Basin Mangrove Research Articles

Pneumatophore CO2 effluxes decrease with increased salinity in mangrove forests of Yucatan, Mexico

Although mangrove forests are great carbon sinks, they also release carbon dioxide (CO2) from soil, plants, and water through respiration. Many studies have focused on CO2 effluxes only from soils, but the role of biogenic structures such as pneumatophore roots has been poorly studied. Hence, CO2 effluxes from pneumatophores were quantified at sediment-air (non-flooded sediment) and water–air (flooded sediment) interfaces along a salinity gradient in three mangrove types (fringe, scrub, and basin) dominated by Avicennia germinans during the dry and rainy seasons in Yucatan, Mexico. Pneumatophore abundance explained up to 91% of CO2 effluxes for scrub, 87% for fringe, and 83% for basin mangrove forests at the water–air interface. Overall, CO2 effluxes were inversely correlated with temperature and salinity. The highest CO2 effluxes were in the fringe and the lowest were in the scrub mangrove forests. Flooding decreased CO2 effluxes from the dry to the rainy season in all mangrove forests. These results highlight the contribution of pneumatophores to mangrove respiration, and the need to include them in our current carbon budgets and models, but considering different exchange interfaces, seasons, and mangrove ecotypes.

Effect of physiographic type and harvesting age on biomass yield, chemical composition, and carbon sequestration of mangrove plantations for biofuel feedstock production

Many coastal communities of SE-Asia, including Thailand have managed mangrove forests for charcoal production. However, understanding and managing the harvesting age of mangrove plantations in different ecotypes is limited for sustainable biofuel production. Therefore, the objectives of this research were to determine the effect of physiographic type and harvesting age on the biomass yield, chemical composition, CO2 adsorption of aboveground mangrove biomass. The data were collected during 2018–2019 from two geographical types including the riverine and basin mangrove plantations in Samut-Songkhram, Thailand. The experimental plots were selected at different ages (5, 10, and 15 years). The riverine mangrove forest had higher dry aboveground woody biomass, calorific value, and CO2 adsorption than did the basin mangrove forest. For both mangrove ecotypes, there were no significant differences in chemical elements. Extending harvesting age from 5 to 15 years tended to increase the woody biomass yield and quality, and CO2 adsorption of mangrove forests. With increasing harvesting age, the dry aboveground woody biomass, calorific value, and CO2 adsorption of mangroves increased 34.4–283.9 t ha−1, 3841.1- 3924.9 kcal kg−1, and 55.6–453.4 t CO2 ha−1, respectively, but ash and N content decreased 4.8–3.4% and 0.2–0.1%, respectively. Compared with other ages, extending harvest until 15 years yielded the highest potential biomass for biofuel feedstock production and carbon sequestration in both mangrove ecotypes.

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.

Porewater Sulfide: The Most Critical Regulator in the Degradation of Mangroves Dominated by Tides

The hydroperiod determines the biogeochemical conditions and processes developing in the mangrove soil. Floods control the input of nutrients and the presence of regulators such as salinity and sulfides that, in high concentrations, degrade mangrove vegetation. This work aimed to determine biogeochemical and hydroperiod characteristics in natural and degraded mangrove conditions. Three sampling sites were placed along a spatial gradient, including fringe and basin mangroves with different conditions. Tree characteristics and biogeochemical variables (temperature, salinity, pH, redox potential, sulfides) were measured. The structural analysis indicated two conditions: undisturbed (Rhizophora mangle fringe and Avicennia germinans basin under natural conditions) and disturbed (degraded basin, with standing A. germinans tree trunks). The soil porewater salinity, concentration of sulfides, and temperature were significantly higher, and redox potential lower in the disturbed site. The fringe mangrove was permanently waterlogged with higher tides than the basin mangrove. There were more extended flooding periods on the degraded mangrove due to the loss of hydrological connection with the adjacent water body. Waterlogging in basin mangroves increased soil porewater salinity to 87.8 and sulfides to 153 mg L−1, causing stress and death in A. germinans mangroves. Our results show that the loss of hydraulic connectivity causes the chronic accumulation of salinity and sulfides, with consequences on tree metabolism, ultimately causing its death. It probably also involves the succession in microbial communities.

