Intertidal Mangrove Research Articles

Estuarine mangrove niches select cultivable heterotrophic diazotrophs with diverse metabolic potentials-a prospective cross-dialog for functional diazotrophy.

Biological nitrogen fixation (BNF), an unparalleled metabolic novelty among living microorganisms on earth, globally contributes ~88-101 Tg N year-1 to natural ecosystems, ~56% sourced from symbiotic BNF while ~22-45% derived from free-living nitrogen fixers (FLNF). The success of symbiotic BNF is largely dependent on its interaction with host-plant, however ubiquitous environmental heterotrophic FLNFs face many limitations in their immediate ecological niches to sustain unhindered BNF. The autotrophic FLNFs like cyanobacteria and oceanic heterotrophic diazotrophs have been well studied about their contrivances acclimated/adapted by these organisms to outwit the environmental constraints for functional diazotrophy. However, FLNF heterotrophs face more adversity in executing BNF under stressful estuarine/marine/aquatic habitats. In this study a large-scale cultivation-dependent investigation was accomplished with 190 NCBI accessioned and 45 non-accessioned heterotrophic FLNF cultivable bacterial isolates (total 235) from halophilic estuarine intertidal mangrove niches of Indian Sundarbans, a Ramsar site and UNESCO proclaimed World Heritage Site. Assuming ~1% culturability of the microbial community, the respective niches were also studied for representing actual bacterial diversity via cultivation-independent next-generation sequencing of V3-V4 rRNA regions. Both the studies revealed a higher abundance of culturable Gammaproteobacteria followed by Firmicutes, the majority of 235 FLNFs studied belonging to these two classes. The FLNFs displayed comparable selection potential in media for free nitrogen fixers and iron-oxidizing bacteria, linking diazotrophy with iron oxidation, siderophore production, phosphorus solubilization, phosphorus uptake and accumulation as well as denitrification. This observation validated the hypothesis that under extreme estuarine mangrove niches, diazotrophs are naturally selected as a specialized multidimensional entity, to expedite BNF and survive. Earlier metagenome data from mangrove niches demonstrated a microbial metabolic coupling among C, N, P, S, and Fe cycling in mangrove sediments, as an adaptive trait, evident with the co-abundant respective functional genes, which corroborates our findings in cultivation mode for multiple interrelated metabolic potential facilitating BNF in a challenging intertidal mangrove environment.

Effects of salinity on physiological responses in the sesarmid crab Episesarma mederi (H. Milne Edwards, 1853)

ABSTRACT The sesarmid crab Episesarma mederi (H. Milne Edwards, 1853) lives in mid to upper intertidal mangroves, while its physiological responses to salinity are still poorly known. Here, we examined the effects of salinity on osmoregulatory and antioxidant enzyme responses of E. mederi. The crabs were exposed to experimental salinities ranging from 5 to 40 PSU for 96 h under the laboratory conditions. After that, haemolymph osmolality, oxygen consumption rates (OCR), gill Na+/K+ ATPase (NKA) activity and selected antioxidant enzyme activities of the crabs were analysed. Our results showed that E. mederi was a euryhaline hyper-hypo-osmoregulator. Hyperosmoregulation at low salinities was achieved by elevated gill NKA activity. The crabs acclimated to 5 PSU exhibited a significant increase in their OCRs compared to those in the control group (25 PSU). Conversely, the gill NKA activities were unchanged at high salinities. The OCRs increased only at a salinity of 35 PSU under high salinity conditions. Salinity changes can cause modulations in gill catalase (CAT) activity, while the gill superoxide dismutase (SOD) activity was unaffected. This result indicates that the crab gills could experience some degrees of oxidative stress during salinity acclimation. Overall, these physiological abilities can enable E. mederi to thrive in salinity-fluctuating areas.

