Mangrove Peat Research Articles

Developmental Processes of Mangrove Habitat Related to Relative Sea-level Changes at the Mouth of the Urauchi River, Iriomote Island, Southwestern Japan

In order to clarify geomorphologically the developmental processes of the mangrove habitats of Iriomote Island, topographic and surface geological surveys were performed along four lines in and around the mangrove habitat at the mouth of the Urauchi River in northwestern Iriomote Island.As a result, it was learned that the mangrove habitat of Iriomote Island has migrated in response to relative sea-level changes. It is especially worth noting that the mangrove habitat abruptly moved seaward by a relative sea-level fall that occurred about 1, 000yrs BP. During the rising sea-level phase between 2, 000yrs BP and 1, 000yrs BP, the mangrove forests of the island retreated, landward, which indicates that they are possibly more sensitive to sea-level changes than mangrove forests of tropical areas such as Micronesia and the Philippines, where landward movement of mangroves during this period has not recognized. On the other hand, at the Rhizophora stylosa habitat situated in the inner mangrove forest, it was found that the mangroves have maintained their habitat and position by accumulating mangrove peat against relative sea-level rise after 260yrs BP.

The Tobacco Range Fracture Zone, Belize, C.A.: a unique system of slumped mangrove peat

The Tobacco Range Fracture Zone, Belize, C.A.: a unique system of slumped mangrove peat

Holocene Siliciclastic-Carbonate Facies Mosaics, Northern Belize: Exploration Analog to Some Midcontinent Pennsylvanian (Morrowan) Reservoirs: ABSTRACT

Abstract Midwinter Lagoon is a large, shallow coastal lagoon, bordered on its seaward side by a barrier bar, along the mainland coast of northern Belize. As much as 19 ft of Holocene sediments, deposited on karsted Tertiary limestones during the Flandrian transgression, consist of a complex mosaic of mixed siliciclastic and carbonate facies. Basal transgressive marine, intra-lagoonal facies are variously siliciclastic-rich carbonates to carbonate-rich siliciclastics, locally with layers of shoreline mangrove peat. These facies shallow-upward to either siliciclastic or carbonate-dominated sands or muds. Lagoonal facies were deposited within a broad topographic low, locally punctuated by bedrock highs, on the underlying limestone. The seaward edge of the barrier bar complex, which was deposited on a linear topographic high, consists mostly of quartz sands, whereas the lagoonal side is a mixture of quartzose and carbonate sediments (sands and muds). The barrier bar appears to have accreted southward in response to southerly longshore drift as a tidal inlet-spit complex; quartz sands are being transported into the lagoon from its seaward side. In terms of geometry, modem and buried, intra-lagoonal carbonate sands occur as lobes deposited proximal to extant and older tidal inlets. Either carbonate or siliciclastic sands variously occur as erratically distributed, anastomosing beach deposits around small mangrove islands and along the irregular mainland coast. In contrast, siliciclastic sands on the seaward side of the barrier bar define a narrow but areally persistent linear trend. Similar complex facies associations and geometries are typical of many Pennsylvanian (Morrowan) reservoirs in the midcontinent United States.

Holocene Palaeosalinity in a Maya Wetland, Belize, Inferred from the Microfaunal Assemblage

A 5.4-m sequence of peat and marl overlying a basal clay in a northern Belize wetland was studied to assess salinity changes over the past 7000 yr. The distribution of ostracods, gastropods, and foraminifers revealed initially freshwater conditions in a terrestrial wetland, changing to at least mesohaline conditions by about 5600 yr B.P. The mesohaline conditions corresponded to the formation of an open-water lagoon (and precipitation of a lacustrine marl) that was contemporaneous with rapidly rising sea level in the area. A mangrove peat filled the lagoon by 4800 yr B.P. probably as a result of increasingly shallow waters as sea level rise slowed and marl precipitation continued. A new lagoon began to form sometime after 3400 yr B.P. Freshwater ostracods and gastropods found in the marl of this lagoon suggest that it formed under near-limnetic conditions. Freshwater input likely resulted from massive deforestation by the Maya that began by 4400 yr B.P. Subsidence of the mangrove peat likely permitted the formation of a lagoon. A peat has filled the lagoon since at least 500 yr B.P.

