Addition of iron does not ameliorate sulfide toxicity by sargassum influx to mangroves but dampens methane and nitrous oxide emissions.

Sargassum spp. strandings in the tropical Atlantic harm local ecosystems due to toxic sulfide levels. We conducted a mesocosm experiment to test the efficacy of iron(III) (hydr)oxides in (a) mitigating sulfide toxicity in mangroves resulting from Sargassum and (b) reducing potentially enhanced greenhouse gas emissions. Our results show that iron addition failed to prevent mangrove mortality caused by highly toxic sulfide concentrations, which reached up to 15,000 µmol l-1 in 14 days; timely removal may potentially prevent mangrove death. Sargassum-impacted mesocosms significantly increased methane, nitrous oxide, and carbon dioxide emissions, producing approximately 1 g CO2-equivalents m-2 h-1 during daylight hours, thereby shifting mangroves from sinks to sources of greenhouse gasses. However, iron addition decreased methane emissions by 62 % and nitrous oxide emissions by 57 %. This research reveals that Sargassum strandings have multiple adverse effects related to chemical and ecological dynamics in mangrove ecosystems, including greenhouse gas emissions.

Ethanol preservation and pretreatments facilitate quality DNA extractions in recalcitrant plant species.

Premise: The preservation of plant tissues in ethanol is conventionally viewed as problematic. Here, we show that leaf preservation in ethanol combined with proteinase digestion can provide high-quality DNA extracts. Additionally, as a pretreatment, ethanol can facilitate DNA extraction for recalcitrant samples. Methods: DNA was isolated from leaves preserved with 96% ethanol or from silica-desiccated leaf samples and herbarium fragments that were pretreated with ethanol. DNA was extracted from herbarium tissues using a special ethanol pretreatment protocol, and these extracts were compared with those obtained using the standard cetyltrimethylammonium bromide (CTAB) method. Results: DNA extracted from tissue preserved in, or pretreated with, ethanol was less fragmented than DNA from tissues without pretreatment. Adding proteinase digestion to the lysis step increased the amount of DNA obtained from the ethanol-pretreated tissues. The combination of the ethanol pretreatment with liquid nitrogen freezing and a sorbitol wash prior to cell lysis greatly improved the quality and yield of DNA from the herbarium tissue samples. Discussion: This study critically reevaluates the consequences of ethanol for plant tissue preservation and expands the utility of pretreatment methods for molecular and phylogenomic studies.

Sediment microbial community structure associated to different ecological types of mangroves in Celestún, a coastal lagoon in the Yucatan Peninsula, Mexico.

Mangroves are unique coastal ecosystems, which have many important ecological functions, as they are a reservoir of many marine species well adapted to saline conditions and are fundamental as sites of carbon storage. Although the microbial contribution to nutrient cycling in these ecosystems has been well recognized, there is a lack of information regarding the microbial composition and structure of different ecological types of mangrove forests. In this study, we characterized the microbial community (Bacteria and Archaea) in sediments associated with five ecological types of mangrove forests in a coastal lagoon dominated by Avicennia germinans and Rhizophora mangle, through 16S rRNA-V4 gene sequencing. Overall, Proteobacteria (51%), Chloroflexi (12%), Gemmatimonadetes (5%) and Planctomycetes (6%) were the most abundant bacterial phyla, while Thaumarchaeota (30%), Bathyarchaeota (21%) and Nanoarchaeaeota (18%) were the dominant archaeal phyla. The microbial composition associated with basin mangroves dominated by Avicennia germinans was significantly different from the other ecological types, which becomes relevant for restoration strategies.

Red Mangrove Propagule Bacterial Communities Vary With Geographic, But Not Genetic Distance.

Bacterial communities associated with plant propagules remain understudied, despite the opportunities that propagules represent as dispersal vectors for bacteria to new sites. These communities may be the product of a combination of environmental influence and inheritance from parent to offspring. The relative role of these mechanisms could have significant implications for our understanding of plant-microbe interactions. We studied the correlates of microbiome community similarities across an invasion front of red mangroves (Rhizophora mangle L.) in Florida, where the species is expanding northward. We collected georeferenced propagule samples from 110 individuals of red mangroves across 11 populations in Florida and used 16S rRNA gene (iTag) sequencing to describe their bacterial communities. We found no core community of bacterial amplicon sequence variants (ASVs) across the Florida range of red mangroves, though there were some ASVs shared among individuals within most populations. Populations differed significantly as measured by Bray-Curtis dissimilarity, but not Unifrac distance. We generated data from 6 microsatellite loci from 60 individuals across 9 of the 11 populations. Geographic distance was correlated with beta diversity, but genetic distance was not. We conclude that red mangrove propagule bacterial communities are likely influenced more by local environmental acquisition than by inheritance.

