populations during the hours of darkness immediately preceding the sampling 

 period. Secondly, greater aeration of the water might have occurred at the 

 mouth of the lagoon due to wave action and mixing of the water at the restric- 

 ted inlet. Any change in oxygen concentration due to the tide reversal which 

 occurred between periods 10 and 11 was either masked or wholly lacking, for 

 the sharp increase in oxygen concentration was noted throughout the lagoon 

 2 hours before the flood tide commenced (between periods 9 and 10). 



No explanation is offered for the erratic pattern of carbon dioxide 

 values. 



Samples for total phosphate were frozen after being collected and 

 remained so until analyzed. Each sample was divided, half being filtered and 

 half remaining unfiltered. An appreciable difference in concentration of phos- 

 phates exists between filtered and unfiltered samples. The difference in con- 

 centration between the filtered and unfiltered samples is indicative of the 

 amounts of phosphates contained in the particulate matter. 



Values were such that no distinction could be made between sam- 

 ples taken during the hours of daylight and those taken during the hours of 

 darkness. Some fluctuations in concentrations of total phosphates were evi- 

 dent, the most striking being at Station III, period 12, where the unfiltered 

 sample contained more than five times as much phosphate as the filtered 

 sample. This particular sample was collected after the turn of the tide and 

 at a time when a strong prevailing current resulted in particulate matter 

 being maintained in suspension. 



Inorganic phosphate samples were left unfiltered. The average 

 values for each station during the daylight hours indicate that an inorganic 

 phosphate gradient exists between the two extremities of the lagoon with the 

 greatest concentration in the Station I area. Values for each station display 

 considerable variation, and it is doubtful whether or not this gradient dis- 

 play is of real significance since there is a relatively small difference in 

 average values between stations. Values during the hours of darkness, al- 

 though still variable, are not quite as erratic as those during the daylight 

 hours. Average nighttime values were of the same magnitude as those of 

 daylight hours at Stations I and II, but slightly higher at Station III with no 

 gradient existing between stations. With the change of the tide, an abrupt 

 drop was noted in the inorganic phosphate content at Station III during 

 period 1 1 . 



When the values for both total and inorganic phosphate at each sta- 

 tion were compared, we noted that the concentration of phosphorus in the un- 

 filtered total phosphate sample was consistently higher than that in the un- 

 filtered inorganic phosphate sample. The difference represented an estimate 

 of the total organic phosphate. The phosphorus contained in the unfiltered 

 inorganic phosphate samples was consistently greater than the amount of phos- 

 phorus contained in the filtered total phosphate samples, indicating more par- 

 ticulate inorganic phosphate than dissolved organic phosphate. 



78 



