to marine conditions is believed to account for the depauperate benthic communities at 
upstream stations. Upstream stations had both lower mean salinity and much more 
variable salinity than outer stations. Many other environmental conditions did not 
systematically vary from upstream to outer stations, owing in part to careful selection 
of stations. These included average water depth, average water-level fluctuation, 
sediment thickness, sediment organic content and sediment particle size. Weather and 
water temperature, light extinction, pH, biochemical oxygen demand (BOD), 
orthophosphate concentration, morning dissolved oxygen, and plankton metabolism also 
did not vary significantly from upstream to downstream. Some parameters did vary 
systematically from outer to upstream stations. These include daily change in dissolved 
oxygen concentration, dissolved oxygen level in the afternoon, and total open-water 
oxygen metabolism (all lower upstream), total nitrogen, total phosphorus, and 
ammonium concentrations (all higher upstream), variation in total nitrogen and 
ammonium concentrations (higher upstream), total suspended solids (lower upstream), 
and bottom water temperature (slightly higher upstream). Some of these tendencies, 
however, could be partially or wholly explained by the lack of vegetation, which if 
present would increase oxygen and decrease nutrient concentrations. Some 
environmental differences were noticed among the three systems (western, central, 
and eastern). The eastern system tributary (Highway Creek) was lower in salinity and 
higher in upstream discharge of water. Differences in benthic community development 
and degree of salinity fluctuation between upstream and outer stations were greatest in 
the western system, perhaps resulting from a lower discharge of freshwater in that 
system. It seems apparent that the US Highway 1 causeway (together with the routine 
plugging of the C-111 canal) accounts for the greater flow of water in the eastern 
system by blocking an apparently historical water flow more to the east (as judged by 
the northwest-to-southeast orientation of tree "islands’ in the marshes on each side of 
the highway). Phosphorus appears to be in very short supply compared to nitrogen in 
the water at our stations. In nature an atom-based nitrogen-to-phosphorus ratio of 
16:1 is often used for comparison. The waters of our stations have an average ratio of 
over 300:1, indicating the likelihood of severe phosphorus limitation. No indication of 
significant supplies of nitrogen or phosphorus from inflowing waters was found, though 
our study was not designed with this objective in mind and did not include all necessary 
measurements for a definitive conclusion about nutrient transport in freshwater flow 
into northeast Florida Bay. Salinity fluctuation is apparently much more influential on 
benthic community development than are nutrients at our stations. Addition of nutrients 
would undoubtedly increase primary production at our stations, but the form of this 
production is difficult to predict. It could be benthic bluegreen algae (e.g. Lyngbya), 
benthic diatoms, planktonic microalgae, or submerged vegetation, such as seagrasses 
and macroalgae. 
1986 - 1987 
Montague, C. L., and J. A. Ley (1993) A possible effect of salinity fluctuation on abundance 
of benthic vegetation and associated fauna in northeastern Florida Bay. Estuaries . 
1 6(4):703-1 7. 
In southern Florida, a vast network of canals and water control structures mediate 
freshwater discharge into the coastal zone. Management protocol for one such canal 
network (C-111) is being modified in part to try to improve habitat for estuarine fish 
and wading birds in northeastern Florida Bay. Changes in canal management could alter 
the spatial and temporal salinity regime in the estuary. To better predict the effect of 
such changes on estuarine habitat, abundances of submersed vegetation and benthic 
animals were sampled repeatedly at 12 stations during 1986 to 1987 that differed in 
salinity. A variety of other parameters were also measured (nutrients, light, 
temperature, oxygen, sediment characteristics, and others). Mean salinity among 
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