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The probability of extreme sea levels along the coasts has always been statistically estimated from the series of local observations. The inference is never conclusive, and an attempt is given here to improve the methods already used with reference to the area of the English Channel. The joint probability method (JPM) is the starting point: In most cases it underestimates the return times (or overestimates extreme levels at a fixed time). The proposed extension is based on a more careful use of observed extremes by fitting a coefficient Cc deduced from the data set, which requires that the maximum record height be in agreement with the return period of the record length. This correction calibrates the whole series of extreme estimations to the observed maximum. Likewise an attempt to roughly explain this correction is given that explores the tide–surge interaction and seasonal dependence. The parameters are specifically computed for 15 tide-gauge stations, and the comparison is extended to other known methods, like the Gumbel one (in most cases overestimating the levels) and GEV simulations (which appear much better). Finally extreme levels with estimated return times of 10, 50, and 100 years, respectively, are proposed for each site, and a test for validity was performed by splitting certain long records into small samples, thus checking the spread of the results.
Foreshore (intertidal) narrowing and steepening have become increasingly discussed issues in coastal management. With rising sea levels they could be expected to lead to higher wave energies reaching the shore, thus enhancing rates of erosion. The present paper investigates changes in the position of the tide lines in Southeast England as measured from historic and modern maps. The changes can be partly explained by sea-level rise and shore platform erosion, but appear to be due mainly to systematic errors associated with the map sources. Comparison of the positional change of tide lines along the 170 km of chalk coast from East Sussex to the Isle of Thanet suggests that evidence for large-scale foreshore narrowing is meagre. The most likely scenario is one of parallel profile retreat resulting from natural processes such as relative sea-level rise.
The accumulation of acid-volatile sulfides and its relation with other trace metal-binding sediment constituents may be important mechanisms to determine the suitability of anaerobic sediments to trap trace metals. An investigation into the relationships among acid-volatile sulfides, total organic carbon, and reactive (hydrogen chloride–soluble) iron, manganese, and trace metals of environmental concern (cadmium, copper, nickel, lead, and zinc) was conduced in anaerobic sediments from a disturbed mangrove ecosystem in Sepetiba Bay (SE Brazil). The two main metal contaminants in the study area (cadmium and zinc) presented levels above regional backgrounds (showing enrichment factors up to 8.5 and 9.1, respectively) and a significant correlation, suggesting a contamination source similarity. Positive correlations among total organic carbon, acid-volatile sulfides, and iron and negative correlations of manganese with total organic carbon and acid-volatile sulfides occurred, probably because of (1) organic matter fuelling of acid-volatile sulfides production and depletion of manganese levels due to manganese oxide consumption by microbial respiration and (2) manganese oxide depletion in reaction with acid-volatile sulfides. The elevated acid-volatile sulfides concentrations and inventories observed, exceeding those of metals of environmental concern, indicate the sediment suitability to trap these metals as metal sulfides. While comparatively low manganese concentrations are probably unable to influence acid-volatile sulfides distribution, results evidenced that acid-volatile sulfides may affect manganese distribution negatively. To our knowledge, this negative metal–sulfur relationship was demonstrated for the first time in sediments from a tropical coastal ecosystem, which may help elucidate the behavior of manganese and manganese-associated elements in anaerobic mangrove sediments.
Direct observations of the storm surge and the subsequent long-wave response induced by Hurricane Wilma's landfall on the West Coast of Florida on 24 October 2005 are presented. The data set consists of weeklong time series of storm surge and barometric pressure measured by the U.S. Geological Survey (USGS) Florida Integrated Science Center. The survey area spanned more than 100 km alongshore from the landfall site northward. The USGS data were augmented with measurements at the National Oceanic and Atmospheric Administration tide gauge and Coastal Marine Automated Network (CMAN) stations. At the time of Wilma's arrival, the storm surge was minimal to the north of landfall site but was significant in the southern sector. Subsequently, it evolved into an edge wave pulse propagating northward as Wilma moved inland and the surge was no longer sustained by the wind forcing. The height of the wave pulse exceeded 1.5 m in detided sea level data. However, its magnitude was somewhat obscured in direct surge measurements because the wave pulse propagated during the low tide. The duration of this wave pulse was approximately 6 hours. The propagation speed of the wave front was ∼25 m s−1, while the pulse crest traveled at a lower speed of ∼10 m s−1, which indicates the dispersion effects. A relatively low phase speed suggests that the wave energy was trapped nearshore, in the water depth of 10–20 m. The wave pulse was followed by a train of weaker wavelike undulations, also propagating northward. The edge wave pulse seemed to be attenuated by a complex topography in the vicinity of Sanibel Island–Pine Island.
