Showing papers in "Mangroves and Salt Marshes in 1997"
TL;DR: In this article, the wave period was investigated in amangrove reforestation area (Kandelia candel) close to aquaculture ponds in the Tong King delta, Vietnam.
Abstract: The wave reduction (wave period; 5–8 sec.) was investigated in amangrove reforestation area (Kandelia candel) close toaquaculture ponds in the Tong King delta, Vietnam. On one site where only young mangrove trees grew, the wavereduction due to the drag force on the trees was hardlyeffective. On the other site where mangrove trees weresufficiently tall, the rate of wave reduction per 100 m was aslarge as 20%. Due to the high density of vegetation distributedthroughout the whole water depth, the effect of wave reductionwas large even when the water depth increased. These resultsdemonstrate the usefulness of mangrove reforestation for coastalprotection.
386 citations
TL;DR: In this paper, it was found that the drag coefficient is related to the Reynolds number and the vegetation length scale LE, which is a function of the projected area of mangrove vegetation and the volume of the vegetation.
Abstract: Field studies of tidal flows in largely pristine mangrove swamps suggestthat the momentum equation simplifies to a balance between the water surfaceslope and the drag force. The controlling parameter is the vegetation lengthscale LE, which is a function of the projected area ofmangrove vegetation and the volume of the vegetation. The value ofLE varies greatly with mangrove species and water depth. It isfound that the drag coefficient is related to the Reynolds number Re definedusing LE. The drag coefficient decreases with increasingvalues of Re from a maximum value of 10 at low value of Re (<104), and converges towards 0.4 for Re < 5 ×104.
294 citations
TL;DR: In this article, simultaneous measurements of vertical accretion from artificial soilmarker horizons and soil elevation change from sedimentation-erosion table (SET) plots were used to evaluate the processes related to soil building infringe, basin, and overwash mangrove forests located in a low-energy lagoon which receives minor inputs of terrigenous sediments.
Abstract: Simultaneous measurements of vertical accretion from artificial soilmarker horizons and soil elevation change from sedimentation-erosion table(SET) plots were used to evaluate the processes related to soil building infringe, basin, and overwash mangrove forests located in a low-energy lagoonwhich receives minor inputs of terrigenous sediments. Vertical accretionmeasures reflect the contribution of surficial sedimentation (sedimentdeposition and surface root growth). Measures of elevation change reflectnot only the contributions of vertical accretion but also those ofsubsurface processes such as compaction, decomposition and shrink-swell. Thetwo measures were used to calculate amounts of shallow subsidence (accretionminus elevation change) in each mangrove forest. The three forest typesrepresent different accretionary environments. The basin forest was locatedbehind a natural berm. Hydroperiod here was controlled primarily by rainfallrather than tidal exchange, although the basin flooded during extreme tidalevents. Soil accretion here occurred primarily by autochthonous organicmatter inputs, and elevation was controlled by accretion and shrink-swell ofthe substrate apparently related to cycles of flooding-drying and/or rootgrowth-decomposition. This hydrologically-restricted forest did notexperience an accretion or elevation deficit relative to sea-level rise. Thetidally dominated fringe and overwash island forests accreted throughmineral sediment inputs bound in place by plant roots. Filamentous turfalgae played an important role in stabilizing loose muds in the fringeforest where erosion was prevalent. Elevation in these high-energyenvironments was controlled not only by accretion but also by erosion and/orshallow subsidence. The rate of shallow subsidence was consistently3–4 mm y–1 in the fringe and overwash island forests butwas negligible in the basin forest. Hence, the vertical development ofmangrove soils was influenced by both surface and subsurface processes andthe processes controlling soil elevation differed among forest types. The mangrove ecosystem at Rookery Bay has remained stable as sea levelhas risen during the past 70 years. Yet, lead-210 accretion data suggest asubstantial accretion deficit has occurred in the past century (accretionwas 10–20 cm < sea-level rise from 1930 to 1990) in the fringe andisland forests at Rookery Bay. In contrast, our measures of elevation changemostly equalled the estimates of sea-level rise and our short term estimatesof vertial accretion exceeded the estimates by the amount of shallowsubsidence. These data suggest that (1) vertical accretion in this system isdriven by local sea-level rise and shallow subsidence, and (2) the mangroveforests are mostly keeping pace with sea-level rise. Thus, the vulnerabilityof this mangrove ecosystem to sea-level rise is best described in terms ofan elevation deficit (elevation change minus sea-level rise) based on annualmeasures rather than an accretion deficit (accretion minus sea-level rise)based on decadal measures.
