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New and Regenerated Productivity References

1967 Dugdale, R.C., and J.J. Goering. 1967. Uptake of new and regenerated forms of nitrogen in primary production. Limnol. Oceanogr. 12:196-206.

1967 Dugdale, R.C. 1967. Nutrient limitation in the sea: Dynamics, identification and significance. Limnol. Oceanogr. 12:655-695.

1969 MacIsaac, J.J., and R.C. Dugdale. 1969. The kinetics of nitrate and ammonia uptake by natural populations of marine phytoplankton. Deep-Sea Res. 16:47-58.

1969 Eppley, R.W., J.N. Rogers, and J.J. McCarthy. 1969. Half-saturation constants for uptake of nitrate and ammonium by marine phytoplankton. Limnol. Oceanogr. 14:912-920.

1979 Eppley R.W., and B.J. Peterson. 1979. Particulate organic matter flux and planktonic new production in the deep ocean. Nature 282:677-680.

How Zooplankton Swim, Feed, and Breed

Zooplankton live in a medium that, to them, is viscous and structured (Koehl, 1993). The process of capturing food does not involve passive sieving as much as it involves purposeful ingestion of particular food targets (see references below). Phytoplankton and other tasty prey items leave a chemical trail in the viscous water, and zooplankton follow such trails to find and eat a particular victim. Data suggest that the same process is at work in finding mates (Howlett, 1998; Yen et al., 1998). This view of the zooplankton world strains our credulity: because of our size, we cannot easily comprehend the low Reynolds number world in which zooplankton—especially copepods and smaller—swim, feed, and breed. This work showed us a world that is very common on our planet, but beyond our ken.

This new understanding has come in large part from the intellectual prodding of a single individual, Rudy Strickler, although he has had some very capable collaborators such as Mimi Koehl, Gus Paffenhöfer, Holly Price, Jeanette Yen, and others. A fascinating thing about this breakthrough is that it was immediately adopted by the field and entrained into the mainstream ideas. Zooplankton "gurus" such as Bruce Frost, Charlie Miller, Mike Roman, Sharon Smith, and Peter Wiebe had prepared the way for rapid assimilation of these new ideas by arguing that zooplankton feeding is selective and purposeful. Miller, in particular, had long emphasized that copepods fed in a viscous medium. Strickler's innovative high-speed movies of live copepod feeding showed how selectivity is realized. The technical breakthrough that made this advance possible was microcinematography. In this case, live copepods superglued to a dog hair on a microscope slide were filmed with a high-speed, strobe movie camera focused on the tethered animal. Innovation has many faces. NSF was the major source of support for this innovative work, which is continuing at an accelerated pace, but the Office of Naval Research (ONR) has also been a significant patron.

How Zooplankton Swim, Feed, and Breed References

1977 Hamner, P., and W.M. Hamner. 1977. Chemosensory tracking of scent trails by the planktonic shrimp Acetes sibogae australis. Science 195:886-888.

1977 Rubenstein, D.I., and M.A.R. Koehl. 1977. The mechanisms of filter feeding: Some theoretical considerations. Amer. Nat. 111:981-994.

1980 Alcaraz, M., G.A. Paffenhöfer, and J.R. Strickler. 1980. Catching the algae: A first account of visual observations on filter feeding calanoids. Pp. 241-248 in W.C. Kerfoot (ed.), Evolution and Ecology of Zooplankton Communities. University Press of New England, Biddefort, Maine.

1981 Koehl, M.A.R., and J.R. Strickler. 1981. Copepod feeding currents: Food capture at low Reynolds number. Limnol. Oceanogr. 26:1062-1073.

1982 Paffenhöfer, G.A., J.R. Strickler, and M. Alcaraz. 1982. Suspension-feeding by herbivorous calanoid copepods: A cinematographic study. Mar. Biol . 67:193-199.

1982 Strickler, J.R. 1982. Calanoid copepods, feeding currents, and the role of gravity. Science 218:158-160.

1983 Price, J.J., G.A. Paffenhöfer, and J.R. Strickler. 1983. Modes of cell capture in calanoid copepods. Limnol. Oceanogr. 28:116-123.

1993 Koehl, M.A.R. 1993. Hairy little legs: Feeding, smelling, and swimming at low Reynolds number. Contemp Math. 141:33-64.

1998 Howlett, R. 1998. Sex and the single copepod. Nature 394:423-425.

1998 Yen, J., M.J. Weissburg, and M.H. Doall. 1998 The fluid physics of signal perception by mate-tracking copepods. Phil. Trans. R. Soc. Lond. 353:787-804.

Iron Hypothesis

The iron issue is an example of classic science progress:

  1. There was a nagging question.

  2. A tentative explanation was advanced.

  3. Available data did not support the explanation.

  4. The data, however, were suspect.

  5. A technical (analytical) breakthrough was made.

  6. The new data suggested an hypothesis.

  7. The hypothesis was tested and confirmed.

  8. Textbooks had to be revised.

For the iron issue the nagging question was: Why do excess plant nutrients persist in the surface ocean in certain regions such as the Antarctic, equatorial Pacific, and Northeast Pacific? For 50 years there had been speculation that iron limitation might be a factor, but measurements showed there was abundant iron in seawater.

John Martin set out to improve the analytical chemistry of iron, and when he had done so, he found that iron was much less abundant in the ocean than previously thought. Martin's innovations in iron chemistry alone would have earned him a place in history, but John Martin continued his quest with great zest. In a 1990 paper in Paleoceanography , he published the "Iron Hypothesis," which proposed that glacial-interglacial changes in atmospheric carbon dioxide were driven by variations in dryness, dust, and iron that forced



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