Showing papers in "Mangroves and Salt Marshes in 1998"

Traditional and medicinal uses of mangroves

Abstract: This review examines the recent investigations on the biological activities of extracts and chemicals identified from mangroves (mangroves, mangrove minors and mangal associates). It describes how people have and are using mangroves on a traditional basis. It also describes the world's mangrove resources and products, in terms of their economical importance, medicinal values and other uses and functions. The economical uses of products from mangrove ecosystems are many and varied. Traditionally, the mangroves have been exploited for firewood and charcoal. Use has also been found for mangroves in the construction of dwellings, furniture, boats and fishing gear, tannins for dyeing and leather production. The mangroves provide food and wide variety of traditional products and artefacts for the mangrove dwellers. Extracts and chemicals from mangroves are used mainly in folkloric medicine (e.g. bush medicine), as insecticides and piscicides and these practices continue to this day. However the extraction of novel natural chemical compounds from mangroves, in addition to those already known to the pharmacopoeia of the people is in its infancy. A knowledge of the biological activities and/or chemical constituents of plants is desirable, not only for the discovery of new therapeutic agents, but because such information may be of value in disclosing new sources of already known biologically active compounds. It is of further value to those interested in “deciphering” the actual value of folkloric remedies.

Extensive shrimp farming, mangrove clearance and marine fisheries in the southern provinces of Vietnam

Abstract: Within the last decade shrimp farming in the Mekong Delta of Vietnam has increased by 3500%. Shrimp farming became un-sustainable in the early 1990's due to the un-planned development of this industry and the resulting self pollution of the farms, the destruction of mangrove forest and the outbreak of viral diseases. Historical data on fisheries, fishing effort and mangrove coverage were obtained from the province Minh Hai (lately divided in Ca Mau and Bac Lieu). Analysis of catch and effort data of marine fisheries in the Mekong Delta indicated a severe danger of over-exploitation of fish stocks and further decline can be expected if fisheries management only considers the demand for fish. The relation between the total fish catch (t/year), the mangrove area (ha), the engine capacity (HP) of the fishing fleet and the social incentive for fishing could be described with the model: Total catch=0.449*Mangrove area + 0.614 Engine capacity + 654 Social factor. One hectare of mangrove forest supports a marine catch of 450 kg/year

Mangrove forest productivity and biomass accumulation in Hinchinbrook Channel, Australia

Abstract: Data on stand structure and rates of photosynthesis were used to estimate net canopy carbon fixation and carbon accumulation as living biomass in mangrove forests in Hinchinbrook Channel, Australia Total annual canopy net carbon fixation was estimated to be about 29 t C ha−1 yr−1 This equates to about 204,000 t C yr−1 for all mangrove forests in Hinchinbrook Channel Of this, only about 12% was stored as living plant biomass Although it is not yet possible to present a robust carbon balance for mangrove trees, the remainder is presumably lost through plant respiration, litter fall, root turnover and exudation of organic compounds from roots

Estimated stocks of organic carbon in mangrove roots and sediments in Hinchinbrook Channel, Australia

Abstract: Above‐ground and below‐ground root biomasses (Babove and Broot) were measured for young, isolated Rhizophorastylosa on Iriomote Island, Japan. The relationship between these two parameters was significant and given as the equation, Broot (g dry weight) = 0.394 × Babove (g dry weight) − 485 (r = 0.986). Multiple regression analyses also revealed good correlation between diameter and biomass of prop roots (Dprop and Bprop) and between prop root and root biomasses. Consequently, root biomass could be estimated from the measurements of diameter and biomass of prop roots using the multiple regression equation, Broot (g dry weight) = 80.0 ×Dprop (cm) + 0.86 ×Bprop (g dry weight) − 251. The relationship between DBH (diameter at breast height) and prop root biomass was also adequately described using an allometric equation. In Hinchinbrook Channel, Australia, redox potential (measured as Eh) and organic carbon stocks in the top 5 cm of mangrove sediments were measured along a 600 m transect from the frequently inundated, Rhizophora dominated zone on the creek edge, towards higher grounds, where Ceriops spp. became increasingly dominant. Eh values were about −60 mV near the creek edge and increased to 260 mV on higher grounds. Organic carbon stocks showed an opposite trend to Eh, with the values decreasing from about 360 t C ha−1 to 160 t C ha−1. At 18 sites, representing six different habitats, organic carbon stocks were also measured along with the DBH of mangrove trees. DBH was converted into above‐ground biomass and then into root biomass using the equations obtained in the study on Iriomote Island. The average organic carbon stocks in the top 50 cm of sediments, above‐ground biomass and root biomass were 296 t C ha−1, 123 t C ha−1 and 52 t C ha−1, respectively, and accounted for 64%, 25% and 11% of the total organic carbon stock.

