Mangrove Ecosystem Function Research Articles

Halogenated organic compounds in mangrove sediments from Bintan Island, Indonesia: Occurrence, profiles, sources, and potential ecological risk.

The first comprehensive analysis of halogenated organic compounds (HOCs), including 209 full congeners of polychlorinated biphenyls (PCBs), 26 organochlorinated pesticides (OCPs), 41 polybrominated diphenyl ethers (PBDEs), and four other brominated flame retardants (BFRs), was performed on surface mangrove sediments from Bintan Island, Province of the Riau Archipelago, Indonesia. Among the measured HOC contaminants, the mean concentration of ∑209PCBs (2.3±0.96 ng g-1 dw) was higher than that of p,p'-DDE (1.8±0.70 ng g-1 dw), ∑41PBDEs (1.8±1.1 ng g-1 dw), trans-nonachlor (0.42±0.13 ng g-1 dw), and other BFRs (0.20±0.29 ng g-1 dw), while other OCP related compounds less than 0.2 ng g-1 dw. In addition, concentrations of unintentionally produced PCBs such as PCB-11 and PCB-47/48/75 ranged from 0.57-1.5 ng g-1 dw. Variations in HOCs accumulation and profiles among mangrove habitats and species indicate different anthropogenic stressors and species-specific accumulations. The ecological risk estimation from HOCs exposure on dwelling sediment biota in mangrove sediments varied from no risk to potentially causing adverse effects in several locations. Overall, this study provides fundamental information on the function of mangrove ecosystems as an accumulation zone for HOCs in tropical regions.

Upscaling the contribution of crab burrows to mangrove ecosystem functioning in French Guiana (South America)

Burrow characteristics and bioturbation activities of benthic organisms play a key role in mangrove ecosystem biogeochemical and sedimentary functioning. In this study, we aimed to understand how small-scale topographic variations in a mud bank might influence burrow morphology and distribution in a French Guiana pioneer mangrove system (Sinnamary estuary), and to upscale spatial patterns using remote sensing. We used burrow resin casting and sediment conductivity measurements to depict subsurface 3D burrow structures. We found that the spatial heterogeneity of burrow sizes (small, medium, large) and morphologies (simple I- and J-shape, complex geometries) depended on the geomorphic units within mudflats (platform, channel, depression). The aperture areas of burrow casts were used to predict the volume and complexity of each burrow type, enabling us to use drone-derived burrow opening distribution maps to calculate burrow volumes and complexity at the mudflat scale. There are clear associations between tidal channels and depressions and voluminous, multi-aperture, complex and multi-species burrows. In contrast, simple I- and J-shaped burrows inhabited by single species were mainly found on platforms. These relationships lead to a comparatively large volume of tidal-irrigated and deeply aerated sediments connected to channels and depressions compared to platform areas. We suggest that, depending on their morphology and connectivity with the topography, burrows may exhibit differences in biogeochemical functioning depending on the geomorphic unit. We warn against generalizing the functioning of mangrove ecosystems across geomorphic units where impacts may differ. Further studies are needed to understand how different burrow morphologies and life cycles may alter hydrological, sedimentary and biogeochemical functioning.

Carbon stocks in mangrove ecosystems of Sri Lanka: Average contributions and determinants of sequestration potential

