Kristin Orians - Academia.edu (original) (raw)

Papers by Kristin Orians

This NCEI Accession includes chemical, discrete samples and profile observations data collected f... more This NCEI Accession includes chemical, discrete samples and profile observations data collected from Canadian Coast Guard Ship John P. Tully in the North Pacific Ocean, coastal upwelling region west of Vancouver Island, Canada from 1998-07-15 to 1998-07-23. These data include dissolved inorganic carbon (DIC), total alkalinity (TA), temperature, salinity, dissolved oxygen, silicate, nitrate and phosphate. The inner-shelf buoyancy current, the outer-shelf and the slope regions are contrasted for both wind regimes (up- and downwelling). Results show strong biological drawdown of the partial pressure of carbon dioxide (pCO2) in response to upwelling over the outer-shelf. In contrast, measured pCO2 is exceptionally high (pCO2>1000ppm) in the inner-shelf current, where biological uptake of carbon is consistently large. The biological C:N uptake ratio appears to increase when nitrogen becomes limiting (during downwelling), while the POC:PON ratio is relatively constant (slightly lower t...

High molecular weight dissolved organic compounds such as peptides, polysaccharides and humic sub... more High molecular weight dissolved organic compounds such as peptides, polysaccharides and humic substances (humic and fulvic acids) play a major role in modifying the distribution and bioavailability of both organic and inorganic pollutants (e.g. pesticides and heavy metals) in natural waters. To predict the rate and extent of such processes, knowledge of the structure and physico-chemical properties of these species is required. Humic substances and their anthropogenic derivatives (e.g. chlorolignosulphonic acids) have proved difficult to characterize using conventional analytical techniques such as UV, NMR and FAB-MS. However, a combination of LC fractionation and electrospray ionization mass spectrometric (ESI-MS) analysis has the potential to provide the type of structural information required, including identification and location of functional groups. ESI is a soft ionization technique, and ESI-MS provides accurate molecular weight determinations for large polar and ionic substa...

Deep Sea Research Part I: Oceanographic Research Papers

Abstract The two pairs of geochemical twins, Zr–Hf and Nb–Ta, have similar chemical properties, l... more Abstract The two pairs of geochemical twins, Zr–Hf and Nb–Ta, have similar chemical properties, leading to their limited fractionation throughout the igneous processes and thus useful and widely used to elucidate rock and mineral formation. In contrast to the analysis of solid samples (e.g. igneous rocks), however, reports of these elements from aquatic samples (e.g. seawater) are very limited due to difficulties in analyzing their very low concentrations in seawater compared to those in solid samples (up to 6 orders of magnitude different). Recent developments of clean sampling techniques coupled with pre-concentration and ICP-MS determination have made trace elements analysis in seawater reliable. Here we report the first vertical distribution of dissolved Zr, Hf, Nb and Ta in the Indian Ocean in addition to those in the Atlantic Ocean, Andaman Sea and Gulf of Thailand. In the Atlantic and northeastern Indian Ocean, Zr, Hf, Nb and Ta show surface depletion and deep water enrichment. The average deepwater Zr/Hf molar ratios in the western North Atlantic, eastern North Atlantic and northeastern Indian Ocean were 270, 315 and 280, respectively. Compared to North Pacific Ocean Zr/Hf ratios of ~500, strong intra- and inter-ocean fractionation, a term that describe a difference between concentration of trace metals in deep Atlantic and deep Pacific seawater, is observed to occur in the global ocean. However, the inter-ocean fractionation of Nb/Ta is weaker due to a more uniform distribution of Nb and Ta in seawater. In contrast to open ocean seawater, Zr, Hf, Nb and Ta concentration at stations close to the continent in the Andaman Sea and Gulf of Thailand were highest in surface water decreasing through deep water, with Zr/Hf and Nb/Ta closer to continental crust ratios indicating significant terrestrial inputs of these elements to seawater. Results suggest that, in spite of the similar chemical properties of these geochemical twin pairs generating coherent fractionation in igneous rocks, strong fractionations of Zr–Hf and Nb–Ta takes place in aquatic environments such as seawater.

