were confined to the freshwater end of the line, followed by values of stem water from 
mangrove margin species. Species found in mangroves, however, had water with 
extremely variable isotopic ratios, ranging from values typical of ocean water to 
values typical of freshwater. This variability is consistent with the hypothesis that 
mangroves are fully capable of growing in freshwater, but are limited to saline habitats 
because of competitive exclusion by fast-growing glycophilic plants. 
1986 - 1987 
Bowman, R., G. V. N. Powell, J. A. Hovis, N. C. Kline, and T. Wilmers (1989) Variations in 
reproductive success between subpopulations of the osprey (Pandion haliaetus) in South 
Florida. Symp. on Florida Bay: A Subtropical Lagoon. Miami, FL. June, 1987. Bull. Mar. 
Sci. . 44(1 ):245-50. 
Reproductive success of ospreys was used to evaluate the habitat quality of Florida 
Bay. Subpopulations that bred and foraged exclusively in Florida Bay were compared 
with those nesting adjacent to the Bay on the Keys and foraging in the Atlantic Ocean, a 
relatively undisturbed habitat. The study took place in 1986 - 1987. Osprey 
reproduction on Gulf side islands in the lower Keys, which have a structure similar to 
keys in Florida Bay but are more affected by oceanic influences, was compared with 
nest success on adjacent mainline Keys. Florida Bay ospreys produced significantly 
fewer fledglings per occupied, active, and successful nest than those on the upper Keys. 
In the lower Keys, however, there was no significant difference between gulfside and 
mainline key nesting success. Ospreys nesting on the upper mainline keys departed on 
foraging trips towards the Bay and the ocean in nearly equal proportions. However, 
47.2% of food deliveries came from the direction of the ocean while only 19.5% came 
from the Bay. Access to the ocean played a significant role in the greater reproductive 
success of birds nesting on the Keys and suggested that Florida Bay ospreys are 
experiencing decreased reproductive success due to an inadequate food supply. 
1986 - 1987 
Lapointe, B. E., J. D. O'Connell, and G. S. Garrett (1990) Nutrient couplings between on-site 
sewage disposal systems, groundwaters, and nearshore surface waters of the Florida Keys. 
Biogeochem. . 10:289-307. 
This paper reports the results of a one-yr study to determine the effects of on-site 
sewage disposal systems (OSDS, septic tanks) on the nutrient relations of limestone 
ground waters and nearshore surface waters of the Florida Bay side of the Florida 
Keys. Monitor wells were installed on canal residences with OSDS and a control site in 
the Key Deer National Wildlife Refuge on Big Pine Key. Ground water and surface water 
samples were collected monthly during 1987 and analyzed for concentrations of 
dissolved inorganic nitrogen (DIN = N0 3 ’ + N0 2 * + NH 4 + ), soluble reactive phosphate 
(SRP), temperature and salinity. Significant nutrient enrichment (up to 5000-fold) 
occurred in ground waters contiguous to OSDS; DIN was enriched an average of 400- 
fold and SRP some 70-fold compared to control ground waters. Ammonium was the 
dominant nitrogenous species and its concentration ranged from a low of 0.77 pM in 
control wells to 2.75 mM in OSDS-enriched ground waters. Concentrations of N0 3 * plus 
N0 2 * were also highly enriched and ranged from 0.05 |iM in control wells to 2.89 mM in 
enriched ground waters. Relative to DIN, concentrations of SRP were low and ranged 
from 30 nM in control wells to 107 ^M in enriched ground waters. N: P ratios of 
enriched ground waters were consistently > 100 and increased with increasing distance 
from the OSDS, suggesting significant, but incomplete, adsorption of SRP by subsurface 
flow through carbonate substrata. Nutrient concentrations of ground waters varied 
seasonally and were approximately two-fold higher during the winter (DIN = 1035 ^M; 
SRP = 10.3 jiM) compared to summer (DIN = 470 nM; SRP = 4.0 |iM). In contrast, 
surface water nutrient concentrations were two-fold higher during the summer (DIN = 
304 