Mangroves are crucial in carbon sequestration despite covering only a small percentage of the Earth's surface. Latitudinal gradient primarily determines the distribution of climatic zones of distinct sunlight, temperature, and precipitation patterns, which influence the community structure of the mangrove ecosystem. The tropical climate of Sri Lanka contributes to the island's lush mangrove forests. The present study estimated that the average island's carbon sequestration capacity of Sri Lankan mangrove ecosystems is 524.25 t/ha representing a substantial volume of carbon storage that contributes to offset greenhouse effect due to increasing atmospheric CO2. Our results substantiated that rainfall positively influences total carbon sequestration capacity of mangrove ecosystems.It was also revealed that a positive relationship exists between vegetation structural complexity and sediment organic carbon, highlighting the influence of vegetation structure, that is primarily dependent on climatic conditions, on production of organic matter and sediment carbon sequestration. Globally, the carbon sink function of mangrove ecosystems is reported to be highest in the tropical areas and it declines towards sub-tropical higher latitudes while those in the southern hemisphere perform better carbon sinks than those in the northern hemisphere.The vertical distribution of total organic matter content in mangrove sediments was revealed to be in a descending order, manifesting the weak tidal removal of surface organic matter under the microtidal conditions in Sri Lankan marine waters, thus qualifying mangrove ecosystems in microtidal coasts as effective carbon sinks.

Colonization characteristics and dynamic transition of archaea communities on polyethylene and polypropylene microplastics in the sediments of mangrove ecosystems

Microplastics are a growing concern in mangrove ecosystems; however, their effects on archaeal communities and related ecological processes remain unclear. We conducted in situ biofilm-enrichment experiments to investigate the ecological influence of polyethylene (PE) and polypropylene microplastics on archaeal communities in the sediments of mangrove ecosystems. The archaeal community present on microplastics was distinct from that of the surrounding sediments at an early stage but became increasingly similar over time. Bathyarchaeota, Thaumarchaeota, Euryarchaeota, and Asgardaeota were the most abundant phyla. Methanolobus, an archaeal biomarker, was enriched in PE biofilms, and significantly controlled by homogeneous selection in the plastisphere, indicating an increased potential risk of methane emission. The dominant archaeal assembly process in the sediments was deterministic (58.85%−70.47%), while that of the PE biofilm changed from stochastic to deterministic during the experiment. The network of PE plastispheres showed less complexity and competitive links, and higher modularity and stability than that of sediments. Functional prediction showed an increase in aerobic ammonia oxidation during the experiment, whereas methanogenesis and chemoheterotrophy were significantly higher in the plastisphere. This study provides novel insights into the impact of microplastic pollution on archaeal communities and their mediating ecological functions in mangrove ecosystems.

Metagenomic analysis of gut microbiome illuminates the mechanisms and evolution of lignocellulose degradation in mangrove herbivorous crabs

BackgroundSesarmid crabs dominate mangrove habitats as the major primary consumers, which facilitates the trophic link and nutrient recycling in the ecosystem. Therefore, the adaptations and mechanisms of sesarmid crabs to herbivory are not only crucial to terrestrialization and its evolutionary success, but also to the healthy functioning of mangrove ecosystems. Although endogenous cellulase expressions were reported in crabs, it remains unknown if endogenous enzymes alone can complete the whole lignocellulolytic pathway, or if they also depend on the contribution from the intestinal microbiome. We attempt to investigate the role of gut symbiotic microbes of mangrove-feeding sesarmid crabs in plant digestion using a comparative metagenomic approach.ResultsMetagenomics analyses on 43 crab gut samples from 23 species of mangrove crabs with different dietary preferences revealed a wide coverage of 127 CAZy families and nine KOs targeting lignocellulose and their derivatives in all species analyzed, including predominantly carnivorous species, suggesting the crab gut microbiomes have lignocellulolytic capacity regardless of dietary preference. Microbial cellulase, hemicellulase and pectinase genes in herbivorous and detritivorous crabs were differentially more abundant when compared to omnivorous and carnivorous crabs, indicating the importance of gut symbionts in lignocellulose degradation and the enrichment of lignocellulolytic microbes in response to diet with higher lignocellulose content. Herbivorous and detritivorous crabs showed highly similar CAZyme composition despite dissimilarities in taxonomic profiles observed in both groups, suggesting a stronger selection force on gut microbiota by functional capacity than by taxonomy. The gut microbiota in herbivorous sesarmid crabs were also enriched with nitrogen reduction and fixation genes, implying possible roles of gut microbiota in supplementing nitrogen that is deficient in plant diet.ConclusionsEndosymbiotic microbes play an important role in lignocellulose degradation in most crab species. Their abundance is strongly correlated with dietary preference, and they are highly enriched in herbivorous sesarmids, thus enhancing their capacity in digesting mangrove leaves. Dietary preference is a stronger driver in determining the microbial CAZyme composition and taxonomic profile in the crab microbiome, resulting in functional redundancy of endosymbiotic microbes. Our results showed that crabs implement a mixed mode of digestion utilizing both endogenous and microbial enzymes in lignocellulose degradation, as observed in most of the more advanced herbivorous invertebrates.

