Mangrove Zone Research Articles

Temporal patterns in a fish assemblage of a semiarid mangrove zone in Madagascar

Gillnet sampling was conducted for a year in a tropical mangrove creek (SW Madagascar), characterized by a limited freshwater influence, a high turbidity and a tidal range up to 3 m. Sixty species of juvenile fishes were caught, 44 species being of commercial interest. Catches were dominated by Gerreidae (27% of total abundance), Teraponidae (16%), Carangidae (13%) and Sparidae (12%). The temporary resident fishes in the mangrove zone represented 50% of the species and 97% of the total abundance, the other species being rare (less than five individuals). The species richness, abundance and biomass per netting were low in the middle of the cool season (July-August). Monthly changes in the fish assemblage were particularly complex, with three species groups displaying a clear seasonal pattern, some species succeeding one another in a rather unstructured way, and three species abundant throughout the year. There was no clear structuring effect of temperature, salinity and turbidity on the fish assemblage. However, tidal, lunar and diel effects on the composition of the fish assemblage were evident. The species overlap between the Sarodrano mangrove fauna and the adjacent coral reef fauna is particularly weak with six species in common and shows that the mangrove plays only a very limited nursery role for coral reef species.

Mangrove Zonation: An Examination of Data from Seventeen Riverine Estuaries in Tropical Australia

To characterize mangrove zonation better under conditions in northern Australia, surveys were undertaken within a number of riverine estuaries along the eastern coast of Cape York Peninsula, in the Gulf of Carpentaria and at one location in Van Diemen Gulf in the Northern Territory. Detailed records were taken of species occurrences along shore normal transects upstream to tidal limits in each system. A simple numeric procedure developed by Williams, Bunt and Clay ( Marine Ecology Progress Series 72: 283–287, 1991) was applied to the data to define species sequential ordering across the intertidal surfaces. Considerable diversity in zonal pattern was found, partly the result of floristic differences between and along rivers within the study area but also arising from variability in the centres of distribution of species across the intertidal surface. Close examination of the data suggests the variability to be attributable to the differing responses of individual species to the character and pattern of environmental controls operating from point to point locally and at larger scales throughout the mangrove environment. It is concluded that constancy of centres of distribution and of sequencing order under conditions in tropical Australia are not to be expected. At the same time, within the range of along transect species distributions, conditions are likely to be encountered which permit individual species, whether rarely or not, to occupy all or most of the intertidal surface. Any other pattern of distribution is interpreted to represent conditions which, at least to a degree, are limiting for the species in question. In mangrove environments of considerable diversity, only extensive survey can be expected to reveal the full extent of zonal pattern in the associated vegetation.

Water circulation dynamics, water column nutrients and plankton productivity in a well-flushed tropical bay in Kenya

Water circulation, water column nutrients and plankton productivity were studied in a tropical bay with high rates of water exchange (60% to 90% per tide) and short residence times (3 to 4 h). The water circulation is predominantly affected by the semi-diurnal tides, which cause strong and reversing currents in the mangrove creeks (0.60 m·s −1) and currents of low magnitude in the neighbouring seagrass and coral reef zones (< 0.30 m·s −1). Tidal asymmetry, with relatively stronger ebb than flood flows in the mangrove creeks, promotes the net export of nutrients from the river mouth and of organic matter from the mangroves to the seagrass beds. The main sources of the dissolved inorganic nutrients are two rivers (the Kidogoweni and Mkurumuji) which discharge (up to 17.0 m 3·s −1) in the upper and lower regions of the bay. The increased input of nutrients did not cause eutrophic conditions since nutrients were rapidly flushed out of the bay. The mangrove biotope generated small amounts of dissolved nutrients which are likely to be used for primary production within the mangrove zone. The production of nutrients in the mangrove zone was masked by high rates of flushing, such that no appreciable nutrient signal was detected in the dry season when the influence of the rivers diminished. The rates of primary production were low in the mangrove, seagrass, and coral reef biotopes in the dry season. Primary production increased slightly during the rainy season. The level of chlorophyll a in the mangrove biotope increased during ebb tides and decreased during flood tides. The highest zooplankton densities, which could not be related directly to primary production in the water-column, occurred at the seagrass station during the wet season.

