Species Rhizophora Research Articles

Complete Chloroplast Genome Variants Reveal Discrete Long-Distance Dispersal Routes of Rhizophora in the Western Indian Ocean

Historical processes of long-distance migration and ocean-wide expansion feature the global biogeographic pattern ofRhizophoraspecies. Throughout the Indian Ocean,Rhizophora stylosaandRhizophora mucronataseem to be a young phylogenetic group with an expansion ofR. mucronatatoward the Western Indian Ocean (WIO) driven by the South Equatorial Current (SEC). Nuclear microsatellites revealed genetic patterns and breaks; however, the estimation of propagule dispersal routes requires maternally inherited cytoplasmic markers. Here, we examine the phylogeography of 21R. mucronataprovenances across a >4,200 km coastal stretch in the WIO usingR. stylosaas an outgroup. Full-length chloroplast genome (164,474 bp) and nuclear ribosomal RNA cistron (8,033 bp) sequences were assembled. The boundaries, junction point, sequence orientation, and stretch between LSC/IRb/SSC/IRa/LSC showed no differences withR. stylosachloroplast genome. A total of 58 mutations inR. mucronataencompassing transitions/transversions, insertions-deletions, and mononucleotide repeats revealed three major haplogroups. Haplonetwork, Bayesian maximum likelihood (ML), and approximate Bayesian computation (ABC) analyses supported discrete historical migration events. An ancient haplogroup A in the Seychelles and eastern Madagascar was as different from other haplogroups as fromR. stylosa. A star-like haplonetwork referred as the recent range expansion of haplogroup B from northern Madagascar toward the African mainland coastline, including a single variant spanning >1,800 km across the Mozambique Channel area (MCA). Populations in the south of Delagoa Bight contained haplogroup C and was originated from a unique bottleneck dispersal event. Divergence estimates of pre- and post-Last Glacial Maximum (LGM) illustrated the recent emergence ofRhizophoramangroves in the WIO compared to other oceans. Connectivity patterns could be aligned with the directionality of major ocean currents. Madagascar and the Seychelles each harbored haplogroups A and B, albeit among spatially separated populations, explained from a different migration era. Likewise, the Aldabra Atoll harbored spatially distinct haplotypes. Nuclear ribosomal cistron (8,033 bp) variants corresponded to haplogroups and confirmed admixtures in the Seychelles and Aldabra. These findings shed new light on the origins and dispersal routes ofR. mucronatalineages that have shaped their contemporary populations in large regions of the WIO, which may be the important information for defining marine conservation units both at ocean scale and at the level of small islands.

MORPHOLOGICAL STRUCTURES OF RHIZOPHORA APICULATA BLUME. and RHIZOPHORA MUCRONATA LAM.

Research on the morphological structures of R. apiculata and R. mucronata was carried out in three different regions from July to December 2018. The research aimed at observing and documenting the morphological structure of R. apiculata and R. mucronata. Samples were collected from selected locations in Peninsular Malaysia. Subsequently, samples were processed as herbarium vouchers. The vegetative and reproductive structures of both species were observed and identified. 55 morphological features were recorded and annotated as result of this research. The research revealed that vegetative and reproductive structures could differentiate R. mucronata from R. apiculata. According to this research, there were no significant differences in the morphological structures of R. apiculata and R. mucronata from three different locations. As a consequence, the data acquired in this research would be valuable for future studies on Rhizophora species.

