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Sandy Beaches (sandy + beach)
Selected AbstractsAbundance, Tidal Movement, Population Structure and Burrowing Rate of Emerita analoga (Anomura, Hippidae) at a Dissipative and a Reflective Sandy Beach in South Central ChileMARINE ECOLOGY, Issue 2 2000Eduardo Jaramillo Abstract. To evaluate the effects of beach morphodynamics upon the abundance, tidal movement, population structure and burrowing rate of the crab Emerita analoga (Stimpson) (Anomura, Hippidae) we sampled two beaches in south central Chile (ca. 42° S), Mar Brava and Ahui with dissipative and reflective characteristics, respectively. The swash zone at the dissipative beach was 5,,,6 times wider than that of the reflective beach. A at the dissipative beach, upwash speeds were higher and the number of effluent line crossings were lower by more than an order of magnitude. To examine the tidal movement of E. analoga, we collected crabs from 5 to 6 tidal levels of each beach every 2 h across 12 h of the tidal cycle. The intertidal distribution of crabs differed between beaches; i. e., at the dissipative beach they were primarily located at the swash zone, while at the reflective beach they were mostly located at the low tide level and shallow subtidal. The change in position of crabs was pronounced across the tidal cycle at the dissipative beach (Mar Brava), with most of the animals remaining in the active swash zone. Body size data were used to construct size frequency distributions for each population. Crabs from the dissipative beach reached larger sizes than those at the reflective beach. Sediments were coarser at the latter versus the former beach. Crabs burrowed at similar rates in the sand from both beaches, a result which supports the idea that E. analoga is a "sediment generalist" capable of burrowing successfully in a wide range of sediment types. This characteristic is likely a key to the broad success of this species on the full range of beach morphodynamic types along the coasts of South and North America. [source] Vehicles versus conservation of invertebrates on sandy beaches: mortalities inflicted by off-road vehicles on ghost crabsMARINE ECOLOGY, Issue 3 2007Thomas A. Schlacher Abstract Sandy beaches face increasing anthropogenic pressures, with vehicle traffic being ecologically highly harmful. Ghost crabs (Fam. Ocypodidae) are conspicuous on many beaches, and they have been used as a bio-monitoring tool to measure the ecological responses to human disturbance. However, the mechanisms causing declines in crab numbers are unknown, yet conservation must target the actual impact mechanisms. Therefore, we quantified the magnitude and mechanisms of off-road vehicle (ORV) impacts on ghost crabs, addressing three key questions: (i) Does abundance of ghost crabs respond to traffic intensity?; (ii) Can burrows protect crabs from vehicles? and (iii) Can mortalities caused by vehicles contribute to population declines? ORV-impacts were measured on North Stradbroke Island (Australia) for Ocypode cordimanus and Ocypode ceratophthalma. Crab densities were significantly lower in areas subjected to heavy beach traffic, suggesting direct crushing by vehicles. Burrows only partially protect crabs against cars: all individuals buried shallow (5 cm) are killed by 10 vehicle passes. Mortality declines with depth of burrows, but remains considerable (10,30% killed) at 20 cm and only those crabs buried at least 30 cm are not killed by ORVs: these ,deep-living' crabs represent about half of the population. After crabs emerge at dusk they are killed in large numbers on the beach surface. A single vehicle can crush up to 0.75% of the intertidal population. While conservation measures should primarily regulate night traffic, our results also emphasise that the fossorial life habits of sandy beach animals cannot off-set the impacts caused by ORVs. [source] Backshore coarsening processes triggered by wave-induced sand transport: the critical role of storm events,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 11 2010Keiko Udo Abstract Spatial backshore processes were investigated through field observations of topography and median sand grain size at a sandy beach facing the Pacific Ocean in Japan. A comparison of the backshore profile and cross-shore distribution of the median sand grain size in 1999 and 2004 revealed an unusual sedimentary process in which sand was coarsened in a depositional area in the 5-year period, although sediment is generally coarsened in erosional areas. In support of these observations, monthly spatial field analyses carried out in 2004 demonstrated a remarkable backshore coarsening process triggered by sedimentation in the seaward part of the backshore during a storm event. In order to elucidate mechanisms involved in the backshore coarsening process, thresholds of movable sand grain size under wave and wind actions (a uniform parameter for both these cases) in the onshore and offshore directions were estimated using wave, tide, and wind data. The cross-shore distributions of the estimated thresholds provided reasonable values and demonstrated a coarsening mechanism involving the intermediate zone around the shoreline under alternating wave and wind actions as a result of which coarse sand was transported toward the seaward part of the backshore by large waves during storms and then toward the landward part by strong onshore winds. The 5-year backshore coarsening is most certainly explained by repetition of short-term coarsening mechanisms caused by wave-induced sand transport occurring from the nearshore to the intermediate zone. Copyright © 2010 John Wiley & Sons, Ltd [source] Field observations