On the coast of Kerala, southwest India, oceanographic measurements were made at the beach, in the surf zone region, and on the inner shelf and then were combined with mechanism-focussed numerical modelling. The goal was to investigate the sedimentary dynamics of an open coast monsoonal beach. A closed sedimentary circulatory system (here described as a “step-ladder”) was identified. Strong annual cycles were observed in waves, winds, and currents. Regional-scale dynamic sediment equilibrium is maintained by an annual net northerly sediment flux in the near-shore, driven by wave-induced currents. This is balanced by a net southerly flux on the inner shelf, but driven instead by wind-induced currents that transport the wave-induced suspended sediment. The two counterdirectional sedimentary pathways are linked by cross-shore bridging transport. A clear association between the annual beach erosion and accretion patterns and the cross-shore direction of the near-bed bridging currents on the inner shelf was recorded and was associated with seasonal and shorter oscillations in the cross-shore component of wind, leading to inner shelf downwelling during the onshore wind periods and upwelling at other times. This occurs in synchrony with wave-induced beach erosion during the stormy onshore wind periods and accretion during the periods of narrow-banded swell and offshore winds, thereby delivering the sediment to or from the beach to be further transported on/offshore by shelf currents. Overall, the synchronous and supportive behaviour of the physical factors results in an unusual sedimentary equilibrium that explains how a strong net littoral drift can be sustained when supplies of nearshore feeder sands are absent.

Violent glacial bursts (jokulhlaup) are huge floods produced by subglacial volcanic eruptions. They are well known in Iceland. The biggest jokulhlaups come from Katla and can discharge water masses on a scale of several cubic kilometers into the ocean in just a few hours. Subglacial volcanoes can melt the glacier fast enough to produce 100,000–300,000 m³/s discharges for a long enough time to produce such floods. Geological evidence of such large floods exists, and it is concluded that historical floods like the one produced by the Katla eruption of 1918 have most likely been of this order of magnitude. Results from a computational fluid dynamics (CFD) simulation of a jokulhlaup down the Markarfljot valley in Iceland are shown. The flood is a translatory wave, and the existence of the translatory wave is established for an inclined plane in a prismatic channel and in a funneling channel as an initial value problem. Inherent instabilities of the wave tail are discussed. The energy and power emitted by the flood wave into the ocean is estimated, and transformation into a wave group suggested as a method to find the height of a tsunami-like wave hitting the Vestmannaeyjar Islands. Edge waves along the coast are discussed. Probabilities of jokulhlaups that might cause tsunami-like waves are reported.

Seabed accretion, formation of a local irregular shoal as the result of disposal of dredged sediment, and modifications of the coastline configuration from anthropogenic action have introduced significant changes in the physical processes involved in wave propagation, and consequently on the wave climate, in the nearshore area of Hac-Sá Bay, Macau. Statistical analysis of the wave data recorded at a wave-rider station located offshore the study area revealed seasonal, energetic, and directional variation tendencies of the wave regime and facilitated schematization of a representative offshore wave regime. Numerical modelling of propagation and transformation of the components of the representative offshore wave regime, including processes of shoaling, refraction, diffraction, reflection, and breaking, was applied to assess the nearshore wave climate before and after the major coastline and seabed morphological changes. An advanced and accurate numerical model, suitable for the case study, was applied. Comparison of the results obtained for both situations showed that significant changes occurred in the wave climate due to the morphological evolution.

Four sets of maps and aerial photographs have been integrated into a Geographic Information System (GIS) project to investigate coastal changes along a 60-km-long littoral sector in south Sicily, Italy. The beaches studied recorded significant morphological changes essentially related to the presence of human structures that interrupted littoral drift. Most of the investigated beaches experienced progressive erosion because of sediments being trapped by human structures resulting in the formation of wide beaches on the updrift side and erosion downdrift. The latter has often been counteracted by the construction of breakwaters. However, local planning authorities did not carry out an assessment of the impacts related to the construction of harbours and ports and their successive enlargement. This article proposes alternative actions concerning the possible future erosion management of the studied littoral.