The transport and distribution of sediments driven by mechanisms such as tides and waves, river discharges, wind stress, and turbidity currents and the sediment transport effects can be studied by remote sensing techniques. The study of total suspended matter concentration has ecological importance since it is the main carrier of various inorganic and organic processes.
The main objective of this work was to evaluate the performance of different statistical methodologies in the estimation of total suspended matter concentration, in the breaking zone and in its adjacent area, using multispectral satellite images from TERRA/ASTER, SPOT/HRVIR, and Landsat/TM. These images cover a particular area of the northwest coast of Portugal.
The relationship between the total suspended matter concentration and the spectral response of the seawater, in the visible and near-infrared regions of the electromagnetic spectrum, was quantified through simulations on different beaches of the study area.
Seven images of TERRA/ASTER, SPOT/HRVIR, and Landsat/TM sensors were calibrated and atmospherically and geometrically corrected. Linear single-band models, linear multiple regressions, and artificial neural networks were applied to the visible and near-infrared bands of these sensors in order to estimate the total suspended matter concentration. Statistical analysis using determination coefficients and error estimation was employed, aiming to evaluate the most accurate approach in the estimation of total suspended matter concentration.
The analysis of the root-mean-square error achieved by both linear and nonlinear models supports the hypothesis that the relationship between seawater reflectance and total suspended matter concentration is clearly nonlinear. Artificial neural networks have been shown to be useful in estimating the total suspended matter concentration from reflectance of visible and near-infrared bands with images of ASTER, HRVIR, and TM sensors, with better results for ASTER and HRVIR sensors. The artificial neural network approach was further applied to the seven processed images, and maps of total suspended matter concentration for all satellite images processed were produced.
Coastal dunes display complex relationships among soil properties, vegetation, and geomorphology driven by marine and atmospheric dynamics. Considering topography as a fundamental control of the relations, this study investigated its influence on the spatial pattern of soil attributes in a coastal dune. We systematically collected 193 soil samples at intervals of 20 m from the Sindu coastal dunefield, South Korea, and analyzed 11 soil attributes. Principal component analysis extracted four main factors explaining ca. 75% of total soil variance. Correlation between each soil factor and topographic attributes calculated from raster digital elevation models permitted us to infer relationships between dune configuration and soil spatial variability. Interpretation of the first two factors demonstrated that nutrient input from marine sources by aeolian processes and topographic relief, an indirect measure of depth to the freshwater table, were two major determinants of the spatial distribution of soil properties. For the first factor, distance from the seashore proved to be the most significant indicator of edaphic conditions. Upslope area and wetness index were good proxies for the second factor, dune relief. These two variables significantly explained the distribution of soil moisture. A conceptual model is presented to describe how complex dune soil systems are created from simple topographic effects. The model addresses the importance of integrating foredune, dune slack, and inner dune ridge into one continuous system because topography, geomorphic (aeolian) processes, vegetation, and edaphic conditions are closely connected in a causal chain across the whole dune area.
In the last few years, radar technology has been given strong consideration for sea level monitoring. France has been a pioneer in the use of radar technology for its tide gauge network, and the first results of an 8-year-long experience are presented. The performance of the radar sensors has been assessed using the Van de Casteele test, which has been revealed to be an efficient method for detecting the main deficiencies of the installations and evaluate the data quality. The experience so far shows that radar tide gauges present interesting advantages with regard to ease of operation and that their accuracy is consistent with GLOSS 1-cm requirements, provided the installation is correctly performed.