Sources, sinks, and export of organic carbon through a tropical, semi‐enclosed delta (Hinchinbrook Channel, Australia)

Abstract: A mass balance for organic carbon in Hinchinbrook Channel was constructed to identify major sources, sinks, and the magnitude of organic matter available for export to the adjacent coastal zone Total organic carbon input from the Herbert River and from net production of mangroves, phytoplankton, seagrasses, and benthic microalgae is 894 ×109 M Corg yr−1 (moles organic carbon per year) Mangroves and river inputs are the largest carbon sources, accounting for 56% and 27% of the total annual input, respectively Benthic respiration and burial in sediments are the major sinks, accounting for 46% and 41% respectively of total losses (309 ×109 M Corg yr−1) This mangrove‐dominated coastal ecosystem is net autotrophic, with 585×109 M Corg yr−1 (65% of total Corg input) available for export to the adjacent nearshore zone Total export of organic carbon from the region (adding carbon export from Missionary Bay mangroves on the northern end of Hinchinbrook Island) amounts to 82,800 metric tons of organic carbon per year These results confirm earlier evidence indicating that much of the particulate sediment carbon in the adjacent coastal zone is of mangrove origin This mass balance, although preliminary, demonstrates the importance of Hinchinbrook Channel as a source of organic matter for the Great Barrier Reef lagoon

Fluxes of nutrients and dissolved and particulate organic carbon in two mangrove creeks in northeastern Australia

Abstract: In Coral and Conn Creek, northeastern Australia, the variations in concentrations of nitrate, phosphate, silicate, dissolved organic carbon (DOC) and particulate organic carbon (POC) were measured over tidal cycles on five occasions and along each creek on four occasions. The fluxes of these five properties were then estimated using two methods. The first method is the so‐called Eulerian method, whereby water flow and material concentration are measured at a fixed station near the creek mouth and the net flux is calculated by adding up flux increments over a tidal cycle. The second method first derives the longitudinal eddy diffusion coefficient from the salt mass balance equation and then calculates material fluxes from their observed gradients along the creek. The use of the latter method is permitted only in the absence of freshwater inputs.

The role of groundwater flow in controlling the spatial distribution of soil salinity and rooted macrophytes in a southeastern salt marsh, USA

Abstract: Groundwater flow is an important factor in governing botanical zonation in the salt marsh at North Inlet, SC Areas of the marsh adjacent to upland forest are characterized by upward flow of fresh groundwater This inhibits the infiltration and evapoconcentration of saline tidal water and the development of a habitat for hypersaline-tolerant fugitive species such as Salicornia europaea Areas of high marsh that are not adjacent to extensive upland forest are characterized by downward gradients in hydraulic head This allows the infiltration and evapoconcentration of tidal water and the development of hypersaline conditions that are suitable for salt-tolerant fugitives

Effects of mangrove deforestation on macrofaunal densities, Gazi Bay, Kenya

Abstract: This study documents comparative variations of macrofaunal densities in a deforested area and a natural mangrove area in Gazi Bay, Kenya, during 1993. Similar groups of both epifauna and infauna were recorded in the two areas with differences in distribution along transects in different sampling sessions. Hence mangrove deforestation decreases biodiversity. Other more striking effects of mangrove deforestation include a decreased availability of wood, fish and prawn, less revenue paid to government in terms of royalties and tourist fees, an increase in coastal erosion and eventual reduction of seagrasses and coral reefs.