of nearshore bar formationEARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2008Troels Aagaard Abstract The formation of an inner nearshore bar was observed during a high-energy event at the sandy beach of Vejers, Denmark. The bar accreted in situ during surf zone conditions and the growth of the bar was associated with the development of a trough landward of the bar. Measurements of hydrodynamics and sediment fluxes were obtained from electromagnetic current meters and optical backscatter sensors. These process measurements showed that a divergence in sediment transport occurred at the location of the developing trough, and observed gradients in cross-shore net sediment flux were consistent with the morphological development. The main cause for the flux gradients were cross-shore gradients in offshore-directed mean current (undertow) speed which depended upon local relative wave height and local bed slope. Copyright © 2007 John Wiley & Sons, Ltd. [source] Patapius spinosus: First record of Leptopodidae (Heteroptera) from JapanENTOMOLOGICAL SCIENCE, Issue 4 2004Kazuo YAMAZAKI Abstract Patapius spinosus, a remarkable leptopodid bug whose body is covered with spines, was collected for the first time in Japan. This species was found in the supralittoral zone of a sandy beach in Osaka Prefecture, central Japan, in autumn 2002 and in spring 2004. Patapius spinosus is known to be distributed in the Mediterranean and North African regions, and has been introduced into North America and Chile. Its occurrence in Japan could signify either an eastern limit of its native distribution or an exotic origin. [source] Wave and sediment dynamics along a shallow subtidal sandy beach inhabited by modern stromatolitesGEOBIOLOGY, Issue 1 2008J. E. ECKMAN ABSTRACT To help define the habitat of modern marine stromatolites, wave-dominated flow and sediment transport were studied in the shallow subtidal region (1,2 m depth) along the slightly concave, windward face of Highborne Cay, Exuma, Bahamas , the only face of the cay that includes a population of stromatolites concentrated near the region of highest curvature of the beach. Wave energy impacting this island's most exposed beach was driven by local wind forcing which increases largely in response to the passage of atmospheric disturbances that typically affect the region for periods of a few days. Although some wave energy is almost always noted (maximum horizontal orbital speeds at the bottom are rarely <10 cm s,1), wave conditions remain comparatively calm until local winds increase above speeds of ,3,4 m s,1 at which point maximum wave speeds rapidly increase to 50,80 cm s,1. Stromatolites, which are largely restricted to the shoreward side of a shallow platform reef, are sheltered by the reef beyond which wave speeds are one to four times higher (depending on tidal stage). Moreover, stromatolite populations are predominantly found along a region of this wave-exposed beach that experiences comparatively reduced wave energy because of the curved morphology of the island's face. Maximum wave speeds are 1.4 to 2 times higher along more northern sections of the beach just beyond the locus of stromatolite populations. A quantitative model of sediment transport was developed that accurately predicted accumulation of suspended sediment in sediment traps deployed in the shallow subtidal zone along this beach. This model, coupled with in situ wave records, indicates that gross rates of suspended sediment deposition should be two to three times higher northward of the main stromatolite populations. Regions of the beach containing stromatolites nevertheless should experience significant rates of gross suspended sediment deposition averaging 7,10 g cm,2 day,1 (,4,6 cm day,1). Results suggest that one axis of the habitat of modern marine stromatolites may be defined by a comparatively narrow range of flow energy and sediment transport conditions. [source] Tidal Effects on Ground Water Discharge Through a Sandy Marine BeachGROUND WATER, Issue 7 2004Daniel W. Urish Tidal fluctuations along the salt water boundary of a sandy beach affect the magnitude, location, timing, and salinity of both subaerial and submarine ground water discharge. Detailed studies of shoreline discharge from an unconfined aquifer at two sites in an embayment on the Cape Cod, Massachusetts, coastline provide insight into the highly dynamic spatial and temporal nature of discharge along sandy beaches affected by the tide. The constantly moving tidal boundary over a sloping beach results in a shoreline-perpendicular discharge zone of 10 to 20 m, with ,35% to 55% of the discharge being submarine discharge. The distribution of fresh ground water through a beach face varies greatly, depending primarily on the tidal cycle and range, the heterogeneous characteristics of the beach sediments, and the beach geometry. The estimated relative volume of discharge varies temporally with tidal fluctuations, with the greatest discharge occurring during early to mid ebbing tide and location of greatest estimated discharge moving seaward during ebbing tide. This is determined using net hydraulic head calculations in monitoring wells set in a shoreline-perpendicular transect in the beach. The salinity of discharge varies temporally from near fresh water values of 1 part per thousand (ppt) to near coastal salt water values of 30 ppt, being saltiest at the start of discharge as the tide ebbs and freshest during a low tide period of ,2 h. Of the discharge volume, ,65% to 85% is estimated to be from salt water that infiltrates during high tide episodes. This study highlights the complexity of the dynamic coastal ground water discharge phenomenon and provides