Removal of beach-cast Posidonia oceanica seagrass litter, called “banquettes,” is a common practice on Mediterranean shores to allow the recreational use of beaches. Ongoing removal practices of P. oceanica banquettes were analyzed on the island of Sardinia to quantify this phenomenon on a broad scale and to evaluate the potential environmental impacts of banquette removal and dumping on the coastal zone.
Data on banquette management were collected by means of a questionnaire given to the coastal municipalities and private companies in charge of beach-cleaning operations during 2004.
P. oceanica banquette removal resulted in a widespread practice applied on 44 beaches (out of 116). The total removed amount for 2004 was estimated at 106,180 m3. Heavy machines were generally used to remove banquettes.
Relationships between banquette removal and beach characteristics showed that higher quantities removed resulted in low-energy beaches.
The amount of sediment subtracted to the beach following removal was evaluated by analyzing sand concentration in banquettes collected at three locations. Mean sediment concentration in banquettes was 92.8 kg m−3. This value, multiplied for the amount of banquettes removed, allowed us to evaluate the sediment subtracted from each beach between 0.5 and 1725 m3. Furthermore, the majority (80%) of the volume removed was dumped in unauthorized areas.
Following the findings of the study, some management measures are suggested in order to minimize environmental impact of banquette removal.
Storm surge is a serious natural disaster coming from the sea. It is an abnormal sea surface rising caused by strong atmospheric disturbances, such as strong winds and sudden changes in atmospheric pressure. Therefore, accurate prediction of surge deviation is an important task to avoid property losses and to reduce risk caused by typhoon surge. Many conventional numerical methods for typhoon surge prediction have been investigated, but it is still a complex ocean engineering problem. This article applied a neural network combined with harmonic analysis to predict storm surge and surge deviation. The original data from the Suao Harbor station, Taiwan, invaded directly by a typhoon, will be used to verify the present model. Comparisons with two numerical methods, the MIKE 21 model and the U.S. Federal Emergency Management Agency's model, indicate that storm surge and surge deviation can be efficiently predicted using a neural network.
Current and sea level measurement data from three ∼75-day deployments at the inlet and the inner shelf of the Caimanero Lagoon were used with data of wind, evaporation, and river discharge to describe the seasonal subtidal exchange in the shelf–lagoon system. During the dry season, the estuary mouths were partially closed by the littoral drift; however, at the shelf, the oceanic mean sea level rose because of a steric response to advection of warm water on the continental shelf. In addition, the annual oscillation reached its maximum in August. Both events induced a barotropic flow of sea water lagoonward. Dry season currents were 8–10 cm s−1. During the wet season, estuary mouths were reopened as result of river discharges, which caused a barotropic flow toward the sea. During this period, river transport occurred at times scales of 2∼10 days; the magnitude of the transport was larger than that caused by the sea level. Wet season currents were 10–40 cm s−1. The observation that this barotropic flow occurred during both seasons is the principal discovery of this work and demonstrates that the barotropic motion is an important component of net circulation. The shelf circulation during the dry season showed a two layer system with a cross-shore flow toward the shore with velocities of about ±5–10 cm s−1, while longshore current flow was southward on the surface and northward (up gulf) below 15 m. This current pattern apparently contributes to the transport of shrimp larvae to the shore, acting as the driving mechanism, knowing that shrimp postlarvae in the area appear in June and disappear in middle August. During the wet season, on the other hand, inner shelf circulation shows currents of mainly barotropic flow that respond to hurricanes with maximum velocities of about 40 cm s−1.
The processes of upwelling off the southern tip (the Kanyakumari coast) and the west coast of India are highly localised features with different forcing mechanisms, and they cannot be treated as a uniform wind-driven upwelling system. Off the Kanyakumari coast, upwelling is due to the south-west monsoon winds that are tangential to the coast. Along the west coast, the area between 8° N and 9° N represents the shadow zone to the influence of the remote forcing on the upwelling; the latter is forced by the longshore wind stress. Moderate to relatively intense upwelling occurs along the Kollam to Mangalore coast (9° N to 13° N) due to the combined action of the longshore wind stress, the coastally trapped Kelvin waves, and the offshore propagating Rossby waves. North of this area (13° N to 15° N), upwelling is weak due to weak wind stress and is closely confined to the coastal belt. This results from the suppressive effect of the southwards-flowing Arabian Sea high saline water on the process of upwelling along this coastal stretch.