Development process of tidal-flat type mangrove habitats and their zonation in the Pacific Ocean

Using the sites of Pagbilao, the Philippines and Pohnpei Island, the Federated States of Micronesia, zonation and development process of mangrove habitats on tidal flats situated in the geomorphic environment excluding estuary, delta, and lagoon or backmarsh behind barrier or beach ridge were discussed from the viewpoint of geomorphology. Zonations of the mangrove forests were observed from seaward to landward in both areas. Most of the zones correspond with the variations of the ground level or deposit. Mangrove peat which has a thickness of about 2 meters was deposited in the main part of the mangrove habitats in both areas. On the other hand, some large Sonneratia alba were observed in the Rhizophora apiculata habitat on Pohnpei Island

Modern stromatolite reefs fringing a brackish coastline, Chetumal Bay, Belize

Reef-forming stromatolites have been discovered along the windward shoreline of Chetumal Bay, Belize, just south of the mouth of the Rio Hondo. The reefs and surrounding sediment are formed by the precipitation of submicrocrystalline calcite upon the sheaths of filamentous cyanobacteria, principally Scytonema , under a seasonally fluctuating, generally brackish salinity regime (0‰10‰). Well-cemented, wave-resistant buttresses of coalesced stromatolite heads form arcuate or club-shaped reefs up to 42 m long and 1.5 m in relief that are partially emergent during low tide. Oncolitic rubble fields are present between well-developed reefs along the 1.5 km trend, which parallels the mangrove coastline 40-100 m offshore. The mode of reef growth, as illustrated by surface relief and internal structure, changes with increasing water depth and energy, proximity to bottom sediments, and dominant cyanobacterial taxa. Sediment trapping and binding by cyanobacteria are of limited importance to reef growth, and occur only where stromatolite heads or oncolites are in direct contact with the sandy sea floor. Radiocarbon-dated mangrove peat at the base of the reef suggests that it began to form about 2300 yr B.P., as shoreline encrustations that were stranded offshore following storm-induced retreat of the mangrove coast.

Natural sinks of CO2: Technical synthesis from the palmas Del Mar Workshop

Natural CO2 sinks in terrestrial and marine environments are important components of the global carbon cycle, yet the sign and magnitudes of key fluxes among them are unknown. The results of the Palmas Del Mar Workshop — Natural Sinks of CO2 presented in this special issue and its companion hardbound volume of Water, Air, & Soil Pollution, provide a synthesis of current research on the carbon cycle, CO2 sinks and associated processes and fluxes, and critical research needs to assess the potential role of forest and land-use management in carbon sequestration. The papers in this volume present data, observations, and model simulations that demonstrate: 1) the existence of natural CO2 sinks that could mitigate a significant amount of CO2 emissions from fossil-fuel combustion; 2) probable, human-caused imbalances in C exchanges among vegetation, soils, and the atmosphere; 3) enhanced C storage in vegetation in response to excess atmospheric CO2; 4) strong interactions among carbon, nutrient and hydrological cycles; and 5) an excess of carbon production over consumption in several, large managed forests. Although it appears unlikely that the search for the “missing” C sink required to balance the C budget will end in the open ocean, new estimates of C storage in mangrove wood and peat, suggest that coastal ecosystems have the capacity to store significant amounts of carbon in vegetation and sediments. Convincing analyses are also presented indicating the technical and economical feasibility of managing existing lands to sequester additional carbon. Long-term field studies of CO2 fertilization effects and carbon cycling by plants and soils in geographically important systems, native forests, and coastal ecosystems will go a long way toward meeting the research needs identified at the workshop.

Mangrove-generated structures and depositional model of the pleistocene fort thompson formation (Florida plateau)