Association of Rhizophora mangle and ascorbic acid in hydrogels: Evaluation of cytotoxic and immunomodulatory effects

Abstract Polyphenolics from Rhizophora mangle (R. mangle) have shown wound healing and anti- inflammatory effects that may be potentiated by being associated with ascorbic acid, an important substance for collagen and elastin synthesis that plays a role in tissue repair. In our study, we aimed to formulate an association of R. mangle and ascorbic acid in hydrogels and evaluate the association's cytotoxic and immunomodulatory effects. In a pre-formulation study, three gelling polymers (i.e.xanthan gum, poloxamer and hydroxyethyl cellulose) were tested. The selected polymer (i.e. xanthan gum) was used to evaluate cytotoxic and immunomodulatory effects using flow cytometry. Xanthan gum (1.5%) had a homogeneous appearance, an orange colour, a smooth surface, intense brightness and the typical odour, as well as non-Newtonian pseudoplastic behaviour. With a pH of 5.0-5.3 and a non-cytotoxic profile, xanthan gum induced the proliferation and activation of CD4 +, CD8+ and NK T lymphocytes and the production of IL- 2, IL-4, IL-10, IL-17 and TNF-α cytokines in stimulated splenocytes. The results suggest that the association of R. mangle and ascorbic acid in 1.5% xanthan gum hydrogel may be promising in preparations for wound-healing processes.

Bacterial communities vary across populations and tissue type in red mangroves (Rhizophora mangle, Rhizophoraceae) along an expanding front.

Plant-associated microbial communities may be important sources of functional diversity and genetic variation that influence host evolution. Bacteria provide benefits for their hosts, yet in most plant systems we know little about their taxonomic composition or variation across tissues and host range. Red Mangrove (Rhizophora mangle L.) is a vital coastal plant species that is currently expanding poleward and with it, perhaps, its microbiome. We explored variability in bacterial communities across tissues, individuals, and populations. We collected samples from six sample types from 5 to 10 individuals at each of three populations and used 16S rRNA gene (iTag) sequencing to describe their bacterial communities. Core community members and dominant bacterial classes were determined for each sample type. Pairwise PERMANOVA of Bray-Curtis dissimilarity and Indicator Species Analysis revealed significant differences in bacterial communities between sample types and populations. We described the previously unexplored microbiome of the reproductive tissues of R. mangle. Populations and most sample types were associated with distinct communities. Bacterial communities associated with R. mangle are influenced by host geography and sample type. Our study provides a foundation for future work exploring the functional roles of these microbes and their relevance to biogeochemical cycling.

Insectivorous birds reduce herbivory but do not increase mangrove growth across productivity zones.

Top-down effects of predators and bottom-up effects of resources are important drivers of community structure and function in a wide array of ecosystems. Fertilization experiments impose variation in resource availability that can mediate the strength of predator impacts, but the prevalence of such interactions across natural productivity gradients is less clear. We studied the joint impacts of top-down and bottom-up factors in a tropical mangrove forest system, leveraging fine-grained patchiness in resource availability and primary productivity on coastal cays of Belize. We excluded birds from canopies of red mangrove (Rhizophoraceae: Rhizophora mangle) for 13 months in zones of phosphorus-limited, stunted dwarf mangroves, and in adjacent zones of vigorous mangroves that receive detrital subsidies. Birds decreased total arthropod densities by 62%, herbivore densities more than fivefold, and reduced rates of leaf and bud herbivory by 45% and 52%, respectively. Despite similar arthropod densities across both zones of productivity, leaf and bud damage were 2.0 and 4.3 times greater in productive stands. Detrital subsidies strongly impacted a suite of plant traits in productive stands, potentially making leaves more nutritious and vulnerable to damage. Despite consistently strong impacts on herbivory, we did not detect top-down forcing that impacted mangrove growth, which was similar with and without birds. Our results indicated that both top-down and bottom-up forces drive arthropod community dynamics, but attenuation at the plant-herbivore interface weakens top-down control by avian insectivores.

Water levels primarily drive variation in photosynthesis and nutrient use of scrub Red Mangroves in the southeastern Florida Everglades.

We investigated how mangrove-island micro-elevation (i.e., habitat: center vs edge) affects tree physiology in a scrub mangrove forest of the southeastern Everglades. We measured leaf gas exchange rates of scrub Rhizophora mangle L. trees monthly during 2019, hypothesizing that CO2 assimilation (Anet) and stomatal conductance (gsw) would decline with increasing water levels and salinity, expecting more considerable differences at mangrove-island edges than centers, where physiological stress is greatest. Water levels varied between 0 and 60 cm from the soil surface, rising during the wet season (May-October) relative to the dry season (November-April). Porewater salinity ranged from 15 to 30 p.p.t., being higher at mangrove-island edges than centers. Anet maximized at 15.1 µmol m-2 s-1, and gsw was typically <0.2 mol m-2 s-1, both of which were greater in the dry than the wet season and greater at island centers than edges, with seasonal variability being roughly equal to variation between habitats. After accounting for season and habitat, water level positively affected Anet in both seasons but did not affect gsw. Our findings suggest that inundation stress (i.e., water level) is the primary driver of variation in leaf gas exchange rates of scrub mangroves in the Florida Everglades, while also constraining Anet more than gsw. The interaction between inundation stress due to permanent flooding and habitat varies with season as physiological stress is alleviated at higher-elevation mangrove-island center habitats during the dry season. Freshwater inflows during the wet season increase water levels and inundation stress at higher-elevation mangrove-island centers, but also potentially alleviate salt and sulfide stress in soils. Thus, habitat heterogeneity leads to differences in nutrient and water acquisition and use between trees growing in island centers versus edges, creating distinct physiological controls on photosynthesis, which likely affect carbon flux dynamics of scrub mangroves in the Everglades.