The ecology of mangrove forest birds in Peninsular Malaysia

The density, distribution and feeding ecology of birds of mangrove forests in Selangor on the west coast of Peninsular Malaysia were investigated between February and May 1989. Excluding aerial hunters and wading birds, 47 species were recorded from four mangrove forest sites in Selangor, though undoubtedly some rarer species were missed due to the brevity of the study. The estimated density of birds, using fixed‐width transects, ranged from 15 to 26 birds per ha. One quarter of all birds counted belonged to just one species, the Ashy Tailorbird Orthotomus ruficeps. Excluding ground feeders (three species), four foraging guilds were recognized among 17 of the commonest bird species: obligate foliage‐foraging insectivores (seven species), bark‐foraging insectivores (four), facultative nectar‐ivores (five) and aerial hawkers (one). Species within the first and third guilds apparently were partitioned by foraging technique and heights, while those of the second guild (woodpeckers) differed mainly in their selection of plant species. The horizontal distribution of several species corresponded to the zonation of mangroves. Avifaunal differences between sites reflected differences in forest floristics. The greatest number of species occurred at the dry landward edge site, which supported seven bird species not encountered elsewhere in Selangor. This habitat has almost completely disappeared from much of the peninsula owing to land reclamation. Four of the six resident mangrove‐specialized bird species in Selangor were regularly recorded at two or more sites, another (Greater Gol‐denback Woodpecker Chrysocolaptes lucidus) occurred at only one site and the last (Ruddy Kingfisher Halcyon coromanda) was never recorded. Two species of sunbirds probably play an important role in the pollination of several species of mangroves. The colonization of anthropogenic habitats by many mangrove‐dwelling bird species is attributed partly to their generalized foraging niches, which may have evolved in response to regular fluctuations in food availability and the dynamic physiography of mangrove communities.

Biomass and above-ground productivity of salt-marsh plants in south-eastern Australia

The above-ground biomass of three dominant salt-marsh vascular plants (Juncus kraussii, Sarcocornia quinquejlora and Sporobolus virginicus) was measured to assess both spatial and temporal variation and to provide baseline data. Additionally, the culm dynamics of the rush J. kraussii were measured so that aboveground productivity could be estimated. No distinct seasonal patterns were detected in above-ground biomass in J. kraussii. Averaged over all sites and times, the above-ground biomass of J. kraussii was 1116 g dry weight m-2. Culms are replaced annually, hence standing crop approximated annual above-ground productivity. Much of the dead aboveground biomass appears to accumulate in the upper marsh, as evidenced by the elevated nutrient and organic carbon content of the soil there relative to the sediment in the mangrove zone. Above-ground biomass of the decumbent perennial grass Sporobolus virginicus and the procumbent perennial chenopod Sarcocornia quinqueflora showed no consistent spatial or temporal trends. The above-ground standing crops of these species were about one-third that of J. kraussii.

Soil Physicochemical Patterns and Mangrove Species Distribution--Reciprocal Effects?

1 The distributions of two dominant mangrove species in a neotropical forest were associated with spatial variation in soil redox potentials (Eh) and interstitial water sulphide concentrations. Mangrove zones dominated by Rhizophora mangle L. alone or in combination with Avicennia germinans (L.) L. were characterized by moderately reducing soils (Eh = 100-300 mV) with low sulphide concentrations (< 0.3 gM), whereas a zone dominated by A. germinans had strongly reducing soils (Eh < -100 mV) with high sulphide (2-4 mM). 2 Less reducing soil conditions near the aerial roots of both mangrove species indicated that the relationship between soil physicochemical patterns and mangrove zonation reflected not only effects of soil factors on the vegetation, but effects of the adult root systems on soil Eh and sulphide. 3 A glasshouse experiment with seedlings demonstrated that although R. mangle and A. germinans are both flood tolerant, the species respond differently to flooding in terms of growth and biomass partitioning, particularly when the soil is strongly reducing and sulphide is present. Flooding under reducing soil conditions resulted in a 20-40% decrease in total biomass of A. germinans seedlings (relative to drained controls), whereas seedling biomass was increased 9-24 % above drained controls in R. mangle. 4 A significant decrease in root oxygen concentrations in response to reducing soil conditions and sulphide was observed in A. germinans, but not R. mangle, and indicated that differential flood tolerance of seedlings is partly due to differences in root aeration. 5 The implication of these findings is that mangrove seedling dynamics are influenced by spatial and temporal variation in soil Eh and sulphide levels, but that these soil factors are also modified by the root systems of adult trees. These reciprocal processes may play an important role in the development of spatial organization in this intertidal community.