insight into the hydraulic mechanisms involved. While there is a general pattern to sandy beach discharge, comparison of results from beaches studied at Cape Cod indicates that the temporal and spatial details of the discharge is very site-specific. [source] Alongshore dispersal and site fidelity of juvenile plaice from tagging and transplantsJOURNAL OF FISH BIOLOGY, Issue 3 2004M. T. Burrows Juvenile plaice Pleuronectes platessa(n = 1281) were tagged and released at two locations 300 m apart on a 1 km long sandy beach. Most (>90%) of the fish were recaptured within 100 m of the release site (shown by the colour of the tag), with very few caught >200 m distance after 6 weeks. The changing spatial distribution of marked fish was adequately reproduced by a simple dispersal model with a single parameter: a 78% probability of remaining in a 100 m wide zone from one day to the next, with a 22% chance that fish move into an adjacent zone. In a subsequent similar study at the same beach, fish were either released at the point of capture (n = 881) or transplanted to the alternate site (n = 910) 100 m distant. After 6 weeks, transplanted fish moved along the shore towards their sites of original capture. Fish replaced at the point of capture showed no such movement along the shore. Further modification of the dispersal model to allow for a distinction between dispersal from home sites and from sites away from the original point of collection, was sufficient to reproduce the behaviour of the populations of both transplanted and control treatment groups. The likelihood of dispersal from home sites was much less than that seen at sites away from home. Juvenile plaice thus have a degree of long-shore site fidelity not expected of a fish with strong depth-related migration behaviour in a relatively homogenous habitat. [source] Environmental niche of the smut lizard population on a sandy coastal ecosystem of Southeastern Tenerife (Canary Islands)MARINE ECOLOGY, Issue 2008Antonio De Los Santos Abstract Relationships among environmental patterns and population size of the smut lizard Gallotia galloti galloti Oudart, 1839 (Sauria Lacertidae) were examined in the context of longer time-scale variability on a sandy beach and adjacent environments of Southeastern Tenerife. Seasonal and yearly patterns in the population size were likewise analyzed in relation to climatic and anthropic variables. Six sampling plots (coastal, sweet tabaiba, tuff, lava, sandy lava and crater) were selected following a perpendicular transect to the sandy fringe that extends from the beach toward the volcanic interior. Pitfall trapping was conducted from 1984 to 2005, and capture,mark,recapture technique and the Jolly,Seber method were used to estimate population sizes. The highest population size estimates were shown on the sandy lava plot and the neighboring lava plot, reaching values of about 3500 individuals ha,1 during the spring. The population was active almost the whole year, with seasonal patterns of activity from March to October. Seasonal temperature and population size patterns were correlated but the ,calima' episodes produced some disturbance. Gallotia galloti galloti was one of the most abundant lizards of all the species studied and its population size has not remained stable over the study period, probably because of the absence of predation and competition, and because of human interference and environmental instability. [source] Structure and distribution of the benthic macrofauna on a Northwest African sandy beach close to a freshwater river dischargeMARINE ECOLOGY, Issue 2008Abdellatif Chaouti Abstract The effects of the freshwater discharge of the Oued Sebou River on the macroinfauna, was studied on the sandy beach of Mehdia through the analysis of the abiotic parameters and of the macrozoobenthos. In autumn 2002 and spring 2003, three beach sites, each with two transects, localized at 50, 3500 and 5720 m from the river mouth respectively, were studied. Positive correlations were recorded for beach slope and pH whereas negative ones were obtained for organic matter content and salinity at increasing distances from the river mouth. Significant differences between beach sites and seasons occurred for median grain size, organic matter content and pH. For each beach site, mean macroinfauna abundance varied between 30 and 100 ind.·m,2 and in spring there was a significant correlation between this parameter and the increasing distance from the river mouth. No significant correlation was instead found between species richness and the increasing distance, although the farthest beach site from the mouth had the highest number of species during both seasons. The results indicated the importance of organic matter content and salinity for the macrofaunal abundance whereas the diversity indices were more affected by beach slope and grain size. The results showed that there was no clear spatial trend in compound indices of the macrofauna across the sampled sites and the influence of the river discharge of Sebou River did not seem to be significant and consistent on the macrobenthos of this mesotidal shore. Comparison with microtidal shores revealed the influence of the tidal excursion and swell characteristics on the response of the benthic structures of sandy beaches to discharges of freshwater. [source] Heart rate variability after horse trekking in leading and following horsesANIMAL SCIENCE JOURNAL, Issue 5 2010Akihiro MATSUURA ABSTRACT Horse trekking (HT) is having a stroll on a horse along a walking trail in a forest, field, and/or sandy beach. Generally in HT, horses exercise in tandem line outside the riding facilities. Because the leading horse will be