MACROFAUNAL DIVERSITY ON THE SURFACE SEDIMENT OF MANGROVE HABITAT ADJACENT TO THE SEAGRASS BEDS AT PUNANG- SARI RIVER ESTUARY (MALAYSIAN BORNEO), SOUTH CHINA SEA

Macrofaunal diversity and composition are essential to understanding the ecosystem structures and functions of mangroves in any dynamic estuarine coast. To understand the temporal distribution of macrofaunal community structures and diversity on the surface sediment in the intertidal mangrove forest next to the seagrass beds, this study was conducted at Punang-Sari-River estuary, Lawas, Sarawak (Malaysian Borneo), South China Sea. Sampling was done during post-monsoon, intermediate-September, pre-monsoon, and monsoon from July 2019 to February 2020. The mean macrofauna abundance was higher pre-monsoon, while Gastropoda Optediceros breviculum (L. Pfeiffer, 1855) was the most abundant (RA = 0.704). Important Species Index (ISI = 70.36) and percentage of contribution (64.97%) were also higher for this species than any other records from the site. The ANOSIM (Analysis of Similarity), Jaccard index and SIMPER (Similarity Percentage Analysis) analysis suggested that the highest species abundance similarity was observed between pre-monsoon and monsoon, while the highest dissimilarity was observed between intermediate-September and pre-monsoon (74.67%). Seasonal PCA, nMDS, and cluster analysis revealed that pre-monsoon and monsoon were comparable in species and individual abundance. The dominance (0.85) was found significantly higher (P < 0.0001) in intermediate-September, while Simpson (0.734), Shannon (1.56) and Evenness indices (0.528) were found higher in monsoon, followed by the higher Margalef richness indices (3.21) in post-monsoon. It was observed that the seasonal ecological parameters were found to be significantly (P < 0.05) different, including the temperature, salinity, rainfall, pore water nitrogenous compounds (NO2, NO3 and NH3-N), phosphorus compound (PO4) and micro minerals. The Canonical Correspondence Analysis (CCA) results suggested that ecological factors influenced several species. Considering the few studies on mangrove macrofauna in Malaysian Borneo, further research on their trophic structures and food web interactions is very important to disclose their overall characteristics and ecosystem functions.

A Study on Spatial Distribution Extraction of Tidal Inundated Mangroves Based on High and Low Tide Level Images

A majority of mangroves are located in the coastal intertidal zone and are subject to tidal periodic inundation. However, the previous vegetation indices used for extracting the spatial distribution of mangroves were not able to effectively extract submerged mangroves, and the applicability of the vegetation indices used on different spatial resolution images obtained from different sensors was not verified. In this study, a new vegetation index, namely the intertidal mangrove identification indices (IMIIs), was proposed, based on GF-2 images of high and low tide levels. Meanwhile, other commonly used vegetation indices were also extracted. All the vegetation indices were used to extract the spatial distribution of mangroves under tidal inundation, and applicability tests of the vegetation indices were conducted on Sentinel-2 images in three different regions. It was found that the IMIIs proposed based on GF-2 images of high and low tide levels can extract submerged mangroves relatively well, and the spatial distribution extraction results of mangroves are better than those of other vegetation indices, with IMII2 outperforming IMII1. At the same time, IMIIs have good applicability in medium resolution Sentinel-2 images, and there are relatively large differences in the extraction results of mangrove spatial distribution among different vegetation indices in areas with significant impact of tidal inundation. Among all vegetation indices, the extraction results of IMIIs are relatively superior. In most cases, multi variables collaborative application can improve the accuracy of mangrove spatial distribution extraction results. Based on the results of this study, it was concluded that the IMIIs proposed in this study can accurately extract the spatial distribution of mangroves inundated by tides from both medium- and high-resolution images, providing accurate basic data for effective management and scientific protection of mangrove resources.

