1989 - 1990 
Ley, J. A., C. L. Montague, and C. C. Mclvor (1994) Food habits of mangrove fishes: a 
comparison along estuarine gradients in northeastern Florida Bay. Bull. Mar. Sci. . 
54(3):881 -99. 
Gut analyses were performed on 1,081 fishes from four species resident in mangrove 
habitats in northeastern Florida Bay to determine: (1) if the diets varied 
systematically along complex salinity gradient; and (2) if diets in the upstream areas 
were of lower overall quality than those from portions of the gradient with less 
salinity variability. Fishes commonly consumed amphipods, isopods, shrimp, 
nematodes, eggs of unknown origin, fish, insects, and algae. Diets of two of the four 
species differed significantly along the estuarine gradient. This systematic variation in 
diet along the longitudinal gradient may distinguish locations in terms habitat quality. 
The tidewater mojarra ( Eucinostomus harengulus) and goldspotted killifish 
(Floridichthys carpio) ingested more algae, a relatively low quality food, upstream in 
areas of high salinity variability. These same species ingested more benthic 
invertebrates, relatively high quality foods, downstream in areas of lesser salinity 
variability. If the premise that gut contents of fishes are a good indicator of habitat 
quality is accepted, then these upstream locations afford fishes a relatively poor 
quality habitat. It is proposed that highly variable amounts of submerged aquatic 
vegetation in upstream locations provide reduced and variable abundances of benthic 
invertebrates for fishes at these sites. Our results, combined with those of others 
cited herein, provide support for the hypothesis that water management practices in 
the catchment of northeastern Florida Bay may be, at least in part, responsible for 
lowered productivity there. We suggest that gut contents of resident fishes can be used 
as one measure of habitat quality as part of a comprehensive monitoring and 
restoration program for the region. Sampling took place in two upstream locations, Joe 
Bay and Highway Creek; two midstream locations, Trout Cove and Little Blackwater 
Sound; and two downstream locations, Buttonwood Sound and Blackwater Sound, from 
1989 to 1990. In addition to the two species mentioned above, gulf killifish ( Fundulus 
grandis) and redfin needlefish ( Strongylura notata) were also collected. 
1989 - 1990, 1992 
Carlson, P. R., L. A. Yarbro, and T. R. Barber (1994) Relationship of sediment sulfide to 
mortality of Thalassia testudinum in Florida Bay. Bull. Mar. Sci. . 54(3):733-46. 
Sediment porewater sulfide concentrations in Florida Bay seagrass beds affected by the 
catastrophic mortality of Thalassia testudinum (turtlegrass) were considerably higher 
than those of seagrass beds in the Indian River, Charlotte Harbor, or Tampa Bay. 
Sulfide concentrations in apparently healthy seagrass beds were highest in fall and 
might have contributed to chronic hypoxic stress of Thalassia roots and rhizomes. High 
porewater sulfide concentrations measured in dying areas of seagrass beds suggest 
that sulfide produced by microbial degradation of dying Thalassia might exacerbate 
stress on adjacent, surviving seagrass. Sulfide concentrations in recent die-off areas 
initially were higher than in adjacent, surviving grass beds. By the end of the study, 
however, the pattern was reversed apparently due to depletion of Thalassia- derived 
organic matter in the sediments of die-off areas. In June 1990 high sulfide 
concentrations preceded a die-off episode at one site, suggesting (1) elevated sulfide 
concentrations might be involved in a suite of factors that trigger die-off episodes or 
(2) elevated porewater sulfide results from death and decomposition of below ground 
Thalassia tissue before necrosis of shoots becomes visible. In either case, elevated 
porewater sulfide concentrations might be of value in predicting die-off. We conclude 
that porewater sulfide probably is not the primary cause, but a synergistic stressor, 
which has acted in concert with factors (such as hyperthermia, hypersalinity, and 
microbial pathogens) suggested by other researchers, to cause Thalassia die-off in 
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