confronted with stressors in the forefront, we hypothesized that the leading horse shows higher stress responses than the following one. In order to verify the hypothesis, we compared short-term stress responses between each position in six horses. Exercise consisted of 15 min of ground riding and 45 min of HT with walking and trotting. Heart rate variability was analyzed for 5 min at 30, 60, and 90 min after the exercising period. There was no significant difference in heart rate during exercise between leading and following positions. The high frequency / low frequency power band of heart rate variability, an index of sympathetic nervous activity, after exercise, tended to be higher in the leading position than following one (P < 0.1). The result in this study can suggest that the leading horse was in a higher stressed state than the following horse after HT. [source] Recovery of sandy beach and maritime forest vegetation on Phuket Island (Thailand) after the major Indian Ocean tsunami of 2004APPLIED VEGETATION SCIENCE, Issue 2 2009D. Hayasaka Abstract Question: How rapidly has the sandy beach and maritime forest vegetation on Phuket recovered and regenerated after the impact of the major Indian Ocean tsunami of 2004? What are the characteristics of sandy beach species for regenerating their populations and the invasion patterns of originally non-sandy beach species or other newcomers after the tsunami? Location: Phuket Island, southern Thailand. Methods: Species composition of beaches was studied on the same research plots 6 months before and 9 months after the tsunami. The changes in individual species cover before and after the tsunami were determined by ,2 tests. Change in community composition was analysed by detrended correspondence analysis. The relationship between species and environmental factors was analysed by canonical correspondence analysis. Results: The sites disturbed by the tsunami were often invaded by annuals, especially grasses and asteraceous plants, rather than by perennials. In contrast, species with clonal growth by stolons decreased significantly. Factors determining the species habitat differences were soil hardness (penetration resistance of sandy soil), per cent silt content, soil water content and beach management. Habitat differences among originally non-sandy beach herbaceous species that expanded their population or moved to the coast after the disaster were defined by sand accretion or erosion caused by the tsunami. Many sandy beach herbaceous communities changed into Dactyloctenium aegyptium communities because of the tsunami were originally constituted by non-sandy beach D. aegyptium with Cenchrus echinatus. Although the forest floors of most maritime forests were invaded by originally non-sandy beach Tridax procumbens, Eleusine indica or D. aegyptium because of the tsunami, this did not result in a change in the vegetation unit, because species' loss was restricted to the understorey. In time, these forests will recover their previous community composition. Conclusions: Our results suggest that originally non-sandy beach native species invaded the disturbed beaches rapidly after the tsunami but their habitats differ. Sites where sand accumulated on a beach because of the tsunami were invaded by D. aegyptium and E. indica, whereas soil erosion permitted invasion by Digitania adscendens. Tridax procumbens establishes rapidly on wet sites with hard soil, high per cent silt content and low beach management pressure. Sandy beach species with subterranean long rhizomes are strongly tolerant of such disasters. We concluded that the species composition of the beaches disturbed by a temporary large disaster is determined by dormancy and growth forms, with radicoid form being influential. [source] Latitudinal patterns in abundance and life-history traits of the mole crab Emerita brasiliensis on South American sandy beachesDIVERSITY AND DISTRIBUTIONS, Issue 2 2004Omar Defeo ABSTRACT Demographic and life-history attributes of the mole crab Emerita brasiliensis were analysed along 2700 km of the Atlantic coast of South America, including sandy beaches at the southernmost limit (Uruguay) and at the core of its geographical range (Brazil). Population features varied markedly within this range and exhibited systematic geographical patterns of variation. Abundance significantly increased from temperate to subtropical beaches, and the same held true for the asymptotic weight of males. Conversely, length at maturity and asymptotic weight of females increased from subtropical to temperate beaches, being inversely related to sea water temperature. Macroecological patterns in abundance and body weight showed the first large-scale evidence of scaling of population density to body size for a sandy beach population. Mortality rates (both sexes) followed a nonlinear increase from low-density temperate beaches to high-density subtropical beaches. The effect of habitat quality and availability could explain discontinuities in the species distribution within its range, and also differential responses in life-history attributes at a local scale. Asymmetries and converse latitudinal trends between sexes suggest that there is not a single general factor determining large-scale patterns in life-history traits of this species. Our results reinforce the view that density-dependent and environmental factors operating together regulate sandy beach populations. The need to develop macroecological studies in sandy beach ecology is highlighted, as knowledge acquired from local to large spatial scales throws light on population structure and regulation mechanisms. [source] Dynamics of multiple intertidal bars over semi-diurnal and