stations ranged from 11.4 to 33.1 °/oo. Densities of benthic plants and animals differed 
among stations by several orders of magnitude. The standard deviation of salinity was 
the best environmental correlate with mean plant biomass and benthic animal density: 
less biota occurred at stations with greater fluctuations in salinity. The two stations 
with the least plant biomass also had the highest mean water temperatures. In a 
stepwise multiple regression analysis, standard deviation of salinity accounted for 
59% of the variation in the logarithm of mean plant biomass among stations. For every 
3 °/oo increase in the standard deviation, total benthic plant biomass decreased by an 
order of magnitude. Mean water temperature accounted for only 14% of the variation, 
and mean salinity was not included for lack of significance. At stations with widely 
fluctuating salinities, not only was biomass low, but species dominance also frequently 
changed. Severe fluctuation in salinity may have prevented abundant benthos by causing 
physiological stress that reduced growth and survival. Salinity may not have remained 
within the range of tolerance of any one plant species for long enough to allow the 
development of a substantially vegetated benthic community. Hence, gaining control 
over salinity fluctuation may be the key to estuarine habitat improvement through canal 
management in southern Florida. 
1986 - 1987 
Swart, P. K., L. D. S. L. Sternberg, R. Steinen, and S. A. Harrison (1989) Controls on the 
oxygen and hydrogen isotopic composition of the waters of Florida Bay, USA. Chem. Geol. 
(Isot. Geosci. Section) . 79(2):113-23. 
The oxygen and hydrogen isotopic composition has been measured in waters from 
Florida Bay and from fluids squeezed from sediments which make up Holocene islands in 
the Bay. Although, these waters ranged in salinity from 27 to 120 g kg' 1 , most were 
found to have very similar hydrogen and oxygen isotopic compositions (8 18 0 = +2 to +4 
%o, 8D = +5 to +25 °/oo). In order to explain these observations, the Craig-Gordon 
and Gonfiantini evaporation models, which account for oxygen and hydrogen isotopic 
fractionation during the desiccation of saline water bodies, were applied. These models 
provide excellent agreement for the evaporation of water into an environment with a 
relative humidity of 77%, a temperature of 25°C and atmospheric water vapor 
possessing 6 18 0- and 5D-values of -11 and -75 °/oo, respectively. The salinity of 
fluids from one core on Cluett Key (26.9 g kg' 1 ) was well below that of the surrounding 
Bay (>40 g kg' 1 ) and the water from this locality was depleted in both D and 18 0. These 
5 18 0- and 5D-values, plotted together with other data from this study, fall on a line 
possessing a slope of 4.90 (± 0.41), similar to what would be expected from the 
evaporation models. This line intersects the meteoric water line at 5 1s O- and 5D-values 
which are within error, similar to average 5 18 0- and 5D-values measured for rainfall 
in the Miami area. Water samples were collected on several occasions from Cluett Key 
and Crane Key during 1986 and 1987. 
1986 - 1988 
Montague, C., [R. D. Bartleson, J. F. Gottgens, J. A. Ley, and R. M. Ruble] (1989) The 
distribution and dynamics of submerged vegetation along gradients of salinity in northeast 
Florida Bay. Symp. on Florida Bay: A Subtropical Lagoon. Miami, FL. June, 1987. Bull. Mar. 
Sci. . 44( 1):521. 
[ABSTRACT ONLY. DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] Submerged 
vegetation, important habitat for juvenile stages of many fish and shellfish, was 
sampled along salinity gradients in three tributary to bay transects (west, central and 
east) each with four stations (Bay to upstream). The three transects are 10 to 12 km 
apart on the eastern 20 km of the mainland coast that borders northeast Florida Bay. 
The objective was to collect information relevant to the effects of changes in 
freshwater delivery to this area. Samples have been collected eight times during 1988 
307 