Sedimentological and palynological assessment of three wells in eastern Dahomey Embayment, southwestern Nigeria, West Africa

Integrated studies were carried out on one hundred and eleven (111) ditch samples retrieved from three wells drilled in Lagos area within the Dahomey Embayment, coastal southwestern Nigeria. The purpose of this study is to determine the provenance, heavy mineral assemblage(s), establish the lowstand - highstand episodes, Quaternary palaeoenvironment and date the encountered lithofacies which constitute sandstones, siltstones with thin beds of lignite. The textural parameters show that the sandstones are medium to fine grained with the lignite consisting of plant fragment remains. Petrographic analyses showed abundant detrital minerals with average modal composition of quartz (Q = 90%), feldspar (F = 2%) and rock fragments (RF = 4%). The QFR ternary plots revealed that the sandstones are quartz arenites of continental block provenance origin deposited under humid climatic setting. This lithofacies has undergone medium distance range of transportation and have been subjected to mechanical and chemical weathering prior deposition. The heavy mineral assemblages and the ratios of Zircon-Tourmaline (ZTR index) in the wells suggest matured sediments. The Apatite: Tourmaline (ATi) ratios showed variations within the studied wells indicating differences in rate of weathering. It is evident that the periods of residence on the floodplain despite similar provenances and fluctuations in ratios, suggest sea level changes. The fluctuations in apatite: tourmaline ratios with respect to weathering are attributed to rapid changes in climatic conditions during the floodplain residence. The high ATi values in sandstone were deposited during relative sea level highstand (transgression), while sandstones with low ATi were deposited during lowstand (regression) in Nigeria and along the West African region. The abundance species of Rhizophora sp., Avicennia africana, Acrostichu mauruem, Laevigatosporite sp., Combretaceae sp., Mitrogynaciliata, Sapotaceae sp., Disopyros sp., Elaeis guineensis and Alchronea spp. indicated depositional transition from mangrove to fresh water swamp due to the episodic highstand and lowstand regimes. The abundance of Podocarpus milianjanus and Retitricolporites hians and the absence of Miocene diagnostic forms suggest late Pleistocene (Tarantian = 0.012–0.126 Ma) deposition.

Diversity and zonation of mangrove flora in Belitung Island, Indonesia

Abstract. Irawan A, Chikmawati T, Sulistijorini. 2021. Diversity and zonation of mangrove flora in Belitung Island, Indonesia. Biodiversitas 22: 2981-2992. Mangrove is an important ecosystem located in the coastal tidal zone in tropical and sub-tropical regions. This ecosystem is characterized by the presence of plant species that can survive in brackish and inundated zone of seawater. There are many mangrove forests in Belitung Island, Indonesia, but the data of mangrove flora diversity and zonation in this island have not been described. This study aims to reveal the diversity and analyze the zonation of mangrove flora in Belitung Island. This research was conducted using a cruising method to explore the diversity of mangrove flora species and a line transect to analyze the zonation of mangrove flora. The exploration locations for diversity of mangrove flora were Kuale Tambak Beach, Asam Beach, Belitung Mangrove Park Area, Manggar River, Sentigi Beach, Sabong Beach, and Kembiri Beach. Mangrove flora zonation was observed in Asam Beach (north), Kembiri Beach (south), and Kuale Tambak Beach (east). The result showed that mangrove flora in Belitung Island consisted of 12 families, 16 genera, and 24 species. Species found were dominated by 8 species from the Rhizophoraceae family with the largest number of species were from the genera of Bruguiera and Rhizophora. The species of Bruguiera included Bruguiera gymnorhiza, Bruguiera sexangula, Bruguiera cylindrica and Bruguiera parviflora. Meanwhile, the Rhizophora species that have been found were Rhizophora apiculata, Rhizophora mucronata, and Rhizophora stylosa. The Kembiri beach had the highest number of species of the mangrove flora with 18 species. The zonation of mangrove flora at each research location showed a different zonation pattern. The mangrove vegetation on Kulae Tambak Beach was behind the Casuarina equisetifolia vegetation, while the mangrove vegetation on the Asam and Kembiri Beaches directly faced the sea. The difference in zonation patterns is likely caused by local topography on Belitung Island, substrate conditions and salinity factors on the mangroves of Belitung Island

Mangrove floristics, forest structure and mapping of Neil Island (Andaman and Nicobar Islands, India) with emphasis on the diversity of Rhizophora species and the significance of small island mangroves

