Tropical Atlantic Study

A better understanding of rainfall variability and its mechanisms in Amazonia requires a clear documentation of the major elements of the warm season precipitation regime, within the context of the annual cycle, and longer time scale variations such as interannual and interdecadal. Rainfall variability in Amazonia has been the subject of several studies regarding physical causes, seasonal variations, and links to the Southern Oscillation (SO), and to SST conditions in the tropical Atlantic (see reviews in Ropelewski... 

Regarding interdecadal circulation changes in the tropical South Atlantic, studies by Wagner (1996) have identified a substantial... 

A comprehensive study of Pseudopterogorgia elisabethae from different regions of the Caribbean Sea and tropical Atlantic areas unveiled a novel class of compounds, known collectively as the pseudopterosins. Pseudopterosins are metabolites which contain diterpene glycoside moieties. Polyhydroxy steroids are another class of compounds commonly isolated from solvent extracts of this specie. 

Sterrer, W. (1998). GnathostomuUda from the (sub)tropical northwestern Atlantic. Studies on the Natural History of the Caribbean Region 74,1-178. 

A study in the tropical Atlantic by Williams et al. involved measuring acetone, methanol, acetonitrile and dimethyl sulfide within the atmospheric marine boundary layer and the upper ocean [116]. Measurements were taken on either side of the intertropical convergence zone. This zone, which sailors commonly refer to as the doldrums, is an area around the equator where the southeast and northeast trade winds meet. Consequently, it is a natural barrier to atmospheric mixing between the hemispheres. This results in hemispheric gradients for VOCs whose atmospheric lifetimes are shorter than interhemispheric mixing times... 

One key factor for tropical diazotrophs may be water temperature. For example, the distribution of Trkhodesmium spp. is roughly limited by the 20°C isotherm, and other planktonic cyanobacteria are likewise primarily tropical or subtropical in distribution. MetabolicaUy active populations of Trkhodesmium have been observed at 18.3°C in the North Atlantic (McCarthy and Carpenter, 1979), but activity was low, and substantial growth is typically not seen until water temperature exceeds 20°C (Carpenter, 1983a,b). Moreover, water temperature co-varies inversely with surface nutrient concentrations (Kamykowski and Zentara, 1986). Indeed, in previous studies we have used sea surface temperature as a proxy for oligotrophic waters in order to estimate the areal range of Trkhodesmium (Capone et al., 2005). 

Sohm et al. (in press) have extended their studies of APA and P uptake kinetics by Trichodesmium colonies in the N. Atlantic to a comparative study of these two indices in the tropical N. Pacific and coastal northern Australian waters as well. They detected sharp contrasts among the sites with much higher Riax and APA values in their tropical N. Atlantic stations compared to the N. Pacific and northern AustraHa indicating more severe P hmitation in the tropical N. Atlantic. Dyhrman et al. (2002) also reported evidence of severe P stress in Trichodesmium in the N. Atlantic based on a enzyme linked fluorescence (ELF) assay. A follow up study also saw less evidence of P stress in samples from the N. Pacific (Hynes et al., Pers. Comm.). 

Some of the highest numbers for the Hemiaulus-Richelia symbioses were reported in the western tropical North Atlantic (WTNA). Carpenter et al. (1999) observed an extensive bloom off the NE coast of South America in autumn of 1996. They reported cell densities from 10 to 10 Richelia Recently, in the same vicinity as the study of Carpenter et al. (1999), Foster et al. (2007) reported extremely high niJH gene copy (>10 copies L ) abundances (proxy for cell abundances) for Richelia associated H. hauckii and Rhizosolenia clevei. In addition, they found within the plume waters of the Amazon River runoff a positive correlation between salinity and the abundance of the H. hauckii-Richelia abundance (Foster et al, 2007). 

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