s similar analytical approach but a different experimental setup. 

 Freshly cut, clean, turtle grass was suspended in 500ml Erlenmeyer 

 flasks. Photosynthetic rates were measured by oxygen production 

 monitored continuously by an IBC Model 170 oxygen analyzer. The 

 samples were stirred by magnetic stirring bars. Illumination was 

 kept at a constant 1,000 lux using fluorescent lights. 



To prevent oversaturation of the sample water with oxygen, the filtered 

 seawater used during the experiment was scrubbed with nitrogen for one 

 hour, lowering the oxygen content to less than 1 mg per liter (five 

 percent saturated). Oxygen was normally low in the effluent and this 

 did not require treatment. 



After a two hour photosynthesis history was obtained for each lot in 

 filtered seawater, toxicants were added and photosynthesis monitored 

 for twenty-four hours. Toxicity was measured as the amount of con- 

 taminant required to lower the photosynthetic rate by 50 percent after 

 twenty-four hours of exposure (Goldman, 1966, A.S.T.M. 1964, Wetzel, 

 1966, Clendenning and North, 1960). 



GRAPHIC TECHNIQUES 



Most of the graphic techniques used in the report are conventional 

 and need no explanation. To compare numerous data points for the 

 several stations involved for a complete year's cycle required use 

 of circular graphs (Fig. 8). While circular graphs are in widespread 

 use for data recording, they have not frequently been used for data 

 reporting. 



By dividing the graphs into twelve radii, each representing a calendar 

 month and arranged as the hours on a watch, average monthly data can 

 be compactly presented. Circular graphs are also useful in presenting 

 data for comparison of one factor versus another. The shapes of the 

 polygons formed by the graphs are representative of general trends and 

 can be visually compared with one another when presented together. 

 Thus, having data from all stations represented on one page (see Fig. 

 26, page 78) enables the reader to compare trends from one station to 

 the next at a single glance. A critical look at Figure 26 yields the 

 following observations: 



1. The percent effluent at the shallow stations 

 (the unshaded, center portions of the graphs) 

 is negligible compared to the amount at the 

 deeper stations (outer portions of the shaded 

 area) . 



2. The amount of effluent is relatively constant 

 at Stations 2 through 6 and erratic at the 

 more distant stations. 



38 



