Aquatic Sciences Meeting, Albuquerque 2001

SS02 Photochemical Reactions In Surface Waters: A Major Issue in the 21st Century? (Environmental Connections)

Date: Thursday, February 15, 2001, Time: 4:30:00 PM

Location: San Miguel

Willey, J, D, University of North Carolina at Wilmington, Wilmington, NC, USA, willeyj@uncwil.edu

Kieber, R, J, University of North Carolina at Wilmington, Wilmington, NC, USA, kieberr@uncwil.edu

Avery, G, B, University of North Carolina at Wilmington, Wilmington, NC, USA, averyg@uncwil.edu

EFFECTS OF RAINWATER Fe(II), Fe(III), AND HYDROGEN PEROXIDE ON CHLOROPHYLL a IN BERMUDA AREA TIME SERIES STATION SEAWATER BIOASSAYS: A DELICATE BALANCE

Our recent study of iron speciation in marine rain defines for the first time realistic concentrations of Fe(II) and Fe(III) deposited to the open ocean via rainwater. These environmentally realistic concentrations of both Fe(II) and Fe(III) were used in several bioassays to investigate the potential link between rainwater iron and marine phytoplankton productivity. No iron response was observed in iron addition bioassays conducted in August 1999 during a Saharan dust storm at the Bermuda Area Time Series Station (BATS). The seawater chlorophyll a content in both three-day bioassays conducted at BATS during the spring plankton bloom in March 2000 increased approximately 50% after addition of synthetic rain containing either FeCl2 or FeCl3 added as a 2% dilution by rain. The presence of hydrogen peroxide equivalent to 20 uM in rain completely removed the chlorophyll a response to iron additions, suggesting that stimulation of phytoplankton by rainwater iron can at times be suppressed by rainwater hydrogen peroxide. These results indicate the response of marine phytoplankton to rainwater is complex, and varies from storm to storm depending upon both iron addition and hydrogen peroxide concentration.

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Aquatic Sciences Meeting, Albuquerque 2001

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