TRACK -f- 



SECTIONS 



A A 



B B 





STATION.BT.a GEK ■ 

 BT a GEK * 



BT ONLY • 



Figure 20.--Track chart of cruise TO-59-2 in the Gulf of Tehuantepec. 



feature itself was less well marked than in 

 any previous survey. Phosphate concentration 

 in surface and near-surface waters was closer 

 to that of TO- 58-1 (May and June) than to 

 that of the other cruises. The biological 

 properties were lower than on other 

 cruises, except productivity which appeared 

 to be a little higher than it was on TO- 

 58-1. 



All these features would be expected for 

 this region, from the average wind and cur- 

 rent picture of figure 2 and the observations 

 made on the previous cruises, at the transi- 

 tion from the calmer conditions of summer 

 to the more disturbed conditions of the 

 Tehuantepecer season. The ocean is highly 

 stratified and its strata are more nearly 

 parallel to the sea surface than at any other 

 time of year (except possibly in midsummer 

 when no observations were made); therefore, 

 the processes (vertical mixing) resulting in 

 production of biota are weakly developed and 

 so are the processes (horizontal transport) 



resulting in redistribution of biota, and 

 this weak development is reflected in the 

 abundance and distribution of biological mate- 

 rial. 



DISCUSSION 



Most features of the data have been dis- 

 cussed in previous sections of the paper. This 

 section comments further on a few of the 

 most interesting features. 



Brandhorst (1958) thought it remarkable 

 that the area of lowest surface temperatures 

 should lie west of instead of at the highest 

 point of the feature he called a dome. Present 

 observations on this point are consistent with 

 his. It is easy to understand the phenomenon 

 if it is considered that the south-moving 

 wind stream acts first to produce a ridge 

 on its left-hand side, and secondly to disturb 

 the part of this ridge lying closest to Its 



24 