The carbonate Fort Thompson Formation (Pleistocene) of the South Florida platform consists of regular alternations of marine, brackish and terrestrial lithofacies 1) mollusk packstones and grainstones (estuaries, banks, patch-reefs, bioturbated nearshore zone, marsh flat); 2) mangrove peats; 3)Helisoma wackestones (saw grass prairie, freshwater pond, buttonwood hummock), and 4) freshwater swamp. The corresponding environments represent a low-energy coastline. Lithofacies are arranged into stacked sequences. Three modal asymmetric regressive parasequences (‘A’;‘B’;‘C’) reflect relative sea-level rises; the lower part of sequence ‘A’ is analogous to the Lofer cycles; sequence ‘B’ is similar to the Holocene cycle from Florida Bay; sequence ‘C’ is analogous to present-day swamp cycles forming in the Everglades. Correlations of transgressive surfaces point out a wedge with parasequences thinning-out and disappearing towards a hinge located to the west. Geometrical considerations suggest that rotational subsidence was initially the main control on sedimentation and led to the deposition of parasequences ‘A’. Subsequently, its attenuation highlighted eustatic changes which are more apparent higher up in the Formation; parasequences ‘B’ and ‘C’ formed under the main influence of eustatic factors.

The Pacific palaeogeography of Rhizophora mangle L. (Rhizophoraceae)

ELLISON, J. C, 1991. The Pacific palaeogeography of Rhizophora mangle L. (Rhizophoraceae). The American red mangrove, Rhizophora mangle is disjunct in its occurrence between the Neotropics and an outlier in the south-west Pacific, a distribution which has been speculated upon for over a century. The species is shown to be indigenous in Tonga, the first such evidence from the outlier, with certain identification of abundantly occurring pollen in an early Holocene mangrove peat, that pre-dates the arrival of man by some 2500 years. It is suggested from review of world-wide fossil records that the species crossed the Pacific eastwards during the Eocene, facilitated by land connections resultant from low stands of sea level and before major subsidence of the Pacific plate. Then subsidence of the Pacific plate caused local extinctions on islands of the central and eastern Pacific as they periodically submerged, the species not able to recolonize from either refuges west of the Andesite line or America due to loss of land connections and its poor dispersal capability.

Upland Soil and Fertilizer in Rhizophora Mangrove Growth on Oiled Soil

ABSTRACT Upland soil placed in small excavated holes in an oiled mangrove forest was found to be markedly superior to adjacent oiled soil as a medium for growing Rhizophora mangrove propagules and seedlings, even though the oil from the 1986 spill had weathered to the extent that it caused no mortality in planted propagules. The low value of oiled soil was not ameliorated by fertilizer. The inferior value of the oiled mangrove soil compared to upland soil appears to derive from the nature of old Rhizophora mangrove peat as a poor substrate for growth of young seedlings, rather than to residual oil toxicity. Planting of propagules in upland soil in the field was substantially less expensive than growing and planting out nursery plants.

Occurrence and origin of carbohydrates in peat samples from a red mangrove environment as reflected by abundances of neutral monosaccharides

Acid hydrolysates of fractionated red mangrove peat samples and handpicked roots and rootlets of Rhizophora mangle (red mangrove) from Jewfish Key in the Florida Everglades were analysed for neutral monosaccharides. In the peat samples two major sources of carbohydrates could be determined: 1. (1) vascular plant carbohydrates derived from Rhizophora mangle and 2. (2) microbially derived carbohydrates. Significant correlations exist between the relative contributions of most neutral monosaccharides and the total carbohydrate concentration. The fine-grained peat fractions yielded low total neutral monosaccharides whose distributions indicate contributions of microbial carbohydrates. The coarse-grained peat samples yielded high total neutral monosaccharides with distributions indicating major contributions of vascular plant carbohydrates. It is estimated that a substantial part of the sugars analysed in the finegrained samples originates from microorganisms ([cyano] bacteria, algae).The absence of a trend in total neutral monosaccharide concentrations with depth suggests that microbial degradation is limited to the upper levels of the peat and that the microbial sugars determined at lower peat levels are derived from nonviable or dormant microorganisms. Results from factor analysis may suggest differences in microbial populations in the various peat samples.

