Mangrove Organic Matter Research Articles

Fate of mangrove organic matter along a subtropical estuary: small-scale exportation and contribution to the food of crab communities

The export of mangrove primary production to adjacent habitats has long been regarded as playing a significant role in estuarine food webs. In the Logan River Estuary, a sub- tropical estuary situated in the southern part of Moreton Bay in Queensland, Australia, we used the fatty acid markers approach to investigate this export and its contribution to the estuarine food web, compared to other sources. During summer and autumn of 2004, 4 stations were sampled along a salinity gradient. Surface sediment samples were collected, using pre-cut syringes, in the mangrove forest of each station and in the adjacent tidal flats. Individuals of dominant crab species were also collected from the mangrove forests. Seasonal differences in fatty acid compositions of the surface sediments within the mangrove forests and along the adjacent banks were recorded, indicating that organic matter inputs varied between summer and autumn. Results also showed that mangrove production was accumulated at the surface sediments in some parts of the estuary during autumn and consequently was not exported to the tidal flat. The fatty acid composition of crab species present in the mangrove showed obvious differences between the grapsid and the ocypodid crabs collected from the estuary. These differences most likely reflect the distinctive feeding strategies of the crab groups, although there was some indication of species-specific biosynthesis/accumulation of certain polyunsaturated fatty acids. The grapsid of this study, Paras- eserma erythodactyla, in addition to being more dependent on mangrove leaves than the ocypodid crabs, is shown to potentially feed on fungal biomass.

Organic carbon sources to SE Asian coastal sediments

The carbon, nitrogen and the stable carbon isotopic composition, δ 13C, of organic matter has been used to elucidate the source(s) of this material to coastal sediments. Sediments were collected at 15 coastal locations in the Philippines and Vietnam, which broadly represented different depositional environments ranging from seagrass meadows, through seagrass meadows located near mangroves and to mangrove stands. In addition, short-term sediment traps were deployed at 12 of the sites where seagrass was present. Mean sediment organic carbon concentration and C/N increased and δ 13C of organic matter decreased from seagrass to mangrove dominated settings. The organic carbon flux measured by the sediment trap deployments was very variable (32±3 to ∼700 mmol m −2 d −1) and represented only a small fraction of the total particle flux. The importance of seagrass as a source of organic matter to the sediments was assessed by using a simple mixing model and the average δ 13C values for seagrass, their epiphytic community and surface water particulate matter (seston). A positive correlation between seagrass leaf biomass and sediment δ 13C in seagrass dominated settings suggests that these macrophytes do significantly influence the composition of sedimentary organic matter. Seagrass was however rarely found to be the dominant source of organic matter to the underlying sediments. Both sediment trap and sediment data suggest that material of planktonic origin was the dominant source of sedimentary organic matter in these settings. At the sites dominated by mangroves the concentration of organic matter ( ∼1–13 ×10 3 mmol g −1 ) in the sediment is generally higher than at seagrass dominated sites due to the outwelling of organic matter from the mangrove stands. Mangrove organic matter often dominates the sedimentary input but other sources of organic matter must contribute to cause the observed range in sediment δ 13C.

Taraxerol and Rhizophora pollen as proxies for tracking past mangrove ecosystems

Angola Basin and Cape Basin (southeast Atlantic) surface sediments and sediment cores show that maxima in the abundance of taraxerol (relative to other land-derived lipids) covary with maxima in the relative abundance of pollen from the mangrove tree genus Rhizophora and that in the surface sediments offshore maxima in the relative abundance of taraxerol occur at latitudes with abundant coastal mangrove forests. Together with the observation that Rhizophora mangle and Rhizophora racemosa leaves are extraordinarily rich in taraxerol, this strongly indicates that taraxerol can be used as a lipid biomarker for mangrove input to the SE Atlantic. The proxy-environment relations for taraxerol and Rhizophora pollen down-core show that increased taraxerol and Rhizophora pollen abundances occur during transgressions and periods with a humid climate. These environmental changes modify the coastal erosion and sedimentation patterns, enhancing the extent of the mangrove ecosystem and/or the transport of mangrove organic matter offshore. Analyses of mid-Pleistocene sediments show that interruption of the pattern of taraxerol maxima during precession minima occurs almost only during periods of low obliquity. This demonstrates the complex environmental response of the interaction between precession-related humidity cycles and obliquity-related sea-level changes on mangrove input.

Anoxic Decomposition in Sediments from a Tropical Mangrove Forest and the Temperate Wadden Sea: Implications of N and P Addition Experiments

The anoxic decomposition processes in sediments from a tropical mangrove forest (Bangrong, Thailand) and a salt marsh in the temperate Wadden Sea (Denmark) were compared, and the effects of increased ammonium and/or phosphate concentrations on the anoxic decomposition were studied. Sediment was incubated in jars (20-ml glass vials) and changes in porewater solutes were followed in a time series of 3 weeks. Furthermore, the short-term fate (days) of dissolved inorganic phosphate (DIP) added to Bangrong mangrove sediment was evaluated from phosphorus fractionation. Although the organic matter at both study sites had relatively high C:N and C:P ratios, the anoxic sediment decomposition was not affected by nutrient enrichments at the level applied in this study. The sediment metabolism (TCO2and DOC production, and sulfate consumption) was 5–10 times higher in Wadden Sea sediment than in Bangrong mangrove sediment, probably due to the higher content of structural carbohydrates (e.g. cellulose) as indicated by higher C:N and C:P ratios in mangrove organic matter. This is substantiated by a lower nutrient release from Bangrong mangrove sediments and suggests a faster turnover of N and P by nutrient deficient bacteria in the mangrove sediment. DIP was released during anoxic decomposition in Wadden Sea sediment, but was retained in Bangrong mangrove sediment. Analysis of phosphorus fractions in Bangrong mangrove sediment revealed that added excess DIP was efficiently taken up by the sediment particles and primarily retrieved in the easily exchangeable and iron bound fractions. The studied mangrove forest sediment seems to be a phosphorus sink.