Stochastic processes drive the diversity and composition of methanogenic community in a natural mangrove ecosystem

Methanogens are considered to be crucial components of mangrove ecosystems with ecological significance. However, understanding the assembly processes of methanogenic communities in mangrove ecosystems is relatively insufficient. In the current study, a natural mangrove in a protection zone was employed to investigate the diversity and assembly processes of methanogenic community by using amplicon high-throughput sequencing, a null model as well as a neutral community model. The results showed that methanogenic community in mangrove sediments were highly diverse, with the predominance of methylotrophic Methanolobus, and hydrogenotrophic Methanogenium, Methanospirillum. The diversity, composition, and gene abundance varied obviously across the mangrove sampling sites, whereas the measured environmental variables exhibited a negligible effect. Null model showed that the values of beta nearest-taxon index were mostly between −2 and 2, indicating that stochastic processes contributed more than deterministic processes driving the methanogenic community assembly in mangrove sediments. Neutral community model revealed a high estimated migration rate of methanogenic community, further substantiating the significance of stochastic processes. Among the keystone species identified in network analysis, methanogens affiliated to hydrogenotrophic Methanospirillum may have a crucial role in maintaining the structure and function of methanogenic community. Notably, these keystone species were almost unaffected by measured environmental factors, indicating that the methanogenic community in mangrove sediments is more likely to be affected by stochastic processes. This study deepens the understanding of the diversity and assembly of methanogenic community in mangrove sediments, and provides clues to maintain mangrove ecosystem functioning.

Carbon reserves in deltaic mangroves of the Colombian Pacific across different disturbance degrees

Mangrove forests occupy less than 1% of tropical forest areas, but account for approximately 3% of global tropical forest carbon sequestration and act as a natural atmospheric CO2 sequestration mechanism, which gives them an important role in climate change mitigation. However, different anthropogenic disturbances continue to negatively impact the structure and function of mangrove ecosystems; therefore, it is important to investigate the effect of specific anthropogenic alterations on the capacity of mangroves to store carbon. The present study aimed to test the hypothesis of a direct relationship between the degree of anthropogenic intervention and the reduction of mangrove carbon stocks. Eight edge forest types with different degrees of anthropogenic intervention and multiple uses were selected. Six 100 m2 plots were established in each forest to determine its structure and evaluate the concentration of sedimentary organic carbon and biomass. The anthropogenic disturbance index (ADI) was used to quantify the degree of specific disturbances in the studied forests. The results supported the proposed hypothesis, showing that the mangroves with the highest anthropogenic disturbance measured through the ADI registered the lowest values in blue carbon. However, it is evident that in addition to anthropogenic disturbances, impacts such as coastal erosion pose a very important threat to some of these forests. Estimated organic carbon losses in the study area were between 8.4% and 49.3%, corresponding to 158 and 929 Mg CO2 eq ha−1, respectively. Logging is one of the main disturbances that affects forests differently according to their structural development. Forests with higher structural development are subject to greater pressure. Carbon losses from logging are not only reflected in aboveground carbon, but are also evident in sedimentary carbon.

Environmental selection and evolutionary process jointly shape genomic and functional profiles of mangrove rhizosphere microbiomes.