lunar tidal cycles, North Lincolnshire, EnglandEARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2008Selma van Houwelingen Abstract Multiple intertidal bars are common features of wave-dominated sandy beaches, yet their short-term (<1 month) and small-scale (<1 km) morphology and dynamics remain poorly understood. This study describes the morphodynamics of multiple intertidal bars in North Lincolnshire, England, during single and lunar tidal cycles under two contrasting conditions , first when significant wave height was <0·5 m and second when significant wave height frequently exceeded 1 m. The relative importance of swash, surf and shoaling processes in determining morphological change was examined using detailed field observations and a numerical model. The beach featured four intertidal bars and both cross-shore and longshore bar morphology evolved during the field investigation, particularly under medium to high wave-energy conditions. Numerical modelling suggests shoaling processes are most common on the seaward two bars under calm wave conditions (Hs < 0·5 m) and that surf zone processes become more common during neap tides and under more energetic (Hs < 0·5 m) conditions. Surf processes dominate the inner two bars, though swash influence increases in a landward direction. The numerical modelling results combined with low tide survey data and high-resolution morphological measurements strongly suggest changes in the intertidal bar morphology are accomplished by surf zone processes rather than by shoaling wave or swash processes. This is because shoaling waves do not induce significant sediment transport to have any morphological effect, whereas swash action generally does not have enough scope to act as the swash zone is much narrower than the surf zone. It was found, however, that the absolute rate of morphological change under swash action and surfzone processes are of similar magnitudes and that swash action may induce a significant amount of local morphological change when the high tide mark is located on the upper bar, making this process important for bar morphodynamics. Copyright © 2007 John Wiley & Sons, Ltd. [source] Characteristics and dynamics of multiple intertidal bars, north Lincolnshire, EnglandEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2006Selma van Houwelingen Abstract Multiple intertidal bars and troughs, often referred to as ,ridges and runnels', are significant features on many macrotidal sandy beaches. Along the coastline of England and Wales, they are particularly prevalent in the vicinity of estuaries, where the nearshore gradient is gentle and a large surplus of sediment is generally present. This paper examines the dynamics of such bar systems along the north Lincolnshire coast. A digital elevation model of the intertidal morphology obtained using LIDAR demonstrates that three to five intertidal bars are consistently present with a spacing of approximately 100 m. The largest and most pronounced bars (height = 0·5,0·8 m) are found around mean sea level, whereas the least developed bars (height = 0·2,0·5 m) occur in the lower intertidal zone. Annual aerial photographs of the intertidal bar morphology were inspected to try to track individual bars from year to year to derive bar migration rates; however, there is little resemblance between concurrent photographs, and ,resetting' of the intertidal profile occurs on an annual basis. Three-dimensional beach surveys were conducted monthly at three locations along the north Lincolnshire coast over a one-year period. The intertidal bar morphology responds strongly to the seasonal variation in the forcing conditions, and bars are least numerous and flattest during the more energetic winter months. Morphological changes over the monthly time scale are strongly affected by longshore sediment transport processes and the intertidal bar morphology can migrate along the beach at rates of up to 30 m per month. The behaviour of intertidal bars is complex and varies over a range of spatial and temporal scales in response to a combination of forcing factors (e.g. incident wave energy, different types of wave processes, longshore and cross-shore sediment transport), relaxation time and morphodynamic feedback. Copyright © 2005 John Wiley & Sons, Ltd. [source] Abundance , occupancy relationships in macrofauna on exposed sandy beaches: patterns and mechanismsECOGRAPHY, Issue 5 2004Matthew T. Frost We studied the relationship between abundance and extent of occupancy of 158 species of macrofauna inhabiting 66 sandy beaches around the coast of Great Britain. We also used these data to test the predictions of two hypotheses proposed to explain positive abundance-occupancy relationships. We found a strong positive relationship between abundance and extent of occupancy; this pattern was apparent in taxonomic subsets of organisms which have contrasting reproductive and dispersal traits such as planktotrophic/lecithotrophic development in the plankton vs brood development under parental care. Moreover, the abundance-occupancy relationships in these taxonomic subsets had statistically indistinguishable slopes, and elevation. We propose that this lends support to the notion that differences in population structure such as the tendency to form metapopulations may not be primary determinants of the abundance-occupancy pattern in these taxa as proposed by the rescue/metapopulation hypothesis. To test the predictions of the niche-breadth hypothesis we derived values describing the range of sediment grain-sizes exploited by members of two taxonomic subgroups: amphipods and bivalves. We found a weak, statistically non-significant relationship between this niche-breadth