Mangroves

Food Web Structure in Exotic and Native Mangroves: A Hawaii-Puerto Rico Comparison

Demopoulos, Amanda W. J., Brian Fry, and Craig R. Smith. 2007. Food web structure in exotic and native mangroves: A hawaii-puerto rico comparison. Oecologia 153 (3) (SEP): 675-86.

Abstract: 
Plant invasions can fundamentally alter detrital inputs and the structure of detritus-based food webs. We examined the detrital pathways in mangrove food webs in native (Puerto Rican) and introduced (Hawaiian) Rhizophora mangle forests using a dual isotope approach and a mixing model. Based on trophic-level fractionation of 0- \%of or <513Can d 2-3%c for Sl5N, among the invertebrates, only nematodes, oligochaetes, and nereid polychaetes from native mangroves exhibited stable isotopes consistent with a mangrove-deriveddi et. Certainf auna,i n particulartu bificid oligochaetes, had Sl3C values consistent with the consumption of mangrove leaves, but they were depleted in 15N, suggesting their primary nitrogen source was low in 15N, and was possibly N2-fixing bacteria. In introduced mangroves, all feeding groups appeared to rely heavily on nonmangroves ources, especially phytoplanktonin puts.M ixing model results and discriminant analysis showed clear separation of introduced and native mangrove sites based on differential food source utilization within feeding groups, with stronger and more diverse use of benthic foods observed in native forests. Observed differences between native and invasive mangrove food webs may be due to Hawaiian detritivores being poorly adapted to utilizing the tannin-rich, nitrogen-poor mangrove detritus. In addition, differential utilization of mangrove detritus between native and introduced mangroves may be a consequence of forest age. We postulate that increasing mangrove forest age may promote diversification of bacterial food webs important in N and S cycling. Our results also suggest a potentially important role for sulfur bacteria in supporting the most abundantin faunalc onsumers,n ematodes,i n the most mature systems.

Estimating the assimilation of mangrove detritus by fiddler crabs in Laguna Joyuda, Puerto Rico, using dual stable isotopes

France, R. 1998. Estimating the assimilation of mangrove detritus by fiddler crabs in laguna joyuda, puerto rico, using dual stable isotopes. Journal of Tropical Ecology 14 (JUL): 413-25.

Abstract: 
Dual stable isotope analyses (delta 13C and delta 15N) of fiddler crabs from a forest-fringed, land-locked lagoon in Puerto Rico indicated the differential assim- ilation of material from ingested sediments. Fiddler crabs preferentially selected foi niitrogen-fixing benthic microalgae (cyanobacteria) over vascular plant detritus. These results question the assumption that mangrove detritus is always the prin- cipal source of energy to estuariiie consumers. Previous research fiom this lagoon as well as from Amazonia suggests that the magnitude of lan-d-wvater ecotonal coupling may be low for these particular tropical systems where benthic algal productivity is presumably high.

Nutrient relations of dwarf Rhizophora mangle L. mangroves on peat in eastern Puerto Rico

Medina E, Cuevas E, Lugo AE (2010) Nutrient relations of
dwarf Rhizophora mangle L. mangroves on peat in eastern
Puerto Rico. Plant Ecol 207:13–24

Abstract: 
Dwarf mangroves on peat substrate growing in eastern Puerto Rico (Los Machos, Ceiba State Forest) were analyzed for element concentration, leaf sap osmolality, and isotopic signatures of C and N in leaves and substrate. Mangrove communities behind the fringe presented poor structural development with maximum height below 1.5 m, lacked a main stem, and produced horizontal stems from which rhizophores developed. This growth form departs from other dwarf mangrove sites in Belize, Panama, and Florida. The dwarf mangroves were not stressed by salinity but by the low P availability reflected in low P concentrations in adult and senescent leaves. Low P availability was associated with reduced remobilization of N and accumulation of K in senescent leaves, contrasting with the behavior of this cation in terrestrial plants. Remobilization of N and P before leaf abscission on a weight basis indicated complete resorption of these nutrients. On an area basis, resorption was complete for P but not for N. Sulfur accumulated markedly with leaf age, reaching values up to 400%, compared with relatively modest accumulation of Na (40%) in the same leaves. This suggests a more effective rejection of Na than sulfate at the root level. Dwarf mangrove leaves had more positive d13C values, which were not related to salinity, but possibly to drought during the dry season due to reduced flooding, and/or reduced hydraulic conductance under P limitation. Negative leaf d15N values were associated with low leaf P concentrations. Comparison with other R. mangle communities showed that P concentration in adult leaves below 13 mmol kg-1 is associated with negative d15N values, whereas leaves with P concentrations above 30 mmol kg-1 in non-polluted environments had positive d15N values.

Nutrient relations of dwarf Rhizophora mangle L. mangroves on peat in eastern Puerto Rico

Medina E, Cuevas E, Lugo AE (2010) Nutrient relations of
dwarf Rhizophora mangle L. mangroves on peat in eastern
Puerto Rico. Plant Ecol 207:13–24

Abstract: 
Dwarf mangroves on peat substrate growing in eastern Puerto Rico (Los Machos, Ceiba State Forest) were analyzed for element concentration, leaf sap osmolality, and isotopic signatures of C and N in leaves and substrate. Mangrove communities behind the fringe presented poor structural development with maximum height below 1.5 m, lacked a main stem, and produced horizontal stems from which rhizophores developed. This growth form departs from other dwarf mangrove sites in Belize, Panama, and Florida. The dwarf mangroves were not stressed by salinity but by the low P availability reflected in low P concentrations in adult and senescent leaves. Low P availability was associated with reduced remobilization of N and accumulation of K in senescent leaves, contrasting with the behavior of this cation in terrestrial plants. Remobilization of N and P before leaf abscission on a weight basis indicated complete resorption of these nutrients. On an area basis, resorption was complete for P but not for N. Sulfur accumulated markedly with leaf age, reaching values up to 400%, compared with relatively modest accumulation of Na (40%) in the same leaves. This suggests a more effective rejection of Na than sulfate at the root level. Dwarf mangrove leaves had more positive d13C values, which were not related to salinity, but possibly to drought during the dry season due to reduced flooding, and/or reduced hydraulic conductance under P limitation. Negative leaf d15N values were associated with low leaf P concentrations. Comparison with other R. mangle communities showed that P concentration in adult leaves below 13 mmol kg-1 is associated with negative d15N values, whereas leaves with P concentrations above 30 mmol kg-1 in non-polluted environments had positive d15N values.
Syndicate content