13C

Feeding preferences of West Indian manatees in Florida, Belize, and Puerto Rico as indicated by stable isotope analysis

Alves-Stanley C.D., Worthy G.A.J., Bonde R.K. Feeding preferences of West Indian manatees in Florida, Belize, and Puerto Rico as indicated by stable isotope analysis. Marine Ecology Progress Series, Vol 402. pp. 255-267, 2010.

Vertical Stratification of δ 13C Values in Closed Natural and Plantation Forests in the Luquillo Mountains, Puerto Rico

MEDINA, E., L. STERNBERG, and E. CUEVAS. 1991. Vertical stratification of delta-C-13 values in closed natural and plantation forests in the luquillo mountains, puerto-rico. Oecologia 87 (3): 369-72.

Abstract: 
The variability of 13C values was measured in leaf, stem and root tissues of several tree species growing in closed natural and plantation forests in the Luquillo mountains of Puerto Rico. Results confirm a significant decrease of <513C values from the tree canopy to the forest floor. The values measured in understory plants growing in gaps were not significantly different from the average for plants growing under the forest shade. Seedling leaf values tended to be more positive than those of saplings, probably reflecting the contribution of organic matter from the mother tree. Photosynthetic independence on the forest floor results in a reduction in ?13C value. Stem and root tissue values of seedlings and saplings were less negative than those of the leaves of the same plants. It is suggested that this difference results from the slower change in isotopie composition experienced by the woody tissue, as the seedlings become photosynthetically independent in the forest floor.

Coral skeletal carbon isotopes (d13C and D14C) record the delivery of terrestrial carbon to the coastal waters of Puerto Rico

Moyer, R. P., and A. G. Grottoli. 2011. Coral skeletal carbon isotopes (delta(13)C and delta(14)C) record the delivery of terrestrial carbon to the coastal waters of puerto rico. Coral Reefs 30 (3) (SEP): 791-802.

Abstract: 
Tropical small mountainous rivers deliver a poorly quantified, but potentially significant, amount of carbon to the world’s oceans. However, few historical records of land–ocean carbon transfer exist for any region on Earth. Corals have the potential to provide such records, because they draw on dissolved inorganic carbon (DIC) for calcification. In temperate systems, the stable- (d13C) and radiocarbon (D14C) isotopes of coastal DIC are influenced by the d13C and D14C of the DIC transported from adjacent rivers. A similar pattern should exist in tropical coastal DIC and hence coral skeletons. Here, d13C and D14C measurements were made in a 56-year-old Montastraea faveolata coral growing *1 km from the mouth of the Rio Fajardo in eastern Puerto Rico. Additionally, the d13C and D14C values of the DIC of the Rio Fajardo and its adjacent coastal waters were measured during two wet and dry seasons. Three major findings were observed: (1) synchronous depletions of both d13C and D14C in the coral skeleton are annually coherent with the timing of peak river discharge, (2) riverine DIC was always more depleted in d13C and D14C than seawater DIC, and (3) the correlation of d13C and D14C was the same in both coral skeleton and the DIC of the river and coastal waters. These results indicate that coral skeletal d13C and D14C are recording the delivery of riverine DIC to the coastal ocean. Thus, coral records could be used to develop proxies of historical land– ocean carbon flux for many tropical regions. Such information could be invaluable for understanding the role of tropical land–ocean carbon flux in the context of land-use change and global climate change.

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.
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