Sexual Maturity and Macronutrient Contents in Diopatra sp. (Onuphidae, Polychaeta) Maintained at Different Salinity Levels

Diopatra sp. (Onuphidae, Polychaeta) is an economically important polychaete species commonly used as a fishing bait by local anglers in Cilacap, Central Java Province. Some biological aspects of this local species, however, have not been studied yet. The aim of this research was to see the effect of salinity levels on the sexual maturity and the macronutrient contents of the animals. Diopatra specimens in the present study were collected from the intertidal mangrove habitats of Jeruklegi Village, Cilacap, in sexually immature condition. The worms were then transported to the laboratory and were maintained in containers with four different salinity levels, i.e. 10, 15, 20 and 25 ppt over the next two months. The sexual maturity of the animals were observed based on the presence or absence of coelomic gametes. Proximate analysis was performed to determine macronutrient contents of the animals. The effect of salinity levels on the animals' sexual maturity and macronutrient contents was analyzed using one-way ANOVA. The results showed that salinity levels did not significantly affect the sexual maturity level of Diopatra worms (p > 0.05). Similarly, they did not affect the protein and fat contents, but impacted the carbohydrate content of the animals (p < 0.05). The protein and the fat contents in Diopatra sp., i.e. 41–43% and 6–9%, respectively, met the amount required to be used as shrimp broodstock and fish feeds. While the species has the potential for use in local aquaculture, the annual reproductive cycle as well as the identity of the species, however, require further research.

Tidal Pumping Controls Dissolved Organic Matter Properties and Outwelling From Mangrove Groundwater to Coastal Water

AbstractDissolved organic matter (DOM) in highly productive intertidal mangroves is an important carbon and nutrient source to the coastal ocean. In highly dynamic mangrove intertidal systems, both tidal pumping or geochemical factors can control DOM characteristics. The influence of groundwater flow on DOM properties and fluxes remains poorly understood. Here, we compared the concentrations, sources, and spectroscopic characteristics of DOM across a recharge‐discharge gradient. We used a three‐dimensional array sampling strategy to reduce spatial biases, groundwater monitoring to quantify tidally driven exchange, and spectrofluoroscopy to quantify DOM fluorescent components. The results showed that tidal hydrology played the key role driving groundwater DOM properties in both horizontal (i.e., from the mangrove to the sea) and vertical directions. Due to the high spatial heterogeneity of dissolved inorganic (DIC) and organic (DOC) carbon concentrations in mangrove groundwater, carbon outwelling showed a high degree of variability at the intertidal scale (54.8–234.8 μmol m−2 d−1 for DIC and 2.5–12.4 μmol m−2 d−1 for DOC). The contribution of terrestrial DOM gradually decreased toward the ocean, but the microbial contributions for recently produced autochthonous DOM increased. Deep groundwater received less terrestrial DOM and experienced anaerobic microbial mineralization, resulting in lower organic carbon than shallow groundwater. Greater variations in spectroscopic characteristics were found in shallow groundwater than in deep groundwater. Overall, tidally driven surface water‐groundwater interactions control the variability in DOM properties and how DOM contributes to carbon budgets and sequestration in mangrove groundwater.

Macro-infaunal diversity and assemblage in the mangrove habitat of Lawas, Sarawak, Malaysia

The diversity and composition of macrofaunal communities are important components to understand the mangrove ecosystem structures and functions. To understand the seasonal distribution of macro-infaunal community and diversity, this study was conducted from July 2019 to February 2020 in the intertidal mangrove forest of Punang-Sari-River estuary, Lawas, Sarawak. Sampling was carried out during post-monsoon, intermediate-September, pre-monsoon, and monsoon. It was observed that, the seasonal physico-chemical parameters were significantly (P < 0.05) different, including the temperature, salinity, rainfall, pore water nitrogenous compounds (NO2, NO3 and NH3-N), phosphate and micro minerals. A total of 39 infaunal macrobenthos taxa from 27 families were recorded while the mean abundance of infaunal macro benthos was found higher in monsoon (997.29 individuals/m2). The most abundant, the highest important species index and percentage contribution species was Bivalvia Eurytellina lineata (W. Turton, 1819) due to year-round favorable ecological condition. Seasonal faunal grouping suggested post-monsoon, intermediate-September and pre-monsoon were comparable in species and individual abundance. The Simpson, and Shannon indices were found significantly (P < 0.0001) higher in monsoon, while Margalef richness was found higher in pre-monsoon. The soil was sandy loam with major portion of sand, and positively correlated with sand and infaunal abundance in all seasons. The ANOSIM and SIMPER analysis suggested that the highest species abundance similarity was observed between post-monsoon and pre-monsoon, while the highest dissimilarity was observed between intermediate-September and pre-monsoon. The Canonical Correspondence Analysis results suggested, a number of species were influenced by ecological factors, for instance, salinity, soil pH, PO4, micro–macro minerals, water pH, and nitrogenous compounds. The relationship within benthic infaunal abundance in the mangrove ecosystem with their seasonality, ecological variables, and soil properties were established and addressed in this study.

