Mangrove Habitats Research Articles

Species pool and soil properties in mangrove habitats influence the species-immigration process of diazotrophic communities across southern China.

Microbial immigration is an ecological process in natural environments; however, the ecological trade-off mechanisms that govern the balance between species extinction and migration are still lacking. In this study, we investigated the mechanisms underlying the migration of diazotrophic communities from soil to leaves across six natural mangrove habitats in southern China. The results showed that the diazotrophic alpha and beta diversity exhibited significant regional and locational variations. The diazotrophic species pool gradually increased from the leaves to nonrhizosphere soil at each site, exhibiting a vertical distribution pattern. Mantel test analyses suggested that climate factors, particularly mean annual temperature, significantly influenced the structure of the diazotrophic community. The diazotrophic community assembly was mainly governed by dispersal limitation in soil and root samples, whereas dispersal limitation and ecological drift were dominant in leaves. Partial least squares path modeling revealed that the species pool and soil properties, particularly the oxidation-reduction potential and pH, were closely linked to the species-immigration ratio of diazotrophic communities. Our study provides novel insights for understanding the ecological trait diversity patterns and spread pathways of functional microbial communities between below- and aboveground habitats in natural ecosystems.IMPORTANCEEnvironmental selection plays key roles in microbial transmission. In this study, we have provided a comprehensive framework to elucidate the driving patterns of the ecological trade-offs in diazotrophic communities across large-scale mangrove habitats. Our research revealed that Bradyrhizobium japonicum, Marinobacterium lutimaris, and Agrobacterium tumefaciens were more abundant in root-associated soil than in leaves by internal and external pathways. The nonrhizospheric and rhizospheric soil samples harbored the most core amplicon sequence variants, indicating that these dominant diazotrophs could adapt to broader ecological niches. Correlation analysis indicated that the diversities of the diazotrophic community were regulated by biotic and abiotic factors. Furthermore, this study found a lower species immigration ratio in the soil than in the leaves. Both species pool and soil properties regulate the species-immigration mechanisms of the diazotrophic community. These results suggest that substantial species immigration is a widespread ecological process, leading to alterations in local community diversity across diverse host environments.

Introducing a new species, Vaginatispora acrostichi (Lophiostomataceae), based on morphology and multigene phylogeny

Abstract Vaginatispora acrostichi sp. nov. was isolated from submerged stems of Acrostichum aureum (Pteridaceae) collected from the mangrove habitats of Pranburi District, Prachuap Khiri Khan, Thailand. Phylogenetic analyses based on the combined dataset of LSU, SSU, ITS, tef1-α, rpb2, and β-tub sequences placed the novel species within Vaginatispora. Vaginatispora acrostichi formed a well-supported sister clade with V. lignicola but differs from it morphologically and phylogenetically. Vaginatispora acrostichi is distinguishable from V. lignicola by ascospore size, septation and colour. The ascospores of V. acrostichi turn light brown at maturity and have a single septum with a minute constriction, while those of V. lignicola appear yellowish at maturity and have 1–3 septa with pronounced constriction. Vaginatispora acrostichi is introduced in this paper as a novel species with a comprehensive description and illustration.

Performance and detection range of acoustic receivers in mangrove habitats.

Acoustic telemetry has been used to monitor the movement of aquatic animals in a broad range of aquatic environments. Despite their importance, mangrove habitats are understudied for the spatial ecology of elasmobranchs, with acoustic telemetry rarely used inside mangrove habitats. One reason for this may be a general assumption that acoustic signals would not be able to be detected by receivers in such shallow, structurally complex, environments. This study tested whether acoustic receivers can be used inside mangrove habitats to track the movement of sharks and rays. Thirty-eight receivers were deployed in a mangrove system in Pioneer Bay, Orpheus Island, Great Barrier Reef, including inside mangroves, mangrove edges, and adjacent reef flat areas. The detection range and receiver performance metrics, such as code detection efficiency, rejection coefficient, and noise quotient, were examined and tested among habitats. The results highlighted that the signal from transmitters was successfully detected inside mangrove habitats as well as on the adjacent reef flat. The range to detect at least 50% of transmissions was up to 20 m inside mangroves and up to 120 m outside mangroves. The performance metrics of acoustic receivers inside the mangrove habitat were characterized by low background noise, low rejection rates, and reasonably high code detection efficiency. Furthermore, this study tested the application of this method on juvenile blacktip reef shark Carcharhinus melanopterus and mangrove whipray Urogymnus granulatus, and demonstrated that it can be used to successfully track animals inside mangrove habitat. This novel method could reveal further information on how sharks and rays use mangrove habitats.

