Estuarine Water Observations During a 24-Hour Cycle 



Ray S. Wheeler 



A study of some of the continuous physical and chemical changes 

 during a 24-hour period in a 1 1/10 -mile lagoon at the northeast end of 

 Gailveston Island was made on July 2 and 3, 1958. This particular body of 

 water was selected for study because of its accessibility and its similarity 

 to other estuarine waters in the area. The East Lagoon sea -water labora- 

 tory was later constructed on this lagoon. 



Samples were collected for oxygen, carbon dioxide, total phosphate, 

 inorganic phosphate, nitrate -nitrite, nitrite, ammonia, carbohydrate, salinity, 



and chlorophyll "a" determinations. 



BEAUMONT ,S:i 



SHIP CHANNEL 



In addition to chemical samples, ob- 

 servations were made of water and 

 air temperatures and tidal fluctua- 

 tions. 



Samples and observations 

 were taken concurrently at 2-hour 

 intervals at each of three stations. 

 These intervals are referred to as 

 periods 1, 2, 3, etc. Period 1 

 started at 0630 hours. Station I was 

 located at a point farthest from the 

 inlet. Station III at the inlet, and 

 Station II halfway between. 



There was a general rise 

 in oxygen values at each of the three 

 stations for the first six periods, 

 i. e. , during the hours in which pho- 

 tosynthetic processes took place. 

 From period 7 to period 9, there 

 was a steady decline in dissolved 

 oxygen, after which an abrupt in- 

 crease was evidenced between 

 periods 9 and 10. If oxygen alone 

 is used as a nneasure of produc- 

 tivity, these data seenn to indicate 

 considerable phytoplankton produc- 

 tion within the lagoon. The chloro- 

 phyll "a" values also support this conclusion, especially as an ebb tide was 

 concurrent with the diurnal phase of this study. 



During sampling period 1, we noted that oxygen values were great- 

 est at Station III and gradually declined in value toward Station I. Two rea- 

 sons for this are suggested. First, the lower values obtained at Station I 

 could have been due to the respiratory demands of the dense floral and faunal 



Sampling stations on East 

 Lagoon, Galveston Island. 



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