139°W to 55°N, 148°W and seasonal occupations of the VERTEX T-4 station (33°N, 139°W). The data indicate the presence of at least two copper binding ligands: L1, the stronger ligand, or ligand class, averages 2 nM with log K′l cond(Cu′) = 11.6; L2, the weaker ligand class varies between 5 and 10 nM witgh log K′2 cond(Cu′) = 8.6. The presence of these ligands strongly buffers the activity of copper(II) in surface waters at all stations. Seasonal variations in the distribution of strong copper complexing ligands follow seasonal variations in the depth of the mixed layer at T-4 and indicate a ligand source in the lower mixed layer. Ligand concentrations do not covary with the rates of primary productivity in a latitudinal transect from the central North Pacific to the subarctic. Ligand concentrations at all stations vary only by a factor of two and hold surface water copper(II) ion activities relatively constant (about 10-14 M), suggestive of a regulated ligand production mechanism. These results comprise a unique data set for copper complexation in the Pacific and may have significantly implications for the distribution of plankton between oligotrophic and subarctic systems. © 1990., Cited By (since 1996):113, Oceanography, ,
Author: Coale, Bruland
Date: 1990-01-01T00:00:00Z