Assessing seasonal vegetation change in coastal wetlands with airborne remote sensing: an outline methodology

Abstract: Airborne remote sensing offers high-density, spatially-averaged synoptic samples of radiation reflected from a surface which can be used to infer ecological processes and community composition. Unfortunately, the cost of the overheads in terms of time and resources, and scheduling constraints when deriving quantitative information have limited its use in operational monitoring programs. When the changes in reflected radiation related to the phenomenon under investigation are large, only minimal low-cost processing is required to identify ecosystem modification if high frequency multi-temporal imagery can be combined with expert knowledge. This methodology is likely to be of particular value in coastal environments where access for conventional measurements is restricted and changes in sensitive tidal wetlands may provide an early indicator of changing natural processes and/or human impact. Regularly acquired airborne remotely sensed imagery has been used in a reconnaissance study to identify and map seasonal vegetation patterns on intertidal surfaces in back barrier environments on the North Norfolk coast, England, U.K. The development of an operational system for coastal zone management is discussed.

Inorganic sediment budget in the mangrove-fringed Fly River Delta, Papua New Guinea

Abstract: Six oceanographic moorings were maintained for 8 weeks across the mouth of the mangrove-fringed Fly River estuary from April to June 1995 in the southeast trade wind season. A further 4 moorings were deployed for 8 weeks along the estuary channel in 1992, also in the southeast trade wind season. These data were used to estimate net exchange of suspended sediment between the estuary and the Gulf of Papua. A net inflow of fine sediment into the estuary from the coastal ocean was found to be considerable, about 40 tonnes s-1 or about 10 times the riverine inflow rate, resulting in a calculated, spatially averaged vertical accretion rate of 2 mm year-1. Mangroves may account for trapping 6% of the riverine sediment inflow or about 1/4 of the riverine clay inflow. If this sediment was distributed only over the observed accumulation zones near islands the local accumulation rates in these zones would reach 4 cm year-1. Estimates of soft sediment mass accumulation rates (1–10 kg m-2 year-1) in the channel from Pb-210 and C-14 measurements from cores of deltaic mangrove mud cannot account for this accumulation rate on a 100–1000 year time scale. The fate of the remaining sediment is unknown, it may be exported from the estuary in the monsoon season.

Field and model studies of the fate of particulate carbon in mangrove-fringed Hinchinbrook Channel, Australia

Abstract: A field and model study was undertaken in 1996/1997 of the dynamics of water, fine sediment and particulate carbon in the northern region of the mangrove‐fringed Hinchinbrook Channel, Australia. The currents were primarily tidal and modulated by the wind. Biological detritus acted as a coagulant for the fine cohesive sediment in suspension in the mangrove‐fringed, muddy coastal waters. Plankton and bacteria were the major aggregating agents at neap tides, and mangrove detritus at spring tides. The micro‐aggregates were typically several hundreds of micrometer in diameter and enhanced the settling rate. The fate of fine sediment and particulate carbon was controlled by the dynamics of the coastal boundary layer, a turbid shallow coastal water zone along the mangrove‐fringed coast. A tidally‐modulated, turbidity maximum zone was found in this layer. Wind stirring increased the turbidity by a factor of five. The channel behaves as a sink trapping fine sediment and particulate carbon. However, the sink was ‘leaky’ because the dynamics of the coastal boundary layer generated a net outflow of fine sediment out of the channel along the western coast. The biologically enhanced settling of cohesive sediment limited the offshore extent of the muddy suspension to within a few hundreds of meters from the coast. At spring flood tides, some of this particulate carbon was advected into the mangrove forest where it would remain trapped. On a yearly basis about six times as much particulate carbon was exported out of Hinchinbrook Channel through the coastal boundary layer than was trapped in the fringing mangroves.

The dynamics of heavy metals through litterfall and decomposition in a red mangrove forest