Effects of Salinity on Assembly Characteristics and Function of Microbial Communities in the Phyllosphere and Rhizosphere of Salt-Tolerant Avicennia marina Mangrove Species.

It is of great significance to explore the structure and salinity response of microbial communities in salt-tolerant plants to understand the mechanisms of plant-microbe interactions. Herein, we investigated the phyllosphere and rhizosphere microbial communities of Avicennia marina, a pioneer salt-tolerant plant, at three sites with different salinities in the coastal intertidal zone. The results showed that salinity had different effects on phyllosphere and rhizosphere microbial communities and had a greater impact on bacterial communities and bacterial network interactions. The rhizosphere bacterial community alpha diversity significantly increased with increasing salinity. Moreover, the relative abundance of Proteobacteria decreased significantly, while that of Bacteroidota and Actinobacteriota, with stronger salt tolerance and nutrient utilization capacity, increased significantly. Functional prediction indicated that the microbial communities could produce catalase, peroxidase, 3-phytase, and tryptophan synthase, which may exert potential antistress and growth-promoting functions. Among them, catalase, 3-phytase, alkaline phosphatase, and acid phosphatase increased significantly in the phyllosphere and rhizosphere bacterial communities and the phyllosphere fungal community with increasing salinity. Importantly, the dominant taxa Kushneria and Bacillus, which are salt tolerant and growth promoting, were isolated from the phyllosphere and rhizosphere, respectively, and verified to have the ability to alleviate salt stress and promote the growth of rice. IMPORTANCE Avicennia marina is a pioneer salt-tolerant plant in coastal intertidal mangroves, an efficient blue carbon ecosystem. It is of great importance to explore how salinity affects the phyllosphere and rhizosphere microbial communities of A. marina. This study showed that the microbial communities in the phyllosphere and rhizosphere of A. marina had different constitutive properties, adaptive network interactions, and potential stress-promoting functions. Furthermore, the dominant bacteria Kushneria and Bacillus were obtained from the phyllosphere and rhizosphere, respectively, and their coculture with rice could effectively alleviate salt stress and promote rice growth. Additionally, the effects of salinity changes on microbial community structure, associations, and functional potential in the phyllosphere and rhizosphere of A. marina were observed. This study has enriched our understanding of the microbial community structure, function, and ecological stability of mangrove species in coastal intertidal zones and has practical significance for improving crop yield by using salt-tolerant plant microbiomes.

Prediction of the joint impacts of sea level rise and land development on distribution patterns of mangrove communities

Mangrove distribution along shorelines shows distinct zonation patterns; thus, different communities may face various influences from sea level rise (SLR) and land use. However, long-term change predictions are usually based only on the total extent of mangroves. Few studies have revealed how SLR and land development such as agriculture, aquaculture, and urbanization jointly affect different intertidal mangrove communities. This study proposed a novel framework combining SLAMM (Sea Level Affecting Marshes Model) and the CLUE-S (Conversion of Land Use and its Effect at Small regional extent) model to assess the potential impacts on upper and lower intertidal mangrove communities. Maoweihai in Guangxi, China, was selected as the study area and the potential impacts from the squeeze effect and mangrove expansion potential were evaluated. We established three scenarios combining SLR and land use patterns to predict mangrove coverage projections by 2070. The results showed that, under a single SLR driver, the upper intertidal mangroves would be more adaptive to rapid SLR than the lower intertidal mangroves. However, under the combined influence of the two drivers, the upper intertidal mangroves would experience larger squeeze effects than the lower intertidal mangroves, with up to 80.5% of suitable habitat lost. Moreover, the expansion potential of upper intertidal mangroves would be considerably more limited than that of lower intertidal mangroves. The length of the expandable habitat patch boundary of upper intertidal mangroves only reached 1.4–1.8 ​km, while that of the lower intertidal mangroves reached up to 99.2–111.2 ​km. Further, we found that aquaculture ponds and cropland are the top two land development types that could occupy suitable habitat and restrict the mangrove expansion potential. Our results highlight that timely improvement of land use policies to create available landward accommodation space for mangrove migration is essential to maintain the coverage and diversity of mangrove communities under SLR. The proposed method can be a helpful tool for adaptive mangrove conservation and management under climate change.

