Search

In this study we apply hyperspectral imagery to identify saline blank patterns within the mixed mangrove forest of Sunderban Bio-geographic Province, West Bengal, India. We use derivative analysis to identify hyperspectral wavelengths that are sensitive to the presence of minerals comprising saline blanks. These wavelengths have been considered for development of a novel saline blank identification model. The wavelength showing derivative value with maximum absorption in the SWIR region at 1780 nm and maximum reflection in the red region at 690 nm has been extracted for development of saline blank index. This index has been compared with the existing salinity indices and a detailed analysis has been carried out. It is found that the index outperforms existing salinity indices – normalized differential salinity index and salinity index, and accurately detects the saline blank areas of Henry Island of the Sunderbans Delta. The accuracy of pixels identified as saline blank pixels has been assessed by comparing the overall accuracy with other existing indices. Physical sampling has also been carried out and the salinity results have been compared with the image-derived results. [ABSTRACT FROM AUTHOR]

The study of mangrove communities (Avicennia germinans, Conocarpus erectus, Laguncularia racemosa and Rhyzophora mangle) in Central America reveals a total diversity of 121 species included in 7 plant communities, of which 15 are characteristic of mangroves and 31 of flooded areas with less pronounced salinity, while 75 are invasive species belonging to neighbouring communities. Frequent fires in the dry forest have caused intense erosion, leading to the silting of the lake basin. As a result, the first belt of Rhizophora vegetation is extremely rare. In contrast, there is a predominance of Laguncularia and Conocarpus mangrove plants, in addition to a belt of Phragmito Magnocaricetea with a high incidence of Phragmites australis, which acts as an indicator of sediment silting due to its shallowness. [ABSTRACT FROM AUTHOR]

Meiofauna are ubiquitous but poorly-studied components of soft-bottom marine habitats around the world, including mangroves. The dynamic environmental conditions and heterogeneous sediments of mangroves present challenges to understanding the structure of mangrove meiofaunal assemblages at various spatial and temporal scales. In this study, we investigated the meiofaunal assemblage structure of sediments colonised by three mangrove species, namely, Avicennia marina, Rhizophora stylosa and Aegiceras corniculatum , at three locations in subtropical eastern Australia. Spatial and temporal variations were tested by sampling at the three mangrove locations (i.e. Tallebudgera, Currumbin and Terranora) in autumn, with samplings repeated at Tallebudgera at two other times broadly representing during dry/cool winter and wet/hot summer seasons. We examined the variability of the sediment environments within each of the different mangrove species, and investigated how meiofaunal assemblages would respond to the particular changes in their habitats to result in differences in assemblage structure between and within sites. Total meiofaunal density was highest in Tallebudgera and Currumbin and lowest in Terranora (mean density of 424, 393 and 239 ind.10 cm −2 , respectively). In Tallebudgera, the density was higher in winter and summer (mean density of 546 and 530 ind.10 cm −2 , respectively). The meiofaunal assemblage in this study shows a trend and association with the environmental variables. High availability of food proxies such phaeopigments, Chl a or TOC, with moderate tannin content and appropriate habitat structure (sediment particle size, belowground root biomass and/or moisture content provide the best condition for the meiofauna to achieve the highest density. However, given the complex dynamic habitats and the spatial heterogeneity of the mangrove environments across different locations and seasons, no clear generalization could be made regarding the key environmental variables that predominantly shape the meiofaunal assemblages’ structure. [ABSTRACT FROM AUTHOR]

Mangrove rehabilitation programs received much attention in the past decades as a response to widespread global degradation. While the documented successes and failures of mangrove rehabilitation accomplishments were varied, the objective and scheme is common, mainly focused on planting and creating monospecific plantations. This study assessed the structural development and complexity of the large-scale plantations in the central part of Philippines and compared it with the adjacent natural stand as reference. Our study showed that planted forest in both sites had lower structural complexity than the reference natural forest. Between sites, secondary succession in the monospecific plantation in Banacon Island was inhibited as reflected by low regeneration potential, whereas recruitment and colonization of non-planted species was promoted in Olango Island. Even 60 years after the forest was created in Banacon Island, it still lacked the understory of young cohorts which together comprise the regeneration potential that can supposedly add to the structural complexity. Although a potential seed source from adjacent natural forest is available, recruitment and colonization of non-planted species did not progress. MDS analysis of tree density data showed clustering of planted forest from the natural stand. The average SIMPER dissimilarity was 79.9% and the species with highest contributions were R. stylosa (74.6%), S. alba (11.1%) and A. marina (10.6%). Within the natural forest, the same species had the highest dissimilarity contribution, whereas in the planted forest, only R. stylosa contributed the highest dissimilarity. The same trend was also revealed in the MDS ordination analysis of diameter at breast height (DBH). A one-way ANOSIM permutation test of the density and DBH showed a significant difference between the planted and natural forests. Thus, as part of silviculture management intervention, the current practices of mangrove reforestation needs to be reviewed and evaluated to determine the trajectories of its conservation objectives to achieve the best outcome and functionality of the restored habitat. [ABSTRACT FROM AUTHOR]