Habitat distinctness doesn't influence on the abundance and relative growth of the juveniles Atherinella brasiliensis (Quoy & Gaimard, 1824) in a subtropical estuarine ecosystem

Shallow coastal habitats with and without vegetation may perform nursery function from distinct way for many species, raising questions about the role of vegetation on structuring nursery ground. Unfortunately, degradation and inappropriate human use of these areas associated with the lack of ecological data about fish populations can limit appropriate strategies to protect both species and habitats. In this paper we examine the nursery value of different estuarine habitats by comparing the abundance and relative growth of juveniles Atherinella brasiliensis. Fish were sampled once a month from November 2018 to October 2019 in five habitats: no vegetation close to the ocean, no vegetation close to the river, no vegetation and distant from other sampling points (control), mangrove and saltmarsh. Juveniles are present and abundant in all habitats and specimens had similar relative growth in the salt marsh, mangrove habitats and non vegetated habitats. The results indicate that estuarine habitats offers suitable conditions to A. brasiliensis in early stages of life, indicating that these sites have nursery value for juveniles of this species. Conservation and/or preservation of estuarine shallows habitats along the coast is important for A. brasiliensis and probably for other species, and the identification of priority areas could help to provide subsidies to management policies on conservation of coastal marine environments.

First report of Mugilogobius rambaiae (Smith, 1945) (Family: Gobiidae) from India along with geographical expansion of two goby fishes from Kerala

The discovery of three previously undocumented gobioid fish species in Kerala's mangrove ecosystems, namely Eugnathogobius mindora, Mugilogobius mertoni, and Mugilogobius rambaiae, marks a significant advancement in our understanding of the region's aquatic biodiversity. These findings highlight the importance of targeted sampling initiatives and underscore the need for continued exploration and conservation efforts to protect Kerala's fragile mangrove habitats. The adaptability of gobioid fish species from the genera Eugnathogobius and Mugilogobius to fluctuating salinity levels makes them particularly well-suited to thrive in the dynamic environments of shallow intertidal and subtidal estuaries, as well as mangrove ecosystems. Their presence is crucial in maintaining the ecological balance of coastal habitats in the Indo-Pacific region, including Kerala. The discovery of these gobioid fish species not only enhances the ecological richness of Kerala but also offers a significant understanding of the intricate relationships between these fish and their habitats. By enhancing the understanding of the range of gobioid fish species found in the mangroves of Kerala, more effective conservation and management approaches to safeguard these vital coastal ecosystems can be developed. Continuing study and conservation efforts are crucial for the preservation of Kerala’s mangrove ecosystems and the species diversity. By comprehending the enigmas of gobioid fish diversity and other fundamental facets of mangrove ecosystems, substantial advancements can be made in guaranteeing enduring sustainability for future generations.

Loss of microbial functional diversity following Spartina alterniflora invasion reduces the potential of carbon sequestration and nitrogen removal in mangrove sediments—from a gene perspective

Mangrove ecosystems play an important role in carbon (C) sequestration and nitrogen (N) removal. Although Spartina alterniflora has successively invaded native mangrove habitats during the preceding two decades, the effects of this invasion on the microbial functional potential involved in nutrient cycling remain unclear. In this study, metagenomic sequencing was used to investigate microbial C and N cycling in sediments derived from S. alterniflora and three native mangrove species (Kandelia obovata, Avicennia marina, and Aegiceras corniculatum). Greater differences in functional profiles of C and N cycling-related genes were observed between S. alterniflora and mangrove sediments than between different mangrove sediments. Functional diversity was lower in S. alterniflora sediments than in native mangrove sediments. The growth of Thaumarchaeota and Proteobacteria, was enhanced due to their resilience to diversity loss, while the growth of oligotrophs, such as Chloroflexi and Firmicutes, was inhibited in S. alterniflora sediments. Compared to mangrove sediments, the abundance of genes involved in C fixation and methane production was lower in S. alterniflora sediments. However, S. alterniflora significantly increased the gene abundance of pmo which controlled the oxidation process of CH4 to carbon dioxide. Additionally, genes involved in nitrification were enriched, whereas genes involved in N reduction processes, such as denitrification and dissimilatory nitrate reduction to ammonium, N immobilization, and N mineralization, were depleted in S. alterniflora sediments compared to mangrove sediments. Partial least squares regression models demonstrated that the decrease in soil organic C and increase in pH after S. alterniflora invasion induced the loss of microbial functional diversity, which was the main driver of changes in the abundances of genes involved in C and N cycling. Overall, our findings indicate that S. alterniflora invasion modifies the microbial functional profile of nutrient cycling in native mangrove ecosystems and potentially weakens the capacity of mangroves to sequester carbon and remove nitrogen.