192 citations
TL;DR: In this article, the establishment of A. germinans seedlings was examined in cagesthat excluded predators and limited horizontal, but not vertical,movement of propagules by the tides and showed that black mangrove could readily establish in the Spartina zone.
Abstract: The black mangrove, Avicennia germinans, occurs sympatric withSpartina alterniflora in coastal Louisiana. Zonation exists alongan elevational gradient with A. germinans dominant at higherelevation creekbanks and S. alterniflora at interior, lowerelevation sites with greater depth and duration of flooding.Establishment of A. germinans seedlings was examined in cagesthat excluded predators and limited horizontal, but not vertical,movement of propagules by the tides and showed that blackmangrove could readily establish in the Spartina zone. Survivalof A. germinans seedlings after one year in cages was notsignificantly different between the two zones, and seedlings weresignificantly taller in the Spartina zone. Thus, neitherinundation per se nor other abiotic factors alone could accountfor the absence of A. germinans in the interior marsh. Althoughpropagules were dispersed into both zones, a net removal ofuncaged propagules from plots in the Spartina zone (–1.3 ± 0.6m-2 d-1) compared to a net addition to plots in the Avicennia zone (+0.5 ± 0.4 m-2d-1) indicated that retention of propagulesdiffered between zones. Causes of mortality were decay (Spartina> Avicennia zone), desiccation (Avicennia > Spartina zone), andpredation (Spartina > Avicennia zone). Although few propaguleswere completely consumed by predators (snails and crabs), damageto the cotyledons promoted decay. The results suggest that tidalaction limits retention and settlement of A. germinans propagulesin the Spartina zone, and a combination of predator damage andfrequent flooding leads to rapid decay of propagules that strandthere.
69 citations
TL;DR: The increasing scarcity of forest species suggest an over-exploitation as well as a degradation of the ecosystem and a management plan is needed to ensure the long-term survival of the resources.
Abstract: Traditional fishing is intensive in Ambaro Bay and around Morondava, respectively on the northwest and western coast of Madagascar. This fishing relies extensively on forest products much of which originates from nearby, readily accessible mangroves. Mangrove wood is used extensively for making the fishing traps and the canoes, for processing the prawn and fish catch, and for domestic use including fencing, housing and fuel for cooking. The increasing scarcity of forest species suggest an over-exploitation as well as a degradation of the ecosystem. A management plan is needed to ensure the long-term survival of the resources.
62 citations
TL;DR: A mangrove stand of Avicennia marina located at the South Corniche of Jeddah city receives about 100 000 m3 of sewage per day as mentioned in this paper.
Abstract: A mangrove stand of Avicennia marina located at the South Corniche of Jeddah city receives about 100 000 m3 of sewage per day. The sewage has high values of BOD, COD, nutrient concentrations, heavy metals and faecal coliform counts. The mangrove stand is very small and occupies an area of about 0.45 km2. The trees are stunted with low pneumatophore density. The pneumatophore distribution is restricted to the area of substrate underneath the plant crown covers and they do not look healthy. A high proportion of them was observed to be dead and/or aberrant. These abnormal induced features were attributed to the sewage discharge in the area. The death of pneumatophores decreases the aeration area which apparently affects the respiration rate of the root system, nutrient uptake and plant growth, consequently leading to a retarded growth of the mangroves.
61 citations
TL;DR: In this article, the authors examined vegetation-environment relationships and found that the first three dominant components influencing the vegetation were salinity, nutrient and soil texture, while tree height and density correlated highly with the soil texture gradients.
Abstract: The study examines vegetation – environment relationships Vegetation measurements included species frequency, density, diameter and tree height, while environmental measurements were soil particle size distribution, acid properties (pH, Al, SO4), nutrient cations (Ca, Na, Mg, K), organic carbon, nitrogen, phosphorus and chloride content Nypa fruticans was the dominant species in the A stratum (> 3 m tall) while Rhizophora mangle was dominant in the B stratum (1–3 m tall) The C stratum (< 1 m tall) was dominated by mangrove, Nypa and Raphia saplings Silt was dominant and the most variable particle size fraction A principal components analysis of the soil data indicated the first three dominant components influencing the vegetation were salinity, nutrient and soil texture Tree height and density correlated highly with the salinity and soil texture gradients (P < 001), while basal area correlated with salinity and nutrient gradients (P < 001) While Avicannia africana in the A stratum was influenced largely by the salinity and soil texture gradients Nypa fruticans in the B stratum was influenced by salinity and nutrients
51 citations
TL;DR: The water, soil and vegetation characteristics of themangroves of the Saloum River estuary, Senegal, in 1995 and 1996 were presented in this article, showing that the health of the remaining mangrove communities depends on the localhydrological and hydrodynamic conditions, the microtopography, the humanexploitation of the forest and the clay-sand composition of the soils.