Mangrove reforestation with introduced species has been an important strategy to restore mangrove ecosystem functioning. However, how such activities affect microbially driven methane (CH4), nitrogen (N), and sulfur (S) cycling of rhizosphere microbiomes remains unclear. To understand the effect of environmental selection and the evolutionary process on microbially driven biogeochemical cycles in native and introduced mangrove rhizospheres, we analyzed key genomic and functional profiles of rhizosphere microbiomes from native and introduced mangrove species by metagenome sequencing technologies. Compared with the native mangrove (Kandelia obovata, KO), the introduced mangrove (Sonneratia apetala, SA) rhizosphere microbiome had significantly (p < 0.05) higher average genome size (AGS) (5.8 vs. 5.5 Mb), average 16S ribosomal RNA gene copy number (3.5 vs. 3.1), relative abundances of mobile genetic elements, and functional diversity in terms of the Shannon index (7.88 vs. 7.84) but lower functional potentials involved in CH4 cycling (e.g., mcrABCDG and pmoABC), N2 fixation (nifHDK), and inorganic S cycling (dsrAB, dsrC, dsrMKJOP, soxB, sqr, and fccAB). Similar results were also observed from the recovered Proteobacterial metagenome-assembled genomes with a higher AGS and distinct functions in the introduced mangrove rhizosphere. Additionally, salinity and ammonium were identified as the main environmental drivers of functional profiles of mangrove rhizosphere microbiomes through deterministic processes. This study advances our understanding of microbially mediated biogeochemical cycling of CH4, N, and S in the mangrove rhizosphere and provides novel insights into the influence of environmental selection and evolutionary processes on ecosystem functions, which has important implications for future mangrove reforestation.

The Artefactual Branch Effect and Phylogenetic Conflict: Species Delimitation with Gene Flow in Mangrove Pit Vipers (Trimeresurus purpureomaculatus-erythrurus Complex).

Mangrove pit vipers of the Trimeresurus purpureomaculatus-erythrurus complex are the only species of viper known to naturally inhabit mangroves. Despite serving integral ecological functions in mangrove ecosystems, the evolutionary history, distribution, and species boundaries of mangrove pit vipers remain poorly understood, partly due to overlapping distributions, confusing phenotypic variations, and the lack of focused studies. Here, we present the first genomic study on mangrove pit vipers and introduce a robust hypothesis-driven species delimitation framework that considers gene flow and phylogenetic uncertainty in conjunction with a novel application of a new class of speciation-based delimitation model implemented through the program Delineate. Our results showed that gene flow produced phylogenetic conflict in our focal species and substantiates the artefactual branch effect where highly admixed populations appear as divergent nonmonophyletic lineages arranged in a stepwise manner at the basal position of clades. Despite the confounding effects of gene flow, we were able to obtain unequivocal support for the recognition of a new species based on the intersection and congruence of multiple lines of evidence. This study demonstrates that an integrative hypothesis-driven approach predicated on the consideration of multiple plausible evolutionary histories, population structure/differentiation, gene flow, and the implementation of a speciation-based delimitation model can effectively delimit species in the presence of gene flow and phylogenetic conflict.

Controlling heavy metals pollution is vital for the restoration of carbon and nitrogen transformation function of mangrove ecosystems in the Greater Bay Area, China