A diagnostic phytolith morphotype found in Porteresia coarctata (Roxb.) Tateoka indicates coastal swampy mangrove environments: A case study from the Indian east coast

Porteresia coarctata (Roxb.) Tateoka is a true halophytic perennial wild grass that grows profusely along newly formed, highly saline landmasses and mudflats in the coastal mangroves of the Indian subcontinent and acts as a pioneer species in mangrove succession. Comprehensive phytolith analyses on sixteen P. coarctata samples collected from different swampy mangrove locations of four mangrove forests (Sundarbans, Bhitarkanika, Godavari and Krishna) along the Indian east coast show the significant and exclusive presence of a new specialized RONDEL having four distinct horns with flat base (named henceforth as RONDEL FOUR HORNED). Significant numbers of this morphotype have also been recorded in the surface sediment samples collected from these swampy mangrove sites. The RONDEL FOUR HORNED is a diagnostic phytolith morphotype of P. coarctata and a useful indicator of coastal swampy or intertidal mangroves of the Indian east coast. This morphotype was then used to identify past coastal intertidal mangrove environments in a late Quaternary sedimentary profile.

Effects of salinity on haemolymph osmolality, gill Na+/K+ ATPase and antioxidant enzyme activities in the male mud crab Scylla olivacea (Herbst, 1796)

ABSTRACT The mud crab Scylla olivacea is a well-known commercially and ecologically important species that inhabits intertidal mangroves. These mud crabs spend juvenile and adult stages in mangroves where they can experience daily fluctuations in salinity. They are almost certainly adapted to deal with salinity challenges. Although S. olivacea has a wide salinity tolerance, there is a lack of studies on its osmoregulatory responses. Antioxidant enzymes play crucial roles to counteract oxidative stress in various tissues of aquatic animals. However, salinity changes affecting antioxidant responses are not well studied in tropical decapod crustaceans. Therefore, this study aims to characterize the osmoregulatory and antioxidant responses of the male S. olivacea when exposed to salinity changes. Haemolymph osmolality, Na+/K+ ATPase and antioxidant enzyme activities in gills were analysed after they were exposed to various salinities. The results showed that S. olivacea is a hyper-hypoosmoregulator. The salinity had greater effects on Na+/K+ ATPase and antioxidant enzyme activities in the posterior gills than the anterior gills. Notably, the modifications of gill SOD activity were detected only in the posterior gills, which function highly in active ion uptake. These findings may imply some associations between osmoregulatory and antioxidant responses during salinity challenges. The increase in gill SOD activities be a response for coping with elevated ROS levels due to high metabolic demands for osmoregulation under salinity stress. Moreover, the crabs exhibited some modified activities of gill CAT in several salinity levels. Overall, the results demonstrated that S. olivacea were well-adapted to the salinity changes based on their osmoregulatory and antioxidant responses. These physiological adaptations may allow these crabs to disperse in some areas of mangroves. The salinity range of 15–25 psu would likely be the recommended optimal range for adult S. olivacea, which may enhance growth and minimize oxidative stress in gills of crabs, especially in aquaculture conditions.