Abstract: The water, soil and vegetation characteristics are presented of themangroves of the Saloum River estuary, Senegal, in 1995 and 1996. Themangroves have changed markedly due to decreasing rainfall and increasingevaporation rates, particularly in the 1980s, as well as new oceanographicconditions resulting from the breaching of a protective sand dune. Thehealth of the remaining mangrove communities depends on the localhydrological and hydrodynamic conditions, the microtopography, the humanexploitation of the forest and the clay-sand composition of the soils.
43 citations
TL;DR: In this paper, the distribution of Cd and Zn in sediment cores taken under Spartina alterniflora Loisel was compared with adjacent mud flats without plant cover, and the results discouraged the indiscriminate use of salt marsh sediments in environmental monitoring of trace metals.
Abstract: We present the distribution of Cd and Zn in sediment cores taken under Spartina alterniflora Loisel. marsh and compare with adjacent mud flats without plant cover. Vertical distribution of Cd and Zn in the mud flat and S. alterniflora cores were different. From 0 to 5 cm of depth Zn and Cd concentrations did not change with depth in the two cores but were higher in the mud flat. From 5 to 15 cm, corresponding to maximum root biomass under S. alterniflora, Zn and Cd concentrations remained constant in the mud flat cores, but increased by a factor of nearly 4 under S. alterniflora. Below this depth concentrations dropped in both cores. Manganese distribution in S. alterniflora cores suggests that oxides are precipitated at the depth of maximum root biomass. More oxic environment under S. alterniflora (average Eh = +5 mV) with low sulfide concentration (0.58 mg l-1) relative to the mud flat cores (average Eh = –204 mV; sulfide 47.1 mg l-1), may favor Fe and Mn oxi-hydroxides precipitation, causing an accumulation of Cd and Zn at the root zone. In the mud flat cores, Zn and Cd highest concentrations were at the sediment water interface, where oxic waters favor their precipitation with Fe and Mn oxi-hydroxides. The results discourages the indiscriminate use of salt marsh sediments in environmental monitoring of trace metals, since the possibility of post-deposition mobilization of trace metals due to root metabolism, will make correlation with trace metal loading rates impossible.
34 citations
TL;DR: In this paper, a set of mangrove trees were propagated and planted over 10 ha of degraded salt-marshy wetlands of Mahanadi delta inpure and mixed stands depending on the intensity and the frequency of tidal flooding at the experimental site.
Abstract: In India, mangroves occupy 6740 km2 of which the Mahanadi delta andBhitarkanika mangrove forests of Orissa cover 191.44 km2, most of whichhas been severely overexploited. World wide concern to conserve mangrovesnecessitated propagation of mangroves to re-establish them on barren andswampy land along tidal creeks around Paradeep port of Orissa. Avicenniaofficinalis, Aegiceras corniculatum, Bruguiera parviflora, B. sexangula,Ceriops decandra, Excoecaria agallocha, Heritiera fomes, Kandelia candel,Rhizophora mucronata, Sonneratia apetala were vegetatively propagated andplanted over 10 ha of degraded salt-marshy wetlands of Mahanadi delta inpure and mixed stands depending on the intensity and the frequency of tidalinundation at the experimental site. Survival was significantly higher(80%) in S. apetala followed by A. officinalis, R. mucronata, K.candel and H. fomes (70–75%). S. apetala recorded the maximumgrowth in height (3.0 m after 2 years) whereas C. decandra showed theminimum growth (0.5 m). Growth performance was better with plants in mixedstands than the plantation with single species. This gives us hope topropagate and re-establish mangroves for conservation in scientificallymanaged plantations in a physiologically arid environment.
27 citations
TL;DR: In this paper, measurements of temperature, wind speed and humidity within 6 m of the surface of a mangrove-fringed tidal tropical salt flat were performed using the aerodynamic method, this data was used to infer evaporation rates from the salt flat.
