Accomplishments & Reports: Hydrogen Peroxide - Distributions, Sources and Sinks

D. Karl, D. Pence and G. Tien
University of Hawaii, SOEST, Department of Oceanography
Honolulu, HI 96822
(dkarl@soest.hawaii.edu)

Our interest in studying hydrogen peroxide (H₂O₂) dynamics in the Southern Ocean was inspired by two potential ecological applications of these data. First, it has been suggested that H₂O₂ concentrations, when coupled with production and decay rates, can be used as a tracer for vertical advection in surface ocean waters (Johnson et al. 1989). To the extent that mixed- layer dynamics are critical to our understanding of microbial rate processes, especially net photosynthesis (see Mitchell and Holm-Hansen 1991) this information is fundamental to the objectives of the Palmer LTER program. Second, because H₂O₂ is a common intermediate or reaction product of photochemical reactions of oxygen with organic compounds (Zafiriou 1983), H₂O₂ fluxes may provide information on photochemical alteration of dissolved organic matter in seawater. Recent studies suggest that photochemical processes may plan a previously unrecognized role in the global carbon cycle (Mopper and Zhou 1990).

Previous research efforts in the LTER study region have documented regional and depth- dependent variability in H₂O₂ concentrations (Resing et al. 1993) and have identified several local H₂O₂ sources and sinks (Tien and Karl 1993), including photochemical interactions with dissolved organic matter (Karl and Resing 1993).

During PD94-12 and PD95-01 we had an opportunity to continue our regional surveys to provide data on interannual concentration variability and production rates following a "heavy" ice year (1994). During the SANTA CLAµS cruise, 15 depth profiles of H₂O₂ concentration were obtained as part of the "LTER Microbiology and Carbon Flux" core measurement program. In addition, numerous experiments were conducted including but not limited to: (1) dark H₂O₂ decay rates, (2) light-stimulated and uv light-stimulated H₂O₂ production rates and (3) organic addition perturbation studies. We also obtained data from diver (S-028) collected sea ice samples and from freshly fallen snow. At Paradise Harbor, we obtained measurements on H₂O₂ concentrations during a comprehensive 3-day diel variability experiment that included most of the other biogeochemical core measurements that should provide invaluable data on coupled microbial rate processes. Finally, H₂O₂ concentrations were measured across Drake Passage along with other ecosystem variables.

References

Johnson, K. S., S. W. Willason, D. A. Wiesenburg, S. E. Lohrenz and R. A. Arnone. 1989. Hydrogen peroxide in the western Mediterranean Sea: A tracer for vertical advection. Deep- Sea Research 36: 241-254.

Karl, D. M. and J. Resing. 1993. Palmer LTER: Hydrogen peroxide in the Palmer LTER region: IV. Photochemical interactions with dissolved organic matter. Antarctic Journal of the United States 28: 231-234.

Mitchell, B. G. and O. Holm-Hansen. 1991. Observations and modeling of the antarctic phytoplankton crop in relation to mixing depth. Deep-Sea Research 28: 981-1007.

Mopper, K. and X. Zhou. 1990. Hydroxyl radical photoproduction in the sea and its potential impact on marine processes. Science 250: 661-664.

Resing, J., G. Tien, R. Letelier, D. M. Karl and D. Jones. 1993. Palmer LTER: Hydrogen peroxide in the Palmer-LTER region: II. Water column distributions. Antarctic Journal of the United States 28: 227-229.

Tien, G. and D. Karl. 1993. Palmer LTER: Hydrogen peroxide in the Palmer-LTER region: III. Local sources and sinks. Antarctic Journal of the United States 28: 229-230.

Zafiriou, O. C. 1983. Natural water photochemistry. In: J. P. Riley & R. Chester (eds.), Chemical Oceanography (vol. 8), Academic Press, New York.