Tannery effluent treatments with mangrove fungi, grass root biomass, and biochar.

Tannery effluents contain high amounts of polluting chemicals, such as salts and heavy metals released often to surface waters. New economic and eco-friendly purification methods are needed. Two adsorbing materials and five salt-tolerant fungal isolates from mangrove habitat were studied. Purification experiments were carried out using the pollutant adsorbents biochar and the biomass of vetiver grass (Chrysopogonzizanioides) roots and the fungi Cladosporium cladosporioides, Phomopsis glabrae, Aspergillus niger, Emericellopsis sp., and Scopulariopsissp., which were isolated from mangrove sediment. They efficacy to reduce pollutants was studied in different combinations. Salinity, turbidity, total dissolved solids, total suspended solids, phenols, nitrogen, ammonia. Biological and chemical oxygen demand (BOD, COD) and several heavy metals were measured. The adsorbents were efficient reducing the pollutants to 15-50% of the original. The efficiency of the combination of biochar and roots was generally at the same level as the adsorbents alone. Some pollutants such as turbidity, COD and ammonium were reduced slightly more by the combination than the adsorbents alone. From all 14 treatments, Emericellopsis sp.with biochar and roots appeared to be the most efficient reducing pollutants to < 10-30%. BOD and COD were reduced to ca 5% of the original. The treatment was efficient in reducing also heavy metals (As, Cd, Cr, Mn Pb, Zn). The fungal species originating from the environment instead of the strains present in the tannery effluent reduced pollutants remarkably and the adsorbents improved the reduction efficiency. However, the method needs development for effluents with high pollutant concentrations to fulfil the environmental regulations.

Seasonal dynamics and habitat preferences of juvenile fish assemblages in the Wanquan Estuary, South China: Implications for conservation and management

Tropical estuaries encompass diverse habitats, which are crucial for supporting juvenile fish by providing nurseries, refuges, and migration routes. In the present study, we investigated the seasonal and spatial dynamics of juvenile fish assemblages in the Wanquan Estuary, Hainan Island, China, examining variations during the wet and dry seasons across four types of habitats. Our research aimed to test the hypotheses: (1) the wet season supports a greater abundance and species richness of juvenile fish compared to the dry season, and (2) juvenile fish showed varying habitat preferences across seasons. We recorded a total of 3617 individuals belonging to 33 families, 50 genera, and 78 taxa. Our findings revealed significant seasonal fluctuations in the assemblage structure, with peak abundance during the wet season in August, primarily consisting of diadromous species. A notable shift towards marine species was observed in March. Spatially, juvenile fish exhibited significant habitat preferences, with a strong preference for sand substrates for most species. Contrary to common expectations, mangrove fringe habitats were not identified as the primary nursery grounds for juvenile fish. Instead, our study highlights the importance of habitat diversity and connectivity in enhancing nursery functions. Water temperature and salinity were the key drivers influencing the seasonal and temporal patterns of juvenile fish assemblages in the Wanquan River estuary The pronounced temporal dynamics of these assemblages, driven by seasonal environmental alterations affecting water variations and habitat connectivity, were more significant than spatial differences. The findings emphasize the need for focused connectivity of various habitats to support the conservation of diverse fish communities in tropical estuarine ecosystems.