Pollutants, especially for heavy metals (HMs), discharged from anthropogenic activities are the potential risks to newly planted mangrove forests in the restoration process. Thus, it is crucial to investigate how HMs affect the biological processes that take place in these mangrove habitats, e.g., the transformation of carbon and nitrogen. In this study, correlations between HMs pollution, carbon storage, and nitrogen biotransformation in the Great Bay Area (GBA) were examined at five typical sites with different mangrove restoration ages. The results indicated that there were distinct differences in the concentration distribution of HMs (ranges: 0.2–369.7 mg/kg) at five sample sites, with Cd (0.2–1.6 mg/kg) being the heavily polluted element in sediments. The fluctuation of SOC (16.0–25.7 mg/kg), δ13C (−27.5 to −20.2), and NO3−-N (1.2–3.3 mg/kg) was positively correlated with the content of HMs in sediments, indicating that these components in mangrove ecosystems might have similar emission source and pose a potential threat to mangrove carbon storage. Notably, sediments with high HMs concentration decelerated carbon decomposition rate of mangrove ecosystems, especially for sites with newly planted mangrove forest. Moreover, a large abundance of Euryarchaeota was found in the HO site, suggesting that HMs may promote the conversion of carbon to CH4. The inflow of contaminants also induced the significant increasing proportion of microorganisms related to nitrogen fixing, denitrification, and dissimilarity nitrogen reduction processes, resulting a decline in the stability of co-occurrence network of nitrogen transformation. Fortunately, mangrove site with the establishment of natural reserves and controlling pollutant discharge could contribute to the rapid restoration of its ecological function, e.g., nutrient cycling and co-occurrence stability, in SZ site. Therefore, future management should focus on the decrease of pollutants discharge and pay more attention to the ecological function restoration of mangrove wetlands in the GBA.

Ecology of the facultative phytotelmic crab Platychirarma buettikoferi (De Man, 1883) (Decapoda, Brachyura, Sesarmidae)

Abstract The mangrove forests surrounding Douala, Cameroon, have a long history of human impact due to rapid urbanization, resulting in patches of true mangrove forest interspersed with areas dominated by the mangrove-associated Pandanus species. A survey carried out to assess the possible shift in crab fauna composition and dominance between mangrove and Pandanus dominated areas revealed an undescribed phytotelmic habitat for Platychirarma buettikoferi. This species was found colonizing the natural reservoirs of fresh water represented by Pandanus spp. Our results show P. buettikoferi to be ecologically dependent upon Pandanus spp., and absent on the mangrove floor and trees, strongly indicating a phytotelmic adaptation. Our data suggest that this species is a facultative phytotelmic species well adapted to Pandanus spp. dominated areas. Further studies on the reproductive biology and feeding behaviour of P. buettikoferi may shed light on this unique phytotelmic lifestyle and its role in mangrove ecosystem functioning.

DNA-based taxonomy of a mangrove-associated community of fishes in Southeast Asia

The Merbok Estuary comprises one of the largest remaining mangrove forests in Peninsular Malaysia. Its value is significant as it provides important services to local and global communities. It also offers a unique opportunity to study the structure and functioning of mangrove ecosystems. However, its biodiversity is still partially inventoried, limiting its research value. A recent checklist based on morphological examination, reported 138 fish species residing, frequenting or subject to entering the Merbok Estuary. In this work, we reassessed the fish diversity of the Merbok Estuary by DNA barcoding 350 specimens assignable to 134 species initially identified based on morphology. Our results consistently revealed the presence of 139 Molecular Operational Taxonomic Units (MOTUs). 123 of them are congruent with morphology-based species delimitation (one species = one MOTU). In two cases, two morphological species share the same MOTU (two species = one MOTU), while we unveiled cryptic diversity (i.e. COI-based genetic variability > 2%) within seven other species (one species = two MOTUs), calling for further taxonomic investigations. This study provides a comprehensive core-list of fish taxa in Merbok Estuary, demonstrating the advantages of combining morphological and molecular evidence to describe diverse but still poorly studied tropical fish communities. It also delivers a large DNA reference collection for brackish fishes occurring in this region which will facilitate further biodiversity-oriented research studies and management activities.