The purpose of our investigation was to assess the water quality around the harbour of Otranto (Lecce, Italy) through an approach that integrates the determination of the classic parameters within traditional microbiological monitoring (the faecal contamination indexes—total coliforms, faecal coliforms, and faecal streptococcus) with the study of autochthon microbiological populations dynamics (hydrocarbon-degrading bacteria and bioluminescent bacteria). The analysis of our data shows that the faecal contamination indexes have values below the limits fixed by the 76/160/EEC directive for the bathing waters, marking the good microbiological quality of these waters. The density of the hydrocarbon-degrading bacteria has been shown to be much higher in the areas designated for the ships' berthing and for the transit of the crafts; therefore, this parameter has shown itself to be useful in the assessment of hydrocarbon contamination in harbour areas. The bioluminescent component of the epibacteria community was set as a marker for the biological quality of the seawater: the relative abundance of the bioluminescent bacteria in the impacted sites is below 5%.
On the morning of August 29, 2005, Hurricane Katrina (a Category 3 hurricane on the Saffir-Simpson scale) made landfall in southeastern Louisiana. Although Dauphin Island, Alabama, is located approximately 180 km to the northeast of where Katrina made landfall, it experienced greater coastal damage than from recent Category 3 hurricanes that were closer to the island (e.g., Frederic in 1979 and Ivan in 2004). This is because the island was within the most intense area of the hurricane as it approached land (i.e., the top-right quadrant). The gulf side of Dauphin Island was impacted by a storm surge of 1.94 m coupled with even higher storm waves. Pelican-Sand Island, to the south of the eastern portion of the island, absorbed much of the storm wave energy, resulting in a lessening of storm water damage to this segment of Dauphin Island. The elevated storm surge and diminished storm waves carried plant debris and sand tens of meters landward across this portion of Dauphin Island. Conversely, with no offshore protection, much of the low-lying western section of the island was completely overwashed. In addition, numerous channels were cut through this section of the island. The greatest change to Dauphin Island was the creation of a 2.0-km wide channel cut through a segment of the undeveloped western end of the island. Hurricane Katrina demonstrated once again the island's fragile nature and precarious setting in the northern Gulf of Mexico.
Molluscan shells were sampled from 31 localities in the South Sea shelf (26 in the southeastern continental shelf and 5 in the southwest sea) to understand the sea-level changes and molluscan thanatocoenoses after the last glacial maximum (LGM). At the southeastern continental shelf, 13,074 shell remains were classified into 119 genera and 170 species (Bivalvia: 73 genera and 105 species; Gastropoda: 43 genera and 60 species; Scaphopoda: 3 genera and 5 species). Cluster analyses were used to group the species into 12 assemblages (Glycymeris–Ventricoloidea–Phacosoma [GVPA], Glycymeris–Paphia–Pitar [GPPA], Glycymeris–Cryptopecten [GCA], Glycymeris–Ventricoloidea–Cryptopecten [GVCA], Pecten–Pitar, Ostrea–Limopsis, Dentalium, Nuculana–Cranulilimopsis, Lucinoma–Glycymeris, Pecten–Acila–Siphonalia, Glycymeris, and Buccium), among which the Glycymeris fauna (GVPA, GPPA, GCA, GVCA) occurred at 11 stations, mainly around Tsushima Island on the South Korean shelf. Radiocarbon dates between late Pleistocene and Holocene were determined for 47 dominant and specific species, which were sampled from 24 stations of the South Sea. Fortunately, the habitats of the molluscan species were depth sensitive, allowing for the discrimination of samples into depth-limited age groups. These groups suggested that the sea level fell by about 150–160 m about 15,000 years ago (during LGM), allowing a land bridge to form between the Korean peninsula and Japan. Subsequently the sea rose approximately 60 m about 9000 years ago. Sea level remained at 50–60 m until about 4000–5000 years ago. About 3000–4000 years ago sea level rose to about 10–20 m (below present) and has remained there to the present. Glycymeris fauna were created on the southeastern shelf about 6000 years ago, whereas Arca fauna prospered in the southwestern sea area about 2000–3000 years ago when the sea level was 10–20 m below present.