Abstract: The cycling of Zn, Mn and Fe through production, decomposition, and export of litter was studied at the Itacurussa Experimental Forest, a red mangrove forest in Southeast Brazil. The total litterfall was 8.69 t ha-1 yr-1. The heaf litter represented 56% to 100% of the total litterfall. The metal concentrations in the fallen leaves were: Mn = 230 ± 50 μg g-1; Fe = 116 ± 44 μg g-1 and Zn = 5.5 ± 1.0 μg g-1 (n = 15). The average transfer rates of heavy metals from canopy to sediment through leaf fall were: 1.39 kg ha-1 yr-1 for Mn, 0.70 kg ha-1 yr-1 for Fe, and 0.03 kg ha-1 yr-1 for Zn. These rates represent 4.5%, 4.0%, and 57.0% of the total forest biomass reservoir for Zn, Fe and Mn, respectively. There was no accumulation of the metals in the first 10 days of decomposition, and since the residence time of leaves in the sediments was less than 6 days, litter exported from the forest had relatively low metal concentrations. Since 7% of the leaf fall (0.42 t ha-1 yr-1) is exported to the sea, we estimated an average export of heavy metals throught leaf detritus as: Mn = 0.097 kg ha-1 yr-1, Fe = 0.049 kg ha-1 yr-1 and Zn = 0.002 kg ha-1 yr-1. The export of metals through leaf fall represents less than 0.01% of the total sediment reservoir. We conclude that mangrove ecosystems are probably efficient biogeochemical barriers to the transport of metal contaminants in tropical coastal areas.

Speciation of phosphorus in a tidal floodplain forest in the Amazon estuary

Abstract: The processes of release and retention of phosphorus (P) in soils of a tidal floodplain were studied at Combu Island (Belem/Brazil) Three parcels of 220m2 were chosen: low floodplain (LF), intermediate floodplain (MF) and high floodplain (HF) Two cores to 04 m depth were collected in each parcel, one week after the highest and lowest tides of the year Organic phosphorus (P—OM) concentrations ranged from 002 ± 001 to 007 ± 002 mg/g, the highest concentrations were found in the HF parcel On the other hand the HF parcel had the lowest concentrations of total inorganic phosphorus (TIP): 010 ± 003 to 011 ± 033 mg/g The speciation of inorganic P suggested that P—Fe/Al is the main chemically bound P in soil (005 ± 001 to 020 — 004 mg/g) The tidal inundation of the floodplain appears to influence these chemical reactions involving phosphate retention and release

Classifying coastal resources by integrating optical and radar imagery and color infrared photography

Abstract: A progressive classification of a marsh and forest system using Landsat Thematic Mapper (TM), color infrared (CIR) photograph, and ERS-1 synthetic aperture radar (SAR) data improved classification accuracy when compared to classification using solely TM reflective band data. The classification resulted in a detailed identification of differences within a nearly monotypic black needlerush marsh. Accuracy percentages of these classes were surprisingly high given the complexities of classification. The detailed classification resulted in a more accurate portrayal of the marsh transgressive sequence than was obtainable with TM data alone. Individual sensor contribution to the improved classification was compared to that using only the six reflective TM bands. Individually, the green reflective CIR and SAR data identified broad categories of water, marsh, and forest. In combination with TM, SAR and the green CIR band each improved overall accuracy by about 3% and 15% respectively. The SAR data improved the TM classification accuracy mostly in the marsh classes. The green CIR data also improved the marsh classification accuracy and accuracies in some water classes. The final combination of all sensor data improved almost all class accuracies from 2% to 70% with an overall improvement of about 20% over TM data alone. Not only was the identification of vegetation types improved, but the spatial detail of the classification approached 10 m in some areas.

Dissolved inorganic nitrogen cycling in Banzu intertidal sand-flat, Japan

Abstract: The sediment-water exchange of nitrogen, nitrification, denitrification and sedimentary oxygen production were simultaneously measured in the Banzu intertidal sand-flat, Tokyo Bay, Japan. The exchange flux across the sediment-water interface showed a sink of dissolved inorganic nitrogen (DIN) in the light. However, in the dark, the intertidal sediment acted as a source. The diffusive flux obtained by the ammonium profile explained only 22% of the source flux directly measured in the dark, suggesting that bioturbation or excretion by macrofauna greatly contributed to the exchange flux. The total microphytobenthic uptake of DIN estimated from O2 productivity and the Redfield ratio was 573.4 ± 64.4 μmol N m2 h-1, 31% (175.9 ± 64.4 μmol N m-2 h-1) of which was assumed to be derived from the overlying water. The release rate of DIN from the sediment to the water column (1.1 mmol N m-2 day-1) was balanced with the removal rate of DIN from the water column by benthic microalgae on a diurnal basis. This result suggests that DIN was recycled within the sediment, and the microalgae on the sediment surface played a significant role in suppressing the release of mineralized DIN from the sediment. The measured denitrification rate using an acetylene inhibition technique was 99.6 ± 23.5 μmol N m-2 h-1. Since the direct supply of nitrate or nitrite from the water column only accounted for 27% of the total denitrification at the highest estimate, nitrogenous oxide in the sediment pool was the major contributor to sedimentary denitrification.