measure and occupancy in bivalves which have been shown to respond to grain-size in previous studies, however this was negated after correction for possible artefacts of sampling effort. All other relationships between abundance or occupancy and grain-size range were non-significant. The consistency of the demonstrated abundance-occupancy relationship with those demonstrated in other studies of primarily terrestrial fauna indicates some shared mechanistic explanation, but our data fail to provide support for the two mechanistic hypotheses investigated. [source] Tidal Effects on Ground Water Discharge Through a Sandy Marine BeachGROUND WATER, Issue 7 2004Daniel W. Urish Tidal fluctuations along the salt water boundary of a sandy beach affect the magnitude, location, timing, and salinity of both subaerial and submarine ground water discharge. Detailed studies of shoreline discharge from an unconfined aquifer at two sites in an embayment on the Cape Cod, Massachusetts, coastline provide insight into the highly dynamic spatial and temporal nature of discharge along sandy beaches affected by the tide. The constantly moving tidal boundary over a sloping beach results in a shoreline-perpendicular discharge zone of 10 to 20 m, with ,35% to 55% of the discharge being submarine discharge. The distribution of fresh ground water through a beach face varies greatly, depending primarily on the tidal cycle and range, the heterogeneous characteristics of the beach sediments, and the beach geometry. The estimated relative volume of discharge varies temporally with tidal fluctuations, with the greatest discharge occurring during early to mid ebbing tide and location of greatest estimated discharge moving seaward during ebbing tide. This is determined using net hydraulic head calculations in monitoring wells set in a shoreline-perpendicular transect in the beach. The salinity of discharge varies temporally from near fresh water values of 1 part per thousand (ppt) to near coastal salt water values of 30 ppt, being saltiest at the start of discharge as the tide ebbs and freshest during a low tide period of ,2 h. Of the discharge volume, ,65% to 85% is estimated to be from salt water that infiltrates during high tide episodes. This study highlights the complexity of the dynamic coastal ground water discharge phenomenon and provides insight into the hydraulic mechanisms involved. While there is a general pattern to sandy beach discharge, comparison of results from beaches studied at Cape Cod indicates that the temporal and spatial details of the discharge is very site-specific. [source] Environmental limits to the distribution of Scaevola plumieri along the South African coastJOURNAL OF VEGETATION SCIENCE, Issue 1 2003Craig I. Peter Dyer (1967) Abstract. Scaevola plumieri is an important pioneer on many tropical and subtropical sand dunes, forming a large perennial subterranean plant with only the tips of the branches emerging above accreting sand. In South Africa it is the dominant pioneer on sandy beaches along the east coast, less abundant on the south coast and absent from the southwest and west coasts. Transpiration rates (E) of S. plumieri are predictably related to atmospheric vapour pressure deficit under a wide range of conditions and can therefore be predicted from measurement of ambient temperature and relative humidity. Scaling measurements of E at the leaf level to the canopy level has been demonstrated previously. Using a geographic information system, digital maps of regional climatic variables were used to calculate digital maps of potential transpiration from mean monthly temperature and relative humidity values, effectively scaling canopy level transpiration rates to a regional level. Monthly potential transpiration was subtracted from the monthly median rainfall to produce a map of mean monthly water balance. Seasonal growth was correlated with seasonal water balance. Localities along the coast with water deficits in summer corresponded with the recorded absence of S. plumieri, which grows and reproduces most actively in the summer months. This suggests that reduced water availability during the summer growth period limits the distribution of S. plumieri along the southwest coast, where water deficits develop in summer. Temperature is also important in limiting the distribution of S. plumieri on the southwest coast of South Africa through its effects on the growth and phenology of the plant. [source] Structure and distribution of the benthic macrofauna on a Northwest African sandy beach close to a freshwater river dischargeMARINE ECOLOGY, Issue 2008Abdellatif Chaouti Abstract The effects of the freshwater discharge of the Oued Sebou River on the macroinfauna, was studied on the sandy beach of Mehdia through the analysis of the abiotic parameters and of the macrozoobenthos. In autumn 2002 and spring 2003, three beach sites, each with two transects, localized at 50, 3500 and 5720 m from the river mouth respectively, were studied. Positive correlations were recorded for beach slope and pH whereas negative ones were obtained for organic matter content and salinity at increasing distances from the river mouth. Significant differences between beach sites and seasons occurred for median grain size, organic matter content and pH. For each beach site, mean macroinfauna abundance varied between 30 and 100 ind.