It is well known that the bioavailability and toxicity of trace metals such as copper, cadmium, z... more It is well known that the bioavailability and toxicity of trace metals such as copper, cadmium, zinc and mercury are not determined by their total concentration but by their chernical speciation. Addition o f free copper ions at a very low concentration stimulated nitrogen fixation and photosynthesis of phytoplankton population in Clear Lake California, but additional copper rapidly reduced activities of phytoplankton (HORNE & ÜOLDMAN 1994). A free copper ion concentration higher than l o-11 mo l/l in seawater reduces growth of phytoplankton, especially o f many dinoflagellate and cyanobacteria species (GAVIS et al. 1981, BRAND et al. 1986, CROOT et al. 2003). Almost all copper in natural water forms complexes with organic ligands (or su1fides), and the inorganic copper concentration, including free copper ion, is estimated to be very low based on speciation calculations. Estimating the effects o f trace metals on phytoplankton, organic speciation, including determination of the com...

Organic complexation affects the bioavailability and distribution of copper in the surface ocean.... more Organic complexation affects the bioavailability and distribution of copper in the surface ocean. The cyanobacterium Synechococcus sp. PCC 7002 was cultured in the lab and subjected to near-toxic Cu concentrations. Strong Cu-binding ligands were produced under these conditions, as found for other species of Synechococcus. The copper-binding ligand produced had a log K&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;cond. (log conditional stability constant) of 12.2, similar

In April 2001, a large dust storm originating in the Gobi and Takla Makan deserts resulted in lar... more In April 2001, a large dust storm originating in the Gobi and Takla Makan deserts resulted in large quantities of dust to be transported to the northeastern Pacific Ocean. Off the California coast, dissolved iron and aluminum concentrations determined before and after the dust traversed the North Pacific show increases of 0.5nM and 2nM respectively (Johnson, 2003). The most concentrated

Cd concentrations are relatively high in oysters harvested from the Pacific Northwest (mean 2.63 ... more Cd concentrations are relatively high in oysters harvested from the Pacific Northwest (mean 2.63 ppm, wet weight) when compared with those from the east coast (0.33 ppm, wet weight). The cause of the concentration discrepancy between coasts is unknown and may result from natural sources such as local geology and upwelling along the coast, or from anthropogenic sources such as mining, forestry, and urban runoff. This study investigates Cd isotopic variations in the marine environment and the potential use of Cd isotopes as a Cd tracer. Cd isotopic composition is determined for BC oyster tissue samples previously measured and found to have relatively high and low Cd concentrations, from both the east and west coasts of Vancouver Island. The study of natural variations in Cd isotopic composition is allowed by the advent of MC-ICPMS. The capability of the MC-ICPMS to measure small variations in Cd isotopic composition in biological matrices will be discussed including matrix effects. Prior to analysis, samples are digested and Cd is isolated using anion exchange chromatography following the method of Mason (2003). Cd isotopes were measured by dynamic multi-collection using a Nu Plasma MC-ICPMS following the methods reported by Wombacher et al. (2003). Reproducibility is estimated from repeat analysis of an in-house gravimetric standard which is prepared to give a del value of -10/00 on 110/111Cd. Measurements of this standard give delta110/111Cd = -0.993 ± 0.066 (2SD, n=13). Sample data is reported in delta notation per atomic mass unit. Isotopic variations were measured between BC oyster tissues, with values between -0.0960/00 and 0.1040/00. Preliminary evidence suggests no significant difference in Cd isotopes between the digestive (0.046) and non-digestive (0.104) tissues of a BC oyster. Data will also be presented for the east coast oyster, lobster hepatopancreas (CRM TORT-2) and BC sediment.

The rapidly changing conditions of the Arctic sea ice system have cascading impacts on t... more The rapidly changing conditions of the Arctic sea ice system have cascading impacts on the biogeochemical cycles of the ocean. Sea ice transports sediments, nutrients, trace metals, pollutants, and gases from the extensive continental shelves into the more isolated central basins. However, it is difficult to assess the net contribution of this supply mechanism on nutrients in the surface ocean. In this study, we used Manganese (Mn), a micronutrient and tracer which can integrate source fluctuations in space and time, to understand the net impact of the long range transport of sea ice for Mn.We developed a three-dimensional dissolved Mn model within a subdomain of the 1/12 degree Arctic and Northern Hemispheric Atlantic (ANHA12) configuration of NEMO centred on the Canadian Arctic Archipelago, and evaluated this model with in situ observations from the 2015 Canadian GEOTRACES cruises. The Mn model incorporates parameterizations for the contributions from river discharge, sediment resuspension, atmospheric deposition of aerosols directly to the ocean and via melt from sea ice, release of sediment from sea ice, and reversible scavenging, while the NEMO-TOP engine takes care of the advection and diffusion of the tracers. Simulations with this model from 2002 to 2019 indicate that the majority of external Mn contributed annually to the Canada Basin surface is released by sediment from sea ice, much of which originates from the Siberian shelves. Reduced sea ice longevity in the Siberian shelf regions has been postulated to result in the disruption of the long range transport of sea ice by the transpolar drift. This reduced sea ice supply has the potential to decrease the Canada Basin Mn surface maximum and downstream Mn supply, with implications for other nutrients (such as Fe) contained in ice-rafted sediments as well. These results demonstrate some of the many changes to the biogeochemical supply mechanisms expected in the near-future in the Arctic Ocean and the subpolar seas.