Significant river discharges are usually associated with episodic rainstorms, leading to turbid storm water plumes clearly visible in the vicinity of river mouths. The composition of the suspended particulate matter transported by these plumes can alter the quality of coastal waters. The survey of marine coastal zones has thus become a major issue for water managers. For several decades, satellite imagery has allowed the daily monitoring of river plumes behavior over large distances. Nevertheless, it fails to provide data on their hourly evolution, which is important to operationally manage coastal waters in tourist areas. This study investigates the possibility of using the Argus video system to continuously survey the evolution of a storm water plume impact region. The system was installed in Anglet, at the Adour River mouth (southwest of France), in February 2005. An image-processing technique, based on pixel intensity clustering, is proposed to delineate river plume fronts along beaches from images collected with the Adour video station. Application of this technique, tested on storm water runoff plume events occurring under different climate conditions, shows promising results.
A process-based numerical modeling system is utilized for predicting littoral sand transport. The intent is to examine conditions slightly more complex than linear waves impinging upon a plane beach. Two factors that we examine are wave skewness and longshore varying bathymetry. An empirical model is used for calculating the skewed bottom wave orbital velocity. The advection of sediment due to the skewed wave velocity is larger and in the direction of the waves, opposite to the results with sinusoidal wave velocities, due to the increase in the bottom shear stress under the wave crests. The model system is also applied to bathymetry containing beach cusps. When the wave field has relatively weak longshore wave power, the currents and the littoral transport exhibit significant longshore variability, thereby altering the overall mean littoral transport.
This paper presents the results of a hydrodynamic study of a cockle population from the Ulla's estuary in Galicia (Spain). An analysis of the parameters has made it possible to determine the hydraulic characteristics of whole cockles during their threshold of movement and suspension.
Dynamic analysis of the forces exerted on the submerged cockles led to a detailed characterization of a final population of 11 cockles, including their characteristic dimensions in addition to shell and body density. The friction angle between the existing sediment in the Ulla's estuary and the cockle shells was also recorded. The particle image velocimetry (PIV) laser technique was successfully applied to obtain an accurate calculation of the threshold velocity fields. This experimental tool provides the means to experiment with various approaches of the velocity governing the onset of motion and to obtain a more detailed definition of the parameters involved. Applying the PIV technique, three drag entrainment coefficients were obtained with different velocity profiles. Using the depth-averaged velocity profile, a constant entrainment drag coefficient value of 0.43 was obtained for this cockle family, whereas the use of the upper tangential velocity on the cockle resulted in a value of 0.56 with a wider range of variation. This velocity may be considered a more intrinsic parameter of the movement of the cockle.
The process of cockle sedimentation was also monitored, enabling us to ascertain the settling velocity and to calculate the settling drag coefficient. Both parameters present constant values in the group of cockles analyzed, with mean values of 0.36 m s−1 and 1.08, respectively. The settling drag coefficient was also calculated. A comparison of these two experimental values with other existing reports exhibited similar results, thus validating both the procedures used and the effect of the shape factor on the settling drag coefficient value.
The Cape Fear River Estuary (CFRE) region is a coastal domain that has experienced considerable threats and impacts from tropical cyclones. It is also an important nursery for juvenile fish, crabs, shrimp, and other biological species. Thus, predictions about the physical responses of the CFRE system to extreme weather events are important to the protection of life and property and to the economical well-being of local residents. In this study, the Princeton Ocean Model (POM) is used to simulate tropical cyclone storm–induced surge, inundation, and coastal circulation in the CFRE and the adjacent Long Bay using a three-level nesting approach. Hindcasts of the hydrodynamic responses of the CFRE system to historic events were performed for Hurricanes Fran, Floyd, Bertha, and Charley. Comparisons were also made for the modeling results and the observations.