Introduced mangroves escape damage from marine and terrestrial enemies.

The enemy release hypothesis (ERH) posits that introduced species often leave their enemies behind when introduced to a new range. This release from enemies may allow introduced species to achieve higher growth and reproduction and may explain why some invaders flourish in new locations. Red mangroves (Rhizophora mangle) were introduced to Hawai'i from Florida over a century ago. Because Hawai'i has no native mangroves, the arrival of R. mangle fundamentally changed the structure and function of estuarine shorelines. While numerous enemies affect red mangroves in their native range (tropical America), in Hawai'i, mangroves apparently experience little herbivory, which may explain why introduced mangroves are so productive, fecund, and continue to spread. In this study, we compared the effects of enemies in native and introduced populations of brackish red mangroves (R. mangle) in 8-10 sites in the native range (Florida, Belize, and Panama) and introduced range of mangroves (Hawai'i). At each site, we measured the (1) occurrence of enemies using timed visual surveys, (2) occurrence of damage to different mangrove structures (leaves, apical buds, dead twigs, roots, propagules, and seedlings), and (3) rate of propagule herbivory using tethering experiments. Consistent with the ERH, we found an order of magnitude less damage and fewer enemies in introduced than native mangrove sites. While introduced mangroves harbored few enemies and minimal damage, native mangroves were affected by numerous enemies, including leaf-eating crabs, specialist bud moths, wood-boring insects and isopods, and propagule predators. These patterns were consistent across all plant structures (roots to leaves), among marine and terrestrial enemies, and across functional groups (browsers, borers, pathogens, etc.), which demonstrates enemy escape occurs consistently among different functional groups and via trophic (e.g., herbivores) and non-trophic (e.g., root borers) interactions. Our study is among the first biogeographical enemy release studies to take a comprehensive approach to quantifying the occurrence of damage from a broad suite of marine and terrestrial taxa across an array of wetland plant structures. Understanding how natural enemies alter this key foundation species will become increasingly relevant globally as mangroves continue to invade new regions through intentional plantings or range expansion driven by climate change.

Antiradical and antiulcer effect of Sonneratia apetala Buch-Ham leaves against alcohol induced gastric mucosal injury / Efecto antirradical y antiulceroso de las hojas de Sonneratia apetala Buch-Ham contra la lesión de la mucosa gástrica inducida por el alcohol

Introducción: Sonneratia apetala Buch-Ham es un verdadero habitante de los manglares en Sunderban indio y se utiliza en la medicina popular para los trastornos digestivos. Método: El extracto hidrometanólico (20:80) de hojas de Sonneratia apetala (SA) se estandarizó químicamente por HPTLC y se evaluó por sus propiedades antirradicales y gastroprotectoras. Se determinaron los fenólicos y flavonoides presentes en SA y se evaluaron las actividades antirradicales mediante métodos in vitro como, DPPH (1,1-difenil-2-picrilhidrazilo), óxidos nítricos, superóxidos, hidroxilo y ABTS (2,2 / -azino-bis- Ácido 3-etilbenztiazolin-6-sulfónico). Además, se evaluó la eficacia gastroprotectora de SA en la ulceración oxidativa inducida por alcohol (50% v / v, 5 ml / kg) en ratas. Resultados: El SA químicamente estandarizado mostró presencia de compuestos polifenólicos. También mostró fuertes propiedades antirradicales. Las administraciones orales de SA (125 mg / kg y 250 mg / kg) protegieron significativamente la membrana mucosa gástrica del daño ulcerativo causado por el alcohol, similar al omeprazol (20 mg / kg) en ratas. Además, el tratamiento con SA redujo significativamente la elevación de los peróxidos de lípidos; mientras que aumentó la concentración de glutatión y catalasa en la mucosa gástrica con respecto a las ratas de control no tratadas inducidas por etanol. Conclusiones: Los resultados obtenidos de este estudio sugieren que la hoja de Sonneratia apetala tiene propiedades antioxidantes y tiene capacidad para proteger la lesión de la mucosa gástrica causada por la ingestión de alcohol. (AU)