Contrasting impacts of localised versus catastrophic oil spills in mangrove sediments

Abstract: Several truckloads of mixed waste oil were dumped onto a short section of road and into the intertidal wetlands near Cairns, Queensland in January, 1994. The oil contaminated a band of mangroves 15–44 m wide along approximately 200 m of road. Impacted marsh included Melaleuca forest and high-intertidal mangroves. The initial concentrations of petroleum hydrocarbons in surface sediments reached 17% of the dry weight in heavily impacted areas. These high concentrations observed in limited spatial areas were similar to those observed over large spatial areas after a catastrophic oil spill in Panama in 1986. No large scale biological damage was observed from this localised spill. Clean up efforts and natural dissipation processes reduced sediment hydrocarbon loads to non-acutely toxic levels in 1.5 years in the intertidal mangroves. High hydrocarbon concentrations remained in the Melaleuca sediments for at least two years post spill. Internal molecular markers were used to detail hydrocarbon dissipation and degradation rates. This study provides a contrast between impacts of localised versus catastrophic oil spills in tropical mangrove habitats.

Spatial variations of groundwater salinity in a mangrove-salt flat system, Cocoa Creek, Australia

Abstract: In this work the average groundwater salt concentration in a mangrove swamp and tropical salt flat system adjacent to Cocoa Creek near Townsville in North Queensland was measured with ground conductivity probes based on low frequency EMI (Electromagnetic Induction) and V-I (Resistivity) Methods Transects of conductivity were measured with the conductivity probes and the spatial variations in the average groundwater salt concentration were determined from conductivity measurement with both probes Lower concentrations occurred within mangrove forest as well as near the edges of the salt flats Comparison of the results above 08 m and below 08 m showed that as depth increases, the concentrations become more homogeneous For example at 04 m, salt concentrations across the salt flat vary from 75 g/l to 175 g/l where at 2 m the variation is only from about 75 g/l to 125 g/l High lateral groundwater salt concentration gradients occured at the boundary between the mangroves and salt flat and also at the edges of the salt flat Typical gradients were about 6 g/l/m and 2 g/l/m respectively

Estuarine reconnection of an impounded mangrove salt marsh in the Indian River Lagoon, Florida: short-term changes in fish fauna

Abstract: Fish population dynamics in a 24.3 ha mangrove-dominated mosquito impoundment in east-central Florida were examined by seining and culvert traps before and after installation of culverts that established estuarine connection for the first time in 39 years. In a 27-day period following the culvert opening, fish species increased from 9 to 21, while total number of fish in the impoundment decreased. Movement of fishes through culverts in both directions commenced immediately following culvert opening. Recruitment of transient species into the impoundment appeared to key on a single wind-driven high tide event. Such short-term events may be important cues for fish movement into and out of impounded salt marshes.

Distribution and fluxes as macrodetritus of phosphorus in red mangroves, Sepetiba Bay, Brazil

Abstract: The distribution and dynamics of phosphorus have been studied in the mangroves of Sepetiba Bay, Brazil. Leaf fall contributes 3.0 kg P ha=1yr=1to the sediment. The total above ground biomass of the R. mangle stand was about 65.3 t ha=1, the P accumulation was 3.9 kg P ha=1where 63% of the total P-biomass was accumulated in the leaves. The biomass of below ground roots was about 8.2 tha=1 and accumulated 16% of total P-biomass. Sediment contained 452 kg P ha=1 where P combined with calcium (P-Ca) was the main fraction (260 kg ha=1). The annual flux of P as litter fall was small (< 1%) compared to total P in the sediment reservoir. The annual export of P by macrodetritus corresponds to 0.05% of the total sediment reservoir.

