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Analytical Chemistry in Oceanography

“Analytical Chemistry in Oceanography” Analytical Chemistry 64 (1992): 1065A-1075A.
Kenneth S. Johnson, Kenneth H. Coale, and Hans W. Jannasch

Chemical measurements in the ocean involve a unique set of challenges related to the distinctive composition of seawater, the large spatial and temporal scales over which measurements are made, and the frequent need to perform analyses while at sea under difficult conditions. These problems are not familiar to many analytical chemists, in part because it is unusual to find chemical oceanographers or geochemists in close contact with their chemistry colleagues (1).

Chemical oceanography has been practiced primarily in departments or institutions oriented toward marine or environmental sciences. Our chemical understanding of the ocean is, however, directly linked to the development of the latest analytical tools and advances in chemistry and engineering. A report soon to be issued by the National Research Council states that a significant increase is needed in our abilities to observe ocean chemistry and to study the biological, physical, and chemical (biogeochemical) processes that control the flow of chemicals through the ocean and its linkage with the atmosphere (2). Rapid improvements in the methods of chemical analysis available to the oceanographers are needed, particularly with respect to sensors that can operate in situ and unattended for long periods of time on deep-sea moorings. These advances will require much closer cooperation between the analytical chemistry and chemical oceanography communities.

Increasing attention has been focused on ocean chemistry because of civilization’s impact on the flow of chemicals through the sea. On a local scale, nutrient loading from sources such as sewage plants or runoff from farmland (e.g., ammonia, nitrates, and phosphates) can lead to increased rates of plant production, or eutrophication, in surface waters. Eutrophication is linked to toxic phytoplankton blooms (e.g., red tides) and the greater oxygen demand in the subsurface waters. Increasing anoxia in the water column attributable to eutrophication has had a negative impact on marine resources in both the New York Bight (3) and the Chesapeake Bay (4). A single episode of anoxia in the New York Bight resulted in a $60 million loss to surf-clam fishery alone (3). In many cases, the impacts of these perturbations are not recognized or understood because we lack records of natural chemical variability in the marine environment or an adequate means to monitor it (5).

On a global scale, the flow of chemicals through the ocean system is closely linked to the climate. The ocean holds 60 times more inorganic carbon than does the atmosphere, and phosphates perturbations in the flow of CO2 through the ocean are related to changes in atmospheric CO2 and global temperature (6). Release of CO2 from the burning of fossil fuels, which has resulted in a 30% increase in atmospheric CO2 since 1850, has the potential to produce even greater climatic changes than were experienced over the last glacial cycle (7). Much of this CO2 will enter the ocean, but the rates CO2 absorption in seawater are not yet well known (8). Rapid changes in ocean circulation may produce large CO2 fluxes between the ocean and the atmosphere (9); small changes in ocean chemistry may also draw large amounts of CO2 from the atmosphere and regulate climate (10).