Setting of and Mixed Carbonate-Siliciclastic Facies Associated with Holocene Nearshore Sabellid Worm Reefs, Northern Belize: ABSTRACT

Communities of sabellid worms (Polychaeta) in northern Belize (mouth of Northern River Lagoon) occur as areally discontinuous, unlithified patch reefs cresting positive features on an irregular depositional topography of Holocene and older sediments. They are found in nearshore marine, moderate energy, tidally influenced environments (intertidal to 60-cm depths) of normal salinity (36%) adjoining subtidal deposits. These colonies, as much as 30 cm thick, are composed of dense thickets of agglutinating worm tubes (1.0 mm diameter, 3.0 cm long) that trap and bind sand to silt-size bioclastic debris and micrite. Worm population density in these communities averages 30 tubes/cm{sup 2}. The antecedent depositional topography beneath the worm reefs and subjacent to adjoining Holocene deposits is characterized by ridges oriented normal to the present shoreline. These ridges are held up by pre-Holocene (latest Pleistocene ) terrigenous sands of probably fluvial distributary origin, occurring at approximately 2.0 m in the subsurface. The overlying Holocene deposits on these ridges are 2.0 m thick and consist of a general upward-coarsening section of terrigenous sandy, carbonate sandy muds to muddy sands punctuated by mangrove peats and capped by the worm reefs. Low areas on the antecedent topography are presently the sites of deposition of deeper subtidalmore » (1.0 m), muddy carbonate sands with some admixed, reworked terrigenous sand. The Holocene section records drowning due to recent (approximately 6 Ka) transgression of the older, lowstand distributary sands on the northern Belize shelf. This mixed carbonate-siliciclastic section and the worm reefs presently are being reshaped and modified by littoral processes.« less

Late Holocene higher sea level indicators from eastern Australia

New age data from intertidal organisms exposed on coastal cliffs in northern New South Wales suggest that in that area sea level was slightly more than 1 m higher about 3420 yrs B.P. and may have fallen to its present level since 1780 yrs B.P. These findings, if regionally significant, are important because they indicate that the tidally constructed zonations of organisms on high-energy, rocky coast could provide a more precise record of sea level behaviour than the study of constructional geomorphic features (often related to storm events) such as beach ridges, chenier plains, tidal deltas etc. or mangrove peats.

Pollen analysis of mangrove sediments as a sea-level indicator: assessment from Tongatapu, Tonga

Increasing necessity for precision in Holocene sea-level records calls for definitive sea-level indicators to be assessed. These are reviewed by use of examples from the S.W. Pacific, and the technique of pollen analysis of mangrove sediments evaluated as a high resolution sea-level indicator. Example is given how a fully calibrated sea-level reconstruction can be gained from Holocene mangrove peat units from Tongatapu, Tonga, by application of features established from a modern analogue of surface samples to interpret fossil pollen patterns.

Taxonomic uniformitarianism: The problem with shoot/root ratios of peats

The ratio of shoot to root debris is readily measured in both ancient and modern peats. Several ecological causes of shoot-poor peats have been suggested, but these are based on comparisons between taxonomically dissimilar peat-forming swamps. Here we evaluate the ecological significance of shoot/root ratios in taxonomically similar, yet ecologically variable communities: mangrove swamps. Our preliminary data indicate that all mangrove peats are shoot-poor regardless of environment of deposition. The shoot-poor nature of mangrove peats may be the result of some factor which is universally present in mangrove swamps and does not vary with local environment. We discuss the possibility that the growth habit of mangroves species themselves may account for the scarcity of aerial debris in mangrove peats. For example, mangrove species tend to have a larger portion of their living biomass as roots when compared to non-mangrove tree species. Further, mangrove species tend to form root mats which would serve to exclude aerial debris from sub-surface layers until aerobic degradation is complete. Neutral pH, which occurred in both the freshwater and saline mangrove localities studied, may also contribute to the production of shoot-poor peats. Since freshwater, shoot-rich peats do occur, we conclude that processes of peat formation vary. Universal statements correlating environments of deposition to peat characteristics should be applied with caution.

Decelerating Holocene Sea-Level Rise and its Influence on Southwest Florida Coastal Evolution: A Transgressive/Regressive Stratigraphy