Elevation and Distribution of Freshwater and Sewage Canals Regulate Canopy Structure and Differentiate Hurricane Damages to a Basin Mangrove Forest

The coastal mangrove forest bears important ecosystem functions and services, including the protection of shorelines and coastal communities. While coastal mangroves often suffer severe damage during storms, understanding the vulnerability and resistance of mangroves to the damage at a landscape scale is crucial for coastal mangrove management and conservation. In September 2017, two consecutive major hurricanes caused tremendous damage to the coastal mangroves in the Caribbean. By utilizing LiDAR data taken before and after the hurricanes in a basin mangrove forest in Northeast Puerto Rico, we analyzed the spatial variation of a canopy structure before the hurricanes and hurricane-induced canopy height reduction and explored possible drivers by means of spatial regressions. Regarding the canopy structure, we found that the pre-hurricane canopy height of the mangrove forest decreased with elevation and distance to the freshwater/sewage canals within the forest, and these two drivers explained 82% of variations in the mangrove canopy height. The model, thus, implies that freshwater and nutrient inputs brought by the canals tend to promote the canopy height, and mangrove trees at lower elevation are especially more advantageous. Similarly, tree densities decreased with the canopy height but increased with the elevation and the distance to the canals. We also found that this mangrove forest suffered on average a 53% canopy height reduction, reflecting mostly heavy crown defoliation and the rupture of branches. The regression, which explains 88% of spatial variation in the canopy height reduction, showed that mangroves with a higher canopy or lower density, or growing in lower elevation, or being closer to the canals suffered more damage. Our findings indicate that delivered freshwater/sewage by means of human-made canals has a strong impact on the canopy structure as well as its resistance to tropical storms. Freshwater and sewage tend to release the salinity stress and nutrient deficit and, thus, to promote the mangrove canopy height. However, the addition of freshwater and nutrients might also increase the risk of mangrove damage during the storms probably because of an altered allometry of assimilates.

Spatial distribution of microplastics in the superficial sediment of a mangrove in Southeast Brazil: A comparison between fringe and basin

The presence of microplastics (MPs) has been observed globally in every marine environment, including mangroves. However, the distribution of MPs in mangroves comparing fringe and basin forests and their ecological consequences need be better investigated. The objectives of this study were to verify the presence, distribution and types of MPs in a mangrove area in southeast Brazil. Further, we linked the presence of vegetation and urban activities with MPs presence at these sites. Eight mangrove sites in Vitória Bay were delimited and classified as fringe or basin, totaling 16 sample points. Superficial sediments were collected, then MPs classified and quantified by shapes and colors. A total of 2175 MPs were observed in the mangrove basin and fringe of sites analyzed (66.4% and 33.6%, respectively), suggesting high levels of MPs in basin sites. The color proportion of MPs found was blue (54%), transparent (21%), black (10%), red and green (6% each) and yellow and white (<1% each). Filaments accounted for 88.7% of the total, compared with 11.3% from fragments. The majority of MPs were found at the basin sites with less preserved vegetation. A positive correlation was found between the total number of MPs and the density of dead vegetation, indicating that degraded environments are more susceptible to MP accumulation. Thus, our data suggest that MPs are widely distributed and associated with lower hydrodynamism (basin region), less preserved vegetation and urban activities.

On further specimens of the Pit viper Trimeresurus erythrurus (Cantor, 1839) (Squamata: Viperidae), with description of a topotype and range extension to the Godavari Basin, peninsular India

We report on a topotypical specimen of the spot-tailed pit viper Trimeresurus erythrurus recorded from Sunderbans in India and a distant, southerly, range extension from Kakinada mangroves, based on preserved (n= 1, seen in 2019) and live uncollected (n= 2; seen in 2014) specimens, respectively. The specimens (n= 3) share the following characteristics: verdant green dorsum, yellow iris, white ventrolateral stripes in males, 23 midbody scale rows, 161–172 ventrals, 61–76 subcaudals, and reddish tail tip. Drawing on the published records, its apparent rarity within its type locality and lack of records from the Circar Coast of India, our study significantly adds to the knowledge of the distribution and morphology of this species. Being a medically important venomous snake, its presence in the Godavari mangrove basin calls for wider dissemination of this information among medical practitioners, in addition to fundamental researchers like academics and herpetologists.