Abstract Mangroves in small islands are critical resources for the stability of the island and the livelihood of local coastal communities. However, scientific inventories of mangroves in small islands are rare due to their limited distribution. Considering this, the present study was conducted during 2014–2015 to determine the species composition, biomass, vegetative carbon stock and spatial distribution of mangroves at Neil Island, one of the small islands of the Andaman and Nicobar Islands, India. The spatial locations of different species of mangroves identified from our extensive field surveys were compared with high-resolution images, and the coverage of mangroves (genus level distribution) was interpreted entirely based on the elements of tone and texture. The results show that the mangroves of Neil Island consist of 17 true mangrove species belonging to 12 genera in eight families. The co-existence of all three Indo-West Pacific mangrove species of the genus Rhizophora (Rhizophora apiculata, Rhizophora mucronata and Rhizophora stylosa), and their hybrids (Rhizophora × annamalayana, Rhizophora × lamarckii and Rhizophora × mohanii) shows that this island is a unique place for studying the hybridization and speciation of Rhizophora, a worldwide dominant mangrove genus. Rhizophora mucronata was found to be the dominant species in terms of density, basal area and biomass estimated from forest structural assessments using the quadrat method. The mean density and basal area were 1162 trees ha−1 and 28 m2 ha−1, respectively. The mean above-ground biomass was 271 Mg ha−1, while the mean below-ground biomass was 104 Mg ha−1. The total mean biomass of Neil Island mangroves was 375 Mg ha−1 and its corresponding vegetative carbon stock was 171 Mg C ha−1. The present study provides a practical approach to species-level mapping and assessment to gain site-specific knowledge of the mangroves of Neil Island. Since mangroves are vital for small islands such as Neil Island to cope with rising sea level and increases in natural calamities, the baseline scientific information provided by this study will be beneficial for Integrated Island Management.

Introduced mangroves in the Society Islands, French Polynesia (South Pacific): invasive species or novel ecosystem?

Biotic mixing, where introduced and native species mix into a newly formed ecosystem, is an increasing phenomenon worldwide. It particularly affects islands, where the number of introduced plants often exceeds native ones, and where invasive alien species are one of the main threats to terrestrial biodiversity. The mangrove tree species Rhizophora stylosa, first introduced in French Polynesia (South Pacific) in the early 1930s, is now well established and found in nearly all the inhabited islands of the Society archipelago (Bora Bora, Huahine, Moorea, Raiatea, Tahaa, Tahiti). It forms dense thickets on coastal habitats and estuaries, and gradually colonizes native tidal grassland marshes and nearshore rocky habitats. In order to assess its current expansion, we mapped its distribution from satellite images interpretation and ground-truthing fieldwork. Results indicate that mangroves currently cover a total of 41 ha in the Society Islands. Expansion rate seems relatively slow, particularly in Moorea where only 2.8% of the coastline is colonized over 90 years after its introduction. A preliminary study of the socio-cultural perception of mangroves was undertaken through an online questionnaire sent to local stakeholders and NGOs. It revealed that although more than 70% of the respondents recognized R. stylosa as an introduced species, 40% considered that it had positive impacts and only 20% that it was a harmful species. A more detailed ecological and socio-economical cost–benefit analysis is still needed to provide clearer conclusions on the invasive status of mangroves in the Society Islands, and the most appropriate management strategies to be implemented by local authorities in collaboration with island communities.