Physical processes in the Rufiji delta and their possible implications on the mangrove ecosystem

The physical processes such as coastal currents, estuarine circulation and monsoon winds prevailing in the Rufiji delta are discussed. The relationship between these processes and the occurrence of long-term trapping of the river discharge and the outflow of waters from the mangrove swamps into the nearshore zone has been observed. The trapped waters in the nearshore zone significantly reduce the mixing between the estuarine and offshore waters, leading to the two waters having distinctive properties. The existence of the trapped waters in the nearshore zone is supported by evidence from a satellite image and aerial photograph and measurements of salinity and suspended sediment concentration. The trapping phenomenon is discussed in the light of its possible implications on the ecology of mangrove ecosystems. Trapping may explain the enhanced growth of the mangrove in the delta compared to other areas. This trapping effect may be providing more time for nutrient retention in the mangrove zone, incorporation of the decomposed leaf litter and fine sediments in the substrate, and settling of fruits and seedlings in the swamps, thereby enhancing the regeneration of the mangrove.

The nematode fauna of a temperate Australian mangrove mudflat; its population density, diversity and distribution

The nematode fauna of an estuarine mangrove Avicennia marina mudflat in Southeastern Australia has been intensively studied. About 85% of the nematodes occur in the top cm of soft mud, but 5–7 species inhabit the deeper anoxic mud down to 10 cm, both at low and high tide. One square metre was intensively sampled from four zones with different nematode faunas. At the low tide zone 58% of the nematodes were epistrate feeders, including many diatom-feeders, but in the mangrove zone selective microbial feeders made up over 60% of the population, while between high water neap and high water spring, above the mangrove zone, omnivore/predators and plant root feeding nematodes increased in relative importance. Random replicate cores reliably sampled species occurrence, but gave a high variance in density estimates. Replicate aliquots from homogenised mud gave lower density variance. Nematode densities (maximum 5 × 106 m-2) were not as high as have been reported from non-mangrove estuaries in other countries, but were within the range found in mangroves elsewhere in Australia. Margalef Species Richness values ranged from 1.7 to 3.89, which is similar to values found in other mangroves mudflats in Australia. Nematode biomass ranged from 888 mg dry weight m2 (383 mg C m-2) at the low tide zone to 19 mg dry weight m-2 (8 mg C m-2) at the upper tide level.

Habitats of Culicoides spp. in an intertidal zone of southeast Queensland, Australia

The distribution of immature Culicoides Latreille (Diptera: Ceratopogonidae) in the intertidal zone was investigated at Redland Bay near Brisbane, southeast Queensland. The aims of this study were to determine the distribution of Culicoides immatures and to identify environmental factors influencing these distributions. Light trapping of adult midges indicated that C.subimmaculatus Lee & Reye, C.marmoratus (Skuse), C.longior Hagan & Reye, C.henryi Lee & Reye, C.cordiger Macfie, may have been breeding in the study site. Soil sampling on six transects traversing mangrove and salt-marsh revealed the breeding habitats from which immature stages of the first four species were obtained. The elevation, vegetation and soils of positive sites were recorded and analysed for each species of Culicoides. The distribution of intertidal vegetation (mangroves and salt-marsh plants) was compared to MacNae's (1966) system of mangrove zonation for eastern Australia. The distribution of immature Culicoides did not correspond with mangrove zones, but was related to the presence or absence of intertidal vegetation. C.subimmaculatus was closely associated with a particular substrate and the presence of burrowing crabs.

Nitrogen pools and soil characteristics of a temperate estuarine wetland in eastern Australia

The nitrogen status of the soil and plant components of an estuarine wetland near Sydney were investigated over 6 months to detect seasonal and spatial changes in nitrogen content. Organic carbon, organic nitrogen and inorganic nitrogen concentrations were measured in the soil at various depths in six vegetation zones across the wetland. Carbon and nitrogen content of the plant biomass were also determined in each of the zones. Soil redox potentials and pH were measured in situ and both were found to vary with depth and inundation frequency. Organic carbon, organic nitrogen and inorganic nitrogen in the soil decreased significantly from the fringe Casuarina forest (1391 g N m −2) through to the Avicennia mangrove zone (133 g N m −2). Exchangeable NH 4 +, NO 3 − and NO 2 − concentrations from less than 1% of the soil nitrogen pool and vary seasonally. The distinctive feature of the mangrove zone is that the plant component of the total nitrogen pool is large (55%). This contrasts with the saltmarsh and fringe communities, where the plant pools are small (15%) in comparison with the soil. These findings are consistent with the hypothesis that mangroves export organic nutrients whereas the saltmarsh and fringe communities act as nutrient sinks.