Abstract: Measurements of temperature, wind speed and humidity within 6 mof the surface of a mangrove-fringed tidal tropical salt flatwere performed. Using the aerodynamic method, this data was usedto infer evaporation rates from the salt flat. For a few daysafter tidal inundation or rain, the salt flats were wet andevaporation rates of about 5×10-3 m day-1 prevailed. By 8 daysafter tidal inundation and with no rain, evaporation rates haddropped to less than 2×10-3 m day-1. The monthly evaporation ratewas about 7×10-2 m. This generates high salinity which, togetherwith surface temperatures exceeding 50°C, prevents colonisationof these areas by mangroves.
TL;DR: In this article, the water budget of a tropical tidal salt flat in dry tropical Australia has been studied with particular emphasis on estimating the groundwater fluxes, and it is concluded that the groundwater loss is less than 40 mm/month.
Abstract: The water budget of a tropical tidal salt flat in dry tropical Australia has been studied with particular emphasis on estimating the groundwater fluxes. Salt was used as a passive tracer to determine some of these fluxes. Groundwater salt accumulation (or loss) was less than 1 kg/m3/month. Surface water leaving the flat at a higher salt concentration than flood water causes a net outwelling of salt of between 0.4 and 1 kg/m2/month. Evaporation from the salt flat was estimated to be 70 mm/month. Using these measurements and a simple model of the groundwater flows, it is concluded that the groundwater loss is less than 40 mm/month. The accuracy of the salt budget was insufficient to rule out the possibility that the net groundwater motion was upwards. Measurements of Si and PO_4 fluxes indicated that the net outwelling due to surface water flows were respectively 3 mmole/m2/month and 0.014 mmole/m2/month. A net groundwater loss of 10 mm would produce a similar magnitude outwelling due to groundwater discharge. The mangrove-fringed tropical tidal salt flats are the source of large quantities of nutrients that are released to the near-shore zone.
TL;DR: The seagrass beds in the mangrove-fringed shallow coastal waters of Hinchinbrook Channel, Australia, survive in shallow waters as mentioned in this paper, and areheltered from excessive sedimentation and turbidity by the plankton and vegetative detritus generating a marine snow that accelerates the settling of fine mud out of suspension.
Abstract: The seagrass beds in the mangrove-fringed shallow coastal waters ofHinchinbrook Channel, Australia, survive in shallow coastal waters. They aresheltered from excessive sedimentation and turbidity by the plankton andvegetative detritus generating a marine snow that accelerates the settlingof fine mud out of suspension.
TL;DR: The early postembryonic stages of C. granulata do not show special bioenergetic adaptations to the non-marine conditions, which prevail in the adult habitat of this species, which reflects a strategy of larval export to the sea, i.e. a reproductive dependence ofThis species on the marine environment.
Abstract: The semiterrestrial grapsid crab Chasmagnathus granulataDana is one of the most predominant inhabitants of brackish salt marsh ecosystems in South America. Its early postembryonic stages were reared in the laboratory from hatching of the first larval stage through the first juvenile crab instar, and changes in the quantity and elemental composition of biomass (measured as dry weight, W; carbon, C; nitrogen, N; hydrogen, H) were investigated in short intervals of time (every 1 or 2 d). In a series of successive developmental stages, the accumulation of biomass per individual can be described as an exponential function of the number of moults. In contrast, the pattern of growth within individual moulting cycles is described with best fit of observed and predicted data as a quadratic function of development time elapsed since last ecdysis. Weight-specific instantaneous growth rates show decreasing trends within the moulting cycle. Cumulative biomass increments during larval development of C. granulata are among the highest on record for brachyuran crabs. The quantities and patterns of larval growth are in this species similar as in most marine brachyuran crabs, for which data are available, but different from those in some other semiterrestrial grapsid crab species, which live in similar brackish water habitats as C. granulata. Hence, the early postembryonic stages of C. granulatado not show special bioenergetic adaptations to the non-marine conditions, which prevail in the adult habitat of this species. This reflects a strategy of larval export to the sea, i.e. a reproductive dependence of this species on the marine environment.
TL;DR: In this article, a manipulation exclusion technique was used to trace the dominant biological interactionsstructuring the meiobenthos of an East African Avicennia marina (Forsk.)Vierh mangrove forest.
Abstract: Many studies in the muddy intertidal zone of temperate regions haveindicated meiofaunal communities to be mainly affected by epibenthicpredation and disturbance rather than competition. Few studies, however,have dealt with mangrove sediments of tropical areas. In addition to aparallel study in a Ceriops tagal (Perr.) Rob. zone, a manipulativeexclusion technique was used to trace the dominant biological interactionsstructuring the meiobenthos of an East African Avicennia marina (Forsk.)Vierh. mangrove forest.