Numerical modeling of bamboo fences with various infill porosities deployed for mangrove restoration

As part of mangrove restoration initiatives eco-friendly fence has been implemented in eroded coastal areas in recent years. These fences provide the capacity to mitigate incoming wave energy and facilitate sediment deposition, thereby promoting the establishment and maintenance of mangrove habitats. Nevertheless, it is crucial to investigate the influence of the infill porosity on the wave dissipation performance of these fences, as the infill porosity can vary considerably across different restoration projects. The aim of this research is to explore the relationship between the infill porosity and wave dissipation effectiveness to identify more efficient designs for these eco-friendly restoration measures. The experiments involving wave interactions with fence models were conducted in a wave flume measuring 0.8 m in width and 25 m in length. Four wooden fences with distinct infill porosities ranging from 0.60 to 0.90 were strategically positioned to assess wave transmission, reflection, and dissipation phenomena under 18 distinct wave conditions. Additionally, the simulating waves till shore (SWASH)model was employed to calibrate critical bulk drag coefficient parameters and simulate the flow velocity distribution surrounding the fences under the experimental wave conditions. The findings indicated that a fence with a reduced infill porosity exhibits a higher wave transmission coefficient. However, this is accompanied by a higher reflection coefficient and lower wave energy dissipation within the fence. Both the infill porosity and incident wave conditions influence the flow velocity distribution characteristics in the vicinity of the fences. The area where the interaction between waves and fences is the most prominent is concentrated in the upper water layer immediately adjacent to the frontal section of the fences. Understanding the velocity distribution and hydrodynamic characteristics of the fence area aids in better determining the suitable porosity of fill materials for engineering applications.

The effects of mangrove growth on sediment nitrogen mineralization and immobilization are more intense on sandy coasts compared to muddy coasts

Mangroves are important ecosystems on the coasts of southeastern and southern China, which have a significant role in altering microbial communities and nutrient cycles. However, the response of sediment nitrogen (N) mineralization (GNM) and ammonium immobilization (GAI) on the different coastal types (muddy and sandy) to mangrove growth remains poorly understood. Here, surface sediment (0–5 cm) GNM and GAI were examined simultaneously in bare flat and mangrove habitats on both muddy and sandy coasts along a coastal transect of South China, using 15N isotope dilution techniques. The results showed that GNM and GAI rates in sediment ranged from 0.31 to 33.94 μg N g−1 d−1 and 0.24 to 41.02 μg N g−1 d−1, respectively, and mangroves significantly increased the two process rates on both muddy and sandy coasts. The magnitude of increase in GNM and GAI was more pronounced for sandy coasts than for muddy coasts. Mangroves also promoted the ratio of GAI to GNM (RAI), but the ratio of GNM to total N (PAM%) generally did not differ between bare flat and mangrove habitats. Sediment total organic carbon, total N, ammonium, ferrous iron, and microbial abundances were crucial factors in regulating GNM and GAI on both two contrasting coasts, but the process rates on sandy coasts were also related to sediment grain size composition and specific surface area. Our results suggested that mangrove growth is more effective in promoting GNM and GAI on sandy coasts than on muddy coasts, which may be important to improving the nutrient cycle and energy flow on sandy coasts. Overall, these findings provide valuable insights into the N transformations and influencing mechanisms on different coastal types influenced by the growth of mangroves and imply that it is significant to advance mangrove restoration on sandy coasts, yet widely overlooked.

A record of late Holocene sea level and human impacts from the southeastern Coast of Sri Lanka

AMS radiocarbon-dated palynological evidence from Embilikala Lagoon in Bundala National Park (one of the Ramsar wetland sites) on the southeast coast of Sri Lanka indicates palaeoenvironmental changes during the last 2,700 years. The persistence of fewer mangroves (eg Rhizophoraceae taxa) suggests that sea level low stands occurred between 2,700 and 1750 cal yr BP. From the later age, the relative sea level rose, and reached the present sea level at 950 cal yr BP as indicated by the mangrove maximum. At 2,250, 700–400 and 200–150 cal yr BP, the sudden increase in marine dinoflagellate cysts (eg Spiniferites mirabilis) and foraminifera (Globigerinoides ruber) suggests increased marine influence. This is consistent with a decrease in mangrove habitats. Between 2,700 and 950 cal yr BP, severely degraded dry monsoon forests and minimal levels mangrove suggest human and marine influences were the critical drivers for changing the major vegetation types along the southeastern coast. Vegetation changes have been drastic over the last millennia.

