amounts of silt and clay (Tables 2 and 3, Fig. 2). 
Abundance was higher for each taxon (except for crus- 
taceans at station 4) at stations 1, 4, and 6 in the shore 
zone where the percentages of silt and clay were lower 
than in the center zone. Abundance of each taxon and 
sediment compositions were similar between zones at 
station 7. 
The compositions of plant material, rather than the 
compositions of sediments which were similar, proba- 
bly caused the large differences in abundance between 
zones at station 8. With the exception of crustaceans, 
the abundance of organisms was much greater in the 
center than in the shore zone. Plant material in the 
center zone was mostly sea grasses and attached 
algae, whereas along shore the plant material was pre- 
dominantly live cord grass roots. 
COMPARISONS BETWEEN CANAL, 
MARSH, AND BAY 
Based on a comparison of mean values for all groups 
combined (Fig. 11), benthic organisms were slightly 
more abundant numerically and over twice as abun- 
dant volumetrically in the marsh than in the canals; 
they were least abundant in the bay. When each group 
was considered separately, however, numeric and 
volumetric abundance by area varied. Polychaetes 
were most abundant numerically in the canals, most 
abundant volumetrically in the marsh; they were least 
abundant in the bay. Crustaceans were over three 
times as abundant in the marsh as in the other two 
areas. Pelecypods were numerically most abundant in 
the bay; volumetrically, they were most abundant in 
the marsh. Nemerteans were most abundant in the 
marsh and least abundant in the bay. 
DISCUSSION 
This and other studies (Reish, 1961; Taylor and 
Saloman, 1968) imply that production of benthic or- 
ganisms will decrease as a result of the type of altera- 
tion of the environment studied here. The magnitude 
of the reduction, however, is dependent on many fac- 
tors. 
The type of vegetative productivity, the segment of 
the area that is developed, and the configuration of the 
canals are of paramount importance in determining 
changes in benthic productivity. In many of the es- 
tuarine areas in Florida, vegetative production occurs 
primarily on the sand flats. Usually, these flats are the 
segments which are developed (extrusion of the 
shoreline). In the estuaries along the northern Gulf 
coast, including Texas, most of the vegetative produc- 
tion occurs in the intertidal zone; this and adjacent 
inland areas are usually the areas developed (intrusion 
of the shoreline). We think, from an ecological stand- 
point, that the types of developments (extruded and 
intruded) should be reversed in respect to the types of 
estuarine area described above. If reversed, the de- 
POLYCHAETA 
MEAN NUMBER PER SAMPLE 
MEAN NUMBER PER M2 
MEAN VOLUME (ML) PER SAMPLE 
MEAN VOLUME (ML) PER M2 
CANAL MARSH BAY 
Figure 11.—Average numbers and volumes of benthic macroinverte- 
brates caught per sample by area, taxonomic group, and for the 
groups combined, March-October 1969. 