ABSTRACT The Ten Thousand Islands (TTI) are a myriad of low-relief mangrove islands that lie along the low energy, subtropical southwest Florida coast. The region has been subjected to a relative rise in Holocene sea level, which has continuously decelerated to its present rate. Data derived from surface and subsurface sampling indicate that the Holocene sediment package of the TTI area consists of two sediment sequences. The lower sequence is transgressive and was generated as coastal salt marsh and/or terrestrial environments were submerged and replaced by a shallow coastal marine setting. The upper sediment sequence consists primarily of 1) biogenic shallowing upwards sequences or 2) thickened mangrove peat layers, reflecting island emergence and shoreline stabilization, respectively. Island emergence compartmentalized the area, further reducing wave and current energy and promoting the infilling of the protected bays through deposition of organic-rich shelly mudstone and wackestone. Based on coastal stratigraphy and 14C dates, the formation of his transgressive/regressive sediment sequence is directly related to changing rates of Holocene sea-level rise, reported to have occurred between 3,500 and 3,200 YBP. Continued regressive sedimentation could eventually generate a 5-10 m thick transgressive/regressive sediment couplet, with an aerial extent of over 300 km2, in roughly 10,000 years. This externally forced sediment couplet compares remarkably well to individual small scale transgressive/regressive cycles which repeat tens to hundreds of times throughout the geologic record (see James 1984). The results of this study thus support the allocyclic mechanism as a viable working hypothesis for the generation of these small scale rock cycles.

Marine sedimentary environments on some parts of the tropical and equatorial Atlantic margins of Africa during the Late Quaternary

From 18,000 y B.P. up to the Present, major climatic changes combined with eustatic sea-level irregular rise controlled important variations in sedimentary conditions on the Atlantic African margin between 6°S and 21°N. The present shelf deposition of material is also controlled by climatic latitudinal gradients acting on the nature, volume and distribution of terrigenous and carbonate sediments. The evolution of sedimentary conditions during this period may be summarized as follows. Coastal terrigenous deposition Fluvial sands were emplaced in inner shelf paleo-valleys during the beginning of the Wiscon sinian regression, following a major erosion phase providing an important source for the siliciclastic part of the terrigenous influx. In tropical regions (Mauritania, Senegal), aeolian dune sands formed during the arid “glacial” period (the so-called Ogolian) on the emerged shelf, but were destroyed during the subsequent transgression. In the vicinity and south of the Equator (Coˆte d'Ivoire, Congo), aeolian input was reduced but litoral dunes of that period occurred whose remnants may be observed close to the present shoreline. At the lower stand of sea level, fine particles directly by-passed the shelf towards the continental rises and abyssal plains. During the Holocene transgression, the main sedimentary processes occurred only when standstill or slowing of the sea-level rise took place. Then littoral deposits (fine sands of the shore, dune sands and even lagoonal deposits with mangrove peats) accumulated still more or less visible paleo-shorelines. However, offshore from the equatorial river mouths, particularly the main ones (Congo), pelitic sediments settled in morphological and structural lows. High sedimentation rates were common at the beginning but they decreased during the final part of the transgression. In the tropical region terrigenous fluvial input is considerably reduced but, in their northernmost parts, aeolian contribution of silts and ultrafine sands is recorded in the surficial sediments. Carbonate biogenic deposition The main sedimentary unit of bioclastic origin formed during the first standstill of the Holocene sea-level rise (12,000 y B.P.). It is a belt of Amphistegina sands, recorded on the outer shelf between 80 and 120 m, which represents a fossil fauna. Recent bioclastic sands are more developed in the tropical region, north of the area which has been studied; they are more dependent on structural rocky shoals, than in the equatorial zone where terrigenous influxes impede their development. Glauconite deposition This kind of sediment is characteristic of the equatorial regions where two major conditions were satisfied during the low-stand phase: (1) the presence of faecal pellet substrates due to the increase of primary productivity related to the stronger upwellings and, (2) larger iron input releases by podzolic soil evolution. Northward of the Congo-Gabon shelf, effectiveness of both conditions decreased. Offshore from the Coˆte d'Ivoire, iron was trapped in ferralitic profiles and on the Senegal and Mauritania shelves the green grains are rare and berthierine occurs in a limited time and space range.

Interpreting ancient swamp communities: Can we see the forest in the peat?