Introduction: Sonneratia apetala Buch-Ham is a true mangrove inhabitant in Indian Sunderban and it is used in folk medicine for digestive disorders. Method: Hydro-methanolic (20:80) extract of Sonneratia apetala leaves (SA) was chemically standardized by HPTLC and evaluated for its antiradical and gastro-protective properties. Phenolics and flavonoids present in SA were determined and antiradical activities were assessed by in vitro methods like, DPPH (1,1-diphenyl-2-picrylhydrazyl), nitric oxides, superoxides, hydroxyl and ABTS (2,2/-azino-bis-3-ethyl benzthiazoline-6-sulphonic acid). Further, gastro-protective efficacy of SA was assessed in alcohol (50% v/v, 5 ml/kg) induced oxidative ulceration in rats. Results: Chemically standardized SA exhibited presence of polyphenolic compounds. It also showed strong antiradical properties. Oral administrations of SA (125 mg/kg and 250 mg/kg) significantly protected gastric mucosal membrane from ulcerative damage caused by alcohol, similar to Omeprazole (20 mg/kg) in rats. Moreover, SA treatment significantly reduced the elevation of lipid peroxides; while enhanced the concentration of glutathione and catalase in gastric mucosa in respect to ethanol induced untreated control rats. Conclusions The results obtained from this study suggest Sonneratia apetala leaf has antioxidant properties and has capabilities to protect gastric mucosal injury caused by alcohol ingestion. (AU)

Brazilian Semi-Arid Mangroves-Associated Microbiome as Pools of Richness and Complexity in a Changing World.

Mangrove microbiomes play an essential role in the fate of mangroves in our changing planet, but the factors regulating the biogeographical distribution of mangrove microbial communities remain essentially vague. This paper contributes to our understanding of mangrove microbiomes distributed along three biogeographical provinces and ecoregions, covering the exuberant mangroves of Amazonia ecoregion (North Brazil Shelf) as well as mangroves located in the southern limit of distribution (Southeastern ecoregion, Warm Temperate Southwestern Atlantic) and mangroves localized on the drier semi-arid coast (Northeastern ecoregion, Tropical Southwestern Atlantic), two important ecotones where poleward and landward shifts, respectively, are expected to occur related to climate change. This study compared the microbiomes associated with the conspicuous red mangrove (Rhizophora mangle) root soils encompassing soil properties, latitudinal factors, and amplicon sequence variants of 105 samples. We demonstrated that, although the northern and southern sites are over 4,000 km apart, and despite R. mangle genetic divergences between north and south populations, their microbiomes resemble each other more than the northern and northeastern neighbors. In addition, the northeastern semi-arid microbiomes were more diverse and displayed a higher level of complexity than the northern and southern ones. This finding may reflect the endurance of the northeast microbial communities tailored to deal with the stressful conditions of semi-aridity and may play a role in the resistance and growing landward expansion observed in such mangroves. Minimum temperature, precipitation, organic carbon, and potential evapotranspiration were the main microbiota variation drivers and should be considered in mangrove conservation and recovery strategies in the Anthropocene. In the face of changes in climate, land cover, biodiversity, and chemical composition, the richness and complexity harbored by semi-arid mangrove microbiomes may hold the key to mangrove adaptability in our changing planet.

Size distribution and sex ratio between populations of the artisanal harvested land crab Cardisoma guanhumi (Decapoda: Gecarcinidae), with the estimation of relative growth and size at sexual maturity in Puerto Rico / Distribución de tallas y proporción de sexos entre poblaciones del cangrejo de tierra cosechado artesanalmente Cardisoma guanhumi (Decapoda: Gecarcinidae), con la estimación del crecimiento relativo y tamaño en la madurez sexual en Puerto Rico

Abstract Introduction: Knowledge of growth patterns, sex ratio, and sexual maturity are of importance to exploited populations. The land crab Cardisoma guanhumi is an artisanal and subsistence exploited species in Puerto Rico. However, the growth patterns and sexual maturity of the local populations are not known. Objectives: This study has a double objective: (1) to compare the size and sex structure between populations and (2) to model the relative growth of structures related to reproduction to estimate the average size of morphometric sexual maturity (MSM) for both males and females. Methods: A total of 2 849 specimens were captured from nine dispersed populations on the island between 2001 and 2020. Carapace width (CW) was measured as an estimator of the absolute size of all individuals, together with the propodus length (PL) in males and the abdomen width in females (AW). Differences in length structure between sexes and populations were tested by applying goodness-of-fit tests based on Kernel Density Estimators (KDE). The relative growth pattern was modeled adjusting a spline from which the maximum of its second derivative was calculated as an estimator of the MSM, and bootstrapping was used to generate confidence intervals. Results: Differences were found in size structures, between sexes, and between sites. Our estimates of morphometric sexual maturity resulted in a sexual maturity size for males between 57.9 and 79.0 mm CW, while in females, morphological maturity occurs between 43.8 to 51.5 mm CW. Conclusions: We found inter-population differences in body size that can be attributed to differences in the history of changes of land use and the exploitation biased towards larger individuals, though differences in recruitment should also be considered. Current regulations in Puerto Rico protect female crabs but not to larger male crabs. The regulation establishes that crabs smaller than 64 mm carapace width cannot be captured, leaving immature male crabs over 64 mm CW unprotected. We suggest considering different size limits depending on the sex of the crab. This will allow the full range of sizes where sexual maturity is reached to be protected, increasing the likelihood of the population's size to increase.