ABSTRACT Ventilation of Canadian Basin Deep Waters (CBDW) may provide a mechanism to export and p... more ABSTRACT Ventilation of Canadian Basin Deep Waters (CBDW) may provide a mechanism to export and preserve organic matter in the Arctic Ocean. Ventilation mechanisms of CBDW, however, are not fully understood. Multiple age models suggest CBDW ages of 300 -500 years. These ages may represent a single renewal event 500 years ago, a steady state average, indicative of ongoing ventilation processes, or a combination of past renewal and a possible recent cessation or decrease in the renewal of Canadian Basin Deep Water (CBDW). Past ventilation of CBDW may have been allowed by cooler, more dense, Atlantic waters. Current potential sources to CBDW include brine rejection during sea ice formation or prospective inputs from the Eurasian Basin via the Makarov Basin. This work examines utilization of O2 and NO3- data to identify markers of CBDW ventilation. Parameters investigated also include the calculated values of apparent oxygen utilization (AOU), NO (NO = 9NO3- + O2), and preformed NO3-. Calculation of conservative NO and preformed NO3- provide indicators of potential distinctive water mass sources along isopycnal surfaces across the Basin. Interannual comparisons allow evaluation of potentially differing source water mass signatures in different years. Application of this method is performed based on data from Louis S. St.-Laurent cruises from 2003 - 2009. Determination of CBDW ventilation is important to assess opportunities for carbon sequestration in the Arctic resulting from climate change, modification of spatial and temporal sea ice extent, and potential primary productivity shifts in the Arctic.

Geochimica et Cosmochimica Acta

Abstract Dissolved iron (DFe) and manganese (DMn) are essential micronutrients involved in vital ... more Abstract Dissolved iron (DFe) and manganese (DMn) are essential micronutrients involved in vital phytoplankton physiological pathways, and their deficit can limit primary production in otherwise nutrient-replete surface ocean waters. In this work we present the spatial distributions and biogeochemical cycling of these metals across the Canadian GEOTRACES transect in the Canadian Arctic Ocean during the summer and autumn of 2015. Surface concentrations are dominated by freshwater inputs showing a strong negative correlation with salinity, especially for DMn which behaves more conservatively than DFe. The highest surface concentrations were measured in the Canadian Arctic Archipelago (Fe: 0.401–1.91 and Mn: 4.33–9.54 nmol kg−1) and the Canada Basin (Fe: 0.225–0.479 and Mn: 3.93–7.02 nmol kg−1), regions highly influenced by riverine inputs, whereas the lowest values were found in the Labrador Sea (Fe: 0.106–0.362 and Mn: 0.450–1.09 nmol kg−1) where freshwater inputs diminished and phytoplankton uptake increased. Subsurface and deep water distributions for both metals are largely controlled by a complex balance between sources (advective inputs and organic matter remineralization) and removal processes. The subsurface peaks (∼100–300 m) observed in the Canada Basin (Fe: 0.541 ± 0.060 and Mn: 1.38 ± 0.42 nmol kg−1) and Baffin Bay (Fe: 0.753–1.03 nmol kg−1) were advected from the Chukchi Sea and the Canadian Arctic Archipelago respectively, where DFe and DMn are released from the benthic boundary layer in these shelf-dominated environments. Advective sources associated with the Arctic Circumpolar Boundary Current, rather than vertical fluxes of DFe and DMn in sinking particles, dominate metal distributions in the deep Canada Basin waters (>300 m). In the highly productive Baffin Bay and the Labrador Sea, organic matter remineralization is a notable source of DFe and DMn to deep waters. In the deepest waters (>1000 m), scavenging of DFe and DMn govern their vertical distributions; a pseudo-first order scavenging model explained the continuous removal of DMn in the Canada Basin, where the concentrations reach uniformly low concentrations (0.150 ± 0.004 nmol kg−1) after ∼400 years. Applying this DMn scavenging model we were able to estimate the age (120–190 years) of deep Baffin Bay waters, a topic of discussion for many years.

