concerns about the ultimate exposure of marine life and the critical pathways back to people through the sea. Of course, the introduction of radioactive elements from the weapons testing that continued through the mid-1960s also provided tracers that would become important in verifying and contributing to advances in our understanding of oceanic processes. In one sense, this was an experiment, albeit an experiment that rational scientists would not design and execute deliberately. However, oceanographers would have been remiss in not taking advantage of the tracers introduced by nuclear weapons testing.

Among those responding to this important challenge was Vaughan T. Bowen, a zoologist who received his Ph.D. at Yale University, studying with Professor G. Evelyn Hutchinson. Bowen had been recruited to the Woods Hole Oceanographic Institution by Alfred Redfield and had been studying the distribution of major and minor elements in marine organisms. Under his leadership, Bowen's research group began conducting research on the biogeochemical cycles of radioactive elements entering the oceans, an effort that Bowen pursued until his retirement in the mid-1980s. Bowen and Sugihara (1957) were among the first in the world to publish data on strontium-90 activity in seawater according to compilations prepared in 1971 (NAS, 1971b)—the first of many papers from this group to contribute to our knowledge of biogeochemical cycles of artificial radionuclides in the oceans. Koczy (1956) was another of the pioneers studying the geochemistry of radioactive elements in the ocean.

This was the decade of explosive growth and maturation in chemical oceanography, marine geochemistry, and marine chemistry. The decade began with the publication of the papers by Sillen (1961) and Broecker et al. (1960, 1961), mentioned earlier, followed by the important papers of Garrels and co-workers (Garrels et al., 1961; Garrels and Thompson, 1962). These efforts of Bob Garrels eventually led to the very productive and influential collaboration with Fred MacKensie and to the influential book Evolution of Sedimentary Rocks (Garrels and MacKensie, 1971).

In 1963, the paper that summarized the thinking and work of Alfred C. Redfield and coworkers on the influence of the chemical composition of organisms, mainly plankton, on the chemical composition of seawater—the famous Redfield or RKR (Redfield, Ketchum, and Richards) ratio (Redfield et al., 1963) was published. In an interview with his daughter (Marsh, 1973), Redfield attributes the origin of that idea to an earlier paper (Redfield, 1958).

Many more scientists were becoming engaged in analyses of seawater for nutrients and other chemicals. In an influential attempt to codify some of the important lessons learned to date, Strickland and Parsons (1965) published their first manual about seawater analysis, which would be followed by a second edition several years later (Strickland and Parsons, 1972). Francis Richards summarized the state of knowledge and importance of studying anoxic basins (Richards, 1965), stimulating several expeditions in future years to the Cariaco Trench and Black Sea (and several fjords) to study the details of biogeochemistry at the interface of oxic and anoxic waters and in anoxic waters.

Scholarship contributions are at the heart of the intellectual enterprise. In addition, organizational leaders with vision, who are also excellent scientists in their own areas of expertise, are important to move fields of research forward. John M. Hunt is this type of person. In 1964, John Hunt was hired away from Carter Oil Company (a subsidiary of Standard Oil of New Jersey) to head the newly formed Chemistry and Geology Department at the Woods Hole Oceanographic Institution. John would chair this department, and later the separate Chemistry Department, for a decade. John made his most important scholarly research contributions in the field of petroleum geochemistry (Dow, 1992). Of equal importance, John Hunt had a lasting impact on marine chemistry, geochemistry, and chemical oceanography through his efforts to build the Chemistry and Geology Department, and later the Chemistry Department, at the Woods Hole Oceanographic Institution with appointments of a diverse group of researchers to yield one of the better marine chemistry and geochemistry departments in the world (Dow, 1992).

During the 1960s, and continuing to the present, C. David Keeling launched into a time-series measurement of carbon dioxide in the atmosphere (e.g., Keeling, 1973; Keeling et al., 1976a,b). This intense focus by Keeling and collaborators on a time-series certainly numbers among the more important individual research group efforts in marine geochemistry and atmospheric chemistry of' the entire period from 1950 to the present. His data, plotted as concentration of carbon dioxide in the atmosphere versus time at the Mauna Loa, Hawaii, sampling station. have become known worldwide among scientists and environmental policy and management practitioners, inclading heads of state.

From my perspective, Revelle and Suess sounded the alarm about the potentially serious climatic consequences of modern civilization's use of fossil fuels, the resultant increase of carbon dioxide in the atmosphere, and the role of the ocean in the global carbon cycle. Keeling and coworkers provided the data documenting the increase of carbon dioxide in the atmosphere attributable to fossil fael combustion and limestone use.

Keeling's data also begged the question of understanding the magnitude of the exchange of cartoon dioxide between the atmosphere and the ocean. This required not only an understanding of air-sea exchange processes, but also an understanding of the general circulation and mixing time of