PHYSICAL MODEL INVESTIGATION OF PARCEL SCALE MANGROVE EFFECTS ON FLOW HYDRODYNAMICS AND PRESSURES AND LOADS IN THE BUILT ENVIRONMENT

Rising seas, tropical cyclones, and tsunamis threaten increasingly populated coastal areas, leaving coastal communities searching for sustainable, resilient adaptation solutions to mitigate the impacts of chronic and acute coastal flood hazards. This work specifically investigates parcel-scale effects of the Rhizophora mangle (red mangrove) species during extreme wave and/or storm surge conditions. We constructed 100 physical models of the Rhizophora species' trunk-prop root system on a 1:16 scale, and conducted tests in Oregon State University's Directional Wave Basin to measure the effects of mangroves of varying cross-shore thickness on water surface elevation, water velocities, and load reduction on idealized inland structural elements. The presence of mangroves affected hydrodynamic conditions near the mangroves and reduced pressures and forces on inland structures.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/XjtCmHYvgVQ

Stand structure, biomass and dynamics of naturally regenerated and restored mangroves in Malaysia

Regeneration of mangroves that occurred within Straits of Malacca over the last 35 years offers an excellent model system to examine how stand dynamics change over time. With exact stand age known, assessment of forest structure, biodiversity and biomass along a natural mangrove development chronosequence provides valuable information to define how long it takes mangrove restoration to return to a natural baseline condition. In natural settings, it is hypothesized that forest structure, diversity and biomass increase with stand age and that these are highest and most complex in intact mangroves. Thus, the study analyzed dynamics in species composition, forest structure and biomass across intact as well as naturally regenerated (NR) stands from 3, 6, 12, 18, and 25 years of age. Intact mangrove stands were structurally more complex and more diverse than younger stands. The preponderance of A. marina regeneration that appear for succession gives rise to a high importance value in the study area. The mean for above-ground and below-ground biomass was 71.00 ± 2.30 and 36.07 ± 0.52 Mg ha−1, respectively. Mean individual tree mass to tree density relationship resembles the mean tree weight–density trajectory of self-thinning even-aged plant populations where mean individual tree mass increased with decreasing density. Naturally regenerated mangroves supported higher tree diversity with complex in stand structure compared to restored mangroves, which were basically comprised of Rhizophora species. Restored mangroves attain higher biomass in a shorter period of time compared to naturally regenerated mangroves. Mangrove restoration should focus on naturally regenerated mangroves in order to increase carbon sequestration and thus provide climate change mitigation. Ecosystem services, biodiversity and climate change mitigation values need to be considered for both mangrove types as restored mangroves lower tree diversity compared to naturally regenerated mangroves of the same age stand. Therefore it is suggested that sustainable management such as silviculture method might be suitable for naturally regenerated mangroves to absorb more carbon from atmosphere and maintain the higher diversity.

Testing species hypotheses in the mangrove genus Rhizophora from the Western hemisphere and South Pacific islands

The determination of species limits is key to biology, with practical implications for conservation policy makers, lawyers and stakeholders. However, naming species may be a difficult task as interspecific hybridization blurs species boundaries. Natural interspecific gene flow has been reported for seven distinct mangrove genera, including the iconic genus Rhizophora. Species limits within this genus have long been debated because of morphological similarity, natural variability in diagnostic traits, disjunct geographic distribution, and recent molecular data have reignited this issue. Here, we used a phylogeographical approach based on genome-wide single nucleotide polymorphism (SNP) data to test species hypotheses of R. mangle, R. racemosa and R. X harrisonii from the Atlantic East Pacific (AEP) biogeographic region and South Pacific islands. Genetic structure patterns and Approximate Bayesian Computation (ABC) analyses revealed that taxonomic identification based only on morphological traits could not predict genetic clustering alone nor the phylogenetic relationships among groups. The American continent plays an important role as a barrier to gene flow within the genus such that trees identified morphologically as R. racemosa from the Atlantic basin are more genetically similar to R. mangle from the same basin than to R. racemosa trees from the Pacific coast. Additionally, our findings supported previous studies that showed that R. samoensis is indistinguishable from R. mangle populations from the Pacific basin. Moreover, we provide novel evidence that R. X harrisonii is likely composed by two independently originated and separately maintained evolutionary lineages in both sides of the American continent. Our findings provide novel evidence of taxonomic inconsistency of current morphology-based species designations in Western hemisphere and South Pacific islands Rhizophora species.