A comparison of the taxonomic composition of mangrove (salt-water) peats from the Everglades National Park and the swamp forests in which the peats accumulated shows that the rank abundance of roots belonging to a taxon in peat can be used to predict the rank abundance of that taxon in the swamp forest. Thus the rank abundance of taxa in permineralized peats can be used to reconstruct ancient swamp-forests. Factors that correlate with salinity, primarily the abundance of detritovores in mangrove swamps, appear to control the shoot-root ratios of the peats studied. Fresh-water swamps peats have few detritovores, low rates of decomposition, and relatively high shoot-root ratios (mean = 2.03).Mangrove peats have many detritovores, high rates of decomposition, and low shoot-root ratios (mean = 0.16). Variation in the shoot-root ratios of marsh peats do not correlate with salinity. However, shoot-root ratios may be useful in predicting the growth environment of ancient permineralized peats derived from ancient swamp forests. Paleotropical permineralized peats of Late Carboniferous age have extremely high shoot-root ratios. A model for peat accumulation based on the work of Janzen (1974) suggests that these high shoot-root ratios may be indicative of tropical blackwater swamps. Factors that are uncorrelated with salinity such as rainfall regime may determine the difference between Okefenokee shoot-root ratios (mean = 2.03) and extremely high shoot-root ratios (> 100) of paleotropical permineralized peats from putative blackwater swamps.

Rate of Sea Level Rise as a Control on Physical versus Biological Sedimentation: Examples from Holocene of South Florida: ABSTRACT

Decelerating late Holocene sea level rise over the south Florida platform has been accompanied by changes in sediment composition which reflect a transition from physically emplaced (allochthonous) sediment to biologically emplaced (autochthonous) sediment. This interpretation is based on a south Florida submergence curve which suggests that the rate of sea level rise has decreased from 26 cm/100 years, prior to 3200 y.B.P., to 3.5 cm/100 years thereafter. These compositional changes are recognizable within both mixed siliciclastic/carbonate and pure carbonate depositional systems. For example, mangrove islands located in the Ten Thousand Islands area of southwest Florida are overlain by a Holocene sediment sequence which consists of (in ascending order) (1) thin basal mangrove peat, (2) thin oyster zone, (3) shelly quartz packstone, (4) oyster or vermetid packstone to boundstone, and (5) mangrove peat. The lower sequence (units 1 through 3) reflects an early deepening phase which accompanied a rapid rise in sea level. Biological sediment production was not rapid enough to keep up with rising sea level and, as such, the mangrove-fringed shoreline was overstepped. The overlying subtidal shelly quartz packstones reflect local reworking of Pleistocene quartz sands and, later, the introduction of quartz sand by suspension from offshore. As seamore » level rise slowed, biological sediment production and accumulation began to exceed rates of sea level rise and subsequently deposits built up to and kept pace with rising sea level (units 4 and 5). Carbon-14 dates confirm this interpretation as the thin basal peats date at 4000 y.B.P. (rapid rise) and oysters at the base of unit 4 date at 1000 y.B.P. (slow rise).« less

A siliciclastic coastal Sabkha, capricorn coast, Queensland, Australia

A small (3 km 2), modern, siliciclastic sabkha occurs landward of Kemp Beach on the Capricorn Coast of central Queensland, Australia. Five sedimentary facies were recognized in shallow cores: (1) surface sand layer and associated halite crust; (2) a mottled clayey peat unit displaying interstitial gypsum (this layer has formed by vertical accretion of algal mats); (3) a unit of mangrove peat and clay with abundant jarosite corresponding to the locations of previous mangrove-lined tidal channels; (4) a carbonaceous sandy unit which represents the sediment that accumulated in a lake bordered by mangroves; and (5) a basal, well-sorted sand unit. Evaporative pumping during dry winter months is the dominant hydrologic process in this sabkha. Water lost from subsurface brines is replenished by subsurface flow of sea water via a pre-existing tidal channel now covered by the prograding sequence. The main aquifer below the sabkha surface is the carbonaceous sandy unit. The construction of a weir across the tidal channel maintains a relatively uniform water level below the sabkha surface during the wet summer period. However, during dry winter months, the piezometric gradient is such that the water flow is primarily unidirectional from the ocean inlet, through the mangrove-lined channel, to the subsurface aquifer below the sabkha. Analyses of subsurface waters revealed a gradient from almost normal marine salinity in the lake to a four-fold increase in subsurface brines. Correspondingly, there is a linear increase in major cation concentrations, with the exception of Ca 2+ which becomes depleted due to precipitation of gypsum. During dry winter months a halite crust forms at the surface. In contrast to most previously described sabkha environments, aragonite does not occur. Its absence may be explained by the large organic matter content of the sediments within the aquifer, inhibiting calcium-carbonate precipitation.