J i eld notes 



Tracking the Travels of 



tcfesmiufti 



A large, orange-brown slick was 

 spotted in late October off Bogue and 

 Shackleford banks and extended 

 offshore to the Gulf Stream. The 

 bloom's reddish color immediately 

 set off alarms in coastal North 

 Carolina, where fishermen and 

 residents alike remember another 

 reddish bloom that sent 

 seafood sales plummet- 

 ing. 



Those reddish waters 

 bore a toxic dinoflagel- 

 late called red tide. 



But this year's 

 coloration had nothing 

 to do with that di- 

 noflagellate. 



Instead, this large 

 surface slick was a 

 harmless blue-green 

 algae, known scientifi- 

 cally as Trichodesmium. 



Hans Paerl, a Sea 

 Grant researcher at the 

 University of North 

 Carolina Institute of 

 Marine Sciences, says the slick 

 stretched 30 to 40 miles, making it 

 the largest Trichodesmium (pro- 

 nounced trick-o-des-me-um) bloom 

 that he has ever witnessed in Tar Heel 

 coastal waters. 



Trichodesmium is not toxic and 

 did nothing more than color the 

 water, Paerl says. The algae had a 

 distinctive "earthy" smell, particularly 

 in large concentrations. 



Sea Grant's algae specialist says 

 the bloom spun ashore on a Gulf 

 Stream eddy, and its arrival was 

 predictable. From the first of August 

 to mid-November, the Gulf Stream 

 hugs closer to the Tar Heel shoreline, 

 and nearshore waters are at their 

 warmest. Add extended periods of 

 calm, dog-day-like weather to the 



equation, and it's a perfect recipe for 

 algal blooms, Paerl says. 



Although the algae posed no threat 

 to people, fish or shellfish, Paerl says 

 Trichodesmium is worth some re- 

 search. The tiny algae possess some 

 scientifically interesting traits that 

 might actually be a bonus to the 



Low magnification picture of a puff-shaped radial colony of 

 aggregated filaments of Trichodesmium. 



productivity of the marine ecosystem. 



Trichodesmium is capable of 

 taking, or "fixing," nitrogen from the 

 atmosphere and biochemically convert- 

 ing it to ammonia, a nutrient vital to its 

 own growth and the growth of other 

 marine organisms. This characteristic is 

 uncommon, but Paerl is unsure how the 

 nitrogen is transferred from the algae to 

 the food chain. 



The algae may be eaten directly by 

 other organisms. Or, when the 

 Trichodesmium die and break open, the 

 nitrogen released into the ecosystem 

 could be assimilated by other organ- 

 isms and passed up the food chain. 



Then again, bacteria that feed on 

 the algae may be the transfer link 

 between the nitrogen and the marine 

 food web. 



Right now, Paerl doesn't know 

 how the nutrient transfer occurs, but 

 he hopes that laboratory experiments 

 will reveal some answers. His labora- 

 tory is one of only two in the world 

 capable of culturing Trichodesmium 

 outside of the natural environment. 

 As part of his Sea Grant project, 



Paerl is also determining a 

 pigment spectrum 

 "fingerprint" on the 

 Trichodesmium algae. By 

 evaluating the type of 

 algal pigment and 

 concentration, Paerl may 

 soon be able to pinpoint 

 algal blooms by color, or 

 spectral, analysis from a 

 satellite orbiting Earth. 



Next year, NASA 

 plans to launch a 

 SeaWiFS satellite, 

 which will be capable of 

 performing detailed 

 spectral analyses. 



Currently, Paerl is 

 investigating the use of 

 thermal infrared satellite technology 

 for bloom detection. The Tricho- 

 desmium blooms are dense and reflect 

 light in the infrared region of the 

 spectrum, which means they can be 

 detected from currently deployed 

 satellites. 



But Paerl believes the SeaWiFS 

 satellite will do a better job of tracking 

 Trichodesmium and other forms of 

 algae and dinoflagellates such as red 

 tide. 



Now, researchers must spend 

 hours sampling large stretches of 

 water to characterize a bloom. 

 Satellite detection could help scientists 

 predict blooms and determine their 

 movement and density without ever 

 leaving the laboratory. 



ByKathyHart 



COASTWATCH 21 