Resumen Introducción: El conocimiento de los patrones de crecimiento, la proporción de sexos y la madurez sexual son de suma importancia para las poblaciones explotadas. El cangrejo terrestre Cardisoma guanhumi es una especie explotada artesanalmente y para subsistencia en Puerto Rico. Sin embargo, se desconocen los patrones de crecimiento y la madurez sexual para la isla. Objetivos: Este estudio tiene un doble objetivo: (1) comparar el tamaño y la estructura sexual entre las poblaciones y (2) modelar el crecimiento relativo de estructuras relacionadas con la reproducción (propodo en machos y abdomen en hembras) para estimar el tamaño promedio de madurez sexual morfométrica (MSM). Métodos: Se capturaron un total de 2 849 especímenes de nueve poblaciones dispersas en la isla, entre 2001 y 2020. Se midió el ancho del caparazón (AC) como un estimador del tamaño absoluto de todos los individuos, junto con el largo de propodo en los machos y el ancho del abdomen en las hembras. Las diferencias en la estructura de tallas entre sexos y poblaciones se probaron aplicando la prueba de bondad de ajuste basado en estimaciones de densidad kernel (KDE). El patrón de crecimiento relativo se modeló ajustando un spline a partir del cual se calculó el máximo de su segunda derivada como estimador del MSM y se utilizó bootstrapping para generar intervalos de confianza. Resultados: Se encontraron diferencias en las estructuras de tallas, entre sexos y poblaciones. Nuestras estimaciones de madurez sexual morfométrica dieron como resultado un tamaño de madurez sexual para los machos entre 57.9 y 79.0 mm AC, mientras que, en las hembras, la madurez morfométrica se produce entre 43.8 y 51.5 mm AC. Conclusiones: La diferencia en el tamaño de la población se puede atribuir a las diferencias entre poblaciones en el cambio de uso de la tierra y la presión de explotación asociada con el sesgo hacia la captura de individuos más grandes o el reclutamiento. Las regulaciones actuales en Puerto Rico brindan protección a las hembras, pero no a los machos más grandes. El reglamento establece que no se pueden capturar cangrejos de menos de 64 mm de AC dejando desprotegidos los cangrejos machos inmaduros de más de 64 mm AC. Sugerimos considerar diferentes límites de tamaño según el sexo del cangrejo. Esto permitirá proteger un rango más amplio de tamaños donde se alcanza la madurez sexual, aumentando la probabilidad de un incremento en el tamaño de la población.

Replacement of oyster reefs by mangroves: Unexpected climate-driven ecosystem shifts.

Increases in minimum air temperatures have facilitated transitions of salt marshes to mangroves along coastlines in the southeastern United States. Numerous studies have documented mangrove expansion into salt marshes; however, a present-day conversion of oyster reefs to mangrove islands has not been documented. Using aerial photographs and high-resolution satellite imagery, we determined percent cover and number of mangrove patches on oyster reefs in Mosquito Lagoon, FL, USA over 74 years (1943-2017) by digitizing oyster reef and "mangrove on oyster reef" areas. Live oyster reefs present in 1943 were tracked through time and the mangrove area on every reef calculated for seven time periods. There was a 103% increase in mangrove cover on live oyster reefs from 1943 (6.6%) to 2017 (13.4%). Between 1943 and 1984, the cover remained consistent (~7%), while between 1984 and 2017, mangrove cover increased rapidly with a 6% year-1 increase in mangrove area on oyster reefs (198% increase). In 1943, 8.7% of individual reefs had at least one mangrove patch on them; by 2017, 21.8% of reefs did. Site visits found at least one mature Avicennia germinans on each tracked mangrove reef, with large numbers of smaller Rhizophora mangle, suggesting the post-1984 mangrove increases were the result of increased R. mangle recruitment and survival. Escalation in the coverage and number of mangrove stands on oyster reefs coincided with a period that lacked extreme freeze events. The time since a temperature of ≤-6.6°C (A. germinans mortality threshold) and ≤-4°C (R. mangle mortality threshold) were significantly correlated with the increased ratio of mangrove area:oyster area, total mangrove area, and number of mangrove patches, with greater variation explained by time since ≤ -4°C. The lack of freezes could lead globally to an ecosystem shift of intertidal oyster reefs to mangrove islands near poleward mangrove range limits.

Phytoremediation of polycyclic aromatic hydrocarbons (PAHs) in mangrove sediments using Rhizophora mangle.