Mangrove-associated fish assemblages off the southern Panama Bight region (tropical eastern Pacific)

ABSTRACT The Panama Bight ecoregion (PBE) in the eastern Pacific contains probably the best developed mangrove forests in the American continent. Fishes inhabiting the mangrove-estuary mosaic play fundamental ecological roles and sustain the artisanal fishery operating there. Here, using data collected along ~300 km between 2012 and 2017, we examine the spatial dynamics of mangrove fish assemblages that undertake intertidal migrations in the southern part of the PBE (southern Colombian Pacific coast), where the largest and least disturbed mangroves of Colombia are located. Sixty-one fish species used intertidal mangrove habitats in these areas, constituting ~30% of all fishes inhabiting the whole mosaic of mangrove habitats in this ecoregion. Species within Clupeidae, Ariidae, Centropomidae and Tetraodontidae, all common in mangroves of the eastern Pacific, were the most dominant. Half of the fish species found are commercially important to the artisanal fishery. Differences in fish community structure could be related to salinity differences, but other environmental and ecological factors could also play a role in explaining these differences. A better understanding of the ecological role of mangrove fishes in the region could be gained by examining the ichthyofauna of other habitats within the mosaic and their trophic relationships.

Habitat, Sexual and Allometric Influences on Morphological Traits of Intertidal Crabs

Intertidal crabs display distinct morphological traits that allow differential interactions with biotic and abiotic features of the intertidal landscape, but are also influenced by allometry and sexual selection. This study aimed to explore the influence of sexual, allometric and habitat factors on morphological variation in the intertidal mangrove crab assemblage. A standardized photographic protocol was developed using readily available, low-cost technology to capture the morphology of carapaces and claws as sets of Cartesian landmarks. Digitization errors were 1 to 2 orders of magnitude smaller than the variation among individuals. In Tubuca seismella and Tubuca signata (superfamily Ocypodoidea), species that have traditionally been studied for sexual dimorphism, standardized major claw sizes were 2.8 and 3.7, respectively, times larger for males than females. Sexual dimorphism in claw size was also observed for Metopograpsus frontalis and Parasesarma longicristatum (superfamily Grapsoidea), with the largest claw in males being 15% and 33%, respectively, larger than in females. In contrast to size, claw shape did not relate to sex, except for T. seismella. Carapace shape, although variable among individuals and displaying asymmetry, was unrelated to sex. Claw and carapace shapes displayed high correlations, with values around 0.78. Carapace shapes grouped into taxonomic families and linked to habitat preferences, while claw shapes varied along a taxonomic gradient. These results complement studies on crab morphology that focus on specific factors or species, and stress the importance of multiple, interacting factors including sexual, allometric and habitat influences as drivers of morphological trait variability.

Assessment of the Effects of Sediment-Associated Metals and Metalloids on Mangrove Macroinvertebrate Assemblages

Although much previous research effort has examined the impacts of metal contamination on macrobenthic assemblages in subtidal sediments, little attention has been directed at macroinvertebrate responses in intertidal mangrove habitats. Thus, in order to assess the unique responses of mangrove macroinvertebrate assemblages to sediment metal(loid) contamination, total, normalised and bioavailable metal(loid)s (Mn, Pb, Cr, Cd, As, Se, Co, Ni, Zn and Cu) were assessed within and between four mangrove locations in Lake Macquarie, NSW, Australia, and compared to resident macroinvertebrate assemblages over two sampling occasions. Mangrove biomass and physicochemical properties of sediment are known to influence macroinvertebrate assemblages, and as such, were also assessed to account for any potential confounding effect on macroinvertebrate assemblage composition. Significant differences in total and bioavailable metal(loid) contamination were found between and within locations and were consistent over time. Sediments at contaminated locations presented a high risk to biota with bioavailable concentrations of Pb, Cd, Zn found to exceed sediment quality guidelines and concentrations of Se capable of adverse impacts to biota. Macroinvertebrate assemblage composition varied with metal(loid) contamination loads present at study locations. Metal(loid) contamination was significantly correlated with macroinvertebrate assemblages over two sampling periods. Further analysis revealed that 71% of macroinvertebrate assemblage composition could best be explained by a combination of five variables namely, bioavailable Mn, Zn, and Se, number of mangrove seedlings and mean mangrove biomass. Rather than tolerant polychaetes dominating metal(loid)-contaminated sediments (as is found generally in subtidal sediments), polychaetes in intertidal mangroves appeared to be relatively sensitive to metal(loid) stress. Further, decapod crustaceans in the family, Varunidae, and gastropod molluscs, in the family, Amphibolidae, were found to be metal-sensitive taxa and may be employed in future studies as indicator taxa of sediment metal(loid)-related impacts in south-eastern Australian mangrove forests.