The failure of coastal rock cliffs is attributed to a variety of factors such as weathering, wave action, ground water level, and rock and joint parameters. The wave-induced undercutting of the vertical cliff face is hereby assumed to play a critical role. Very little attention has, however, been paid to the gravity-induced stresses within the cliff face. A numerical analysis of the stress distribution in idealised rock cliffs of varying slopes (50–90°) and in various stages of undercutting has been conducted. Investigated parameters included slope angle, cliff height, influence of a cliff base cavity, front face loading, and cliff surcharge loading. The analysis showed that stresses in the cliff face geometry immediately after a failure were insignificant. With the steepening of the cliff, stresses increased to reach very high values for a vertical cliff face. Additional undercutting of the cliff resulted only in a slight increase of those stress magnitudes. The steepened rock cliff can result in an unstable equilibrium condition, depending on cliff geometry and the ratio of gravity-induced stresses (a function of cliff height) and material strength, which can lead to sudden cliff failure. The results of this study indicate that the most important parameter in cliff destabilization is wave-induced steepening of the cliff slope.

A two-dimensional wave flume investigation was conducted to examine the effect of multiple steps on the form of breaking waves. The study was initiated to gain a better appreciation of the design tolerances for artificial surfing reefs. The geotextile bags used to form an artificial surfing reef create multiple steps in the seabed; reducing the size of these steps improves the quality of waves for recreational surfing but comes at considerable economic cost. Sets of steps were placed on a 1 : 15 slope, and image analysis methods were used to quantify the effects of increasing step size on the form and intensity of the breaking waves. The vortex area, angle, and length-to-width ratio were quantified for various step sizes. It is shown that breaking intensity decreases with increasing step size. Variations in wave reflection were measured using a three-element surface-piercing wave gauge. Wave reflection coefficients were found to be unchanged for all step sizes implemented in this experiment, and reflection was not found to significantly affect the form of the breaking waves in the current tests. The quality of the surfing waves for recreational surfing was seen to degrade measurably with increasing step size, with a higher degree of variability and irregularity in the vortices of the plunging breakers. A qualitative assessment of the quality of the breaking waves suggests that step size should be limited to approximately 23% of the design wave height.

Anglet beach, located in the south of the French Atlantic coast, has been experiencing severe erosion for several decades, whereas recurrent dredging has been necessary to fight against the shoaling of the mouth of the Adour River. The channel entrance is protected from the very energetic wave climate by a main jetty, the effect of which on the system appears to be crucial. In this paper, we study the relationship between the two systems in terms of sedimentary exchanges. First, we determine the time history of volume of subtidal beach sand with a bathymetry dataset spanning 24 years. This analysis highlights continuous and large erosion affecting the subtidal part of Anglet beach. This phenomenon had been masked until 1990 thanks to dredged sand releases. However, after that date, the drastic reduction of artificial sediment intakes led to a drop in the sand volume. Numerical modeling is used to study the flow pattern around the mouth of the river. Different wave scenarios are simulated with the TOMAWAC spectral model. The flows induced by waves and tides are then computed with TELEMAC2D (EDF/DRD). The sheltering effect of the jetty on waves is found to generate cross-currents directed to the river mouth. The magnitude of these currents is strongly dependent on the wave class energy and sea level. Local sediment fluxes are then estimated at the limit between systems. This calculation shows that cross-currents induced by the three most energetic wave classes could be entirely responsible for the sediment motion from the coast of Anglet to the mouth of the Adour River.

A comparison of two sections of the Outer Banks, North Carolina, USA (Pea Island and Avon-Buxton areas), reveals the importance of the interplay between oceanic and estuarine shoreline dynamics to long-term changes in barrier island width. From 1852 to 1998, the northern portion of Pea Island experienced an average net increase in width of 431 m (3 m/y); this area experienced low to moderate rates of oceanic shoreline erosion and high rates of back-barrier land accretion via overwash and formation of flood tidal delta islands. In contrast, between 1852 and 1998, the width of the southern portion of Pea Island and the Avon-Buxton area decreased an average of 515 m (4 m/y) and 594 m (4 m/y), respectively, because of high rates of oceanic shoreline erosion and variable changes in estuarine shoreline accretion and erosion. Net gain or net loss of barrier island width is strongly dependent on the natural depositional processes of overwash and flood tide delta formation. Anthropogenic modifications to the barrier island, such as construction of barrier dune ridges, planting of stabilizing vegetation, and urban development, can curtail or even eliminate the natural, self-sustaining processes of overwash and inlet dynamics.

