ENHANCEMENT OF CHLOROPHYLL-A PRODUCTION IN GULF-STREAM SURFACE SEAWATER BY RAINWATER NITRATE

The concentration of nitrate commonly found in rain from continental storm systems passing over eastern North Carolina was sufficient to stimulate chlorophyll a production in surface Gulf Stream water collected over the continental slope near Cape Hatteras, NC, in mid-October 1989. Two bioassay experiments were conducted on board ship by mixing Gulf Stream surface seawater with synthetic rainwater (5% rainwater). These bioassays indicated an increased production of chlorophyll a in response to rainwater nitrate but not phosphate. The response was apparent after incubation for 2 days, and the chlorophyll a concentrations increased approximately 2.5 times relative to controls in both experiments.