Estimation of chlorophyll content in intertidal mangrove leaves with different thicknesses using hyperspectral data

Abstract Mangrove forests worldwide are mostly degrading and the degradation can be monitored by the leaf chlorophyll (Chl) content, which can be estimated from a quick non-destructive remote measurement. Although there are extensive studies on spectrometric remote sensing methods, few studies on intertidal mangroves are available, and the non-destructive Chl content monitoring method for mangrove with unique leaf characteristics has not been proposed. To develop a valid, non-destructive method for Chl estimation, this study examined nine commonly used vegetation indexes (VIs) for both adaxial and abaxial leaf surfaces of four mangrove species with different leaf thicknesses. Results showed that the modified Datt index (MDATT) was the most effective for estimating the Chl content for both leaf surfaces of various species. An improved MDATT index (IMDATT), in the form of (R527 − R746)/(R527 − R747), performed best with r = −0.88 and RMSE = 8.70 µg/cm2, among all the optimal VIs tested, and proved to be applicable to monitor Chl content with low sensitivity to the variations of leaf surfaces. It proved to be applicable to monitor Chl content in the validation data sets of all species (r = 0.87 and RMSE = 8.20 µg/cm2) and it could be more effective for specific species, with larger r and smaller RMSE. In addition, the different performances of IMDATT could be attributed to the species, as well as the leaf thickness. In conclusion, IMDATT could be broadly applicable to intertidal mangrove plants, especially for species with thin leaves. The research provides a robust tool for monitoring mangrove Chl content.

Foraminiferal zonation from a subtropical mangrove in Bertioga Channel (São Paulo, SP, Brazil)

This study focus on foraminiferal distribution is from two intertidal mangrove ecosystems is located in the Bertioga Channel (São Paulo, Brazil) and its correlation to environmental gradients. Despite of its vicinity to Sao Paulo and Santos cities, the most populated regions in the country, Bertioga Channel is still partially pristine showing that the balance between fresh water and marine waters still provides natural estuarine variability, which are responsible for the foraminiferal zonation of agglutinated species. The zonation mainly relates to tidal influence, where Haphlophragmoides wilberti inhabits less saline environments than Arenoparrella mexicana. The mangrove located closer to the northern mouth of the Bertioga Channel is a more saline environment with higher numbers of dead calcareous species, evidencing greater tidal influence than the mangrove located near the southern mouth. Distribution of Bolivina striatula and Pararotalia sp, demonstrate a greater marine influence in the Crumaú River than in the Trindade River. Here we show what and why the differences between foraminiferal associations from two mangroves and surroundings are taking place in the recent environment establishing a baseline of understanding paleoclimate alterations and sea level changes.

Spatial and temporal heterogeneity in the structure and function of sediment bacterial communities of a tropical mangrove forest.

Bacterial communities of mangrove sediments are well appreciated for their role in nutrient cycling. However, spatiotemporal variability in these communities over large geographical scale remains understudied. We investigated sediment bacterial communities and their metabolic potential in an intertidal mangrove forest of India, Bhitarkanika, using high-throughput sequencing of 16S rRNA genes and community-level physiological profiling. Bulk surface sediments from five different locations representing riverine and bay sites were collected over three seasons. Seasonality largely explained the variation in the structural and metabolic patterns of the sediment bacterial communities. Freshwater Actinobacteria were more abundant in monsoon, whereas γ-Proteobacteria demonstrated higher abundance in summer. Distinct differences in the bacterial community composition were noted between riverine and bay sites. For example, salt-loving marine bacteria affiliated to Oceanospirillales were more prominent in the bay sites than the riverine sites. L-asparagine, N-acetyl-D-glucosamine, and D-mannitol were the preferentially utilized carbon sources by bacterial communities. Bacterial community composition was largely governed by salinity and organic carbon content of the sediments. Modeling analysis revealed that the abundance of δ-Proteobacteria increased with salinity, whereas β-Proteobacteria displayed an opposite trend. Metabolic mapping of taxonomic data predicted biogeochemical functions such as xylan and chitin degradation, ammonia oxidation, nitrite reduction, and sulfate reduction in the bacterial communities suggesting their role in carbon, nitrogen, and sulfur cycling in mangrove sediments. This study has provided valuable clues about spatiotemporal heterogeneity in the structural and metabolic patterns of bacterial communities and their environmental determinants in a tropical mangrove forest.