Isles Dernieres is a transgressive barrier island arc in southeast Louisiana associated with the Bayou Grand Caillou headland of the Lafourche delta complex, which was abandoned 600 to 800 years ago. During the past two decades Trinity and Whiskey Islands have been eroding at rates of >18 m/y, and East Island has been eroding at a rate of 11.8 m/y. The Isles Dernieres Barrier Island Stabilization Project, implemented in 1998, dredged material from various sites in the bay behind the barriers for dune and marsh restoration of East, Trinity, and Whiskey Islands. The 1998 restoration increased the overall height and width of the islands but marsh habitat has not developed on the restored material behind the barriers. This study characterizes the physical and chemical properties of soil from restored and natural back-barrier salt marsh on Isles Dernieres to determine the restoration timeframe in which restored marsh soils develop to conditions more similar to natural marsh soils. Additionally, the goal is to identify the soil properties in restored marsh that could be modified to enhance back-barrier marsh habitat.

Laboratory analyses of 60 cores from four different vegetation density classes in restored marsh and nine cores from natural marshes included bulk density, soil moisture content, grain size, sorting, pH, conductivity, total carbon, and total nitrogen. Vegetation density in restored marshes had no significant effect on soil properties, with the exception of bulk density. Marsh type had a significant effect on all measured soil properties. Variations in the soil properties of restored and natural back-barrier salt marsh are primarily the result of differences in soil texture and elevation.

The inner zone of Bahía Blanca Estuary is a shallow, well-mixed, highly turbid, and nutrient-rich temperate ecosystem. The phytoplankton annual cycle is characterized by a recurrent winter/early-spring diatom bloom. From May to August 2002 a research program aimed to describe the potential relations between the dynamics of phytoplankton and nutrients was carried out. Phytoplankton composition, abundance, chlorophyll a (Chl a), and dissolved inorganic nutrients (nitrate, nitrite, ammonium, phosphate, and silicate) were measured. The species involved were classified in blooming (including Thalassiosira spp. and Chaetoceros spp.) and nonblooming species (including other diatoms and dinoflagellates).

The results show: (1) a prebloom period, which includes low biomass values and a strong decrease of NO₃⁻; (2) an initial bloom period characterized by high diatom abundance and Chl a, a marked dominance of Thalassiosira curviseriata, and a strong decrease of NH₄ ; (3) an intermediate bloom period of high abundance, codominance of blooming species, and a strong decrease of PO₄³⁻; and (4) a final bloom period with a decrease in abundance of blooming species and a general nutrient recovery. Thalassiosira curviseriata seems to be a species associated with high nutrient stock and low light intensity. Its growth, mainly concurrent with DIN decrease, was related to new production in this area. The obtained data suggest that low phosphate concentrations, more than DIN and silicates, contributed to the diatom bloom collapse. According to our results, this high production during winter can be explained as a net growth of phytoplankton because of a successful low light- and temperature-acclimated species, possibly favored by low predation and high nutrient availability.

Towed underwater video has become a widely used method for bottom habitat mapping in coastal waters, but very little has been published on this relatively new and effective approach. We use a case study on two oyster reefs to illustrate the pros and cons of towed video, visualization techniques, and future research topics. Towed video is deployed in similar fashion to single-beam sonars, yielding narrow swaths of video imagery that are recorded concurrently with global positioning system (GPS) data for georeferencing. The major advantages over acoustic (sonar) methods are that image processing and interpretation are relatively simple, and there is little or no need for subsequent ground-truthing. The system used in the present study consists of an underwater black and white camera mounted on a steel frame, differential GPS unit, and digital video camera for recording. It was assembled from off-the-shelf items, and total cost was approximately $3500 (2006 US$). The imagery from both study reefs was of sufficient quality to allow classification of the surveyed bottom into three categories: nonreef, low-density shell, and high-density shell. Some reef characteristics such as the amount of vertical relief were easily discernable and showed substantial differences between the two reefs. Reef bottom areal coverages determined from the video imagery compared well with recent previous studies on the two reefs using other methods. Water clarity limitations represent the major obstacle to widespread use of video for routine mapping of oyster reefs. Turbidity–image quality relations remain to be quantified.

