Abstract-We examined uncertainties associated with the routine computation of 0, solubility (C,,*) at 1 atm total pressure in pure water and seawater in equilibrium with air as a function of temperature and salinity. We propose formulae expressing C,* (at STP, real gas) in cm3 dm-3 and pmol kg-' in the range (tF L t z 40°C; 0 2 S 1 42%~) based on a fit to precise data selected from the literature.

No abstract

The submarine hydrothermal activity on and near the Galápagos Rift has been explored with the aid of the deep submersible Alvin. Analyses of water samples from hydrothermal vents reveal that hydrothermal activity provides significant or dominant sources and sinks for several components of seawater; studies of conductive and convective heat transfer suggest that two-thirds of the heat lost from new oceanic lithosphere at the Galápagos Rift in the first million years may be vented from thermal springs, predominantly along the axial ridge within the rift valley. The vent areas are populated by animal communities. They appear to utilize chemosynthesis by sulfur-oxidizing bacteria to derive their entire energy supply from reactions between the seawater and the rocks at high temperatures, rather than photosynthesis.

Although NO,--is generally considered to limit primary productivity in most of the world's oceans, previous studies have suggested the Mediterranean Sea may be an exception. In this study of the southeastern Mediterranean, we found that all the POd3-was removed from the upper water column during the winter phytoplankton bloom in the core and boundary of a warm-core eddy, while measurable (0.3-0.6 PM) NO,-remained. The N: P (N0,-:P0,3-) ratio in the core and boundary of the Cyprus eddy was 27.4 and the slope of the linear portion of the N vs. P scattergram was 25.5 with a positive intercept of 0.5 PM on the NO,-axis. A similar N : P ratio (28-29), slope (21-23), and intercept (0.9-l. 1) was found for the water column across much of the southern Levantine basin. These data, taken together with the results of incubation experiments, lead us to conclude that the southeastern Mediterranean is strongly P limited. The degree of P limitation increases from west to east across the entire basin. We suggest that removal of PO,'-by adsorbtion on Fe-rich dust particles may bc an important process controlling the concentration of P in the water column.N03-is generally considered to be the master chemical variable limiting primary productivity throughout much of the ocean (Codispoti 1989). It is based principally on considerations of the N : P ratios of upwelling waters which are generally < 16 : 1 I At present: Department of Earth Science, Leeds University, Leeds L52 9JT, U.K. AcknowledgmentsThe chemical determinations of dissolved nutrients were carried out by L. Israilov. We thank U. Fiedler for technical help on-board ship; we also thank members of the Physics and Electronic department of IOLR. The data collected in September 1989 were sampled as part of a Group for Aquatic Productivity (GAP) cruise to the eddy organized by T. Berman. We thank the captain (A. Ben-Nun) and crew of the RV Shikmona. This manuscript was written while M.D.K. was on sabbatical leave at the University of Rhode Island. We thank M. E. Q. Pilson and D. Kester for the use of their facilities and for the many discussions which went into the preparation of this manuscript. We thank M. Wood for pointing out the importance of P limitation in this area and for critical reading of the manuscript by her and T. Berman. Finally we greatly appreciate the detailed comments of two reviewers, who helped us improve the quality of the final version of this manuscript.

No abstract