A phytoremediation experiment was carried out in mesocosms to investigate the performance of Rhizophora mangle in the remediation of polycyclic aromatic hydrocarbons (PAHs) in mangrove sediment contaminated with crude oil. The water pH of the experiments (phytoremediation and natural attenuation) ranged from 4.9 to 8.4 at 0 and 90 days, respectively. The oxy-reduction potential (Eh) ranged from oxidising (108.0 mV, time 0) to reducing (approximately -110.0 mV, time 90) environments. Dissolved oxygen (DO) ranged from 5.7 mg L-1 (time 0) to 4.5 mg L-1 and 3.6 mg L-1 (time 90) in phytoremediation and natural attenuation, respectively. The sediments had silty texture and an average concentration of 5% organic matter (OM). Phytoremediation (60.76%) showed better efficiency in the remediation of the 16 PAHs compared to natural attenuation (49.57%). Principal component analyses showed a correlation between the concentrations of PAHs with pH, Eh, OM and DO in both experiments.

Tannins from senescent Rhizophora mangle mangrove leaves have a distinctive effect on prokaryotic and eukaryotic communities in a Distichlis spicata salt marsh soil.

Due to climate warming, tannin-rich Rhizophora mangle migrates into tannin-poor salt marshes, where the tannins interfere with the biogeochemistry in the soil. Changes in biogeochemistry are likely associated with changes in microbial communities. This was studied in microcosms filled with salt marsh soil and amended with leaf powder, crude condensed tannins, purified condensed tannins (PCT), all from senescent R. mangle leaves, or with tannic acid. Size and composition of the microbial communities were determined by denaturing gradient gel electrophoresis, high-throughput sequencing and real-time PCR based on the 16S and 18S rRNA genes. Compared with the control, the 16S rRNA gene abundance was lowered by PCT, while the 18S rRNA gene abundance was enhanced by all treatments. The treatments also affected the composition of the 16S rRNA and 18S rRNA gene assemblies, but the effects on the 18S rRNA gene were greater. The composition of the 18S rRNA gene, but not of the 16S rRNA gene, was significantly correlated with the mineralization of carbon, nitrogen and phosphorus. Distinctive microbial groups emerged during the different treatments. This study revealed that migration of mangroves may affect both the prokaryotic and the eukaryotic communities in salt marsh soils, but that the effects on the eukaryotes will likely be greater.

Laguncularia racemosa (Combretaceae) y bacterias terrestres asociadas medio siglo después de la contaminación crónica por hidrocarburos

La evaluación del impacto del petróleo en la interacción suelo-raíz de la planta de mangle blanco, Laguncularia racemosa, es básica para identificar los cambios en la actividad microbiana y en el potencial biotecnológico para la remediación de histosoles contaminados. El objetivo de la investigación fue evaluar la distribución espacial de los hidrocarburos totales del petróleo (HTP) en el suelo orgánico, la densidad poblacional de bacterias promotoras del crecimiento vegetal, así como la respiración microbiana en el rizoplano (RI) en la rizósfera (RZ) y en suelo no rizosférico (SNR) de L. racemosa. Una superficie de 8 000 m2 de un histosol afectado desde 1967 y 1968 se evaluó por derrame crónico de petróleo y lodos de perforación provenientes del pozo petrolero La Venta 248. Se seleccionaron 15 árboles de L. racemosa y se extrajeron muestras del RI, RZ y SNR. Los HTP se extrajeron en equipo soxhlet con diclorometano durante ocho horas y se cuantificaron por gravimetría. La cantidad promedio extraída de HTP permitió la diferenciación de cuatro suelos (S) en el área evaluada, con valor promedio para el S1 de 1 797 mg kg-1 (no contaminado para la normativa mexicana) y tres suelos contaminados: S2 con 3 294, S3: 5 249 y S4: 10 389 mg kg-1. Los resultados evidencian diferencias estadísticas (Duncan, P ≤ 0.05) entre medias de las variables evaluadas. La mayor acumulación de HTP fue 22 962 mg kg-1, se extrajo del SNR en el S4. Las mayores densidades de bacterias fijadoras de N, solubilizadoras de P, Azospirillum y Azotobacter fueron bioestimuladas por la presencia de niveles altos de HTP en el suelo, sin embargo la respiración microbiana fue inhibida. Los resultados sugieren que L. racemosa es sostenible en suelos con petróleo intemperizado, y es un bioestimulador de la actividad microbiana para la atenuación natural.