Intertidal zone preferences of fiddler crabs in tropical mangroves reflect species specific selection across multiple spatial and temporal scales

In mangroves, species specific spatial habitat zonation preference of fiddler crabs could influence the functioning of mangrove ecosystems. Spatial zonation of fiddler crabs in tropical Malaysian mangroves across different temporal scales has not been studied extensively. In this study, the abundance and species richness of several fiddler crab species across a mangrove intertidal zone were examined in relation to environmental variables. Fiddler crab abundance was sampled with salinity, pH, temperature, and sediment grain size in three mangrove sites in Penang Island, Malaysia. The sampling design involved collecting crabs and environmental habitat variables in six 2 m × 2 m quadrats within three mangrove study sites from March 2017 to February 2018. Data were analysed using multivariate (PERMANOVA, SIMPER, and BEST in PRIMER v7.0) and univariate analyses (ANOVA and Pearson’s r in STATISTICA v 13.30). Univariate and multivariate analysis revealed multiple spatial and temporal scales influenced each fiddler crab species differently (ANOVA p < 0.05). Fiddler crab abundance varied across and within sites, intertidal zones, and sampling months (PERMANOVA, p < 0.001). Austruca annulipes, Gelasimus vocans and Tubuca paradussumieri were found mostly at the lower intertidal zone, which was characterized by a higher sand faction. Tubuca rosea, Tubuca forcipata, and Austruca bengali occupied and coexisted in the middle and higher zones of the intertidal, although this pattern varied across the different sites in this study. BEST analysis indicated that porewater salinity and sediment particle size were important factors in structuring patterns of fiddler crab assemblages. Based on univariate correlation analyses, the total abundance of fiddler crab increased with increased temperature (temperature ranged from 26.9 °C to 31.7 °C), and increased porewater salinity (salinity ranged from 10‰ to 35‰).

Monitoring the rapid changes in mangrove vegetation of coastal urban environment using polynomial trend analysis of temporal satellite data

Over the last few decades, anthropogenic activities have triggered the rate of change in the function of mangrove ecosystems in coastal urban areas. Satellite imagery provides valuable information for mangrove mapping and monitoring. Metrics derived from the linear regression analysis of spectral indices (SIs) derived from satellites are commonly used for change analysis. This study examines the robustness of the widely used SIs derived from Landsat satellite image to distinguish mangroves and non-mangrove features and identify the non-linear changes over mangrove forest using the polynomial trend analysis. Airborne Visible and Infra-Red Imaging Spectrometer Next Generation (AVIRIS-NG) data was resampled to simulate the spectral-response of the Landsat sensor. One-way analysis of variance (ANOVA) and mutual information (MI) were applied to the simulated data to identify the optimal SIs. Based on the statistical analysis, modular mangrove recognition index (MMRI), modified normalized difference water index (MNDWI) and normalized difference built-up index (NDBI) were identified to delineate the mangrove, inundated and built-up region. Finally, time-series profiles of the identified spectral indices were generated using Landsat-8 (L8) and Landsat-7 (L7) data to analyse the change dynamics of the mangrove vegetation from 2002 to 2019. The proposed methodology was applied to study the changes in mangroves in the coastal areas of Kochi (Ernakulam District, Kerala State, India). The temporal-non-linear changes in the mangrove area were identified based on polynomial regression that revealed abrupt decline (42% decrease) in the mangrove area due to large-scale infrastructure development projects. The proposed approach is easy to implement, which enables the frequent monitoring of extensive mangrove forests.

Food sources for camptandriid crabs in an arid mangrove ecosystem of the Persian Gulf: a stable isotope approach

ABSTRACT Crabs of the family Camptandriidae are the most dominant burrowing crabs inhabiting arid mangrove forests of the Persian Gulf. They play important roles in the structuring and functioning of mangrove ecosystems by modulating biogeochemical processes and cycling of nutrients, serving as important ecosystem engineers. We analysed stable carbon (13C) and nitrogen (15N) isotope values of three camptandriid crabs (Opusia indica, Nasima dotilliformis, and Manningis arabicum) and their potential food sources in the Hara Biosphere Reserve, northern Persian Gulf. A Bayesian mixing model was used to estimate the contribution of potential food sources for consumers. The results showed that to some degree, all the four sources selected contributed to the camptandriid diets, but microphytobenthos made the most important contributions to the diet of the consumers. Mangroves do not appear to be a significant source of carbon in the diet of camptandriid crabs in the arid mangrove system of the Persian Gulf. Rather, they offer favourable growing conditions, thus boosting microphytobenthos production and availability for consumers which prefer a high nutritional and palatable source.