Coastal dynamics and shoreface relief in ice-free seas are a function of hydrodynamic interactions between the sea and bottom sediments. In the Arctic, additional, cryogenic factors such as permafrost and the action of sea ice influence coastal processes. The goal of our paper is to assess this influence, mainly on the profile shape. Mathematical analyses of the shape of 63 shoreface profiles from the Laptev, Beaufort, and Chukchi Seas were carried out. The shapes of Arctic shoreface profiles and those of ice-free seas are compared. We found that large ice and silt content in perennially frozen sediments composing Arctic coasts favor their erosion. Sea ice plays an important role in sediment transport on the shoreface and correspondingly changes shoreface relief significantly. Some effects of ice intensify coastal erosion considerably, but others play a protective role. The overall influence of cryogenic processes on Arctic coasts composed of loose sediments is seen in that the average rate of coastal retreat is larger than in the temperate environments, even though Arctic coasts are protected by a continuous ice cover most of the year. The shape of the shoreface profile in the Arctic does not differ from that in ice-free seas, and is satisfactorily described by the Bruun/Dean equilibrium profile equation. The explanation of this fact is that all changes of the profile shape, caused by cryogenic processes, are short lived and quickly eliminated by wave action.

Ammophila arenaria (L.) Link (marram grass) is the most important sand-fixing plant species along the northwestern European and Mediterranean coast, and it is also planted worldwide for sand dune stabilization. In spite of the intense use of this species in foredune restoration and stabilization programs, little is known about the genetic diversity within and between populations. We analyzed the genetic diversity of seven European populations of A. arenaria using inter-simple sequence repeats (ISSR) markers. The studied populations were selected in Wales, England, Belgium, the Netherlands, Portugal, and France. One half of the populations showed similar values of genetic diversity. The lowest values (Nei's index =0.17) were found in the population from the Netherlands, which had been established after a foredune reinforcement project, and in a declining population in the south of Portugal. Statistical and phylo-genetic analyses revealed genetic differences between populations, and northern and southern clusters that corresponded to the two subspecies of A. arenaria. We propose that plant material for dune vegetation re-establishment programs should be collected locally rather than from remote populations that might be less well adapted to the local conditions of the planting site. However, when using local clonal plant material, care should be taken to collect the plant material from a number of sampling sites in order to ensure the genetic diversity of the new stands.

As Australia's longest fringing reef, Ningaloo Reef lies close to the mainland of northwest Australia in an area of high tourism potential. The establishment of sanctuary zones in and around the northern Ningaloo Marine Park has necessitated improvements in understanding of the biodiversity and distribution of habitats and substrates in the reef lagoon, its seaward barrier, and the adjacent shelf environments. Using a combination of video transects in forereef-to-shelf environments, global positioning system-controlled ground-truthing of colour satellite images, and aerial photography for shallow lagoon settings, 16 habitat types were identified and mapped regionally. Lagoon substrates described in previous reconnaissance were mapped here in greater detail, and some of the first data on poorly known forereef and shelf communities have been analysed from the video transects. There is a strong correlation between reef morphology, inherited substrate type, and coral communities across reef lagoons and their associated barriers, where an energy gradient controlled by wave-driven and tidal circulation in reef flat and lagoon environments is reflected in the distribution and cover of robust to more delicate coral communities. Morphological controls are less distinct in island-associated habitats, where increased turbidity, differing wave energy, and more variable topography result in higher substrate variability and increasing soft coral communities. The data obtained in this study provide a background for management of biodiversity and monitoring of future impacts in some of the sanctuary zones likely to experience increased use in the northern Ningaloo Reef.

Over the past 20 years, fractal geometry has gained acceptance as a valid quantitative method for describing complex geomorphic patterns in nature. One goal of geomorphology is to relate geologic processes to the development and evolution of landforms. The processes (factors) that shape a landform might produce a characteristic geometry that can be interpreted through fractal analysis. The geometry of a shoreline is often cited as an example of a fractal pattern. Previous studies on shoreline geometries have used relatively small-scale maps and aerial photographs, and have not studied the changing geometry of a shoreline over time. This study, in contrast, examines the fractal geometry of six wave-dominated marsh shorelines in Rehoboth Bay, Delaware, at a relatively large scale, and investigates how these geometries change over time. The results help to understand the relation between geomorphic features and processes. An automated box-counting method was used to calculate fractal D values for each shoreline. D values ranged from 1.01 to 1.19, which are lower than previous shoreline studies. The greater D values are associated with sites that experienced the greatest wave erosion. Furthermore, the geometric complexity of these shorelines did not change over 3 years. In comparison, D values obtained from a tide-dominated marsh shoreline were greater (1.27), suggesting that the dominant formative process (e.g., tides vs. waves) may be distinguished through geometric analysis. However, to use fractal data as a comparable geomorphic tool, it is necessary to choose features of a similar size (scale) and from a similar geomorphic setting. In this way landform complexity (D) is likely due to either (1) the type of shaping process in different geographic settings, or (2) the magnitude of a single shaping process within a single geographic setting.

