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Hogle, SL, Thrash JC, Dupont CL, Barbeau KA.  2016.  Trace metal acquisition by marine heterotrophic bacterioplankton with contrasting trophic strategies. Applied and Environmental Microbiology. 82:1613-1624.   10.1128/aem.03128-15   AbstractWebsite

Heterotrophic bacteria in the SAR11 and Roseobacter lineages shape the marine carbon, nitrogen, phosphorous, and sulfur cycles, yet they do so having adopted divergent ecological strategies. Currently, it is unknown whether these globally significant groups partition into specific niches with respect to micronutrients (e.g., trace metals) and how that may affect marine trace metal cycling. Here, we used comparative genomics to identify diverse iron, cobalt, nickel, copper, and zinc uptake capabilities in SAR11 and Roseobacter genomes and uncover surprising unevenness within and between lineages. The strongest predictors for the extent of the metal uptake gene content are the total number of transporters per genome, genome size, total metal transporters, and GC content, but numerous exceptions exist in both groups. Taken together, our results suggest that SAR11 have strongly minimized their trace metal uptake versatility, with high-affinity zinc uptake being a unique exception. The larger Roseobacter genomes have greater trace metal uptake versatility on average, but they also appear to have greater plasticity, resulting in phylogenetically similar genomes having largely different capabilities. Ultimately, phylogeny is predictive of the diversity and extent of 20 to 33% of all metal uptake systems, suggesting that specialization in metal utilization mostly occurred independently from overall lineage diversification in both SAR11 and Roseobacter. We interpret these results as reflecting relatively recent trace metal niche partitioning in both lineages, suggesting that concentrations and chemical forms of metals in the marine environment are important factors shaping the gene content of marine heterotrophic Alphaproteobacteria of the SAR11 and Roseobacter lineages.

Semeniuk, DM, Taylor RL, Bundy RM, Johnson WK, Cullen JT, Robert M, Barbeau KA, Maldonado MT.  2016.  Iron-copper interactions in iron-limited phytoplankton in the northeast subarctic Pacific Ocean. Limnology and Oceanography. 61:279-297.   10.1002/lno.10210   AbstractWebsite

In August 2010, iron (Fe) and Fe and copper (Cu) addition incubation experiments were conducted at two low Fe stations (P20 and P26) along Line P, off the western coast of British Columbia, to investigate Cu physiology in Fe- and Fe-light co-limited phytoplankton. Chlorophyll a concentrations ([Chl a]), maximum variable fluorescence yield (F-v/F-m), and Fe uptake rates by the Cu-dependent high-affinity Fe transport system (HAFeTS) were measured. Additions of Fe resulted in an increase in [Chl a] and F-v/F-m at both stations compared with the controls, regardless of light availability, and confirmed that the phytoplankton communities were Fe-limited. Uptake of Fe by the HAFeTS in both incubations increased with the addition of Fe, and likely reflects luxury Fe uptake and storage. While the in situ inorganic Cu concentrations were similar to those that can induce Cu-limitation in laboratory cultures, increasing Cu availability had no effect on biomass accumulation during both incubations, regardless of Fe availability or light regime. At P26, additions of 1 nmol L-1 CuSO4 resulted in a short-term increase in F-v/F-m of the phytoplankton community, and an increase in Fe uptake rates by large phytoplankton (>5 mu m), but only when light was not limiting. These data confirm a complex interaction between light, Fe and Cu physiology in indigenous phytoplankton communities, and suggest that these interactions may be both spatially heterogeneous and different for different phytoplankton size classes.

Earley, PJ, Swope BL, Barbeau K, Bundy R, McDonald JA, Rivera-Duarte I.  2014.  Life cycle contributions of copper from vessel painting and maintenance activities. Biofouling. 30:51-68.   10.1080/08927014.2013.841891   AbstractWebsite

Copper-based epoxy and ablative antifouling painted panels were exposed in natural seawater to evaluate environmental loading parameters. In situ loading factors including initial exposure, passive leaching, and surface refreshment were measured utilizing two protocols developed by the US Navy: the dome method and the in-water hull cleaning sampling method. Cleaning techniques investigated included a soft-pile carpet and a medium duty 3M((TM)) pad for fouling removal. Results show that the passive leach rates of copper peaked three days after both initial deployment and cleaning events (CEs), followed by a rapid decrease over about 15days and a slow approach to asymptotic levels on approximately day 30. Additionally, copper was more bioavailable during a CE in comparison to the passive leaching that immediately followed. A paint life cycle model quantifying annual copper loading estimates for each paint and cleaning method based on a three-year cycle of painting, episodic cleaning, and passive leaching is presented.

Bundy, RM, Barbeau KA, Buck KN.  2013.  Sources of strong copper-binding ligands in Antarctic Peninsula surface waters. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 90:134-146.   10.1016/j.dsr2.2012.07.023   AbstractWebsite

Copper-binding organic ligands were measured during austral winter in surface waters around the Antarctic Peninsula using competitive ligand exchange-adsorptive cathodic stripping voltammetry with multiple analytical windows. Samples were collected from four distinct water masses including the Antarctic Circumpolar Current, Southern Antarctic Circumpolar Current Front, Bransfield Strait, and the shelf region of the Antarctic Peninsula. Strong copper-binding organic ligands were detected in each water mass. The strongest copper-binding ligands were detected at the highest competition strength in the Antarctic Circumpolar Current, with an average conditional stability constant of logK(CuL,Cu2+)(cond) = 16.00 +/- 0.82. The weakest ligands were found at the lowest competition strength in the shelf region with logK(CuL,Cu2+)(cond) = 12.68 +/- 0.48. No ligands with stability constants less than logK(CuL,Cu2+)(cond) = 13.5 were detected in the Antarctic Circumpolar Current at any competition strength, suggesting a shelf source of weaker copper-binding ligands. Free, hydrated copper ion concentrations, the biologically available form of dissolved copper, were less than 10(-14) M in all samples, approaching levels that may be limiting for some types of inducible iron acquisition. (C) 2012 Elsevier Ltd. All rights reserved.