The habitat preference of mangrove crabs in different mangrove forests of Penang, North Peninsular Malaysia

Different crab assemblage compositions may result in distinct pathways in mangrove ecosystem function, attributed to specific preferences and habitat selection criteria by each crab species. This study assessed the preference of crabs to different mangrove forests at Balik Pulau, Penang, Malaysia across temporal scales of four months and spatial scales across three forests. Sites were characterized by Avicennia, Rhizophora and Bruguiera species. Crabs were sampled using hand-catch method, which was then preserved in 70% ethanol and identified to the lowest taxonomic level possible. Environmental variables were determined by in-situ and ex-situ analysis and comprised the collection of canopy cover, root cover, surface temperature, sediment salinity and organic matter data. PERMANOVA analysis showed there was a difference in crab abundance and environmental variables across Month and Forest (p < 0.05). SIMPER analysis revealed that the Grapsidae family dominated mangroves of Balik Pulau, with Perisesarma eumolpe and Perisesarma foresti found to be most abundant in Avicennia and Bruguiera forests respectively. However, in the Rhizophora forest, dominant crab species varied, with Parasesarma sp2. and Perisesarma indiarum found in high abundance in June and August, respectively. In October and December, however Perisesarma foresti was the major contributor to patterns observed in crab assemblage composition in Rhizophora forest. BEST correlation varied among month and forest, with different combinations of salinity, pH, canopy cover and root density explaining patterns in crab assemblages.

Mapping mangrove dynamics and colonization patterns at the Suriname coast using historic satellite data and the LandTrendr algorithm

Mangroves play an important role in protecting coasts against wave energy and storms. Mangrove ecosystems provide important habitats for fauna and flora and are an important carbon sink. Loss of mangroves forest may lead to enhanced coastal erosion. Mangroves are complex ecosystems and processes of settling and development are not fully understood. Characterizing the rates and patterns of mangrove gains and losses is needed to better understand the functioning of mangrove ecosystems, how mangrove dynamics are linked to coastal morphological behaviour and how human interference with the coastal system impacts mangroves. Here we present a study of the mangrove ecosystems at the Suriname coast, which are relatively pristine and characterized by strong dynamics due to migrating mudbanks along the coast. Satellite images between 2000 and 2018, available in the historic satellite image archives, were analysed using the LandTrendr (Landsat-based detection of trends in disturbance and recovery) algorithm to identify locations of mangrove erosion, mangrove colonization, surface areas of change and patterns of settlement, as indicated by (sudden) changes in NDVI. The algorithm requires careful setting of various parameters for successful detection of (abrupt) temporal changes in mangrove coverage. The algorithm was evaluated on its robustness using various parameter settings. Results show the value of the timeseries of Landsat imagery to detect locations of coastal erosion of up to 50 m/yr and accretion where loss or settlement of mangroves is prevailing between 2000 and 2018. Locally differences are very large. An overall westward mangrove progression along the coast is apparent from the images and probably linked to mud bank migration. Various patterns of mangrove colonization and development such as arc-, zonal- and patch- arrangements were identified, although at some locations the Landsat resolution of 30 m is somewhat coarse to allow detailed analysis. The success and robustness of the LandTrendr algorithm are controlled by NDVI threshold values, number of allowed breakpoints in the timeseries and fitting parameters. The presented method requires further testing and evaluation but is a promising tool for semi-automatic detection of coastal mangrove erosion and colonization that can be applied to other mangrove ecosystems in the world. The satellite timeseries analyses generate valuable information on coastal dynamics, which is helpful to identify coastal areas prone to erosion and mangrove retreat and provide as such a valuable tool for coastal management and protection.

