Florida Bay is the major nursery area for Florida's spiny lobster, Panulirus argus. It is 
characterized by a series of shallow hardbottom or seagrass covered basins separated 
by seagrass covered mud banks less than one meter in depth. Because these mud banks 
serve as barriers to circulation, the basins formed between the banks may experience 
extreme fluctuations in temperature and salinity due to reduced tidal influx and high 
rates of evaporation. Larval transport to areas of Florida Bay that experience these 
temperature/salinity fluctuations were monitored monthly (March 1992 - July 1992) 
using artificial benthic collectors. Diver surveys to monitor new recruits and 
characterize lobster habitat were also conducted at eight sites along two transects 
(four sites per transect) leading from the cuts between the Florida Keys and extending 
north and northwest to Twin Key Bank and the subsequent basin. Concurrently, 
postlarval P. argus were reared in the laboratory, in a completely crossed design, at 
four temperatures (18°C, 22°C, 29°C, and 33°C) and four salinities (25, 35, 45, and 
50 °/oo). Survival, time to metamorphosis, and growth to first stage juvenile were 
measured. Results from monthly benthic collector censuses suggest that postlarvae are 
not regularly transported beyond Twin Key Bank, however, diver surveys indicate that 
some recruitment does occur in the western and central position of Twin Key basin, but 
not in the eastern portion of the same basin. During this study, temperature and salinity 
readings in this basin ranged from 21 °C to 32°C and 35 %o to 45 °/oo , respectively. 
Laboratory results indicate that this range of temperatures and salinities could be 
tolerated, however, mortality is greatest at high temperatures in conjunction with high 
salinities. 
1992 0 
Fourqurean, J. W. (1992) The roles of resource availability and resource competition in 
structuring seagrass communities of Florida Bay. Ph. D. Dissertation. University of 
Virginia, Charlottesville, VA. 280 pp. 
[DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] This dissertation examines the 
effects of the availability of light and nutrients on the structure of seagrass beds of 
Florida Bay. The tradeoffs made in resource acquisition strategy by the three most 
common seagrass species from the Bay, Thalassia testudinum, Halodule wrightii, and 
Syringodium filiforme, determined the distributions of these three species. The relative 
importance of the nutrients, nitrogen and phosphorus, in limiting the productivity of the 
seagrass-dominated Florida Bay ecosystem was also evaluated. Laboratory measures 
of photosynthetic and respiratory rates were made for leaves, non-photosynthetic 
portions of the short shoots, rhizomes and roots of all three species. A carbon budget 
model of the light requirements of seagrasses was developed. Observed differences in 
the light requirements of seagrasses were explained using this budget model. 
Differences in light requirements were shown to be caused by interspecies differences 
in apportionment of biomass into photosynthetic and non-photosynthetic structures, as 
well as differences in metabolic rates. Light requirements of all three species was a 
function of the relative apportionment of biomass to different plant tissues: the more 
plant biomass allocated to nutrient gathering organs, the greater the light requirement. 
Phosphorus availability limited the phytoplankton and seagrass productivity of Florida 
Bay. The main sources of P for Florida Bay was shown to be the Gulf of Mexico, while 
freshwater runoff from the Everglades was a source of N. The density of seagrass in 
Florida Bay was directly related to the concentration of P, but not N, in the sediment 
porewater. P availability also determined the species composition of seagrass beds. The 
P content of Thalassia testudinum leaves from Florida Bay was highly variable, and the 
elemental content of seagrass tissue proved to be an indicator of the availability of 
nutrients to seagrasses, both on local and regional scales. Changing the nutrient supply 
rates to seagrass beds in Florida Bay caused the species composition of the seagrass 
beds to shift. Both this shift, and the normal successional sequence and distributional 
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