·m,2 and in spring there was a significant correlation between this parameter and the increasing distance from the river mouth. No significant correlation was instead found between species richness and the increasing distance, although the farthest beach site from the mouth had the highest number of species during both seasons. The results indicated the importance of organic matter content and salinity for the macrofaunal abundance whereas the diversity indices were more affected by beach slope and grain size. The results showed that there was no clear spatial trend in compound indices of the macrofauna across the sampled sites and the influence of the river discharge of Sebou River did not seem to be significant and consistent on the macrobenthos of this mesotidal shore. Comparison with microtidal shores revealed the influence of the tidal excursion and swell characteristics on the response of the benthic structures of sandy beaches to discharges of freshwater. [source] Assessing inter-beach differences in semi-terrestrial arthropod assemblages on Maltese pocket sandy beaches (Central Mediterranean)MARINE ECOLOGY, Issue 2008Alan Deidun Abstract The distinctiveness of macrofaunal assemblages on different sandy beaches in the Maltese Islands was previously suggested by different single-season studies. A multi-seasonal sampling programme using pitfall trapping was implemented on four Maltese beaches to test the occurrence of this phenomenon. A total of 29,302 individuals belonging to 191 species were collected over a 2-year period, during which the beaches were sampled once per calendar season. A total of 77 species were recorded from single Maltese beaches only, of which nine were psammophiles. Non-metric multidimensional scaling analyses of pitfall trap species-abundance data resulted in a weak separation pattern, with samples grouping mainly in terms of beach and island rather than in terms of season or year of sampling, No physical variable could conclusively explain these patterns. It is concluded that although operating on Maltese beaches, macrofaunal assemblage distinctiveness is weaker than originally thought and can be attributed to the presence/absence or abundance of just a few psammophilic species. It is postulated that this phenomenon may be related to the ,pocket beach' nature of Maltese beaches, where headlands on either side of the beach to a large extent prevent the occurrence of longshore currents, resulting in semi-isolation of the populations of psammophilic species. A large number of single-beach records reported in this study highlight the high degree of beta diversity and spatial heterogeneity of Maltese beaches, and the conservation importance of the individual beach macrofaunal assemblages. [source] Vehicles versus conservation of invertebrates on sandy beaches: mortalities inflicted by off-road vehicles on ghost crabsMARINE ECOLOGY, Issue 3 2007Thomas A. Schlacher Abstract Sandy beaches face increasing anthropogenic pressures, with vehicle traffic being ecologically highly harmful. Ghost crabs (Fam. Ocypodidae) are conspicuous on many beaches, and they have been used as a bio-monitoring tool to measure the ecological responses to human disturbance. However, the mechanisms causing declines in crab numbers are unknown, yet conservation must target the actual impact mechanisms. Therefore, we quantified the magnitude and mechanisms of off-road vehicle (ORV) impacts on ghost crabs, addressing three key questions: (i) Does abundance of ghost crabs respond to traffic intensity?; (ii) Can burrows protect crabs from vehicles? and (iii) Can mortalities caused by vehicles contribute to population declines? ORV-impacts were measured on North Stradbroke Island (Australia) for Ocypode cordimanus and Ocypode ceratophthalma. Crab densities were significantly lower in areas subjected to heavy beach traffic, suggesting direct crushing by vehicles. Burrows only partially protect crabs against cars: all individuals buried shallow (5 cm) are killed by 10 vehicle passes. Mortality declines with depth of burrows, but remains considerable (10,30% killed) at 20 cm and only those crabs buried at least 30 cm are not killed by ORVs: these ,deep-living' crabs represent about half of the population. After crabs emerge at dusk they are killed in large numbers on the beach surface. A single vehicle can crush up to 0.75% of the intertidal population. While conservation measures should primarily regulate night traffic, our results also emphasise that the fossorial life habits of sandy beach animals cannot off-set the impacts caused by ORVs. [source] Relationships Between Community Structure of the Intertidal Macroinfauna and Sandy Beach Characteristics Along the Chilean CoastMARINE ECOLOGY, Issue 4 2001Eduardo Jaramillo Abstract. Eight sandy beaches were seasonally sampled along the coast of Chile, from ca. 21 to 42° S (about 3000 km) to study the relationship between community structure of the intertidal macroinfauna and beach characteristics. Sediment samples (0.1 m2, 30 cm deep) were collected (July , September 1998 and December 1998 , January 1999) with plastic cylinders at 15 equally spaced levels along three replicated transects extending from above the drift line to the swash zone. The sediment was sieved through a 1 mm mesh and the organisms collected stored in 5 % formalin. To define beach types, Dean's parameter (,) was calculated from wave heights and periods, and fall velocity of sand particles from the swash zone. Crustaceans (mainly peracarids) were the most diverse group with 14 species, followed by polychaetes with 5 species. The talitrid amphipod Orchestoidea tuberculata, the cirolanid isopods Excirolana braziliensis and E. hirsuticauda and the anomuran decapod Emerita analoga were the most widely distributed and common species. Regression analyses between species richness, abundance and biomass of the whole macroinfauna versus sediment characteristics, beach face slopes and morphodynamic beach states showed no significant relationships. Thus, macroinfaunal