The evaluation of the impact of oil on the soil-root interaction of the white mangrove plant, Laguncularia racemosa is essential to identify changes in microbial activity and biotechnological potential for remediation contaminated histosols. The objective was to evaluate the spatial distribution of total petroleum hydrocarbons (THP) in organic soil, the population density of plant growth promoting bacteria, also in microbial respiration in the rhizoplane (RI), in the rhizosphere (RZ) and in non-rhizospheric soil (NRS) of L. racemosa. An area of 8 000 m2 of an affected histosol was evaluated, during 1967 and 1968, by chronic oil spill and drilling mud from the La Venta 248 oil well. Fifteen trees of this species were selected to obtain samples of the RI, RZ and NRS. The TPH were extracted in soxhlet with dichloromethane for eight hours and quantified by gravimetry. The average amount extracted from TPH allowed the differentiation of four soils (S) from the evaluated area, the average values were for S1: 1 797 mg kg-1 (not contaminated for Mexican regulations) and three contaminated soils, the values are S2: 3 294, S3: 5 249, and S4: 10 389 mg kg-1. The results show statistical differences (Duncan, P ≤ 0.05) between means of the evaluated variables. The greatest accumulation of TPH was 22 962 mg kg-1, it was extracted from the NRS in S4. The highest densities of N-fixing bacteria, P solubilizers, Azospirillum and Azotobacter were biostimulated by the presence of high levels of THP in the soil, however microbial respiration was inhibited. The results suggest that L. racemosa is sustainable in soils with weathering oil, and is a biostimulator of microbial activity for natural attenuation.

Non-native mangroves support carbon storage, sediment carbon burial, and accretion of coastal ecosystems.

Mangrove forests play an important role in climate change adaptation and mitigation by maintaining coastline elevations relative to sea level rise, protecting coastal infrastructure from storm damage, and storing substantial quantities of carbon (C) in live and detrital pools. Determining the efficacy of mangroves in achieving climate goals can be complicated by difficulty in quantifying C inputs (i.e., differentiating newer inputs from younger trees from older residual C pools), and mitigation assessments rarely consider potential offsets to CO2 storage by methane (CH4 ) production in mangrove sediments. The establishment of non-native Rhizophora mangle along Hawaiian coastlines over the last century offers an opportunity to examine the role mangroves play in climate mitigation and adaptation both globally and locally as novel ecosystems. We quantified total ecosystem C storage, sedimentation, accretion, sediment organic C burial and CH4 emissions from ~70 year old R. mangle stands and adjacent uninvaded mudflats. Ecosystem C stocks of mangrove stands exceeded mudflats by 434 ± 33 Mg C/ha, and mangrove establishment increased average coastal accretion by 460%. Sediment organic C burial increased 10-fold (to 4.5 Mg C ha-1  year-1 ), double the global mean for old growth mangrove forests, suggesting that C accumulation from younger trees may occur faster than previously thought, with implications for mangrove restoration. Simulations indicate that increased CH4 emissions from sediments offset ecosystem CO2 storage by only 2%-4%, equivalent to 30-60 Mg CO2 -eq/ha over mangrove lifetime (100 year sustained global warming potential). Results highlight the importance of mangroves as novel systems that can rapidly accumulate C, have a net positive atmospheric greenhouse gas removal effect, and support shoreline accretion rates that outpace current sea level rise. Sequestration potential of novel mangrove forests should be taken into account when considering their removal or management, especially in the context of climate mitigation goals.

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in a diesel oil-contaminated mangrove by plant growth-promoting rhizobacteria.

In this study, Rhizophora mangle L. mangrove plants and plant growth-promoting bacteria were evaluated for their ability to degrade polycyclic aromatic hydrocarbons in diesel oil-contaminated sediment. The diesel-contaminated soil was sown with plant growth-promoting bacteria in the R. mangle L. rhizosphere and monitored for 120 days in a greenhouse. The plant growth-promoting bacteria Pseudomonas aeruginosa and Bacillus sp. were analyzed for their ability to degrade eight priority polycyclic aromatic hydrocarbons, achieving a removal rate for naphthalene (80%), acenaphthene (> 60%), anthracene (> 50%), benzo(a)anthracene (> 60%), benzo(a)pyrene (> 50%) and dibenzo(a,h)anthracene (> 90%) in the treatments with and without plants. R. mangle L. demonstrated a removal rate above 50% for acenaphthene and fluoranthene. The bacterial strains promoted the development of the plant propagule in 55% of sediment contaminated with diesel. Scanning electron microscopy revealed the formation of biofilms by the strains in the roots of the plants in contact with the diesel. Thus, the interaction between Rhizophora mangle L. and the bacterial strains (Bacillus sp. and P. aeruginosa) demonstrated the potential of the strains to degrade diesel and bioremediate mangroves impacted by diesel oil.

Extremophiles as a Model of a Natural Ecosystem: Transcriptional Coordination of Genes Reveals Distinct Selective Responses of Plants Under Climate Change Scenarios.