Ecosystem‐Atmosphere Exchange of CO2, Water, and Energy in a Basin Mangrove of the Northeastern Coast of the Yucatan Peninsula

AbstractCoastal settings variations are linked to composition, structural, and functional differences among mangrove ecotypes. Basin mangroves undergo larger flooding and salinity fluctuations, yet remain understudied, compared to other ecotypes. We evaluated the effect of flooding and air temperature (T a) on the surface energy balance and eddy covariance‐derived net CO2 ecosystem exchange (NEE) of a basin mangrove with sporadic freshwater flooding. During the study period (June 2017–November 2018) the site was more frequently not flooded. Under these conditions, in combination with high T a (&gt;27°C), daytime CO2 uptake was significantly lower, while evapotranspiration and sensible heat flux were higher than when flooded. CO2 uptake increased with T a and vapor pressure deficit, but after exceeding a threshold (29°C and 1.4 kPa), uptake declined. Flooding extended this T a threshold by 3°C and increased the radiation saturation point of NEE. The ecosystem is a net sink of CO2 annually (709 ± 09 g C m−2 yr−1), however, it turned a net source of CO2 for 3 months of prolonged rainfall deficit. Most of the precipitation input is returned to the atmosphere (evaporative index: 0.94) and on average, for each gram of atmospheric carbon assimilated into the ecosystem, 2.21 ± 0.50 kg of water was returned to the atmosphere. This ecosystem‐level water‐use efficiency decreased with flooding, but the correlation was not strong. Future temperature increases and lower precipitation (local and regional), combined with lower water table (and/or stronger saline intrusion), imply important losses of primary productivity and stored soil carbon in basin mangroves of northeast Yucatan Peninsula.

Examining the response of an eastern Australian mangrove forest to changes in hydro-period over the last century

This study examines mangrove substrate production within a mangrove basin forest in the Tweed Estuary, northern New South Wales, Australia. This is achieved using high resolution dating of 239+240Pu, 236U and 210Pb in mangrove sediments to examine both the modes and rates of mangrove substrate production. Results show a shift in the mode of substrate production occurred approximately 70 years ago in response to human modification of the Tweed Estuary (hydrologic changes). At that time, mangrove substrate production shifted from being dominated by sedimentation processes (fine silt accumulation) to being dominated by biological processes (mangrove root production). Since that time, mangrove peat has been accreting at the study site at the same rate as local sea level rise (SLR), implying current rates of peat substrate development are tuned to increasing sea level. A further implication of the shift to biological accretion at rates corresponding with SLR is that the studied mangrove basin is sequestering C at increasing rates due to subsurface root production.

Isotopic Evidence that Nitrogen Enrichment Intensifies Nitrogen Losses to the Atmosphere from Subtropical Mangroves

Nitrogen (N) enrichment can have large effects on mangroves’ capacity to provide critical ecosystem services by affecting fundamental functions such as N cycling and primary productivity. However, our understanding of excess N input effects on N cycling in mangroves remains quite limited. To advance our understanding of how N enrichment via water or air pollution affects mangroves, we evaluated whether increasing N inputs would decrease biological N fixation (BNF), but intensify N dynamics and N losses to the atmosphere in these systems. We measured N concentrations in sediment and vegetation, rates of BNF in sediment and litter, and net sediment ammonification and nitrification rates. We also evaluated long-term integrated N dynamics and N losses to the atmosphere using the natural abundance of N stable isotopes (δ15N) in the sediment–plant system and in estuarine water. We performed these analyses at non-N-enriched and N-enriched (that is, polluted) fringe and basin mangroves in southeastern Brazil. The δ15N in the sediment–plant system was higher at N-enriched than non-N-enriched fringe sites, indicating increased N losses to the atmosphere from N-enriched sites. However, N concentrations in sediment and vegetation were similar or lower at N-enriched relative to non-N-enriched sites. BNF and net ammonification and nitrification rates were also similar between N-enriched and non-N-enriched sites. Excess N inputs intensified N losses to the atmosphere from mangroves, but N pools, BNF, and net ammonification and nitrification rates were not affected by N enrichment, likely because excess N was quickly lost from the system by direct denitrification and volatilization.

