Florida Mangrove Research Articles

Mangrove ecosystem development in Biosphere 2

Southwest Florida mangrove forest vegetation was successfully transplanted into a mesocosm within Biosphere 2. Dense stands of mangroves with characteristics comparable to natural Florida mangrove forests developed from the small seedlings and saplings initially installed in the mesocosm. Mangrove overstory was evaluated by leaf area index which ranged from 2.16 to 4.02 m 2/m 2. Mangrove understory decrease was monitored as the mangrove overstory developed. The Biosphere 2 mesocosm is compared with a similarly planted mesocosm at the Smithsonian Institution in Washington DC. The performance of these mesocosms is used to evaluate existing theories on natural mangrove forest species composition.

Spongivory by Parrotfish in Florida Mangrove and Reef Habitats

Abstract. Although parrotfish are generally reported to be herbivorous, increasing evidence suggests that some Caribbean species feed on sponges. After observing grazing scars on the barrel sponge, Xestospongia muta, 40 sponges were videotaped on three reefs for >0.5 h to determine the frequency of parrotfish bites on this species. A total of 10 h of video recording captured 45 bites on normally coloured X. muta and 527 bites on four bleached X. muta by the parrotfish Sparisoma aurofrenarum, Scarus croicensis and Scarus taeniopterus. The viscera gut and liver of 55 parrotfish collected from mangrove and reef habitats were digested in nitric acid and analysed for spicule content. The parrotfish collected in the mangroves mostly Scarus guacamaia and Sparisoma chrysopterum had significantly higher masses of spicules in their viscera than did parrotfish collected on the reef Sparisoma aurofrenatum, Sparisoma viride, Sparisoma chrysopterum, Scarus vetula, Scarus coelestinus and Scarus taeniopterus. The spicules of Geodia gibhrrosa, a chemically undefended sponge that is common in the mangroves but rare in exposed locations on the reef, were abundant in the viscera of parrotfish collected in the mangroves. These results provide further evidence that fish predation has an important effect on the distribution and abundance of Caribbean sponges.

Rhizophora mangle L. Seedling Development into the Sapling Stage across Resource and Stress Gradients in Subtropical Florida1

ABSTRACTNutrient, light, salinity, soil redox potentials, and other soil characteristics were determined across a range of mangrove forest heights across the South Florida peninsula encompassing large‐stature trees (> 10 m) on the west coast and dwarf forms (< 1 m) in the southeast Everglades. Relationships were established between abiotic factors and Rhizophora mangle seedling growth rates in four height (cm) classes, 25‐40, > 40‐55, > 55–70, and > 70–85. Light in open canopy gaps was an important determinant of seedling growth. Growth rates in gaps (0.32 ± 0.04 to 1.89 ± 0.18 mm/d) were two‐ to five‐fold greater than adjacent closed canopy forests (0.14 ± 0.01 to 0.40 ± 0.07 mm/d). Among open canopy sites, labile soil phosphorus and soil redox potentials were significantly correlated to growth (P < 0.05; r= 0.98 and 0.89, respectively). Interstitial salinity ranged from 0 to 27 ppt across sites, well below hypersaline conditions. Thus, under low salinity stress and high light availabiliry, soil fertility is proposed to be the dominant factor controlling R. mangle seedling development to a sapling stage (> 85 cm) in South Florida mangrove forests. In addition, soil anoxia is hypothesized to be an important stressor in lagoonal‐bay estuaries and marsh‐mangrove ecotones with minimal tidal exchange.

Distribution and Sampling of Aedes taeniorhynchus (Diptera: Culicidae) Eggs in a Florida Mangrove Forest

The distribution of Aedes taeniorhynchus (Wiedemann) eggs in a Florida mangrove basin forest was quantified and used to design a sampling plan. Eggs were found in detritus-rich soil with the highest densities in a band at elevations 0.1-0.2 m above the water line. Dispersion indices (k and Taylor's b) indicated that the eggs were aggregated; 14 of 16 populations tested fit the negative binomial distribution. A fixed-size sampling plan using systematic sampling was designed from these data.

Isopod and Insect Root Borers May Benefit Florida Mangroves

Far from threatening the persistence and geographic extent of red mangrove (Rhizophora mangle) in Florida, wood-boring marine isopods may aid the plant to survive wave action by initiating branching of aerial prop roots. Evidence for a recent, sudden increase in density or range of one such isopod, Sphaeroma terebrans, is anecdotal and weak. Insect damage to mangrove aerial roots even before they descend to the water is at least as great as that wrought by isopods and also causes root branching. Aerial and submarine damage combine to stimulate root initiation so that, for every root produced aerially by the tree, at least 1.4 roots reach the substrate. Similar responses to herbivory, which have been reported for other plants, suggest that herbivores may both benefit and harm plants, and that their impact may be more difficult to assess in specific instances than has been realized.

Biological dinitrogen fixation (acetylene reduction) associated with Florida mangroves.

Biological dinitrogen fixation in mangrove communities of the Tampa Bay region of South Florida was investigated using the acetylene reduction technique. Low rates of acetylene reduction (0.01 to 1.84 nmol of C(2)H(4)/g [wet weight] per h) were associated with plant-free sediments, while plant-associated sediments gave rise to slightly higher rates. Activity in sediments increased greatly upon the addition of various carbon sources, indicating an energy limitation for nitrogenase (C(2)H(2)) activity. In situ determinations of dinitrogen fixation in sediments also indicated low rates and exhibited a similar response to glucose amendment. Litter from the green macroalga, Ulva spp., mangrove leaves, and sea grass also gave rise to significant rates of acetylene reduction. Higher rates of nitrogenase activity (15 to 53 nmol of C(2)H(4)/g [wet weight] per h were associated with washed excised roots of three Florida mangrove species [Rhizophora mangle L., Avicennia germinans (L) Stern, and Laguncularia racemosa Gaertn.] as well as with isolated root systems of intact plants (11 to 58 mug of N/g [dry weight] per h). Following a short lag period, root-associated activity was linear and did not exhibit a marked response to glucose amendment. It appears that dinitrogen-fixing bacteria in the mangrove rhizoplane are able to use root exudates and/or sloughed cell debris as energy sources for dinitrogen fixation.