Potensi biofisik ekosistem mangrove untuk ekowisata di kampung parambu, kabupaten jeneponto

This research was conducted in Kampung Parambu, Kab. Jeneponto in February-March 2020. This study aims to (1) determine the potential of the mangrove ecosystem in Kampung Parambu, Kab. Jeneponto; (2) knowing the potential of mangrove ecosystem stands in Kampung Parambu, Kab. Jeneponto. The approach used is survey research. The data obtained were analyzed descriptively and quantitatively. The results obtained from the potential of mangrove ecosystems in Parambu Village are dominated by mangrove species Rhizophora sp. with a total area of ??10 Ha (6 Ha is good, 3 Ha is slightly damaged and 1 Ha is heavily damaged) while the potential of mangrove stands is on average 20,000 trees / ha and volume 648.41 m3 / ha. These conditions illustrate that the existence of mangrove ecosystem resources in Kampung Parambu, Kab. Jeneponto has enough potential to be utilized by the local community. Therefore, policies in managing mangrove ecosystem resources need to consider biophysical aspects for further development.
 Keywords: potential, biophysical, ecotourism, mangrove

Chemical Structure of Mangrove Species Rhizophora stylosa as Natural Dyes

Textile dyes are divided into two types, natural dyes and synthetic dyes. Natural dyes commonly made from extraction. Extraction is a process in which one or more components are separated selectively from a liquid or solid mixture, the feed, by means of a liquid immiscible solvent. Extraction can be classified into two group, liquid extraction and solid-liquid extraction. Solvents that are usually used in the extraction of natural dyes are aquades and ethanol. The purpose of this research was to determine the chemical structure, especially tannin in natural dyes from mangrove species Rhizophora stylosa through several samples testing natural dyes. Rhizophora stylosa that have been extracted and evaporated will conducted several tests to obtain chemical structures in natural dyes and yield of tannin in natural dyes. Tests carried out include testing FT-IR, and HPLC. Based on FT-IR analysis, the extraction of Rhizophora stylosa containing tannin indicated by the presence of hydroxyl (O-H) in the area of 3385.36 cm-1, aromatic (C-H) in the area of 1365.53 cm-1, carbonyl (C=O) in the area 1646.36 cm-1, esters (C-O) in the area 1217.30 cm-1. While tannin content obtained from the analysis of HPLC were 6.087 ppm.

Anti-wood-fungal performance of methanol extracts of Rhizophora apiculata and R. mucronata barks

Various plant parts of Rhizophora species have been used in the treatment of a variety of diseases and illnesses. However, they have not been tested for antifungal properties related to wood decay fungi, especially the bark extractives. This study examined the methanol (MeOH) crude extracts of R. apiculata and R. mucronata barks in terms of the amount of extracts obtained and their antifungal properties. The antifungal activities of the crude MeOH extracts of both species were determined using the agar dilution method. Methanol crude extract from R. apiculata and R. mucronata were 10.8% and 15.7%, respectively and were toxic to Chaetomium globosum and Gloeophyllum trabeum at the concentration of 50 mg/mL.

Climatic Controls on the Distribution of Foundation Plant Species in Coastal Wetlands of the Conterminous United States: Knowledge Gaps and Emerging Research Needs