Heavy-metal pollution is an issue of concern in estuaries influenced by agriculture, urban, and harbor activities. Foraminiferal assemblages have been shown to be effective indicators of pollution. Sediment samples (n = 110) from Biscayne Bay were analyzed for heavy metals, foraminiferal assemblages, and grain-size distribution. Highest Cu, Zn, Cr, Hg, Pb, and Ni concentrations were found closest to Miami and near the mouths of several canals along the western margin of the bay. Few samples exceeded limits of possible biological effects as defined by previous studies. Ammonia and Cribroelphidium, two known stress-tolerant genera, correlated positively with Cu, Zn, Hg, and Ni (r ≥ 0.43). Symbiont-bearing foraminifers, Archaias, Laevipeneroplis, and Androsina, correlated negatively with Cu, Zn, Hg, and Ni (r ≤ −0.26).

Scarce land resources and growing population are compelling issues for intensively developing coastal zones in China. During the past 30 years, many coastal tidelands have been enclosed for cultivation and development. To plan and implement large-scale reclamation programs in coastal zones, timely and reliable information concerning the nature, extent and physicochemical characteristics of the coastal saline soils land is essential. Because extracting useful information from optical remote sensing imagery is often hampered by the presence of clouds and wet weather, in this study we used multitemporal European remote sensing satellite (ERS)–2 PRI synthetic aperture radar (SAR) images only for coastal land use mapping. The SAR multitemporal backscattering characteristics of main land use categories were first investigated after pseudocolor synthesizing of three temporal SAR images, extracting dikes and partitioning the study area into six subzones according to the reclamation years. Next, an iterative self-organizing data analysis (ISODATA) unsupervised classifier and a BP neural network classifier were used for the land use classification in different subzones, achieving an overall classification accuracy of 77.34% and a kappa coefficient of 0.74. In this study, we demonstrated that SAR imagery, instead of or complementary to optical satellite data, has great potential for land use mapping or resource investigations in coastal zones under rapid development.

Fossil molluscan assemblages from 12 radiocarbondated short cores have been considered and integrated with information from archaeology, tectonics, and relative sea-level change in order to define the Holocene evolution of the Stagnone di Marsala, a sound along the western coast of Sicily that experienced at least 3000 years of human impact, since the Phoenician times.

During the considered time span, we have no evidence of emersion, though the occurrence of a very restricted circulation is recorded at the base of very shallow cores dated 1240 ± 50 and 1560 ± 40 years BP. We hypothesise that the Phoenician road, now submerged, connecting the Island of Mozia with the Sicilian mainland, was critical in isolating a marshy environment along the southeastern coast of the Stagnone before about 1600 years BP. Our cores show that the molluscan association typical of the superficial muddy sand in sheltered areas (SVMC) has been always dominant at the basin scale, conformably to the present-day situation.

Multivariate statistical analyses were performed on abundance data of molluscan associations resulting in four clusters that describe different aspects of the SVMC biocoenosis: the first characterised by the sediment-related SVMC species, and the other three associated with a more mud-rich sediment, with a prevalence of taxa related to the leaf stratum of Posidonia, Cymodocea, or to seaweeds. In contrast with the present-day situation, we record a past occurrence of Posidonietum in the northern basin at about 3600 years BP, corresponding to a period of more open circulation. This phenomenon was induced by channels, now closed by saltworks, that cut the present-day Isola Grande into islets.

Sandy bay beach in static equilibrium is the only physiographic feature that could remain stable without sediment supply in a persistent swell environment anywhere around the world. With a continuing trend of erosion to sandy beaches worldwide, a conservative and practical hypothesis is not to consider the mobile dynamic wave parameters but to safeguard against a sandy beach under vanishing supply in the future. To achieve this, an empirical bay shape equation is strongly recommended as one of the best coastal management options. Combining with MEPBAY, software derived for implementing the static bay beach concept on a display unit, this empirical bay shape equation is readily applicable to verify the stability of numerous headland bay beaches in natural and man-made condition. It is also adequate for coastal managers to apply this empirical equation as a valuable tool to aid in the creation of headland bay beaches for shore protection, recreation, and coastal management before embarking on sophisticated numerical modeling.