Discrimination of 3 dominant mangrove species from the Pacific coast of Mexico by spectroscopy on intact leaves

Spectral discrimination of mangrove leaves is the first step in classifying remotely sensed imagery of mangrove forests. The objective of this study was to analyze spectroscopic data on leaves from the upper and lower parts of mangrove canopies to discriminate species and physiognomic types. Leaf samples from the upper and lower parts of the canopies of 3 mangrove species (Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle) in 2 physiognomic types (basin and fringe) were collected during 2 seasons (dry and rainy). Probability distribution and first-derivative plots were generated for every wavelength (450–1,000 nm) detected in all samples. With the plots, optimal wavelengths were selected and subsequently verified with a canonical discriminant analysis. Results indicated that all species in basin mangrove forests showed a unique distinction between the upper and lower leaves during the dry season. By contrast, species in fringe mangrove forests did not show this difference during both seasons. Optimal wavelengths for species discrimination were located between 540–560 nm and 700–720 nm, which correspond to the green and red-edge wavebands, respectively. Future studies using remote sensing data with the aforementioned wavebands can be conducted to discriminate physiognomic mangrove forest types and to increase accuracy in the classification of mangroves at the canopy level on the Pacific coast of Mexico.

Stabilization of carbon in mineral soils from mangroves of the Sin\xfa river delta, Colombia

Mangrove forests of the Sinú river delta in Cispatá bay, Colombia, show large differences in soil carbon storage between fringe (oceanic) and basin (estuarine) mangroves. We were interested in testing whether these differences in soil carbon are associated with sediment transport processes or whether most of the carbon is produced in situ within the mangrove system. Given past sedimentation dynamics of the Sinú river, we hypothesized that a large portion of soil carbon in basin mangroves is due to sedimentation. We determined total organic carbon content (TOC) as 660.93 ± 259.18 MgC ha−1 for basin soils up to a sampling depth of 1 m, and as 259 ± 42.61 MgC ha−1 for fringe soils up to 80 cm depth (maximum soil depth for fringe soils). Using analyses of mineralogy (Al- and Fe-oxides, clay minerals) as well as isotopic analyses of carbon (δ13C), the origin of the sediments and their carbon was determined. We found that basin soils in Cispatá bay show similar mineralogical composition than those of fluvial sediments, but the carbon concentration of river sediments was close to zero. Given the large capacity of the Fe and Al oxides in clay minerals to store dissolved carbon, and that the isotopic composition of the carbon is mostly of plant origin, we concluded contrary to our initial hypothesis that the carbon stored in basin mangrove soils are produced in situ. The deposited fluvial sediments do play an important role for carbon storage, but mostly in providing binding surfaces for the stabilization of organic carbon.

Water Quality and Mangrove-Derived Tannins in Four Coastal Lagoons from the Gulf of Mexico with Variable Hydrologic Dynamics

ABSTRACT Lopez-Portillo, J.; Lara-Dominguez, A.L.; Vazquez, G., and Ake-Castillo, J.A., 2017. Water quality and mangrove-derived tannins in four coastal lagoons from the Gulf of Mexico with variable hydrological dynamics In: Martinez, M.L.; Taramelli, A., and Silva, R. (eds.), Coastal Resilience: Exploring the Many Challenges from Different Viewpoints. Journal of Coastal Research, Special Issue No. 77, pp. 28–38. Coconut Creek (Florida), ISSN 0749-0208. This study explored the spatial variability of physico-chemical water variables (i.e., salinity, nitrogen, phosphorus and tannins) in contrasting seasons in four coastal lagoons (Chica y Grande, La Mancha, Sontecomapan and El Ostion) along Veracruz state, Mexico. We also calculated the mangrove and central basin water areas and associated them to physico-chemical data to analyze them by means of Principal Component Analysis (PCA) due to high correlation among variables. Finally, we elaborated coded maps of each lagoon to represent the gradients of the vari...