D13C Signatures of Flora, Macrofauna and Sediment of a Mangrove Forest Partly Affected by Sewage Wastes.

Stable carbon isotope ratios (d13C) of sediments, suspended particulate matter, and crab gut content from Maruhubi mangrove forest, Zanzibar, were determined. Stable carbon isotope ratios were used to determine sources of organic matter in the forest. Mangrove organic carbon (d13C±SD = - 27.97±0.25) was found to be an important component of the sediment organic matter except at the marine fringe zone (d13C±SD = - 17.26±0.83). The areal distribution of d13C values show that the marine fringe zone was rich in organic carbon of marine origin. The terrestrial fringe zone was dominated by a mixed source of sediment organic carbon (d13C±SD =-24.89± 0.72). Vertical variations in d13C were not so obvious, showing a diminishing importance of mangrove organic matter below 60 cm in the sediments of the terrestrial fringe zone. Stable carbon isotope ratios of the major primary producers in the mangrove forest were reflected to a reasonable extent in the terrestrial fringe surficial sediment organic carbon. Stable carbon isotope ratios for plant and sediment organic carbon gave values in the range of - 27.67 to - 28.31 o/oo for mangroves and - 17.57 to - 24.89 o/oo for surface sediment (0 - 5 cm). Marine fringe sediments receive organic matter of marine origin to a large extent, in comparison to terrestrial fringe sediments, which contain mainly organic matter of mangrove origin. Tanzania Journal of Science Volume 26 (2000), pp. 15-28

The Effect of Mangrove Leaf Litter Enrichment on Macrobenthic Colonization of Defaunated Sandy Substrates

The importance of exported mangrove materials to nearshore macrobenthos has largely been predicted based upon decomposition and utilization studies conducted within the mangrove environment, and from quantitative measurements of export. The present study evaluated the impact of mangrove leaf litter enrichment on non-mangrove substrates in a high-salinity microcosm experiment. Fortnightly addition of Kandelia candel leaf detritus at levels equivalent to 0·66 and 0·33mgcm−2day−1in defaunated sand in microcosms maintained under high salinity conditions and on a sandy substrate resulted in no significant differences from the control in total faunal dry biomass or ash-free dry weight (AFDW) after 28, 73, 137 and 217 days of experiment. Duration of experiment was significant in determining the biomass (both dry weight and AFDW) of the macrofaunal assemblage in the microcosms, but neither enrichment nor its interaction with time had an effect. Species richness, Shannon diversity and evenness, and the total number of individuals, however, decreased in the order control>low enrichment>high enrichment for almost all sampling dates. By contrast, soluble tannins in the microcosm sediment demonstrated the reverse pattern. Both duration of experiment and enrichment were significant in determining species richness and the total number of individuals. The interaction between time and enrichment level was significant in the former but not the latter case. Discriminant analysis performed on the species abundance data indicated distinct animal assemblages characteristic of the three enrichment levels. These findings suggest that mangrove organic matter may not necessarily result in enhancement effects on marine benthos but high concentrations of tannins may hamper colonization by the macrobenthos.

Potential trophic importance of the faecal material of the mangrove sesarmine crab Sesarma messa

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 159:275-284 (1997) - doi:10.3354/meps159275 Potential trophic importance of the faecal material of the mangrove sesarmine crab Sesarma messa S. Y. Lee* The Swire Institute of Marine Science, and Department of Ecology & Biodiversity, The University of Hong Kong, Pokfulam Road, Hong Kong *Present address: School of Applied Science, Griffith University Gold Coast, PMB 50 Gold Coast Mail Centre, Queensland 9726, Australia. E-mail: joe.lee@gu.edu.au The potential trophic importance of the sesarmine crab Sesarma messa Campbell in a northeastern Australian mangrove dominated by Rhizophora stylosa Griff. was evaluated by quantifying the rates of mangrove leaf litter consumption, the corresponding faecal production and assimilation efficiency of mangrove organic matter by the crab. S. messa seems to remove primarily carbon rather than nitrogen from the mangrove litter, as is reflected by the decrease in C but slight increase in N content of the faeces over mangrove litter. Assimilation efficiency for mangrove organic matter was only at about 50%. The potential significance of the crab faecal material in initiating a coprophagous food chain involving mangrove invertebrates was assessed by a series of growth experiments using the hyalid amphipod Parhyalella sp., which is commonly (mean density of 204 ind. l-1 of detritus) found amongst accumulated detritus near the mangrove forest. Parhyalella sp. individuals fed with crab faecal material or a mixture of faecal material and mangrove detritus attained significantly higher moulting frequency but lower mortality rates than their counterparts in the mangrove detritus only treatment and the control (no food) over a period of 26 d, although % gut fullness was not significantly different amongst the 3 diet treatments. Assimilation of crab faecal material by Parhyalella sp. was almost complete, while individuals fed with R. stylosa litter could assimilate only about 51% of the organic matter in their diet. Decomposition of crab faecal material resulted in a significant increase in N but decrease in C content over 24 d. The C/N ratio of the faecal material was significantly lower than that of the mangrove litter from which it was generated and decreased linearly with time of decomposition. S. messa therefore are not only important as a significant agent effecting fast recycling of mangrove leaf litter, but their faeces, from leaf litter consumption, may also form the basis of a coprophagous food chain contributing to mangrove secondary production by small invertebrates such as Parhyalella sp. Coprophagy · Mangrove leaf litter · Sesarmine crabs · Amphipod · Assimilation efficiency Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 159. Publication date: November 29, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.