Observations of hurricane impacts on coastal communities and predicted increases in tropical storm activity have spurred an interest in protection and restoration of coastal dunes. Dunes are valued for their role in the protection of infrastructure and aesthetic beauty. Past research on dune erosion has focused primarily on laboratory research or mathematical models. We directly assessed impacts of Hurricanes Ivan (2004) and Dennis (2005) on coastal dunes along Santa Rosa Island, a barrier island in the Gulf of Mexico. We recorded dune area for foredunes and secondary dunes, examined the spatial context of each dune, and recorded structural features of each dune before and after each hurricane. Both hurricanes severely impacted foredunes, and removal of foredune protection by Ivan led to severe impacts on secondary dunes from Dennis. Structural features of the dune, such as height and width, influenced resistance against storm-related erosion, but spatial context, such as location with respect to shoreline, also was important. Coastal dunes on this barrier island may be shifting to a state where their formation, recovery, and restoration are influenced heavily by tropical storm activity. The future success of coastal restoration efforts for maintenance of infrastructure or habitat protection should be cognizant of the importance of spatial context in addition to the structural and vegetation characteristics of dunes.
To reveal the implications of iron deficiency in the occurrence of harmful algal blooms, the physiological status of Prorocentrum micans Ehrenberg (Dinophyceae) was observed through laboratory-culture experiments at different iron levels. The results showed that iron deficiency led to a slowdown in growth rate of algal cells, a twisted structure, and metamorphosed function of chloroplast and mitochondrion. When iron supply was sufficient to meet the algal requirement, it could promote their development and metabolism and facilitate the uptake of micronutrients. Cellular Fe increased with increasing Fe level in the range of 0–10 µM. Low irradiance resulted in an increased uptake of Fe as well as Zn, Mn, and Co. The cellular molar ratio of P : Fe was ∼356 : 1, implying a synergistic uptake of phosphorus and iron. These findings are important in understanding crucial limiting factors during harmful algal blooms in natural environments.
This paper develops an evolutionary model of shoreline retreat along the cliffed coast of Forte Novo–Garrão (Algarve, Portugal) and investigates the relationship of the retreat pattern to coastal protection works, to the Quarteira fishing harbor, and to artificial beach nourishment at Vale do Lobo. The amounts and rates of cliff retreat for six coastal cliff sectors were measured using high-precision digital photogrammetric techniques utilizing data from three aerial photograph surveys conducted in 1991, 1999, and 2001. A geographic information system was used to integrate photogrammetric data and to quantify the temporal and spatial patterns of retreat. Forte Novo was the cliff sector with the highest amount of retreat, 22.7 m between 1991 and 2001. The other coastal sectors recorded retreats of less than 10 m for the same period. Retreat rates ranged from 2.27 m/y−1 at Forte Novo to a minimum retreat rate of 0.14 m/y−1 at Garrão. The replenishment measures at the Vale do Lobo beachfront have been largely successful, as there was negligible erosion between 1999 and 2001 along the cliff sectors protected by beach enlargement. These coastal management measures have been significant in reducing the coastal hazard to people and property located near, and downdrift of, the replenishment.
The present study contributes to the knowledge of the biogeochemistry of Pb, Cd, Cu, and Ni in the Mediterranean Thau Lagoon, southern France, which is an important shellfish farming system. The concentrations of the metals were determined in sediment cores and the overlying waters using inductively coupled plasma mass spectrometry. Particular attention was given to the determination of dissolved Cu species because of their dual role as essential nutrient and toxicant to planktonic organisms. Dissolved Cu speciation was determined using the diffusive gradient in thin-film technique (DGT) and competitive ligand exchange–adsorptive cathodic stripping voltammetry (CLE-ACSV). Our data indicated a significant historical contamination of the sediments, which commenced in the second half of the 19th century, with trace metal inputs persisting until the end of the 20th century. In recent years a decrease in metal contamination has become apparent. The maxima observed for Pb, Cd, and Cu profiles probably indicate the occurence of anoxia crises. A strong complexation of the dissolved Cu species was observed in the waters of the Thau Lagoon, which reduced the bioavailability of Cu. The dissolved Cu2 concentrations were probably too low to cause direct toxic effects on shellfish, but the highest concentration (5.29 pM) observed in this study can potentially influence phytoplankton communities. A comparison between the Cu speciation data indicates that up to 50% of the complexed Cu determined using CLE-ACSV was DGT labile.