Abundance and characteristics of microplastics in the mangrove sediment of the semi-enclosed Maowei Sea of the south China sea: New implications for location, rhizosphere, and sediment compositions

Microplastic pollution of intertidal mangrove ecosystems is receiving growing attention, and scientists suspect that the microplastic pollution of semi-enclosed seas is significantly different from that of other coastal types because of their unique geographical features. However, data on the distributions and characteristics of microplastics in the mangrove sediment of semi-enclosed seas are very limited. This study selected the Maowei Sea, a typical semi-enclosed sea, as its representative study site. The analysis revealed that the microplastic abundances in the river estuaries were much lower than those at the oceanic entrance zones, with values ranging from 520 ± 8 to 940 ± 17 items/kg. Polyethylene (PE)/polypropylene (PP)/polystyrene (PS), white/transparent, and <1 mm were the dominant type, colour, and size of the microplastics, respectively, in the observed mangrove sediments. Moreover, some other factors, including the rhizosphere/non-rhizosphere and the proportion of organic matter, codetermined the distribution and characteristics of microplastics. Specifically: (1) the percentage of colorful microplastics were higher in the rhizosphere due to the microbial activities and (2) positive linear relationships were found between the pore volume (PV) values of the free particulate organic matter (FPOM), occluded particulate organic matter (OPOM) (1.6–2.0 g/cm3 and >2.0 g/cm3), and the abundance of very small microplastics (<1 mm).

Seasonal Variation of Bivalves of Intertidal Mangrove Area of Shirgaon, Ratnagiri, Maharashtra

Seasonal Variation of Bivalves of Intertidal Mangrove Area of Shirgaon, Ratnagiri, Maharashtra

Quantitative contribution of primary food sources for a mangrove food web in Setiu lagoon from East coast of Peninsular Malaysia, stable isotopic ([formula omitted] and [formula omitted]) approach

Applying stable isotopes to explore insight into the food web structure in marine ecology have been increasing recently. Tropical mangrove forest, one of the vital marine habitats, has been received intensive attentions in the field. However, there is still controversy about the important roles of primary carbon sources provide to consumers in the ecosystem. In this study, stable isotopic (13C and 15N) ratios were used to determine food web and to estimate quantitative contributions of primary carbon sources for invertebrates and four fish species in the tropical mangrove from Setiu lagoon, Malaysia using the Bayesian mixing model (SIAR). The primary nutrient sources showed δ13C values ranging from −18.7 to −31.1‰ and δ15N from 2.5 to 3.8‰. The wide range of the isotopic composition of consumers (−26.1 to −18.4‰ and 4.3 to 10.2‰ for δ13C and δ15N, respectively) indicated that a variety of carbon sources provided to the intertidal mangrove food webs. Mixing model outputs indicated that mangrove-derived carbon was important food sources for gastropod, Littoraria carinifera, Neritina violacea, N. coromandeliana, N. cornucopia, Cerithdea quadrata, and sesarmid crab, while the benthic microalgae (BMA) mainly fueled to Cerithidea djadjariensis, Cerithium coralium, fiddler crab and the crenate crab Thalamita crenata. Two Scylla species relied largely on BMA and SOMs. Bivalve species mainly assimilated phytoplankton-derived carbon, however, the difference of stable carbon isotope ratios among these bivalve species might relate to feeding selectivity or a small portion of BMA contributed to their diets. The model also resulted that BMA and seston sources might be important to the studied fish species rather than mangrove-derived carbon sources. However, further studies are needed to elucidate insight into the fish food web, and to determine whether there is ecological connectivity between habitats inside and outside of the lagoon.