Measurement of dark, particle-generated superoxide and hydrogen peroxide production and decay in the subtropical and temperate North Pacific Ocean

Abstract

Reactive oxygen species (ROS), which include the superoxide radical (O 2-) and hydrogen peroxide (H 2 O 2), are thought to be generated mostly through photochemical reactions and biological activity in seawater and can influence trace metal speciation in the ocean. This study reports the results of an intercomparison of two methods to measure particle-generated [O 2-concentrations that ranged from undetectable to 0.02 nM, with production rates less than 0.6 nM hr-1 and decay rate coefficients from 0.003 to 0.014 s-1. The southern California Current Ecosystem had particle-generated O 2 concentrations that ranged from undetectable to 0.05 nM, with production rates up to 4.7 nM hr-1 and decay rate coefficients from 0.006 to 0.017 s-1. H 2 O 2 concentrations were measured by chemiluminescence detection, using dark incubations of unfiltered water samples to simultaneously determine production and decay rates. H 2 O 2 concentrations at Station ALOHA ranged from 7 to 88 nM. Dark production rates and decay rate coefficients were low (mostly <1.5 nM hr-1 and <0.03 hr-1 , respectively); higher values were detected when biota were pre-concentrated with net tows. These rates of ROS production are lower than those reported by previous studies in other regions of the Pacific Ocean, but could still be significant compared to photochemical production.

Species-specific control of external superoxide levels by the coral holobiont during a natural bleaching event

“…1). Background superoxide levels within the reef seawater located at the same depth as the corals but >10 cm from their surface ranged from 4 to 11 nM—values consistent with previously reported superoxide levels in productive marine waters but up to several orders of magnitude higher than in typical open ocean sites3536373839. Average superoxide concentrations measured only millimetres above coral surfaces ranged from levels below bulk seawater ( M. capitata ) to steady-state concentrations that were ∼120 nM higher than bulk seawater ( P. lobata ) (Fig.…”

“…To measure superoxide, both the analyte solution and the MCLA reagent are independently flushed through the FeLume system at an identical flow rate using a peristaltic pump. The MCLA reagent consisted of 4.0 μM MCLA (similar to concentrations used previously and by other investigators38397071) in 0.10 M MES with 50 μM DTPA adjusted to pH 6.0. The solutions converge in a spiral flow cell immediately adjacent to a photomultiplier tube, which continuously acquires data that is displayed in real time using a PC interface.…”

Ammonia Oxidation in the Ocean Can Be Inhibited by Nanomolar Concentrations of Hydrogen Peroxide

“…There are also biological sources of ROS; phytoplankton produce H 2 O 2 as part of their metabolism during photosynthesis and respiration ( Figure 1A; Palenik et al, 1987;Zepp et al, 1987;Palenik and Morel, 1988) up to 0.46 nmol h −1 cell −1 (Twiner and Trick, 2000), though some pathways are not directly linked to photosynthesis. Extracellular biological ROS production (O − 2 and H 2 O 2 , specifically; Figure 1D) in the absence of light has also been observed, with rates 0.01-11 nM h −1 (Palenik and Morel, 1988;Moffett and Zafiriou, 1990;Roe et al, 2016) that have been attributed to microorganisms such as heterotrophic bacteria and phytoplankton (Palenik et al, 1987;Rose et al, 2008;Diaz et al, 2013).…”

Cross‐protection from hydrogen peroxide by helper microbes: the impacts on the cyanobacterium Prochlorococcus and other beneficiaries in marine communities

“…O 2 2 may also be generated aphotically from reduced labile redoxactive compounds (LRAC) such as metals and DOM. Finally, O 2 2 can be generated biologically by microbes, at rates that approach photochemical production measurements (Micinski et al, 1993;Petasne and Zika, 1997;Rose et al, 2008;Hansard et al, 2010;Shaked et al, 2010;Roe et al, 2016). The relative contribution of this LRAC redox cycling pathway to O 2 2 formation is unknown but under current investigation (Rose, 2012;2016).…”