Oceanic and climatic drivers of mangrove changes in the Gulf of Urabá, Colombian Caribbean

The Gulf of Uraba is the largest estuary on the Caribbean coast of Colombia. The aim of this research was to analyse the oceanic, climatic and environmental variables that influence mangrove structure and composition in the gulf. Based on the availability of remote sensing, the study area was divided into western and eastern zones. The spatial pattern of environmental variables (water salinity, pH and percentage of organic matter, sand, silt and clay in the soils) and oceanic and climatic variables (winds, wave height and wave period) was analysed. The relationship of these variables with variables of vegetation structure (basal area, diameter at breast height, tree height, and abundance of seedlings of mangrove species in 1 m2 subplots) was analysed in 27 plots of 500 m2 containing fringe mangroves and 5 plots containing basin mangroves. Mangroves of the western zone showed a higher structural development and were dominated by Rhizophora mangle (red mangrove). This zone is supplied by fresh water and sediments, and the soils have a high content of organic matter and clay and a low degree of anthropogenic disturbance. The eastern zone was characterized by higher pore water salinity due to lower freshwater input from rivers. In this area there is a smaller impact of waves and winds, higher sedimentation rates, high anthropogenic disturbance and mangroves are dominated by Avicennia germinans (black mangrove). Although Laguncularia racemosa (white mangrove) did not show a particular spatial pattern, due to its tolerance to open canopy conditions it was commonly found in anthropogenically disturbed areas.

Assessment of Hammocks (Petenes) Resilience to Sea Level Rise Due to Climate Change in Mexico.

There is a pressing need to assess resilience of coastal ecosystems against sea level rise. To develop appropriate response strategies against future climate disturbances, it is important to estimate the magnitude of disturbances that these ecosystems can absorb and to better understand their underlying processes. Hammocks (petenes) coastal ecosystems are highly vulnerable to sea level rise linked to climate change; their vulnerability is mainly due to its close relation with the sea through underground drainage in predominantly karstic soils. Hammocks are biologically important because of their high diversity and restricted distribution. This study proposes a strategy to assess resilience of this coastal ecosystem when high-precision data are scarce. Approaches and methods used to derive ecological resilience maps of hammocks are described and assessed. Resilience models were built by incorporating and weighting appropriate indicators of persistence to assess hammocks resilience against flooding due to climate change at “Los Petenes Biosphere Reserve”, in the Yucatán Peninsula, Mexico. According to the analysis, 25% of the study area is highly resilient (hot spots), whereas 51% has low resilience (cold spots). The most significant hot spot clusters of resilience were located in areas distant to the coastal zone, with indirect tidal influence, and consisted mostly of hammocks surrounded by basin mangrove and floodplain forest. This study revealed that multi-criteria analysis and the use of GIS for qualitative, semi-quantitative and statistical spatial analyses constitute a powerful tool to develop ecological resilience maps of coastal ecosystems that are highly vulnerable to sea level rise, even when high-precision data are not available. This method can be applied in other sites to help develop resilience analyses and decision-making processes for management and conservation of coastal areas worldwide.

Can mangroves keep pace with contemporary sea level rise? A global data review

Coastal vegetated wetlands such as mangrove forests provide multiple ecosystem services, though are potentially threatened by contemporary accelerated sea level rise (SLR), in addition to other immediate threats such as agriculture and coastal development. Several studies have revealed that mangroves are able to adapt to, and keep pace with local relative SLR through vertical surface elevation change (SEC), however data are lacking, with often only surface accretion rate (SAR) data available. We systematically review published studies of SEC and SAR from globally distributed monitoring sites using meta-analysis, and compare them with the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5) SLR scenarios. Hydro-geomorphic setting plays an important role, with basin mangroves potentially less vulnerable to SLR through land building processes. We find that SAR in both basin and fringe mangroves can cope with low SLR scenario (RCP 2.6) throughout the 100 years projection period. However, SAR can only keep pace with high SLR scenario (RCP 8.5) up to year 2070 and 2055 in basin and fringe mangrove settings respectively. These were associated with potential sediment accumulation of 41 cm and 29 cm respectively from the baseline. Mangrove degradation promoted lowering trends of SEC, while mangrove management such as rehabilitation practice stimulated positive trends of SEC. Mangrove ecosystems may be vulnerable to contemporary SLR in small island locations such as the Caribbean, East Africa and parts of the Indo-Pacific that are dominated by fringe mangroves and where SEC cannot keep pace with both low and high IPCC AR5 SLR scenarios. A global expansion of current mangrove surface elevation monitoring effort is urgently needed in order to better assess the vulnerability of mangroves, and the factors affecting their resiliency in the face of rising sea levels.