DNA barcoding of common freshwater eleotrids (Gobiiformes: Eleotridae) in the Philippines, with a global comparison and notes on their conservation and management

Eleotrids, also known as gudgeons or sleeper gobies, are found mostly in freshwater and mangrove habitats of tropical and subtropical regions. Some eleotrids exhibit minimal morphological variation at the species level. In this study, DNA barcoding was used to assess the molecular diversity of common freshwater eleotrids in the Philippines in relation to other eleotrid species from other countries with available DNA sequences in public databases. A total of 422 mitochondrial DNA cytochrome c oxidase I (COI) gene sequences were analyzed: 107 of which were generated from this study, while the remaining 315 sequences were mined from Barcode of Life Data System and GenBank. Both the neighbor-joining and maximum likelihood trees constructed based on the COI sequences clustered most of the species in concordance with their taxonomic classification. The mean Kimura 2-parameter genetic distances within species and genera were 1.31% and 11.60%, respectively. As expected, the mean interspecific distance was higher than the mean intraspecific distance except in some species. This study revealed the presence of nine distinct eleotrid species belonging to five genera in the Philippines. These species include Giuris laglaizei, G. tolsoni, Eleotris acanthopomus, E. fusca, E. melanosoma, Belobranchus sp., Belobranchus belobranchus, Butis butis, and Ophiocara ophicephalus. This study also revealed the presence of possibly undescribed Belobranchus species in the Philippines. This undescribed Belobranchus species differs by a high percentage of genetic divergence from the other species of Belobranchus (3.00% from B. segura and 13.40% from B. belobranchus). Furthermore, high genetic distance (2.62%) was also observed between G. laglaizei species of Laguna de Bay and Mindanao. This study strongly recommends a taxonomic review of the Laguna de Bay G. laglaizei and the Philippine Belobranchus spp., as these species may harbor species complexes that require closer examination so that proper conservation and management measures can be implemented for each species.

A preliminary checklist of Copepoda in the mangrove areas of Munroe Island, adjacent to Ashtamudi estuary, Kerala, India

The present investigation was conducted to assess the species composition of Copepoda in Munroe Island from October 2020 to September 2022. As the information about the species composition of Copepoda is scarce in the mangrove habitats of the southern part of Kerala, their appraisal assumes greater significance. Copepod samples collected from the mangrove habitats of Munroe Island of Kerala (southern India) revealed 31 species belonging to 18 genera and 15 families. The order Calanoida was recognized as the most dominant taxa with 23 species, followed by Harpacticoida (five species) and Cyclopoida (three species). Among the 15 families encountered, Acartiidae, Centropagidae, Harpacticidae, Paracalanidae and Pseudodiaptomidae were the most diverse. Species such as Acartia bilobata, Paracalanus parvus, Pseudodiaptomus aurivillii, Pseudocalanus elongatus, Microsetella norvegica, and Oithona similis were found to be perennial. The investigation calls for intensive copepod surveys to reveal their ecology and diversity in the hitherto less-studied region in southern India.

Uncovering mangrove range limits using very high resolution satellite imagery to detect fine‐scale mangrove and saltmarsh habitats in dynamic coastal ecotones

AbstractMangroves are important ecosystems for coastal biodiversity, resilience and carbon dynamics that are being threatened globally by human pressures and the impacts of climate change. Yet, at several geographic range limits in tropical–temperate transition zones, mangrove ecosystems are expanding poleward in response to changing macroclimatic drivers. Mangroves near range limits often grow to smaller statures and form dynamic, patchy distributions with other coastal habitats, which are difficult to map using moderate‐resolution (30‐m) satellite imagery. As a result, many of these mangrove areas are missing in global distribution maps. To better map small, scrub mangroves, we tested Landsat (30‐m) and Sentinel (10‐m) against very high resolution (VHR) Planet (3‐m) and WorldView (1.8‐m) imagery and assessed the accuracy of machine learning classification approaches in discerning current (2022) mangrove and saltmarsh from other coastal habitats in a rapidly changing ecotone along the east coast of Florida, USA. Our aim is to (1) quantify the mappable differences in landscape composition and complexity, class dominance and spatial properties of mangrove and saltmarsh patches due to image resolution; and (2) to resolve mapping uncertainties in the region. We found that the ability of Landsat to map mangrove distributions at the leading range edge was hampered by the size and extent of mangrove stands being too small for detection (50% accuracy). WorldView was the most successful in discerning mangroves from other wetland habitats (84% accuracy), closely followed by Planet (82%) and Sentinel (81%). With WorldView, we detected 800 ha of mangroves within the Florida range‐limit study area, 35% more mangroves than were detected with Planet, 114% more than Sentinel and 537% more than Landsat. Higher‐resolution imagery helped reveal additional variability in landscape metrics quantifying diversity, spatial configuration and connectedness among mangrove and saltmarsh habitats at the landscape, class and patch scales. Overall, VHR satellite imagery improved our ability to map mangroves at range limits and can help supplement moderate‐resolution global distributions and outdated regional maps.

