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means exhaustive, it is well to have a general feeling for the distribution 
of the flora which supports the wet lands community before proceeding 
to a discussion of the factors controlling the processes of production. 
FOOD PRODUCTION . 
Studies of primary production carried out in the wet land tend to be 
of a few types, including measurements of photosynthetic activity and 
concurrent measurement of factors which the experimentor suspects 
of influencing this activity. Most studies on the actual production are 
limited in time to the duration of the experiment, which may be a few 
hours, and in space to the area under the bell jar, or the volume of the 
sample bottle. Care must be exercised, therefore, in generalizing the 
results of these experiments, which may or may not be representative 
of the area of study. There have been a sufficient number of produc- 
tivity studies in some regions, however, to warrant generalization. 
Production studies can be divided into those studies which measure 
the total net production of plants in and on the sediment, including 
higher plants, attached algae, and microscopic benthic algae, and 
those which measure phytoplankton production. 
Production studies of the first type commonly deal with salt marsh 
productivity. Pomeroy® made bell jar experiments on algal produc- 
tivity in Georgia salt marshes. Photosynthesis during low tide was 
significantly higher than at high tide in winter, while photosynthesis 
at high tide was higher in late summer. This is because illumination is 
inhibiting both in excess and insufficient quantities. Taken over a tidal 
cycle, the gross productivity is almost constant throughout the year, 
at about 1800 keal/m? yr. The net production he calculated to be not 
less than 90 percent of this gross production. Smalley, and Teal and 
Kanwisher’ have investigated the productivity of Spartina, both 
by harvesting at regular intervals, and by respiration methods. 
Unlike algal production, the production by higher plants varies 
seasonally. For example, short Spartina may give values of respiration 
of 235 kcal/m? for 2 months of winter, and 6450 kcal/m? for 4 months 
in the summer. Averaged over the salt marsh, the gross production 
was calculated to be 24580 kceal/m? yr. of which net production consti- 
tuted less than 25 percent. Thus, though the higher plants have much 
ereater gross production, the net production of higher plants is some 
6580 keal/m? yr.® 
Studies of plankton productivity in estuarine waters near salt 
marshes have been made by several, workers.*:° Using light and 
dark bottle measurements, Ragotzkie obtained slightly negative values 
of net production in the estuary for the plankton community including 
organic detritus and its associated bacterial flora.’ He cited the 
salt marsh as the probable outside source of organic material required 
by his results. Whether these results can be taken to indicate that 
there is actually a negative net. production in the estuary is doubtful, 
in view of the time limitation in the experimental technique and the 
extreme variability of phytoplankton production. It is clear, however, 
that taken over its entire depth, the estuary has a much lower net 
production than the salt marsh. 
Pomeroy compared the relative importance of various plant popu- 
lations in Boca Ciega Bay, Fla.,? and found that in waters less than 
2 meters depth (which constitutes some 75 percent) of the area, phyto- 
Footnotes at end of article. 