Structure and floristic composition of mangroves in the Bahía de Cispatá, Colombian Caribbean

&lt;p&gt;Los manglares son asociaciones de plantas que se adaptan fácilmente a las condiciones salinas y los niveles fluctuantes de inundación. Estos ecosistemas suministran gran cantidad de bienes y servicios tales como el almacenamiento de carbono. Diferencias estructurales, de composición de especies y de características micro-ambientales entre tipos fisiográficos implican diferencias en el almacenamiento de carbono en sus suelos. La presente investigación tuvo como objetivo identificar la variación de las especies de mangle a través de los cambios en las variables físico-bióticas de bosques de manglar de la bahía Cispatá, Colombia. Se realizaron mediciones de variables estructurales del bosque (&lt;em&gt;D, H, &lt;/em&gt;densidad de individuos) y medición de variables físico-bióticas (nivel de inundación, cobertura de &lt;em&gt;A. aureum&lt;/em&gt;, salinidad del agua intersticial, pH del suelo, % N, % limo, % arena, % COs, raíces y densidad aparente en el suelo) en 12 parcelas establecidas aleatoriamente. Con un CCA identificaron tres manglares: cuenca, borde en buen estado de conservación y borde con intervención antropogénica. El primero dominado por &lt;em&gt;A. germinans&lt;/em&gt; y los otros por &lt;em&gt;R. mangle&lt;/em&gt;. El manglar de cuenca se diferencia de los de borde en términos estructurales y en variables físico-bióticas, presentó los valores más altos de COs, salinidad, densidad aparente y pH. Aunque los dos manglares de borde presentan características físico-bióticas similares, la alteración antropogénica cambia fuertemente la estructura de uno de ellos. Se ha concluido que la distribución de las especies de manglar de la bahía responde a la variación espacial de las características ambientales. Sin embargo, la intervención antropogénica es una variable determinante en la estructura de los manglares lo cual afecta las estimaciones del papel de diferentes tipos de manglar como sumideros de carbono.&lt;/p&gt;

Root biomechanics in Rhizophora mangle: anatomy, morphology and ecology of mangrove’s flying buttresses

Rhizophora species of mangroves have a conspicuous system of stilt-like roots (rhizophores) that grow from the main stem and resemble flying buttresses. As such, the development of rhizophores can be predicted to be important for the effective transmission of dynamic loads from the top of the tree to the ground, especially where the substrate is unstable, as is often the case in the habitats where Rhizophora species typically grow. This study tests the hypothesis that rhizophore architecture in R. mangle co-varies with their proximity to the main stem, and with stem size and crown position. The allometry and wood mechanical properties of R. mangle (red mangrove) trees growing in a mangrove basin forest within a coastal lagoon in Mexico were compared with those of coexisting, non-buttressed mangrove trees of Avicennia germinans. The anatomy of rhizophores was related to mechanical stress due to crown orientation (static load) and to prevailing winds (dynamic load) at the study site. Rhizophores buttressed between 10 and 33% of tree height. There were significant and direct scaling relationships between the number, height and length of rhizophores vs. basal area, tree height and crown area. Wood mechanical resistance was significantly higher in the buttressed R. mangle (modulus of elasticity, MOE = 18·1 ± 2 GPa) than in A. germinans (MOE = 12·1 ± 0·5 GPa). Slenderness ratios (total height/stem diameter) were higher in R. mangle, but there were no interspecies differences in critical buckling height. When in proximity to the main stem, rhizophores had a lower length/height ratio, higher eccentricity and higher xylem/bark and pith proportions. However, there were no directional trends with regard to prevailing winds or tree leaning. In comparison with A. germinans, a tree species with wide girth and flare at the base, R. mangle supports a thinner stem of higher mechanical resistance that is stabilized by rhizophores resembling flying buttresses. This provides a unique strategy to increase tree slenderness and height in the typically unstable substrate on which the trees grow, at a site that is subject to frequent storms.

