MEPS 178:145-150 (1999)  -  doi:10.3354/meps178145

Impact of rainwater hydrogen peroxide on chlorophyll a content of surface Gulf Stream seawater off North Carolina, USA

Joan D. Willey1,*, Hans W. Paerl2, Malia Go2

1Department of Chemistry and Marine Science Program, University of North Carolina at Wilmington, 601 S. College Road, Wilmington, North Carolina 28403-3297, USA
2Institute of Marine Sciences, University of North Carolina at Chapel Hill, 3431 Arendell Street, Morehead City, North Carolina 28557, USA

ABSTRACT: Bioassays indicate addition of hydrogen peroxide in concentrations similar to rain sometimes decreases chlorophyll a (chl a) production in surface Gulf Stream seawater. Bioassays were conducted on shipboard in the spring and autumn of 1993, 1994, and 1995, using surface Gulf Stream seawater collected off the coast of North Carolina. Chl a increases were observed after addition of FeCl3 (in 1 of 5 bioassays), iron (III) EDTA (6 of 6 bioassays), or EDTA alone (4 of 4 bioassays). The chl a increases were suppressed significantly in 7 of 11 of these bioassays when the bioassay seawater was initially diluted by 1% with a 30 or 40 µM solution of hydrogen peroxide (a concentration similar to rainwater). Hydrogen peroxide induced inhibition of chl a production was not observed in bioassays in which chl a increased in response to addition of nitrate or ammonium, hence the growth inhibition was associated with added metal or complexing agent. Rainwater therefore plays a complex role in primary productivity in surface seawater, with the specific effect dependent upon rainwater concentrations of nitrate, ammonium, trace metals and hydrogen peroxide, as well as on the extent of nitrogen limitation and the oxidant concentration in the surface seawater.


KEY WORDS: Hydrogen peroxide · Rainwater · Chlorophyll a · Bioassays · Gulf Stream · Seawater


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