not heavily taxed by the benthos and probably equilibrates

to near the saturation point at night more as a result of

diffusion across a concentration gradient at the air-sea

interface than as a result if respiratory depletion which

would be expected to cause a continued fall in the dissolved

oxygen curve to levels further Below the saturation point

than were actually encountered. In fact, the curves show

a definite leveling off just at or below the saturation

levels.

 A similar situation is indicated at Station 11

 (Figure 14) where, however, daytime levels do not reach as

 high and there is a greater depletion at night. The depth

 here is only one-fifth that at Station 2, the bottom is clear

 white sand with a rich infauna, but practically no grass or

 algae.

 Oxygen curves from Station 4 (Figure 10) are closest

to a simple diurnal pattern and indicate an extremely pro-

ductive area where photosynthesis rapidly builds up dissolved

oxygen during the daytime, where this production ceases and

a net respiratory depletion begins in the evening and where

nighttime demands continue to reduce dissolved oxygen levels.

 Station 4 is characterized by an extremely rich algal-

grass community, very good water clarity and almost continuous

water movement from the reef northward. In such clear waters

over Thalassia beds we have observed thousands of small oxy-

gen bubbles rising to the surface from the grass leaves.


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