area to sediment particle size, amount of plant matter, 
and dissolved oxygen. 
STUDY AREA AND METHODS 
The study area in West Bay, Texas, a part of the 
Galveston Bay System (Fig. 1), included a natural 
marsh area, an open bay area, and an area that was 
similar to the natural marsh prior to alteration by 
channelization, bulkheading, and filling for the 
Jamaica Beach housing development. The developed 
area, which included about 45 hectares of emergent 
marsh vegetation, intertidal mud flats, and subtidal 
water area prior to alterations was reduced to about 32 
hectares of subtidal water area by dredging and filling 
between 1958 and 1960. The water volume (mean low 
tide level) was increased from about 184,000 to about 
394,000 cubic meters. 
Six sampling stations—two in the canals of the al- 
tered area, three in the natural marsh, and one in the 
open bay—were established (Fig.1). The stations were 
numbered nonconsecutively and correspond to those 
reported by Trent, Pullen, and Moore (1972). Sam- 
pling was conducted in two zones, ‘‘shore’’ and 
“center,” at each station except at the open bay sta- 
tion. In the altered area, shore samples were taken on 
each side of the canal at each station (1 and 4) 1 m 
away from each bulkhead; center samples were taken 
near the center of the canal along a transect perpen- 
dicular to the bulkheads. Replicate samples were 
taken from the center at each station, so that two sam- 
ples were available from each zone for each sampling 
date; the average of the two samples was used as the 
observation in the statistical tests. Samples similar to 
those from the canal area were taken at stations 6, 7, 
and 8 in the intertidal zone adjacent to the cord grass 
and near the center of the bayou or lake along tran- 
sects perpendicular to the shoreline. Replicate sam- 
ples were taken at station 10 in the open bay. 
Bottom samples were taken at 14-day intervals from 
25 March to 21 October 1969, with a metal cylinder 14 
cm long and 9.6 cm in diameter. To obtain a sample 
the cylinder was pressed about 11 cm into the bottom 
sediments, capped on each end with plastic lids, and 
brought to the water’s surface. Each sample contained 
about 800 cm® of bottom materials and represented a 
surface area of 1/138 m?. 
The samples were refrigerated within 2 hr after col- 
lection. The following day, each sample was emptied 
into a sieve having a mesh size of 420 um, and the 
material was washed until the fine sediments passed 
through the sieve. The remaining material, including 
macroinvertebrates, was stored in a 10% Formalin 
solution. 
Macroinvertebrates and plant material in the pre- 
served samples were separated from the shell and 
sand. Animal volume for each pair of samples was 
determined to the nearest 0.1 ml by displacement in a 
graduated 10-ml centrifuge tube containing a previ- 
ously recorded volume of water. The volume of each 
phylum taken at each station and zone was determined 
at the end of the study by combining the individuals of 
a phylum from the 32 samples. The volume of plant 
material was determined to the nearest milliliter in a 
30-ml graduated cylinder. 
The animals were separated and identified, usually 
to family, and the number of individuals in each group 
was recorded for each pair of samples. As suggested 
by Holme (1964), only whole animals or portions of 
animals containing the anterior end were counted to 
avoid recounting the same animal. 
The dissolved oxygen content of the water, taken 15 
cm above the bottom at the center habitat of each 
station, was measured using a modified Winkler 
method. The water samples were taken about midday 
and midnight during the same 24-hr period that the 
bottom samples were collected. 
Samples for sediment analyses were taken at each 
station and zone on 12 August. Particle-size composi- 
tions (percents by weight) were determined using a 
series of sieves and soil hydrometers. Ranges in parti- 
cle size were: sand, 2.0-0.62 mm; silt, 0.061-0.004 mm; 
clay, 0.0039-0.001 mm. 
STATION DESCRIPTION AND 
ENVIRONMENTAL DATA 
Sampling stations were located at various distances 
from the West Bay shoreline (Fig. 1). Water depths 
(mean low tide level) in the shore zone ranged from 0.0 
to 0.6 m and in the center zone from 0.2 to 1.6 m. 
The percentage compositions of bottom sediments 
varied considerably between stations and between 
zones (Fig. 2). In the canals, silt and clay components 
were more abundant in the center than in the shore 
zone. In the marsh, compositions of sediments were 
similar between zones at stations 7 and 8, but at station 
6 a higher percentage of silt and clay occurred in the 
center than in the shore zone. 
The plant material taken in the samples was com- 
posed of live cord grass roots, attached marine grasses 
(mostly Diplanthera wrightii), algae (mostly 
Ectocarpus sp.), and detritus. In general, all organic 
matter collected at the canal stations (both zones) and 
in the open bay consisted of detritus and small 
amounts of attached algae. Cord grass roots were 
dominant in the samples from the shore of the marsh, 
whereas in the center, detritus was usually dominant, 
although attached grasses and algae were also present. 
The volume of plant material was many times great- 
er in the shore zone (stations 6, 7, and 8) of the marsh 
than in either zone within the canals (Fig. 3). Most of 
this vegetation, however, was not decomposed; thus, 
detrital and filter feeders could not utilize it. 
Differences in the volume of plant material in the 
center zones of all stations indicated that a major 
source of plant material in the canals originated from 
an outside source. The lowest volume of plant material 