In this study, we aimed to document the run-up and inundation of recent tsunamis and loss of life in the December 26, 2004, tsunami in the Andaman and Nicobar Islands. An estimated 1925 people lost their lives and 5555 were reported missing in the Andaman and Nicobar Islands because of the tsunami. The Nicobar group of Islands—namely Great Nicobar, Katchall, Teressa, Nancowry, Trinkat, Car Nicobar, and others—were severely affected by tsunami because they were close to the epicentre. The effect on the Andaman Islands was less severe because of the island's geometry and topography. Because the settlements in the South Andaman Islands are largely confined to sheltered areas like bays that are far from the coast, and more importantly, in elevated areas (except for certain low-elevation, far inland locations like the Sippighat area) there was almost no loss of life. However, damage to property, especially fishing vessels, was high in most of the area, where seawater inundated the land completely. This field survey was conducted at 26 sites; the Little Andaman passenger jetty area recorded the highest run-up of 17.26 m, and the Chidiyatopu area had the highest inundation at 500 m. Furthermore, this survey also supports the assertion that the low-lying areas of Little Andaman were severely affected by the tsunami waves because of their gradual elevation increase.

A significant challenge to remote sensing of submerged ecosystems in the littoral zone is correcting the signal received at the sensor for the complex and variable effects of the water column. Remote sensing scientists often assume that the optical properties of a scene do not vary horizontally and thus assume that a single attenuation coefficient can be applied for water column correction. The validity of this assumption is tested in this case study. Multispectral vertical water column profiles were collected in the field with a dropsonde radiometer to examine the wavelength-specific behaviour of light in a tropical coral reef environment with variable water depths and bottom types. Cluster analysis results indicated that on a wavelength-specific basis, the majority (no less than 70%) of both the downwelling irradiance and upwelling radiance profiles can be categorized as one cluster, indicating that the assumption of horizontal consistency is valid. ANOVA revealed that significant variability in downwelling irradiance and upwelling radiance attenuation coefficients is explained by water depth when bottom type remains constant. Conversely, ANOVA also revealed that insignificant variability is explained by change in bottom type when water depth remains constant.

Nearshore turbidity due to suspended fine sediment is a natural phenomenon around much of the western coast of southern Africa. However, there is concern about the potential impact on biotic communities of an increase in turbidity as a result of mining by means of marine dredgers. This paper discusses field measurements and the validation and application of mathematical models in investigations of the structure, composition, and decay of fine sediment plumes induced by dredging on a wave-dominated coast. In addition, the resuspension and mobility of the fine sediment deposited as a result of dredging are assessed. The expected trends of horizontal decay of concentrations with distance from the dredger and higher concentrations at greater depths were confirmed. The extent of plumes (i.e., where concentrations return to background levels) was predicted to be some 4 km at most, while a plume life span well in excess of 3 h was indicated. This extent and longevity of suspended sediment plumes were attributed to the high mobility of fine sediment in a wave-dominated environment resulting from elevated bed shear stress induced by swell wave action. Predictions indicate that these highly mobile fine sediments are transported tens of kilometres within weeks after discharge.

To determine whether multipolarized spaceborne synthetic aperture radar could be used to monitor the health of a mangrove forest, leaf area index, as well as other biophysical parameter data, from stands dominated by white mangrove (Laguncularia racemosa) and located within a degraded mangrove forest were examined in relation to backscatter coefficients from ENVISAT synthetic aperture radar scenes. The results indicate that polarization and, to a lesser extent, incident angle play a significant role in the ability to estimate both leaf area index and mean tree height. No significant linear coefficients of determination were observed between the recorded parameters and the backscatter coefficient from any of the copolarized scenes. With regards to leaf area index, r² values of 0.82 and 0.73 were calculated for the cross-polarized data at two incident angles. For mean tree height, the linear coefficient of determination was much higher for the smaller incident angle data than for the larger incident angle data. No significant relationships were identified for stem density, basal area, or mean diameter at breast height. It is postulated that the inability of the copolarized ENVISAT advanced synthetic aperture radar data to differentiate between dead mangrove stands and healthy ones is the result of equally high backscatter resulting from strong scattering from trunk–ground double bounce and crown volume, respectively.