TL;DR: The Kosi system is the only pristine estuarine system left in KwaZulu-Natal and possibly the whole of South Africa and isfacing increasing development pressure as mentioned in this paper.
Abstract: The Kosi system is the only pristine estuarine system left inKwaZulu-Natal and possibly the whole of South Africa and isfacing increasing development pressure. Well-sortedunconsolidated quartz sand mantles the entire system with asapropelic ooze (gyttja) forming in the deeper lacustrine regionswhilst peat deposits occur on most of the low lying areas aroundthe lake shore. The lower part of the system comprises extensivetidal flats and mangal communities, whilst the upper partcomprises a series of linked, groundwater controlled, fresh tobrackish lakes. Fish traps, built from Avicennia marina, arelocated throughout the tidal sand-flats and lower lakes, causelocalised sedimentation and modify the tidal flow. Waves, formedfrom the prevailing winds, form both accretionary cusps and bermsas well as local beach erosion, especially in Lake Nhlange, whichhas the greatest fetch. Erosion and associated shallowing of thechannels linking the lakes is caused by excessive powerboatspeeds.
TL;DR: The results for NAPP obtained from the salt marshes at Tollesbury and Stiffkey are discussed in relation to results obtained by other workers from comparable areas in England and the Netherlands as discussed by the authors.
Abstract: This study presents data on the biomass and net aerial primaryproductivity (NAPP) of two contrasting East Anglian salt marshes.One site was at Tollesbury, Essex where the marshes are of theestuarine type and are subject to marsh degradation and erosionwhile the other site was 130 km to the north at Stiffkey, Norfolkwhere the barrier-type marshes are still actively developing withno signs of erosion. The NAPP was determined by the method ofSmalley with quadrats being harvested monthly with replacement.At the lowest levels at Tollesbury there was “Pioneer Marsh”which was dominated by a mixture of Salicornia spp. and Astertripolium. At higher levels at Tollesbury there was ’LowerMarsh’ which was dominated by a mixture of Atriplex portulacoides andPuccinellia maritima. Over the four years of the studyPuccinellia became the dominant species following a markeddecrease in the extent and vigour of Atriplex. At Stiffkey the‘Middle Marsh’ was at a much higher level and the vegetation waspredominantly a short dense sward with Atriplex portulacoides,Puccinellia maritima and Limonium vulgare together with smallerquantities of Armeria maritima and Plantago maritima. The meanNAPP‘s over three years of the Pioneer and Lower Marsh atTollesbury (467 & 519 g m-2 yr-1respectively) were similar butin 1993 the NAPP‘s recorded at Tollesbury were higher than thoserecorded at Stiffkey (625 & 583 compared with 458 g m-2yr-1).Smalley‘s method is difficult to apply to communities wherespecies dominance is variable, especially when dominance isshared between species with markedly different growth patterns.The results for NAPP obtained from the salt marshes at Tollesburyand Stiffkey are discussed in relation to results obtained byother workers from comparable areas in England and theNetherlands. Attention is also drawn to the possibly largerbelow-ground component of production that is frequentlyoverlooked. The importance of salt marshes in relation to othercoastal communities lies in the export of a proportion of theorganic matter produced and this mainly depends on theabove-ground production.
TL;DR: The absence of creeks and pans in many temperate Australian salt marshes is not compatible with current models of salt marsh formation and needs to be taken into account in the development of new models as mentioned in this paper.
Abstract: The absence of creeks and pans in many temperate Australian salt marshes is not compatible with current models of salt marsh formation and needs to be taken into account in the development of new models.
TL;DR: In this article, a simple in situ sampler for extracting pore water from sediment has been developed, working as a convective sampling device (harpoon) or a solute diffusion device (peeper) used asa harpoon, it avoids modification of vertical gradients of soluteconcentrations, because no suction is applied.
Abstract: A simple versatile in situ sampler for extracting pore water fromsediments has been developed, working as a convective samplingdevice (harpoon) or a solute diffusion device (peeper) Used asa harpoon, it avoids modification of vertical gradients of soluteconcentrations, because no suction is applied Used as a peeper,because of its higher diffusion/volume ratio, its contact timewith the sediment is reduced by 50%, compared to that of theconventional peeper, which makes a higher sampling rate possible