The goal of this research was to generate networks of co-expressed genes to explore the genomic responses of Rhizophora mangle L. populations to contrasting environments and to use gene network analysis to investigate their capacity for adaptation in the face of historical and future perturbations and climatic changes. RNA sequencing data were generated for R. mangle samples collected under field conditions from contrasting climate zones in the equatorial and subtropical regions of Brazil. A gene co-expression network was constructed using Pearson's correlation coefficient, showing correlations among 78,364 transcriptionally coordinated genes. Each region exhibited two distinct network profiles; genes correlated with the oxidative stress response showed higher relative expression levels in subtropical samples than in equatorial samples, whereas genes correlated with the hyperosmotic salinity response, heat response and UV response had higher expression levels in the equatorial samples than in the subtropical samples. In total, 992 clusters had enriched ontology terms, which suggests that R. mangle is under higher stress in the equatorial region than in the subtropical region. Increased heat may thus pose a substantial risk to species diversity at the center of its distribution range in the Americas. This study, which was performed using trees in natural field conditions, allowed us to associate the specific responses of genes previously described in controlled environments with their responses to the local habitat where the species occurs. The study reveals the effects of contrasting environments on gene expression in R. mangle, shedding light on the different abiotic variables that may contribute to the genetic divergence previously described for the species through the use of simple sequence repeats (SSRs). These effects may result from two fundamental processes in evolution, namely, phenotypic plasticity and natural selection.

Wood anatomy of Laguncularia racemosa (Combretaceae) in mangrove and transitional forest, Southern Brazil / Anatomía de la madera de Laguncularia racemosa (Combretaceae) en manglar y bosque de transición en el sur de Brasil

Abstract Mangroves represent an environment of great heterogeneity and low diversity of plant species that have structural and physiological adaptations linked to a high salinity environment. Laguncularia racemosa is a typical tree species in mangroves and transitional zones. This study aimed to compare the wood anatomy of L. racemosa (Combretaceae) in two different forests (mangroves and transitional forests), which have different soil conditions. For this, we obtained wood and soil samples in March 2016. We analyzed soil nutritional contents in one 15 cm deep soil sample per forest type. In addition, we selected five mangrove trees in each formation for wood anatomy analysis and took one wood sample per individual, per area. We prepared histological slides and separated materials following standard methods for wood anatomy studies. Soil analysis showed that mangrove soils had higher phosphorus, potassium and calcium contents. The transitional soil had lower pore water salinity and soil pH, probably due to high aluminum levels. Anatomical attributes differed between different forest populations. In the different wood aspects evaluated, we obtained higher values in mangrove individuals when compared to the transitional forest population: vessel elements length (375.79 mm), tangential vessels diameter (75.85 mm), frequency of vessels (11.90 mm) and fiber length (889.89 mm). Moreover, parenchyma rays height was larger in the samples of the transitional forest (392.80 mm), while the mangrove population presented wider rays (29.38 mm). The structure of the secondary xylem in the studied species apparently responds to edaphic parameters and shows variations that allow it to adjust to the environmental conditions. The population of the transitional forest showed a secondary xylem that invests more in protection than the mangrove population. Rev. Biol. Trop. 66(2): 647-657. Epub 2018 June 01.

Resumen Los manglares representan un ambiente de gran heterogeneidad y baja diversidad de especies vegetales que tienen adaptaciones estructurales y fisiológicas ligadas a un ambiente de alta salinidad. Laguncularia racemosa es una especie de árbol típico en los manglares y en zonas de transición. El objetivo de este estudio fue comparar la anatomía de la madera de L. racemosa (Combretaceae) en dos bosques distintos (manglares y bosques de transición) que tienen diferentes condiciones edáficas. Para esto se obtuvieron muestras de madera y suelo en marzo 2016. Se analizaron los contenidos nutricionales de una muestra de suelo de 15 cm de espesor por tipo de bosque. Además, se seleccionaron cinco árboles de mangle en cada formación para el análisis de la anatomía de la madera y se tomó una muestra de cada individuo por área. Se prepararon láminas histológicas y se separaron los materiales siguiendo métodos convencionales para estudios de anatomía de la madera. El análisis del suelo mostró que en el manglar hay mayor contenido de fósforo, potasio y calcio. El suelo del bosque de transición tiene menor salinidad del agua capilar y pH del suelo, probablemente debido a los altos niveles de aluminio. Los atributos anatómicos difirieron entre las distintas poblaciones de bosque. En los distintos aspectos de la madera evaluados, se obtuvieron valores más altos en los individuos del manglar comparados con los de la población del bosque de transición: longitud de los elementos de los vasos (375.79 mm), diámetro de los vasos tangenciales (75.85 mm), frecuencia de vasos (11.90 mm) y longitud de la fibra (889.89 mm). Además, la altura de los rayos de parénquima fue mayor en las muestras del bosque de transición (392.80 mm) mientras que la población de manglar presentó rayos más anchos (29.38 mm). La estructura del xilema secundario en la especie estudiada aparentemente responde a los parámetros edáficos y muestra variaciones que le permiten adecuarse a las condiciones ambientales. La población del bosque de transición mostró un xilema secundario que invierte más en protección que la población del manglar.