Trends in Mangrove meiobenthic studies in India: an overview

In spite, of being the most threatened coastal habitats in the world, mangrove ecosystems offer a host of goods and services to the coastal communities. With over 4,975 sq.km of the mangrove area, India has the largest mangrove in Asia that constitutes about 45% of the total mangrove cover in South Asia. Mangroves are ecologically significant for their role in shoreline protection but it also acts as important reservoirs of biodiversity comprising both terrestrial and aquatic species. In the present communication, we reviewed the published literature on meiofauna found associated with mangroves. These microscopic organisms occur in very high densities in mangrove sediment and thus constitute a major component of the diet of commercially important fish and prawn larvae. In addition to the importance of meiofauna in the benthic food chain, larval feeding, meiofauna is also used very effectively in coastal environmental monitoring. While a significant number of scientific reports are published involving studies on meiofauna of Indian mangroves, the majority of these studies have focused only on the phylum of taxon or group level identification. Moreover, only a few of the studies have highlighted the role of food availability and abundance of meiofauna within the mangrove mudflat. Consequently, we recommend that future studies should explore the role of meiofaunal species, especially the dominant taxa, in the mangrove ecosystem functioning.

Diversity, function and assembly of mangrove root-associated microbial communities at a continuous fine-scale

Mangrove roots harbor a repertoire of microbial taxa that contribute to important ecological functions in mangrove ecosystems. However, the diversity, function, and assembly of mangrove root-associated microbial communities along a continuous fine-scale niche remain elusive. Here, we applied amplicon and metagenome sequencing to investigate the bacterial and fungal communities among four compartments (nonrhizosphere, rhizosphere, episphere, and endosphere) of mangrove roots. We found different distribution patterns for both bacterial and fungal communities in all four root compartments, which could be largely due to niche differentiation along the root compartments and exudation effects of mangrove roots. The functional pattern for bacterial and fungal communities was also divergent within the compartments. The endosphere harbored more genes involved in carbohydrate metabolism, lipid transport, and methane production, and fewer genes were found to be involved in sulfur reduction compared to other compartments. The dynamics of root-associated microbial communities revealed that 56–74% of endosphere bacterial taxa were derived from nonrhizosphere, whereas no fungal OTUs of nonrhizosphere were detected in the endosphere. This indicates that roots may play a more strictly selective role in the assembly of the fungal community compared to the endosphere bacterial community, which is consistent with the projections established in an amplification-selection model. This study reveals the divergence in the diversity and function of root-associated microbial communities along a continuous fine-scale niche, thereby highlighting a strictly selective role of soil-root interfaces in shaping the fungal community structure in the mangrove root systems.

Species Composition and Functional Traits of Macrofauna in Different Mangrove Habitats in the Persian Gulf

Macrofauna play a key role in the functioning of mangrove ecosystems. Nevertheless, our understanding of the diversity and functional structure of macrofaunal communities across different habitats in the mangrove forests of the Persian Gulf is limited. In this study, we investigated species diversity and biological trait patterns of macrofauna in different mangrove-associated habitats, i.e. encompassing actual mangrove forests, and adjacent Beaches and Creeks, which exhibit different levels of habitat heterogeneity. Samples were collected from the different habitats in five different locations, over four seasons. A total of 122 macrofauna taxa were identified. The diversity of species was higher in summer than in winter. In the Beach habitats, species diversity showed an increasing trend from land towards the mangrove, whereas in Creek habitats diversity decreased from the Creek towards the mangrove. Multivariate community analysis showed differences in the distribution of abundant species and biological traits across all habitats. Deposit-feeding, crawlers, medium-size, and free-living were the dominant trait modalities in all habitats. The similarities within habitats over the four seasons had the same specific pattern of species and biological trait abundance in the Beach and the Creek, increasing from the non-covered habitat into the mangrove trees. Although many species shared similar traits, the abundance-driven differences in trait expression between habitats showed the importance of habitat filtering. The results of this study will be useful in the conservation of mangrove forests and they give a deeper understanding of the ecological patterns and functions of benthic macrofaunal communities in the Persian Gulf.