Spatio-temporal distribution of copepods in the mangrove areas of Munroe Island, adjacent to Ashtamudi estuary, Kerala, India

ABSTRACT The study was conducted to assess the species composition of copepods around Munroe Island of Kerala (South India) from October 2020 to September 2022. Copepod samples collected from the mangrove habitats around Munroe Island revealed 31 species belonging to 18 genera and 15 families. The order Calanoida was recognized as the most dominant taxon, with 23 species, followed by Harpacticoida (5 spp.) and Cyclopoida (3 spp.). Spatially, sampling station 3 (Palliyanthuruthu) had the highest species richness (28 spp.); in contrast, the lowest species richness was found at sampling station 1 (Villimangalam, 13 spp.). When exploring the seasonal effects on copepod richness it was found that the highest species richness was seen in the post-monsoon season (31 spp.) followed by the pre-monsoon season (29 spp.), while the least diversity was found during the monsoon season (28 spp.). Species such as Acartia bilobata, Paracalanus parvus, Pseudodiaptomus aurivillii, Pseudocalanus elongatus, Microsetella norvegica, and Oithona similis were found to be perennial in nature. The investigation calls for intensive surveys of copepods to reveal their ecology and diversity in the hitherto less studied region in South India.

Variations in macrobenthic fauna of mangrove and unvegetated habitats in an Amazon estuary

Variations in macrobenthic fauna of mangrove and unvegetated habitats in an Amazon estuary

Sosialisasi dan Penanaman Mangrove Bersama Masyarakat Pesisir Desa Sungai Pasir, Kecamantan Lunci, Kabupaten Sukamara

One of the regions in Indonesia that has mangrove forests is Sukamara Regency, Central Kalimantan Province. With this location, this Community Service (PKM) will provide outreach regarding the understanding of the residents of Sungai Pasir Village about the Types, Characteristics and Habitat of Mangroves and 2) Planting Mangroves on the Coastal Coast of Sungai Pasir Village, Sukamara Regency. The method used is socialization in providing education to the community on the Coastal Coast of Sungai Pasir Village, Sukamara Regency. The PKM results show that there is cooperation between the community, the village government, representatives of the Watershed and Protected Forest Management Center (BPDASHL) and the Head of the Aquatic Resources Management Study Program, Faculty of Agriculture, Antakusuma University, Pangkalan Bun in preserving Mangroves.

Habitat of the amphibious mudskipper Periophtalmodon schlosseri in Songkhla Lake, Thailand

Abstract. Pattaratumrong MS, Pompha T. 2024. Habitat of the amphibious mudskipper Periophtalmodon schlosseri in Songkhla Lake, Thailand. Biodiversitas 25: 1875-1881. This study aimed to investigate the preferred habitat of giant mudskippers, Periophtalmodon schlosseri Pallas 1770. It was conducted from August to October 2022 at six sampling stations in Koh Yoh, a small island in the Lower Songkhla Lake. Environmental parameters such as organic matter and organic carbon in sediment, temperature, salinity, dissolved oxygen, and substrate were observed. The results indicate that the density of giant mudskipper weak to moderate correlates with all studied environmental parameters (P&lt;0.05). Within the study area, the highest population density of P. schlosseri was recorded in the mudflat habitat adjacent to mangroves, and the lowest density was recorded in the mudflat habitat with a seawall, absent with nearby mangroves. This study suggests that environmental conditions affect the abundance of giant mudskippers, but this does not reach the limiting threshold; the more influential factor for this species is the character of the habitat. The mangrove habitat should be conserved and protected from development and urbanization. These results provide insights into the preferred habitat and offer a better understanding of the ecology of these fishes in the estuarine lake.