Decomposition of leaf and root litter of Avicennia marina at Westernport Bay, Victoria, Australia

After 3 days in sea water, leaching losses caused a 13% reduction in the weight of new leaf litter of Avicennia marina (Forsk.) Vierh., and a 20% reduction of N, 35–40% of P, 60–85% of K, 30–40% of Mg and 0–12% of Ca. In the field, leaf litter in litter bags lost 80–90% of its initial weight and 89–99% of its initial K, 90–95% of its Mg, 85–90% of its P, 70–80% of its Ca and 60–80% of its N after 230–270 days. During this same period, Avicennia fibrous- and main-root litter in bags buried at a depth of 10–15 cm lost an average of 10–15% and 60% of their initial weight, respectively. Fibrous roots lost 80% of their K, 40–50% of their P, 15% of their N, 10–15% of their Mg and 5–10% of their Ca. Elemental losses from main roots ranged from 90% for K to 30% for Mg, with P, Ca and N losses of 70, 70 and 50%, respectively. Litter decomposition curves for leaf litter and fibrous-root litter begun at different times were not significantly different. A study with unbagged leaf litter indicated that crabs ate about 50% of the litter retained in the mangrove zone. Unbagged litter not eaten by crabs lost weight more rapidly than bagged litter because it lost leaf fragments more readily as it aged. We estimate from our studies and field observations that about 40% of the leaf litter produced each summer is exported from the mangrove zone in the form of whole leaves, particulate organic matter and dissolved organic matter. Root litter is neither exported from the mangrove zone nor eaten by crabs.

Cultivation of the green alga, Caulerpa racemosa, in tropical waters and some aspects of its physiological ecology

Caulerpa racemosa var. occidentalis, a benthic siphonaceous green alga, has its natural habitat in the sublittoral of tropical shallow water reef areas. In the Philippines, where C. racemosa is esteemed as a vegetable, it is cultivated in artificial ponds in the intertidal mangrove zone. The culturing of C. racemosa in ponds is described. In addition to a comparison of the ecological conditions in the natural habitat and the culture ponds, the responses of C. racemosa to the most important environmental factors have been studied. In contrast to the conditions in its natural habitat, Caulerpa in culture ponds is subjected to considerable changes of environmental factors such as salinity, temperature, light and pH. Experiments show that fluctuations of the parameters investigated in the culture ponds are usually within the physiological tolerance of Caulerpa. Under extreme conditions, however, detrimental effects may occur. The possibilities of controlling such factors are discussed.

Distribution and zonation of mangroves in the northern part of the Negombo lagoon (Sri Lanka)

The Journal of the National Science Foundation of Sri Lanka publishes the results of research in all aspects of Science and Technology. The journal also has a website at http://www.nsf.gov.lk/. 2021 Impact Factor: 0.682The JNSF provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge.

Distribution of Juvenile, subadult and adult Scylla serrata (Crustacea: Portunidae) on tidal flats in Australia

In Deception Bay, northern Australia, during 1979–1981, a study was made of the distribution of Scylla serrata (Forskal) in an area having a broad intertidal zone. Juveniles (20 to 99 mm carapace width) were resident in the mangrove zone, remaining there during low tide. The majority of subadult crabs (100 to 149 mm) migrated into the intertidal zone to feed at high tide and retreated to subtidal waters at low tide. Adults (150 mm and larger) were caught mainly subtidally and only small numbers were captured in the intertidal at high tide. Few crabs were captured in the coolest months (May to August). Adults were captured on the flats mainly in the warmest months (January to April), but subadults could be captured over the entire summer (September to March). Juveniles were found in the upper intertidal throughout the year.

Studies in the analysis of data from Australian tidal forests (‘Mangroves’). I. Vegetational sequences and their graphic representation

AbstractDifficulties have been experienced in reconciling field observations of tidal forests in north‐east Queensland with published accounts of their vegetational character. Modern classificatory techniques have been applied to information on forest composition at 803 widely‐distributed sites. A novel method has been developed to represent a set of thirty association groups linked through a minimum spanning tree. This approach has provided new insights into tidal forest expression, the range of vegetational sequences present, and their relationships. Current views of mangrove zonation in north‐east Queensland are found inadequate.