Foundation plant species play a critical role in coastal wetlands, often modifying abiotic conditions that are too stressful for most organisms and providing the primary habitat features that support entire ecological communities. Here, we consider the influence of climatic drivers on the distribution of foundation plant species within coastal wetlands of the conterminous USA. Using region-level syntheses, we identified 24 dominant foundation plant species within 12 biogeographic regions, and we categorized species and biogeographic regions into four groups: graminoids, mangroves, succulents, and unvegetated. Literature searches were used to characterize the level of research directed at each of the 24 species. Most coastal wetlands research has been focused on a subset of foundation species, with about 45% of publications directed at just one grass species—Spartina alterniflora. An additional 14 and 8% have been directed, respectively, at two mangrove species—Rhizophora mangle and Avicennia germinans. At the national scale, winter temperature extremes govern the distribution of mangrove forests relative to salt marsh graminoids, and arid conditions can produce hypersaline conditions that increase the dominance of succulent plants, algal mats, and unvegetated tidal flats (i.e., salt flats, salt pans) relative to graminoid and mangrove plants. Collectively, our analyses illustrate the diversity of foundation plant species in the conterminous USA and begin to elucidate the influence of climatic drivers on their distribution. However, our results also highlight critical knowledge gaps and identify emerging research needs for assessing climate change impacts. Given the importance of plant-mediated processes in coastal wetland ecosystems, there is a pressing need in many biogeographic regions for additional species- and functional group-specific research that can be used to better anticipate coastal wetland responses to rising sea levels and changing temperature and precipitation regimes.

LARGE-SCALE PHYSICAL MODELING OF COASTAL PROTECTION PROVIDED BY A MODEL RHIZOPHORA MANGROVE FOREST

Mangrove forests exist in intertidal areas of tropical zones and most are characterized by their complex root systems, which attenuates flow energy. Among the mangrove species, Rhizophora species is the most common one, representing approximately 90% of the world mangrove distribution (Ohira et al., 2013). In addition, this species is used in the majority of restoration projects. Rhizophora plants are characterized by their aerial roots, which form a network above the substrate. Although several studies have been performed in the last decade to characterize flow interaction with mangrove trees (e.g.: Zhang et al., 2015), there is still a lack of knowledge of the forces exerted on the trees and the attenuation produced under waves, currents and waves and currents flowing simultaneously action.

Reproduction of the mangrove species Rhizophora stylosa Griff. at its southern latitudinal limit

A study of reproductive phenology and reproductive performance of the mangrove species Rhizophora stylosa was conducted in three estuaries spanning the southernmost 265 km of its known range on the east Australian coast. The timing of reproductive primordia, buds, flowers, fruit and propagule fall did not differ significantly over the latitudinal range of the study. Peak propagule fall occurred in April after a mean 19–20 months of development, only slightly longer than accounts for tropical latitudes. On average, 2.1% of buds matured to form viable propagules, with an average of 17.2% of buds becoming advanced fruit and 11.9% of advanced fruit becoming mature propagules, which compares well with the ranges published accounts for Australian tropical R. stylosa trees. However, there were relatively few buds per inflorescence on recorded shoots in this study, although formal studies on this in the tropics are absent. Within-site variation in bud and propagule production per shoot was greater than variability between sites in many cases, though our sample size was necessarily low due to the rarity of the trees at the southern limit and the detailed recording method. The species reproduces successfully at its known southern limit, with notable comparability to the eastern Australian Tropics. This suggests there is little thermal limitation on reproduction at the southern limit, where there is evidence of slow spread. “Precocious” reproduction as observed for young R. mangle at range limits in North America was not detected.

Effect of Pollution and Seasonal Changes on Litter Fall and Accumulation in Mangrove Forest (Rhizophora Species) of the Niger Delta, Nigeria

Effect of Pollution and Seasonal Changes on Litter Fall and Accumulation in Mangrove Forest (Rhizophora Species) of the Niger Delta, Nigeria

Hydrodynamics of mangrove-type root models: the effect of porosity, spacing ratio and flexibility