Contrasting stocks and origins of particulate and mineral-associated soil organic carbon in a mangrove-salt marsh ecotone

The global warming-driven poleward expansion of mangrove habitats (e.g., Avicennia germinans and Rhizophora mangle) into temperate salt marshes (e.g., Spartina alterniflora and Juncus roemerianus) has been shown to alter coastal soil organic carbon (SOC) storage. However, the taxa-specific consequences of this vegetation shift on the origin and size of SOC sub-fractions (particulate OC (POC); mineral-associated OC (MAOC); and reactive iron-associated OC (FeR-MAOC)) remain largely unexplored. In this study, we used a particle size-based SOC fractionation method to compare quantity and δ13C composition of bulk and each SOC sub-fractions in soil cores collected from Apalachicola Bay barrier islands in Florida, USA, the highest latitude where monospecific communities of all four aforementioned plants co-occur. Depth-dependent variation of bulk soil δ13C clearly showed the global warming-driven replacement of S. alterniflora by mangroves, as well as reciprocal substitutions of S. alterniflora and J. roemerianus, probably driven by changes in wetland elevation. Higher OC burial rates in mangrove habitats suggested that mangrove soils were principally developed by particle deposition. In contrast, comparatively lower OC burial rates but higher OC stocks in salt marsh habitats illustrated subsurface OC input from salt marsh roots. POC was primarily derived from contemporary plant detritus; its concentration was higher in salt marsh habitats (58.8 ± 9.0 % of SOC) relative to mangroves (38.4 ± 6.0 % of SOC). In contrast, MAOC content did not vary across plant habitats (53.5 ± 10.9 % of SOC), and principally originated from microbially-transformed OC and pre-existing plants. FeR-MAOC was essentially absent in R. mangle soils (2.9 ± 3.6 % of SOC) while representing a minor fraction of MAOC in three other plant habitats (7.8 ± 7.0 % of SOC). The δ13C of FeR-MAOC was more like the present-day surface plants, highlighting the in situ FeR-MAOC formation in their active oxidizing rhizospheres.

Phylogenomic evaluation of Mangrovimicrobium sediminis gen. nov. sp. nov., the first nitrogen fixing member of the family Halieaceae adapted to mangrove habitat and reclassification of Halioglobus pacificus to Pseudohaliglobus pacificus comb. nov.

The taxonomic position and genomic characteristics of a nitrogen fixing and polymer degrading marine bacterium, strain SAOS 164 isolated from a mangrove sediment sample was investigated. Sequence analysis based on 16S rRNA gene identified it as a member of family Halieaceae with closest similarity to Haliea salexigens DSM 19537T (96.3 %), H. alexandrii LZ-16-2T (96.2 %) and Parahaliea maris HSLHS9T (96.0 %) but was distantly related to the genera Haliea, Parahaliea and Halioglobus in phylogenetic trees. In order to ascertain the exact taxonomic position, phylogeny based on RpoBC proteins, whole genome, core and orthologous genes, and comparative analysis of metabolic potential retrieved the strain in an independent lineage clustering along with the genera Halioglobus, Pseudohalioglobus and Seongchinamella. Further, various genome based delimitation parameters represented by mol % GC content, percentage of conserved proteins (POCP), and amino acid identity (AAI) along with chemotaxonomic markers (i.e. fatty acids and polar lipids) supported the inferences of genome based phylogeny and indicated that the strain SAOS 164 belongs to a novel genus. The genome was mapped to 4.8 Mb in size with 65.1 % DNA mol% G + C content. In-silico genomic investigation and phenotyping revealed diverse metabolite genes/pathways related to polymer hydrolysis, nitrogen fixation, light induced growth, carbohydrate, sulfur, phosphorus and amino acid metabolism, virulence factors, defense mechanism, and stress-responsive elements facilitating survival in the mangrove habitat. Based on polyphasic taxonomic approach including genome analyses, a novel genus Mangrovimicrobium sediminis gen. nov. sp. nov. (=SAOS 164T = MTCC 12907T = KCTC 52755T = JCM 32136T) is proposed. Additionally, the reclassification of Halioglobus pacificus (=DSM 27932T = KCTC 23430T = S1–72T) to Pseudhalioglobus pacificus comb. nov. is also proposed.