Chemical Geology

Abstract Trace metals are essential micronutrients for phytoplankton, as well as useful tracers o... more Abstract Trace metals are essential micronutrients for phytoplankton, as well as useful tracers of biogeochemical processes in aquatic systems. The largest Arctic rivers are known to play an important role in the cycling of trace metals in the Arctic Ocean; however, these systems account for little more than half of Arctic freshwater discharge, leaving a major gap in our understanding of the trace metal geochemistry from smaller river systems. This is especially problematic for rivers draining the Arctic coastal margins, as these continuous permafrost systems are anticipated to be particularly sensitive to climate change. This study presents the first observations of dissolved and particulate trace metal concentrations and lead isotopes in 14 rivers in the Canadian Arctic Archipelago (CAA). Dissolved concentrations of aluminum, iron, manganese, nickel, copper, zinc, cadmium, and lead display clear spatial variability in their distributions. Small rivers located in the central islands of the CAA have remarkably low concentrations of these trace metals, while the rivers draining the southern continental landmass have higher values. This geographic variability in dissolved metal concentrations reflects both differences in bedrock geology and the South-North environmental gradients in the Archipelago. We extrapolate these findings to estimate the dissolved trace metal concentrations for other rivers draining the CAA based on their geographic location. Elemental ratios measured in the suspended particulate matter in several rivers indicates a significant enrichment of nickel, copper, zinc, and lead over the crustal composition. In particular, lead isotope composition shows an extremely large range, varying from the highly radiogenic Tree River (206Pb/207Pb: 1.5121) in the south, to the relatively unradiogenic Glacier River (206Pb/207Pb: 1.0153) in the central CAA. Lack of correlation between the Pb isotopic composition and Pb enrichment, suggests Pb is derived from within the watershed. This work presents the first observations of dissolved and particulate trace metal concentrations in small coastal draining rivers from the CAA, an important first step in developing a baseline against which to evaluate future change in the high Arctic.

Chemie der Erde - Geochemistry, 2007

Trace elements serve important roles as regulators of ocean processes including marine ecosystem ... more Trace elements serve important roles as regulators of ocean processes including marine ecosystem dynamics and carbon cycling. The role of iron, for instance, is well known as a limiting micronutrient in the surface ocean. Several other trace elements also play crucial roles in ecosystem function and their supply therefore controls the structure, and possibly the productivity, of marine ecosystems. Understanding the biogeochemical cycling of these micronutrients requires knowledge of their diverse sources and sinks, as well as their transport and chemical form in the ocean. Much of what is known about past ocean conditions, and therefore about the processes driving global climate change, is derived from trace-element and isotope patterns recorded in marine deposits. Reading the geochemical information archived in marine sediments informs us about past changes in fundamental ocean conditions such as temperature, salinity, pH, carbon chemistry, ocean circulation and biological productivity. These records provide our principal source of information about the ocean's role in past climate change. Understanding this role offers unique insights into the future consequences of global change. The cycle of many trace elements and isotopes has been significantly impacted by human activity. Some of these are harmful to the natural and human environment due to their toxicity and/or radioactivity. Understanding the processes that control the transport and fate of these contaminants is an important aspect of protecting the ocean environment. Such understanding requires accurate knowledge of the natural biogeochemical cycling of these elements so that changes due to human activity can be put in context. Despite the recognised importance of understanding the geochemical cycles of trace elements and isotopes, limited knowledge of their sources and sinks in the ocean and the rates and mechanisms governing their internal cycling, constrains their application to illuminating the problems outlined above. Marine geochemists are poised to make significant progress in trace-element biogeochemistry. Advances in clean sampling protocols and analytical techniques provide unprecedented capability for high-density sampling and measurement of a wide range of trace elements and isotopes which can be combined with new modelling strategies that have evolved from the World Ocean Circulation Experiment (WOCE) and Joint Global Ocean Flux Study (JGOFS) programmes. A major new international research programme, GEOTRACES, has now been developed as a result of community input to study the global marine biogeochemical cycles of trace elements and their isotopes. Here, we describe this programme and its rationale.