Distribution of Mangrove Habitats of Grenada and the Grenadines

Moore, G.E.; Gilmer, B.F., and Schill, S.R., 2015. Distribution of mangrove habitats of Grenada and the Grenadines.Mangroves of Grenada and the Grenadines represent significant habitat within the regional context of the Eastern Caribbean. Losses of mangroves through storms, development, and climate change have negative impacts on critical ecosystem services. Estimates of mangrove area exist in the literature but do not fully reflect current conditions, effects of disturbance, and results of recovery; they also do not differentiate these areas by community types. Advances in imagery and remote sensing approaches allow higher-resolution resource mapping. We used remote sensing, image interpretation, and field verification techniques to provide current estimates of the extent and distribution of mangroves. Our results provide the greatest areal total of mangroves to date. Despite loss of mangroves in the recent past, we accounted for approximately 15% more hectares than estimated in the 1990s and 28% more than predicted by hypothetical models for 2005. The discrepancies between prior and current mapped areas are likely due to differences in mapping precision and incomplete surveys that omitted the smaller Grenadine islands but also reflect actual increases in cover from natural recovery and recruitment following historic storm events. Basin mangroves represented the greatest area, while riverine and scrub contributed the least. Fringe mangroves were moderately abundant but were composed of small, isolated patches with high vulnerability to coastal storms and limited opportunity for inland retreat. Documenting the presence and distribution of mangroves, and specifically mangrove community types, will be of value to conservation, restoration, and management planning in light of predicted sea level rise and climate change effects.

Spatial and temporal variability in spectral-based surface energy evapotranspiration measured from Landsat 5TM across two mangrove ecotones

Coastal mangroves lose large amounts of water through evapotranspiration (ET) that can be equivalent to the amount of annual rainfall in certain years. Satellite remote sensing can play a crucial role in identifying regional ET trends and surface energy changes after disturbances in isolated and inaccessible areas of coastal mangrove wetlands, like those found in Everglades National Park in southern Florida. Using a combination of long-term datasets acquired from the NASA Landsat 5TM satellite database and the Florida Coastal Everglades Long-Term Ecological Research project, the present study investigates how ET as well as radiation and other energy balance parameters in the Everglades mangrove ecotone have responded to multiple hurricane events and restoration projects over the past two decades. An energy balance model using satellite data was used to estimate latent heat (λE) in tall and scrub mangrove environments. An eddy-covariance tower and weather tower supplied long-term data of multiple environmental and meteorological parameters that were used in calibrating and testing the modeled results from the Landsat images. Results identified significant differences in λE and soil heat flux measurements between the tall and scrub, and fringe and basin mangrove environments. The scrub mangrove site had the lowest λE rates, highest soil heat flux and lowest biophysical index (i.e., Fractional Vegetation Cover (FVC), Normalized Difference Vegetation Index (NDVI), and Soil-Adjusted Vegetation Index (SAVI) values. Mangrove damage and mortality associated with two strong hurricanes decreased FVC, NDVI, and SAVI, and increased soil heat flux at the tall mangrove site located in a basin-type environment. Recovery of the spectral characteristics, energy balance parameters and λE following hurricane disturbance was quicker in fringe mangroves than in basin mangroves. Latent heat fluxes (λE) were also relatively high after each storm and may have increased as a result of increasing vapor pressure deficits. Remote sensing of the surface energy balance and λE of mangrove forests can help our understanding of how these environments respond to disturbances to the landscape and the effect that these changes can have on the energy and water budget. Moreover, relationships between energy and water balance components developed for the coastal mangroves of southern Florida could be extrapolated to other mangrove systems in the Caribbean to measure changes caused by natural events and human modifications.