It is sometimes assumed that changes in risks of coastal flooding can be computed by just adding mean sea level changes to existing statistics of tidal and meteorological effects. This assumption can be examined by looking at trends in separate tidal and nontidal sea levels, but suitable sites with long records of good quality sea level measurements are rare. As an example, hourly sea level data from the well-maintained tide gauge at Newlyn in southwest England has been critically edited for errors and separated into tidal, nontidal, and mean sea level components. These components have then been analysed for significant trends, and possible correlations with meteorological indicators. There is a small (0.16 mm y−1) increase in standard deviation of the observations, and consistent increases in the M2 and M4 tidal amplitudes. An apparent reduction in the standard deviation of the nontidal residuals can be attributed to a change to a different measuring system in 1984, as can a sudden decrease of 2° (4 min earlier) in the phase lag of M2. There are weak correlations between nontidal (surge) statistics and meteorological parameters, including the North Atlantic oscillation (NAO). Observed annual maximum sea levels are increasing at a rate not significantly different from the observed increase in mean sea level of 1.77 ± 0.12 mm y−1. These very exact analyses of a high-quality consistent long sea level series may indicate limits on the types of trends to be expected elsewhere in the region. Application of this type of analysis for estimating future flooding risks is discussed.
Subtropical coastal sand dune ecosystems have been greatly altered by agricultural use, invasive exotic encroachment, urban development, and beach raking, rendering several plant species endangered or threatened. Restoration planning of this ecosystem will benefit from a comprehensive study on how environmental variables change across the coast-to-inland gradient of this ecosystem and it is therefore presented here. We also examined the relationship between the environmental characteristics and plant species composition across the gradient. We used the two largest extents of remaining dune ecosystem on the southeastern coast of Florida, where relatively intact populations of endangered species occur. Vegetation and environmental data were collected from 97 3 × 8 m plots in two sand dune parks along the coast–inland gradient. Soil moisture, most nutrients, cation exchange capacity, and organic matter accumulation increased with distance from the coast, whereas pH and salt spray decreased. The number of species per plot was higher at further distances from the coast at one site only, and higher woody cover was associated with less species diversity at the other site. Canonical correspondence analysis revealed the importance of P, Mg, Ca, pH, cation exchange capacity, organic matter, estimated nitrogen release, and salt spray in affecting vegetation zonation. We conclude that soil chemistry is the most determinant factor of community zonation in these subtropical dunes. Restoration planning should be site specific because of the differences in environmental factors between the two study sites.
The Cabiúnas Lagoon is a narrow water body that is perpendicular to the sea and isolated from it by a sandbank. Before 1991, the sandbank was sometimes opened for a few days by local residents, but at present seawater only enters by limited groundwater seepage or by overtopping the sea barrier in storms. In 1998 the Restinga de Jurubatiba National Park was established, including the Cabiú nas Lagoon. Studies on the structure and spatial distribution of the fish assemblage were performed between 1991 and 1994; we carried out one year (2001–2002) of monthly monitoring of the lagoon to identify spatiotemporal variations in the lagoon fish assemblage. The closed sandbank altered salinity content, and favoured oligohaline conditions and the increase of the aquatic macrophyte abundance, promoting freshwater species dominance and reduction of the marine dependent and some coastal lagoon resident species of fish adapted to paralic ecosystems. Two freshwater, two coastal lagoon resident, and five marine dependent fish species, which had been registered in the first studies (1991 and 1994), were not captured in the subsequent samplings. The mean number of individuals (N m−2) decreased significantly (Kruskal-Wallis [KW] = 9.977; p = 0.0068); the decrease in biomass was found to be 80%. Species richness and diversity were also significantly reduced. Differences in the current conditions regarding specific composition along the longitudinal axis of the lagoon were observed. Temperature, salinity, and macrophyte coverage were important variables that influenced fish spatial distribution, abundance, and biomass.