Six Mile Reef, a sandy, 22-m-high shoal trending east–west and located about 7.8 km off the Connecticut coast, has a core of postglacial marine deltaic deposits mantled by tidally reworked modern sediments. Sedimentary environments off the eastern end of the shoal are characterized by processes associated with long-term erosion or nondeposition, a mobile-sediment-limited seafloor armored by gravelly sand, and scattered elongate fields of barchanoid sand waves. The barchanoid waves reach amplitudes of 20 m, are concave westward, and occur in individual and coalesced forms that become progressively more complex westward. The seafloor on and adjacent to the shoal is characterized by processes associated with coarse bedload transport and covered primarily with asymmetrical transverse sand waves. The transverse waves exceed 8 m in amplitude, have slip faces predominantly oriented to the west and southwest, and have straight, slightly sinuous, and curved crests. Megaripples, which mimic the asymmetry of the sand waves, are commonly present on stoss slopes and in troughs; current ripples are ubiquitous. The amplitude and abundance of large bedforms decrease markedly westward of Six Mile Reef. The seabed there is covered with small, degraded ripples, reflecting lower-energy environments and processes associated with sorting and reworking of sea-floor sediments.

Megaripples and current ripples on the sand waves suggest that transport is active and that the bedforms are propagating under the present hydraulic regime. Net bedload sediment transport is primarily to the west, as evidenced by textural trends of surficial sediments, orientation of the barchanoid waves, and asymmetry of the transverse waves and of the scour marks around bedrock outcrops, boulders, and shipwrecks. One exception occurs at the western tip of the shoal, where sand-wave morphology indicates long-term eastward transport, suggesting that countercurrents in this area shape the shoal and are important to its maintenance.

Many previous studies demonstrate that carbon stable isotope composition (usually expressed as isotopic ratio, δ¹³C) can reflect the integrated response of physiological processes to environment, but little is known of the variation in δ¹³C of mangrove plants as affected by salinity, especially in response to long term saline environment. The variation in δ¹³C of three dominant mangroves growing in long-term saline environments in the field was assessed. Mature leaves of Avicennia marina (Forsk) Vierh., Kandelia candel (L.) Duce., and Aegiceras corniculatum Blanco. were collected at seven sample sites covering seven salinity levels (14.07%–19.83%) at a natural mangrove wetland located in southeast China. The δ¹³C values varied from −31.46% to −27.33‰ with increasing salinity, reflecting the typical C₃ pathway of CO₂ fixation. The δ¹³C was positively related to salinity in K. candel and A. marina, and the reverse was observed in A. corniculatum, even though the correlations were not statistically significant for A. corniculatum and A. marina. The mean δ¹³C at high salinity was, in descending order, K. candel > A. marina > A. corniculatum. It is concluded that responses of δ¹³C to salinity is species-dependent and assessment of carbon isotopic composition is helpful for evaluating the salt tolerance of mangrove species, but it should be used with caution when comparing the salt tolerance between different species, particularly when they have the different patterns of δ¹³C in response to salinity.

This study applied a new approach to distinguish between breaking waves and nonbreaking waves in the wind–wave time series through the use of wavelet analysis.

In this paper, the wavelet power spectrum is computed to identify the variations in the energy content of the wind–wave time series with time, and then it is integrated over frequency to provide the temporal variation of localized total energy.

The study shows that the fluctuations of the time series of wind–wave are highly intermittent, i.e., the energy at different scales varies considerably with time. Furthermore, the local peaks of the energy densities correspond to the events of wave breaking in the wind–wave time series.

Passage of hurricane Wilma (October 2005, category 4, duration ∼60 h) over Puerto Morelos, Mexican Caribbean, allowed verification of a previous experiment simulating hurricane-like impacts on the seagrass beds in its back-reef lagoon. At two mid-lagoon stations, numbers of the seagrass Syringodium filiforme and macroalgae Udotea spp., Penicillus spp., and Rhipocephalus spp. were reduced significantly, whereas populations of the seagrass Thalassia testudinum and Halimeda spp. were unaffected. These impacts of the hurricane supported the results of the simulation experiment. Differential results were registered at one station for the spongy-like algae Avrainvillea spp. and Cladocephalus sp., which were not affected by the simulation treatments but were reduced in number by the hurricane. Thus, apart from known impacts such as complete or partial destruction of seagrass beds, hurricanes may also change the community structure of persistent beds through species-specific elimination.