While current coastal erosion solutions have had limited success in controlling coastal erosion, the gradual expansion of mangrove areas was effective in stabilizing an actively eroded mangrove dominated muddy coast in Vam Ray, Kien Giang, Vietnam for a short time period. The gradual expansion method was developed as a result of local comprehensive involvement and capacity, and the integration of different knowledge systems. However, the method was not sufficiently reported. Local involvement and capacity were not adequately emphasized during the reporting process. Insufficient reporting caused the failure in replicating the method elsewhere in Kien Giang. Inadequate emphasis of local involvement and capacity probably breached moral rights for the Vam Ray community. This manuscript documented the gradual expansion method using different sources of data and information and inputs from the key Vam Ray community members. The gradual expansion method involved closure of current mangrove gaps by transplanting mangroves protected by appropriate fences as the first stage, and gradual expansion of the mangrove belt seawards in the second stage. The method has a potential replication elsewhere in Vietnam and in Southeast Asia. [ABSTRACT FROM AUTHOR]

Mangroves are seafaring taxa through their hydrochorous propagules that have the potential to disperse over long distances. Therefore, investigating their patterns of gene flow provides insights on the processes involved in the spatial genetic structuring of populations. The coastline of Cameroon has a particular geomorphological history and coastal hydrology with complex contemporary patterns of ocean currents, which we hypothesize to have effects on the spatial configuration and composition of present-day mangroves within its spans. A total of 982 trees were sampled from 33 transects (11 sites) in 4 estuaries. Using 11 polymorphic SSR markers, we investigated genetic diversity and structure of Rhizophora racemosa, a widespread species in the region. Genetic diversity was low to moderate and genetic differentiation between nearly all population pairs was significant. Bayesian clustering analysis, PCoA, estimates of contemporary migration rates and identification of barriers to gene flow were used and complemented with estimated dispersal trajectories of hourly released virtual propagules, using high-resolution surface current from a mesoscale and tide-resolving ocean simulation. These indicate that the Cameroon Volcanic Line (CVL) is not a present-day barrier to gene flow. Rather, the Inter-Bioko-Cameroon (IBC) corridor, formed due to sea level rise, allows for connectivity between two mangrove areas that were isolated during glacial times by the CVL. Genetic data and numerical ocean simulations indicated that an oceanic convergence zone near the Cameroon Estuary complex (CEC) presents a strong barrier to gene flow, resulting in genetic discontinuities between the mangrove areas on either side. This convergence did not result in higher genetic diversity at the CEC as we had hypothesized. In conclusion, the genetic structure of Rhizophora racemosa is maintained by the contrasting effects of the contemporary oceanic convergence and historical climate change-induced sea level rise. [ABSTRACT FROM AUTHOR]

The aim of this study is to understand the relationship between radar backscattering (σ° and ρ°) of a multi-polarized Radarsat-2 C-band image with the structural attributes of regenerating mangrove vegetation located at the mouth of the Amazon River. CBH (circumference at breast height), height and species data were collected to characterize vegetation structure and above-ground biomass (AGB) at 17 plots with a total of 3090 measured individuals. Significant relationships between the linear σ° in VH (vertical transmit, horizontal receive) cross-polarization produced r² values of 0.63 for the average height, 0.53 for the DBH, 0.46 for the basal area (BA) and 0.52 for the AGB. Using co-polarized HH (horizontal transmit, horizontal receive) and VV (vertical transmit, vertical receive), r² values increased to 0.81, 0.79, 0.67 and 0.79, respectively. Vegetation attribute maps of average canopy height, DBH and AGB were generated for the study area. We conclude that multi-polarized Radarsat-2 images were adequate for characterization of vegetation attributes in areas of mangrove regeneration. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the author reflects on how the adaptive capacity of many tidal-zone forests will be outpaced by current rates of sea-level rise and the impact that land-use changes and river damming is having on river sediment availability necessary for mangrove survival.