community characteristics did not increase linearly from lower intermediate to higher intermediate or dissipative beach states as had been found before in Chile or in other coasts. A comparative analysis with data from sandy beaches of other world regions showed that the number of species inhabiting Chilean sandy beaches was generally lower, whereas total population abundances were generally higher compared with values reported elsewhere. [source] ENVIRONMENTAL FACTORS INFLUENCING THE DISTRIBUTION OF SOUTHERN RIGHT WHALES (EUBALAENA AUSTRALIS) ON THE SOUTH COAST OF SOUTH AFRICA I: BROAD SCALE PATTERNSMARINE MAMMAL SCIENCE, Issue 3 2004Simon H. Elwen Abstract Aerial surveys over the last 32 yr have shown that the distribution of southern right whales Eubalaena australis along the south coast of South Africa is markedly discontinuous, but highly predictable. A GIS was used at a variety of scales to investigate whether this pattern was related to environmental characteristics. Whale distribution was analyzed as density per 20-min bin of longitude over two temporal and spatial scales, namely 15 bins for 32 yr, and a wider scale but shorter time period, 23 bins for 19 yr, as well as using three years of GPS accuracy data (15 bins) for finer scale analysis. Environmental factors tested were depth, distance from shore, sea floor slope, protection from swell, protection from wind, and shore type. The majority of whales were concentrated in areas that provided reasonable protection from open ocean swell and seasonal winds, and had sedimentary floors with gentle slopes. They generally avoided exposed rocky shorelines. Cow-calf pairs were found significantly closer to shore and in shallower water than unaccompanied whales, particularly off sandy beaches. Habitat choice at this time of year may be related both to energy conservation for calves and lactating females (calm sea conditions) and to protection of the new-born. [source] Amphidiniopsis uroensis sp. nov. and Amphidiniopsis pectinaria sp. nov. (Dinophyceae): Two new benthic dinoflage llates from JapanPHYCOLOGICAL RESEARCH, Issue 2 2002Saburo Toriumi SUMMARY Two new armoured, heterotrophic sand-dwelling marine dinoflagellates, Amphidiniopsis uroensis Toriumi, Yoshimatsu et Dodge sp. nov. and Amphidiniopsis pectinaria Toriumi, Yoshimatsu et Dodge sp. nov. were collected from Japanese sandy beaches, and their morphological features observed by light microscopy and scanning electron microscopy (SEM). The cell size of A. uroensis is 28,31 ,m in length and 23,28 ,m in width. The plate formula is Po 3,, 3a, 6,, 3c, 4s (+1 acc.), 5,,, 2,,. The thecal surface is ornamented with small processes, pores and spines, however, the surface of plate 2a is smooth. The epitheca possesses a narrow ridge that is extended along on the suture between 1, and 3,. Plate 1, connects with the right sulcal (Sd) and right sulcal accessory (Sda) plates, so the cingulum is incomplete. A nucleus is situated in the central part of the cell. There are a few small spines at the antapex. There are no stigma or chloroplasts. Amphidiniopsis pectinaria cells are 33,40 urn in length and 29,35 ,m in width. The plate formula is Po 4,, 3a, 7,, 3c, 4s (+1 acc.), 5,,, 2,,. Plate 1, connects directly with Sd and Sda plates, so the cingulum is incomplete. The thecal surface is ornamented with small processes, spines and pores. The epitheca is provided with a narrow ridge that is extended along on the suture between plates 1,, 4, and 7,. The ornamentation on the antapical plates is unique. It is arranged in 10 straight rows on the hypotheca; each row has a strong spine at its posterior end. In addition, there is a long spine at the antapex. There are no stigma or chloroplasts. A nucleus is located in the central part of the cell. [source] Using aerial photography for identification of marine and coastal habitats under the EU's Habitats DirectiveAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2003Jan Ekebom Abstract 1.Implementation of the E.U. Habitats Directive requires information on the distribution, abundance and area covered by the habitats listed in Annex I of the Directive. 2.In Finland, 21 of these habitats occur in marine and coastal areas. The demand for spatial information of these habitats is increasing, so rapid and relatively inexpensive mapping methods are needed. 3.This study examines the identification of 15 habitats using high altitude black and white aerial photographs. Our goal was to find out how well these habitats could be identified using these types of photographs. We used a test group of 34 persons who were given only brief instructions on how to identify the habitats prior to the test. Their results were compared to a set of field data from an archipelago area at the entrance of the Gulf of Finland, in August 1999 and autumn 2000. 4.The test group identified sandy beaches, lagoons, submerged sandbanks and cliffs with an accuracy of 82%, 71%, 66% and 65%, respectively. The main reasons for these high accuracy percentages were apparently the high contrast and/or easy delineation of the habitat from the surrounding areas. 5.Reefs, wooded dunes and submerged reefs were identified with an accuracy of 39%, 44% and 45%, respectively. The remaining habitats were less precisely identified, apparently due to their small size or poor contrast to the surrounding areas. 6.High altitude aerial photographs are shown to be a useful tool for identifying several of these habitats and can be used as a complement to field mapping methods, GIS methods and other remote sensing techniques. The use of high altitude photographs for monitoring change is discussed. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||