A review of coastal palaeoclimate and relative sea-level reconstructions using δ13C and C/N ratios in organic material

Morphodynamics of Holocene salt marshes: a review sketch from the Atlantic and Southern North Sea coasts of Europe

/pdf/the-role-of-standing-dead-spartina-alterniflora-and-benthic-2l8o0q83du.pdf

The role of standing dead Spartina alterniflora and benthic microalgae in salt marsh food webs: Considerations based on multiple stable isotope analysis

https://www.whoi.edu/cms/files/goni_et_al_GCA_1998_35807.pdf

A reassessment of the sources and importance of land-derived organic matter in surface sediments from the gulf of mexico

The stable isotope compositions (C and N) of plants and animals of a marsh dominated by Spartina alterniflora in the Delaware Estuary were determined. The study focused on the juvenile stage of the Atlantic blue crab, Callinectes sapidus, and the importance of marsh-derived diets in supporting growth during this stage. Laboratory growth experiments and field data indicated that early juvenile blue crabs living in the Delaware Bay habitat fed primarily on zooplankton, while marsh-dwelling crabs, which were enriched in 13C relative to bay juveniles, utilized marsh-derived carbon for growth. In laboratory experiments, the degree to which juvenile blue crabs isotopically fractionated dietary nitrogen, as well as the growth rate, depended on the protein quality of the diet. The range of δ13C of amino acids in laboratory-reared crabs and their diets was almost 20‰, similar to the isotopic range of amino acids of other organisms. In laboratory studies, the δ13C of nonessential and essential amino acids in the diet were compared to those in juvenile crabs. Isotopic fractionation at the molecular level depended on diet quality and the crabs' physiological requirements. Comparison of whole-animal isotope data with individual amino acid C isotope measurements of wild juvenile blue crabs from the bay and marsh suggested a different source of total dietary carbon, yet a shared protein component, such as zooplankton.

A food web analysis of the juvenile blue crab, Callinectes sapidus, using stable isotopes in whole animals and individual amino acids

Organic matter preserved in sediments of Georgia salt marshes derives from Spartina alterniflora and planktonic and bacterial substances. Sources and diagenesis of sedimentary organic material were studied by means of stable C and N isotopes and gas chromatography of pyrolysates from plants, suspended sediments, and a series of muds (modern to 1400 years old) from St Catherines Island, Georgia. Suspended particulate matter ( > 20 μm) has isotopic compositions (δ 13 C = −18 to −22), which are composed of an average 34–42% plankton carbon and 58–65% higher plant detritus, as determined by isotopic mass balance of the system. The δ 13 C of bulk sediments and humic acids (δ 13 C = −18 to −19) extracted from them remain relatively constant over time. The δ 13 C of acid hydrolysates, however, changed from − 15‰ in surface marsh sediment to a δ 13 C of −19 from sediment sampled at a depth of 125 cm. Higher-plant normal-hydrocarbons are present in muds and in particulate matter from the water column, and δ 13 C in lipids and gas chromatography of pyrolysates of samples reflect this addition. With increasing age, δ 15 N of total sediments and acid hydrolysates increases, and the ratio of odd-to-even hydrocarbons in the pyrolysates decreases. Initially, low density material in sediments consists primarily of plant fragments. With time, this material is decayed and diluted by microbial material, changes that are reflected by more negative δ 13 C of −15 to −17·5, as compared to δ 13 C of −12 for moden Spartina , and the addition of n-alkanes in the range of C 13–19 . The isotopic heterogeneity in surface sediments with carbon as an example, ranged from a δ 13 C of −15 (plant fragments) to −22 (sediment following lipid, humic acid, and plant fragment extraction). Nowhere was the C isotopic composition of total Spartina expressed even though microscopic plant pieces, lignocellulose pyrolysis fragments, and n-alkanes from C 22–27 were detected in suspended particulate matter, total sediments, and humic acids.

Andrew P. Gize

Papers

Diagenesis of organic matter in georgia salt marshes