thick peat present under the eastern side. The island developed over a slight 
topographic low on the microkarstic bedrock surface. The sediment sequence is of type 
(A) with all units from (a) through (e) present. The eastern side of the island is firm 
and appears erosional, whereas the western side is soft mud and appears depositional. 
From this evidence and distribution of sediments, it is interpreted that the island is 
migrating westward. 
1909 0 
Merriam, D. F., S. Sengupta and C. E. Sorensen (1989) Definition and implications of the 
subenvironments of Florida Bay. Bull. Mar. Sci. . 44:520. 
[ABSTRACT ONLY.] The subenvironments of Florida Bay have been defined in several 
different ways. Salinity levels have been used to subdivide the Bay into hydrographic 
zones; molluscan assemblages have been used to recognize subenvironments, and the 
net sediment budget used to arrive at sediment accumulation zones. Water properties 
such as salinity, pH, dissolved oxygen, dissolved carbon dioxide, turbidity, Ca, and Mg 
along with sedimentological, geochemical, and biological properties of the sediments 
were analyzed statistically to outline four sub-environments, the three peripheral ones 
- Northern, Gulf, Atlantic - and an Interior restricted zone. Because the water and 
sediment parameters are changing constantly, the boundaries of the different 
subenvironments fluctuate reflecting the dynamic conditions in the Bay. The water 
properties, particularly susceptible to change, show a distinct reorientation from 
winter to summer reflecting the change from the dry to wet season. These changes are 
attributed to various causes chief among them being wind direction, nutrient supply, 
rainfall, water circulation, and basin configuration. Water properties of salinity, pH, 
dissolved C0 2 and 0 2 , and turbidity were subjected to trend-surface analysis to 
determine the regional pattern of values for each variable. Salinity is normal marine in 
the center of the Bay, decreasing to brackish conditions along margins where the 
circulation is more restricted. Dissolved C0 2 is higher in the central part of the Bay, 
but dissolved C0 2 decreases towards the center of the Bay as does the pH and turbidity. 
In general, the salinity of C0 2 of the water decreases as 0 2 , pH and turbidity increase. 
These conditions are the result of a complex interplay of basin configuration, 
circulation, dilution and pollution, animal activity and vegetation, light, temperature, 
agitation, sediment supply and many other variables. The Northern subenvironment, 
which is in proximity to the mainland, and is characterized by a freshwater influx from 
the Everglades. Depth ranges from 2 - 4 ft, sediment grain size is from fine to coarse 
sand. Shallow regions are covered with vegetation, whereas the deeper areas are 
barren. Laurencia and Thalassia are abundant and the water usually is turbid and 
brackish. Gastropods and pelecypods comprise the fauna. Salinity is high in the Interior 
Subenvironments because of restricted circulation. Water depth ranges from 3 - 8 ft, 
and sediment grain size from medium to coarse sand. Although much of the substracte 
is bare, Thalassia and Penicillus, and other forms of algae are abundant locally. Because 
of the restricted circulation and limited nutrient supply, the flora and faunal diversity 
are low. The Gulf and Atlantic Subenvironments are regions of deeper waters (average 
7 ft) and the sediment grain size is dominantly coarse sand. A high floral and faunal 
diversity is observed because of an open tidal exchange with the Gulf and Atlantic 
Ocean. Thalassia is abundant along with Laurencia, Penicillus, Udotea, Halimedia and 
other forms of algae, and Porites, sponges and shrimp mounds. 
1989 0 
Mukherki, K. K. (1989) Holocene development of Sandy Bank in the western Florida Bay. 
Symp. on Florida Bay: A Subtropical Lagoon. Miami, FL. June, 1987. Bull. Mar. Sci. . 
44(1): 521-2. 
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