Mangrove Zonation Along an Eroding Coastline in King Sound, North-Western Australia

Mangrove Zonation Along an Eroding Coastline in King Sound, North-Western Australia

Early Growth of Mangrove Seedlings in Panama, and an Hypothesis Concerning the Relationship of Dispersal and Zonation

Propagules of four genera (Avicennia, Laguncularia, Pelliciera and Rhizophora) of mangroves in Panama were planted in reciprocal gardens with solid stands of each genus. In most cases, mangrove seedlings grow and survive in the habitats of the adults of other species as well or better than they do in the habitats of adults of their own species. Seedlings do not shown superior growth (measured as five traits) in those sites where their adults customarily occur. I found little support for the idea that mangrove zonation is controlled by the species' differential tolerance to or preference for physiological conditions occurring along the tidal gradient. An hypothesis is proposed that mangrove zonation may be controlled by tidal sorting of the propagules according to size and by differential ability of propagules to establish in deep water. In Panama and other portions of the world, mangroves found in the seaward and deep water portions of swamps have larger, heavier propagules than do mangroves found in the landward and shallow water portions of the swamps. Selective pressures for efficient dispersal and establishment in a tidal environment may override selec- tion for habitat expansion on one hand or avoidance of competition and habitat specialization on the other hand. The seed morphology of upland ancestral forms may be a major evolutionary determinant of propagule and hence dispersal characteristics in the unrelated Panamanian mangroves. Physiologic specializa- tion and optimal growth in a restricted band within the swamp may be precluded by fluctuating conditions that vary annually in concert over the entire swamp.

Mangroves of Arid Environments in Puerto Rico and Adjacent Islands

The structure of mangrove vegetation, soil salinity, and topographic relief of the mangrove ecosystem were studied along the south coast of Puerto Rico, Culebra, and Mona Island. All systems, with the exception of the forest at Mona Island, were characterized by having a coastal fringe of live vegetation (usually dominated by the red mangrove), a zone of dead trees, and a hypersaline lagoon or dry salt flat on the landward side. Mean soil salinities were 44 0/00 for the zone of live trees, 72 0/00 for the zone of dead trees, and 87 0/00 for the salt flats. The Mona Island forest grew over a sandy hardpan that prevented mixing of sea water and the fresh water. Soil salinities were low in this forest, and trees reached a height of 15 m. Tree height was inversely proportional to soil salinity (r = 0.72) between 17 and 72 0/00. When soil salinities exceeded 65 0/00, dead tree basal area was higher than live tree basal area. It is suggested that mangrove growth is limited by soil salinities higher than 90 0/00. Mangrove succession in offshore overwash islands and arid coastlines is described. It is proposed that cyclic rainfall patterns and hurricanes act as regulators of speed and direction of succession. Rainy periods are associated with lower soil salinities and expansion of the red mangrove zone. Droughty periods result in high soil salinities, mangrove mortality, and expansion of salt flats. Hurricanes set back succession and reverse successional trends that reduce mangrove areas. A model of mangrove ecosystem function and implications for management are also discussed.

Field experiments on growth and mortality of Penaeus vannamei in a Mexican coastal lagoon complex

Growth in total length of juvenile Penaeus vannamei Boone was between 0·8 and 1·4 mm per day at water temperatures between 25 and 35 °C. Growth was density dependent at densities higher than 2·5 m −2. Substrate characteristics such as combustible organic content and rate of oxygen consumption, appeared to influence growth rate of shrimp. Mortality rate in enclosures at the lagoon edge was 41% per week. Population densities averaged about 0·3 individuals m −2 on the lagoon flats, but were higher in the canals and mangrove zones. Practical implications of the results for the commercial fishery are discussed.

Vegetation Change Along an Altitudinal Gradient, Santa Cruz Island, Galapagos

Quantitative study of the vegetation along a limited altitudinal gradient (183 m rise in 12,900 traverse) on Santa Cruz Island, Galapagos, demonstrates the presence above the coastal mangrove zone of three distinctive zones, the Cryptocarpus, arid, and protean (transition) zones. The Cryptocarpus (immediate coastline) and arid zones differ only in species composition, while the protean zone vegetation differs from that of the lower altitudes in both species representation and stand organization. The two lower zones are dominated by one or two species; the protean zone contains a larger number of more equitably represented species. Much of the variability of the vegetation is continuous and associated with altitude (39.8%, first canonical variate). Deviation from the altitudinal trend is evidenced in the arid zone vegetation where local patchiness is characteristic. Factors contributing to the continuity include precipitation, evaporation, and substrate, but all associated with altitude. Cover provided by the tree canopy also increases with altitude. Discrete breaks in continuity were observed between zones. This disjunction might result from the effect of steep slopes on the physical environment; it is evidenced wherever a 10-meter rise in altitude occurs in a relatively short distance when compared with the remainder of the gradient. At this scale, few associations were observed among plant species; individual species presumably appear and disappear according to their range of tolerances. El Cambio de la Vegetacion a lo Largo del Declive Altitudinal, Isla de Santa Cruz, Gala'pagos2