Evolutionary Ecology, 1977

Systems of communal or cooperative breeding in which several adults help to feed one brood (Lack,... more Systems of communal or cooperative breeding in which several adults help to feed one brood (Lack, 1968, p. 72) have been considered to be relatively rare among birds, but recent evidence suggests strongly that the habit may be very widespread especially in tropical and subtropical regions (Fry, 1972; Harrison, 1969). An excellent review is provided by Brown (1974) who also discusses several theories for the evolution of this and related forms of breeding. He points out that known communal breeders are nearly all permanent residents in relatively stable habitats where their populations are likely to be at or close to the carrying capacity of the environment most of the time. He postulates that a period of K-selection, followed by a period of kin selection are the normal prerequisites for the evolution of communal breeding.

ACS Earth and Space Chemistry

This study addresses an important knowledge gap in the distribution of lead (Pb) in the Arctic Oc... more This study addresses an important knowledge gap in the distribution of lead (Pb) in the Arctic Ocean, by presenting dissolved Pb concentrations from samples collected during the GEOTRACES Canadian cruise in 2015. Dissolved Pb showed an increase in concentration from the Canada Basin toward Baffin Bay and the Labrador Sea. Canada Basin was the most isolated region from anthropogenic Pb inputs with low background concentrations (1.4−6.2 pmol kg −1) across most of the basin, although higher Pb features from the advection of Pacific-derived waters and sea ice meltwater were present. Likewise, high-Pb peaks (13.5−26.6 pmol kg −1) along narrow isopycnal surfaces (σ θ , 27.4−27.6) in Baffin Bay were attributed to the advection of North Atlantic waters spreading a high-Pb signature into the bay, contrasting with the low values (2.5−7.4 pmol kg −1) present in the mixed layer, Arctic and Baffin Bay deep waters. The Labrador Sea, largely influenced by the recirculation of North Atlantic waters, had the highest Pb concentrations (∼17−34 pmol kg −1) measured in this study. The Canadian Arctic Archipelago (CAA) represents a transition environment influenced by Arctic waters imprinting a low-Pb signature in the western CAA and the southern side of Parry Channel, while Baffin Bay waters prevailed in the eastern CAA recirculating westward along the northern side of Parry Channel and progressively losing their relatively high Pb signature. Extremely low concentrations were measured in Canada Basin and CAA waters, which reflect the remoteness of this region from anthropogenic inputs as well as the old ventilation age of deep waters' masses, providing a baseline for assessing future Pb studies. Finally, we successfully integrate modeling data with field observations demonstrating that dissolved lead, due to its distinctive anthropogenic signature in North Atlantic waters, can be a useful complementary tracer of water masses in the Canadian Arctic Ocean.

Environ Pollut, 2001

Field results have shown that Mytilus californianus is able to release its Cd concentrations sign... more Field results have shown that Mytilus californianus is able to release its Cd concentrations significantly in just a few days. The existing paradigm states that Cd elimination from Mytilus soft tissues is a very slow process. This discrepancy was investigated in the laboratory, testing the effect of two Cd levels (10 and 1 microgram l-1) on its release from Mytilus trossulus and M. californianus soft tissues. After exposure to 10 micrograms l-1, both species showed a significant uptake with no elimination after several days of depuration. After exposure to 1 microgram l-1, the responses were different. No significant Cd uptake was seen in M. trossulus while in M. californianus uptake was significant but returned to the background level after just 1 day of depuration. This response of M. californianus is consistent with that reported from field studies. These results are important for environmental monitoring programs since M. californianus has been used as equivalent to other Mytilus species in the assessment of Cd pollution.

Marine Chemistry, Mar 16, 2008

This paper demonstrates a method to isolate and characterise strong biogenic copper-binding ligan... more This paper demonstrates a method to isolate and characterise strong biogenic copper-binding ligands from an artificial seawater matrix. Pseudo-polarography is used to detect the ligands, determine their ionic strength-corrected binding constants, and track them through each step of the extraction process. Two ligand types are found, one strong and one relatively weak, with log K′ values of 49.4 ± 1.1 and 19.8 ± 5.5 respectively, assuming that the metal is bound as copper(II). If a copper(I) complex, the log K′ of the strong copper-binding ligand would be 25. Pseudo-polarography is then used to assess different resins for ligand extraction and to determine the eluent fraction in which the strong ligand is recovered. XAD-16 is found to be a suitable resin for extracting the strong binding ligand from salt water into methanol, suggesting that the ligand is weakly hydrophobic. As ligands are identified by their complexation of copper, no assumptions are made regarding the functional groups of these natural ligands. The copperbinding ligands are successfully extracted into solvents suitable for mass spectrometric analysis using soft ionisation methods such as electrospray and MALDI.

Egs Agu Eug Joint Assembly, Apr 1, 2003

Earth and Planetary Science Letters, 1986