A literature survey was made for the occurrence of C, and C, photosynthetic pathways in the United States Gramineae. Distinctive characteristics of the two photosynthetic pathways are discussed. Leaf anatomy, CO, compensation point, net enhancement of photosynthesis in oxygen-deficient atmosphere, QC discrimination, and initial product labeling were criteria selected to evaluate data for 6 subfamilies including 25 tribes, 138 genera, and 632 species. The Arundinoideae, Bambusoideae, Oryzoideae, and Pooideae (Festucoideae) are composed of species with C, pathways. All tribes within the Eragrostoideae have C, pathways with the exception of Unioleae. Within the Panicoideae, the Andropogoneae and all of the Paniceae, excepting the genera Sacciolepus, Isachne, Oplismenus, Amphicatpum, and Panicum, have C, pathways. The subgenus Dichanthelium within Panicum is C, while the Bupanicum subgenus contains plants with both C, and C, photosynthetic pathways. Plant productivity is dependent on several environmental and biological factors. The most important single factor is photosynthesis. A pathway for carbon dioxide (CO;?) fixation was described by Calvin and Bassham (1962) in which CO2 was incorporated into a 6-carbon compound and rapidly converted to a 3-carbon compound, 3-phosphoglyceric acid (3PGA). Previous to discoveries of Kortschalk et al. (1965) and Hatch and Slack (1966), the Calvin cycle (C,, reductive pentose pathway) was considered the major photosynthetic mechanism for carbon (C) fixation. However, Hatch and Slack (1966) described CO;! fixation in which labeled CO;! was first incorporated in 4-carbon compounds (malic, aspartic , or oxaloacetic acid) prior to transfer to sugars by way of 3-phosphoglycerate. The proposed mechanism involved the operation of two interconnected metabolic cycles. Downton (1970) described carbon fixation into Cd-dicarboxylic acids in mesophyll cells and subsequent incorporation into the Calvin cycle located in the bundle sheath cells. Plants (Cd plants) possessing the 4-carbon pathway (also called Cd, dicarboxylic acid, Kranz type, low CO;! compensation, tropical, Hatch and Slack, or p carboxylation pathway) were of tropical ongm and more efficient. They produced two-to threefold more dry matter than plants possessing the 3-carbon pathway (C, plants), especially in relatively sunny, warm, dry climates (Black 197 1). Distinctive characteristics associated with the Ca pathway prompted intensive research in photosynthetic processes of flowering plants. The most important photosynthetic pathways

Although model simulations that assimilated the radar observations produced currents that were in general agreement with the pattern seen in the radar data, Lewis et al. [1998] expressed concern that errors in the radar data could cause problems in the simulations. Horizontal divergences calculated from the radar data showed unrealistically large magnitudes, changes in sign from time step to time step, and little coherence between adjacent grid cells. These horizontal divergence patterns, when assimilated into the model, would tend to produce unrealistic sea level differences of the order of meters at adjacent grid cells separated by 2.8 km. Lewis et al. [1998] concluded that additional processing of the radar data would be useful in order to minimize such effects. This issue is one of the subjects of this paper.The experiences of Lewis et al. [1998] are likely to be repeated by other coastal zone modelers. This is because in recent years there has been a dramatic increase in the capability to provide high-resolution space and time data of estuarine and coastal regions. HF radar data are but one example. Others are synthetic aperture radars, Lagrangian drifters, new generation passive remote-sensing platforms, and a variety of towed instrumentation suites that provide fine-scale information on the density and velocity fields along ship tracks. These developments have been matched by equally dramatic increases in computational capabilities. Consequently, oceanographers now routinely access both observational and computational capabilities unimagined even a few years ago. 3425

No abstract

During 1985 and 1986, a Gulf of Mexico ring shed by the Loop Current was observed to migrate toward the western Gulf of Mexico. This movement across the gulf was well documented by observations that included drifter data within and outside the ring, sea surface temperature at weekly intervals, expendable bathythermograph surveys at various times, one major hydrographic cruise when the ring was in the northwestern gulf, and currents from moorings over which the ring passed. The drifter data were used to infer the movement of the ring center as well as the eccentricity and orientation of the major axes. The data from the drifters bridge the gaps between detailed surveys to the extent that a daily history of the position and shape of the ring can be constructed. The synthesis of these diverse but complimentary data sources provides a detailed description of how the ring interacted with the bathymetry of the northern Gulf of Mexico as well as with previously and subsequently shed rings.

No abstract