Mangrove trees play a prominent role in coastal tropic and subtropical regions, providing habitats for many organisms and protecting shorelines against high energy flows. In particular, the species Rhizophora mangle (red mangrove) exhibits complex cluster roots interacting with different hydrological flow conditions. To better understand the resilience of mangrove trees, we modeled the roots as a collection of cylinders with a circular pattern subject to unidirectional flow. We investigated the effect of porosity and spacing ratio between roots by varying both the diameter of the patch, D, and inset cylinders, d. In addition, we modeled hanging roots of red mangroves as cantilevered rigid cylinders on a hinge. Force and velocity measurements were performed in a water tunnel (Reynolds numbers from 2200 to 11 000). Concurrently, we performed 2D flow visualization using a flowing soap film. We found that the frequency of the vortex shedding increases as the diameter of the small cylinders decreases while the patch diameter is constant, therefore increasing the Strouhal number, . By comparing the change of Strouhal numbers with a single solid cylinder, we introduced a new length scale, the effective diameter. The effective diameter of the patch decreases as the porosity increases. In addition, we found that patch drag scales linearly with the patch diameter but decreases linearly as the spacing ratio increases. After a spacing ratio of (), the force scales linearly with the free stream velocity, and the mean velocity behind the patch is independent of the Reynolds number and the patch effect disappears. For flexible cylinders, we found that a decrease in stiffness increases both patch drag and the wake deficit behind the patch in a similar fashion as increasing the blockage of the patch. This information has the potential to help in the development of methods to design resilient bio-inspired coastline structures.

Attenuation of waves from boat wakes in mixed mangrove forest of rhizophora and bruguiera species in matang perak

Attenuation of waves from boat wakes in mixed mangrove forest of rhizophora and bruguiera species in matang perak

Monitoring mangrove forests after aquaculture abandonment using time series of very high spatial resolution satellite images: A case study from the Perancak estuary, Bali, Indonesia

Revegetation of abandoned aquaculture regions should be a priority for any integrated coastal zone management (ICZM). This paper examines the potential of a matchless time series of 20 very high spatial resolution (VHSR) optical satellite images acquired for mapping trends in the evolution of mangrove forests from 2001 to 2015 in an estuary fragmented into aquaculture ponds. Evolution of mangrove extent was quantified through robust multitemporal analysis based on supervised image classification. Results indicated that mangroves are expanding inside and outside ponds and over pond dykes. However, the yearly expansion rate of vegetation cover greatly varied between replanted ponds. Ground truthing showed that only Rhizophora species had been planted, whereas natural mangroves consist of Avicennia and Sonneratia species. In addition, the dense Rhizophora plantations present very low regeneration capabilities compared with natural mangroves. Time series of VHSR images provide comprehensive and intuitive level of information for the support of ICZM.

Inverse relationship between salinity and 2H/1H fractionation in leaf wax n-alkanes from Florida mangroves

The effect of salinity on hydrogen isotope fractionation during the production of leaf wax n-alkanes was assessed for Laguncularia racemosa (white mangrove), Rhizophora mangle (red mangrove), and Avicennia germinans (black mangrove) along a 31 ppt (parts per thousand) salinity gradient in the Shark River estuary, Florida, USA. Significant variation in hydrogen isotope ratios was observed among these three Atlantic-East Pacific (AEP) species, with increasing leaf wax n-alkane 2H/1H fractionation with increasing salinity. Net 2H/1H fractionation for hentriacontane (n-C31) increased by 0.8, 1.4 and 1.8‰/ppt in R. mangle, A. germinans and L. racemosa, respectively. The observations are consistent with published δ2HnC31 data from 5 species of Indo-West Pacific (IWP) mangroves, which increased with salinity by 0.7–1.5‰/ppt. Although all measured species from both the AEP and IWP regions have more 2H/1H fractionation at high salinity, differences in slope and intercepts of these relationships are observed among genera. The differences may result from variation in the composition of compatible solutes, reliance on storage carbohydrates, and/or physiological response to salt. However, no statistically significant difference in the sensitivity of δ2HnC31 to salinity was observed in four Rhizophora species from both Indo-West Pacific and Americas-East Atlantic regions, which makes sedimentary Rhizophora lipids a promising target for paleohydroclimatic reconstruction.