were smothered by the oolite or exposed subaerially with the withdrawal of the sea 
from the area. 
1990 0 
Walter, L. M., W. P. Patterson, and K. Muehlenbachs (1990) Variation in carbon isotopic 
composition of surface seawater on tropical carbonate platforms; Florida Bay and Atlantic 
reef tract, Florida. EOS. Transactions . 71 (43): 1390. 
[ABSTRACT ONLY. DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] Although 
fluctuations in the C isotopic compositions of ancient shallow marine carbonates are 
used in constructing geochemical cycling models, relatively little is known of C isotopic 
variation in waters associated with modern carbonate platforms. Investigation of C 
isotopic composition along with other chemical parameters (Cl, alkalinity, TIC, Ca) of 
surface seawaters overlying shallow platforms of the Florida Keys revealed significant 
spatial variability. Carbon isotopic compositions of the least chemically evolved waters 
sampled seaward of the reef tract were about +1.8 °/oo PDB, slightly lighter than 
values for Atlantic surface waters. C isotopic compositions decreased by up to 1.5 %o 
in more restricted waters (salinity of about 38 %o) of the inner shelf. In even more 
restricted waters of Florida Bay, where salinities increased up to 60 %o, depletions in 
alkalinity and Ca were more severe, and C isotopic values decreased to values as low 
as -4 %o. Although associated with changes in water chemistry driven by CaC0 3 
precipitation, the magnitude of isotopic variations (nearly 6 °/oo) is inconsistent with 
fractionation during precipitation. Instead, we attribute the isotopic variations to 
recycling of isotopically light organic C from sediment pore waters which would have 
greatest impact on surface waters with longer residence times. Less detailed C isotopic 
data on sediment samples show that those from Florida Bay are about 1.5 %o lighter 
than those of the inner reef tract. Thus, isotopic differences in the waters are long- 
lived and reflected in the sediment record over the last several 1000 yrs. 
1990 - 1991 
Peters, D. S., L. Settle, J. Burke, and E. Laban (1994) Comparative utilization of Florida 
Bay as a nursery area by juvenile grunts. Bull. Mar. Sci. . 54(3): 1082. 
Seven trawl surveys of Florida Bay, Everglades National Park, were conducted 
between June 1990 and October 1991, in order to describe spawning times, size at 
recruitment to the bay, relative abundance, and distribution and growth rate of juvenile 
grunts. Species present in decreasing order of abundance, were white grunt, blue 
striped grunt, pigfish, sailors choice and French grunt. The northern and western 
regions of the Bay, with high turbidity and dense grassbeds, were the only regions used 
by pigfish and contained the highest density of white grunt. Sailors choice and blue 
striped grunt were present in all areas though more common in the east. Pigfish (as 
small as 15 mm and 50 days old) recruited to the nursery area in March, grew more 
rapidly than other species (0.76 mm day 1 ) and by winter were either gone or no longer 
available to our gear. Blue striped grunt were spawned throughout the year with a peak 
from February through April, recruited to the Bay at approximately 30 mm SL and 70 
days old, grew 0.46 mm SL day 1 and remained in the bay up to a year. White grunt, the 
product of spring (May - June) and fall (September November) spawnings, recruited to 
the western bay at about 20 mm SL and 50 days old and central bay at about 50 mm SL 
and 130 days old. They remained in the bay up to a year, growing on average 0.23 mm 
day' 1 , however, those in the turbid west grew much faster than those in the clearer 
central region. 
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