Seabirds and freshwater bird species have increasingly colonised urbanised landscapes. However, there have been few multispecies studies of the ecological impacts of shoreline development and nonriverine features on waterbird habitation and conservation. This article examines the relationship between waterbird foraging presence and associations and landscape variation of the Rivers Clyde and Kelvin in Glasgow, Scotland. Fifteen species were observed over the period September 2003 to September 2004. The dependent variables were the 15 recorded waterbird species. The independent variables were river width, depth, and flow speed; riverbank and nearby landscape features; and human presence. The results showed that the impact of the independent variables varied seasonally with stronger impacts on bird distribution in the summer than during the winter. River depth was more important than width or flow. Gulls favoured grass and grass–tree areas and had the strongest associations with human presence and nonriverine environments. Concrete pavements were common foraging areas. Other waterbirds favoured shrub–undergrowth associations and were rarer in nonriverine areas. Seasonal changes in vegetation appeared to be important for nongull species. Therefore, the development of mixed riverbank landscapes, including built features, dense vegetation, and open grass, with mixed human presence may offer an effective conservation strategy for waterbirds.
Empirical data ultimately form the basis for most environmental studies. This work uses extensive data sets from the Baltic Proper on total phosphorus, total nitrogen, chlorophyll, temperature, and salinity. We present trend analyses to see whether there have been any changes in these variables between 1990 and 2005 (and between 1974 and 2005 for chlorophyll). To put these results into a wider context, we have used data from more than 500 systems throughout the world. Selected results: The total phosphorus and total nitrogen values in the Baltic Proper are fairly stable between 1990 and 2005. There are no major changes in surface-water temperatures or salinities this period. Chlorophyll shows a slowly decreasing trend in the surface-water layer since 1974. Compared to the situation in many other marine areas, the eutrophication in the Baltic Proper is moderate. The total river inflow of total phosphorus to the Baltic Proper is 30 to 40 kt/y; about 14 kt/y of total phosphorus come from the Kattegat and about 160 kt/y from land uplift. The inflow of total nitrogen to the Baltic Proper from the Kattegat is about 120 kt/y, and about 480 kt total nitrogen per year come from land uplift. Denitrification is about 660 kt/y. The total turnover of total phosphorus in phytoplankton is about 488 kt/y. The median monthly total nitrogen/total phosphorus ratio has been higher than 7.2 (the Redfield ratio) all months since 1994, indicating that the primary production in the system is generally limited by phosphorus rather than nitrogen. If the total nitrogen/total phosphorus ratio is lower than 15, there are increasing risks of blooms of cyanobacteria, especially if the water temperature is above 15°C. If the total nitrogen input to the Baltic Proper is lowered, it will mean a lowering of the total nitrogen/total phosphorus ratio and greater risks for blooming of harmful algae.
After hurricane overwash, restoration of dune ecosystems requires information on when, where, and how to replace plants removed by storms. Survival and subsequent growth of Schizachyrium maritimum (Chapman) Nash, Morella cerifera (L. Small), and Ceratiola ericoides Michx., transplanted at increasing distances from the Gulf of Mexico (92, 124, 179, and 200 m landward of the Gulf) with increasing protection from salt spray and desiccating winds by developing dunes, were evaluated. Survival and growth was followed for 15 months. Schizachyrium maritimum survival and growth was high regardless of distance from the Gulf. Ceratiola ericoides and M. cerifera did not survive when planted 92 m from the Gulf behind embryo dunes approximately 0.5–1 m tall. Foliage loss was noted at all distances but survival and regrowth were higher at 170 and 200 m behind two to three ridges of embryo dunes 0.5–1 m tall.
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