Concentration and molecular weight distribution of dissolved organic carbon in a mangrove creek in the Hinchinbrook area, Australia

Abstract: The concentration and molecular weight distribution of dissolved organic carbon (DOC) are reported for a mangrove creek in the Hinchinbrook area, Australia. DOC concentration ranged from 1.0 mg C l−1 near the creek mouth to 2.2 mg C l−1 at the innermost part of the creek. There was no apparent spatial trend in molecular weight distribution of DOC, with a >300 g mol−1 fraction accounting for about 70% of the total in all samples. DOC concentration fluctuated between 0.5 and 1.2 mg C l−1 over one tidal cycle. The samples collected at low tide and during the rising tide were dominated by DOC of >300 g mol−1 and <300 g mol−1, respectively. This suggested the export of high molecular weight DOC, probably originating from litter leachates, and the import of low molecular weight DOC to the creek.

Field measurements of gas exchange in Avicennia marina and Bruguiera gymnorrhiza

Abstract: Diurnal gas exchange characteristics were measured simultaneously in two mangrove species, Avicennia marina and Bruguiera gymnorrhiza, over 7 d in summer (February–March), to compare their productivity. The study was undertaken in the Beachwood Mangroves Nature Reserve, Durban, South Africa, using fully expanded leaves of young and mature trees at the top of the canopy. Gas exchange was strongly influenced by photosynthetic photon flux density (PPFD), leaf temperature and the accompanying leaf to air vapour pressure deficit (Δ w). Carbon dioxide exchange was saturated at a PPFD of about 600 μmol m-2s-1 in B. gymnorrhiza compared to 800 μmol m-2s-1 in A. marina. Maximal CO2 exchange occurred between 12h00 and 14h00 and was consistently greater in A. marina (8.8 μmol m-2s-1) than in B. gymnorrhiza (5.3 mu;mol m-2s-1). Mean internal CO2 concentrations ( ci) were 260 μl l-1 in A. marina and 252 μl l-1 in B. gymnorrhiza. Photorespiratory activity was 32% in A. marina and 30% in B. gymnorrhiza. Mean water use efficiency (WUE) was 8.0 μmol mmol-1 in A. marina and 10.6 μmol mmol-1 in B. gymnorrhiza. Diurnal leaf water potentials ranged from –0.8 to –3.5 MPa and were generally lower in A. marina.

Variations in condition and body constitution in a tropical estuarine fish with year-round recruitment

Abstract: Fish condition (Fulton's K) and the abundance of biochemical constituents (water, protein, lipid and carbohydrate) of juveniles of the tropical estuarine fish, Ambassis vachelli, were monitored over a 15 month period. Fulton's K and biochemical constituents of juveniles recruiting into the adult habitat varied significantly throughout the study. Correlations between Fulton's K and all biochemical measures were weak, with a maximum correlation of 0.1379 (with protein abundance). Significant differences in condition and body constitution of individuals suggest that juveniles recruiting into the adult habitat are not in equal condition and therefore survivorship and success may vary within and among cohorts. Temperature (and salinity) display greater variation in tropical estuarine waters than in other tropical waters and are likely to play a role in determining recruit condition and body constitution. However, the exact role of physical parameters in determining condition and body constitution of fishes is still unknown.

Modelling chemical changes of tidal waters emerging from a mangrove forest at Cananeia, Brazil

Abstract: Chemical changes in anoxic tidal waters, emerging from the mangrove forest of Cananeia, (48° W, 25° S; Brazil), were interpreted using a stoichiometric approach. Significant depletion of magnesium and sulphates were observed and were apparently due to magnesium-iron replacement in octahedral sheets of clay minerals, and sulphate reduction, respectively. Iron release from clays, after bacterial-mediated reduction, apparently reacted with sulphides produced by sulphate reduction to form nono- and di-sulphides. Production of 41.5% of FeS and 58.5% of FeS2satisfactorily explained all the stoichiometric relations between concentration changes of magnesium, sulphates, sulphides, iron and alkalinity expected by the model. As a consequence, the decomposition rate of organic matter in these prevailing anoxic conditions, would mainly stem from sulphate reduction (90% against 10% for ferrireduction). The simultaneous bacterial processes of uptake and release of ammonium included in the model would explain why the mangrove forest does not export significant amounts of nitrogen toward the adjacent lagoon.